Adaptive coloration

Acknowledgments List of Illustrations Figures Plates Preface to the Anniversary Edition by Paul Ekman Preface to the Third Edition by Paul Ekman Preface to the Second Edition by Francis Darwin Introduction to the Third Edition by Paul Ekman The Expression of the Emotions in Man and Animals Introduction to the First Edition 1. General Principles of Expression 2. General Principles of Expression -- continued 3. General Principles of Expression -- continued 4. Means of Expression in Animals 5. Special Expressions of Animals 6. Special Expressions of Man: Suffering and Weeping 7. Low Spirits, Anxiety, Grief, Dejection, Despair 8. Joy, High Spirits, Love, Tender Feelings, Devotion 9. Reflection - Meditation - Ill-temper - Sulkiness - Determination 10. Hatred and Anger 11. Disdain - Contempt - Disgust - Guilt - Pride, Etc. - Helplessness - Patience - Affirmation and Negation 12. Surprise - Astonishment - Fear - Horror 13. Self-attention - Shame - Shyness - Modesty: Blushing 14. Concluding Remarks and Summary Afterword, by Paul Ekman APPENDIX I: Charles Darwin's Obituary, by T. H. Huxley APPENDIX II: Changes to the Text, by Paul Ekman APPENDIX III: Photography and The Expression of the Emotions, by Phillip Prodger APPENDIX IV: A Note on the Orientation of the Plates, by Phillip Prodger and Paul Ekman APPENDIX V: Concordance of Illustrations, by Phillip Prodger APPENDIX VI: List of Head Words from the Index to the First Edition NOTES NOTES TO THE COMMENTARIES INDEX

@book{doi10103710001000,
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    title = "The expression of the emotions in man and animals.",
    year = "1872",
    booktitle = "John Murray eBooks",
    abstract = "Acknowledgments List of Illustrations Figures Plates Preface to the Anniversary Edition by Paul Ekman Preface to the Third Edition by Paul Ekman Preface to the Second Edition by Francis Darwin Introduction to the Third Edition by Paul Ekman The Expression of the Emotions in Man and Animals Introduction to the First Edition 1. General Principles of Expression 2. General Principles of Expression -- continued 3. General Principles of Expression -- continued 4. Means of Expression in Animals 5. Special Expressions of Animals 6. Special Expressions of Man: Suffering and Weeping 7. Low Spirits, Anxiety, Grief, Dejection, Despair 8. Joy, High Spirits, Love, Tender Feelings, Devotion 9. Reflection - Meditation - Ill-temper - Sulkiness - Determination 10. Hatred and Anger 11. Disdain - Contempt - Disgust - Guilt - Pride, Etc. - Helplessness - Patience - Affirmation and Negation 12. Surprise - Astonishment - Fear - Horror 13. Self-attention - Shame - Shyness - Modesty: Blushing 14. Concluding Remarks and Summary Afterword, by Paul Ekman APPENDIX I: Charles Darwin's Obituary, by T. H. Huxley APPENDIX II: Changes to the Text, by Paul Ekman APPENDIX III: Photography and The Expression of the Emotions, by Phillip Prodger APPENDIX IV: A Note on the Orientation of the Plates, by Phillip Prodger and Paul Ekman APPENDIX V: Concordance of Illustrations, by Phillip Prodger APPENDIX VI: List of Head Words from the Index to the First Edition NOTES NOTES TO THE COMMENTARIES INDEX",
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@article{doi101038005443a0,
    author = "Mcintosh, W.",
    title = "Adaptive Coloration, Phosphorescence, \&\#38;c.",
    year = "1872",
    journal = "Nature",
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    doi = "10.1038/005443A0",
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    title = "Adaptive Coloration in Animals",
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    title = "Adaptive Coloration in Animals",
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@article{doi1023071468,
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@article{doi1023071788577,
    author = "S., W. L. and Cott, Hugh B.",
    title = "Adaptive Coloration in Animals",
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@article{doi1023072420875,
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@article{doi1023071437762,
    author = "Schmidt, Karl P. and Cott, Hugh B.",
    title = "Adaptive Coloration in Animals",
    year = "1941",
    journal = "Copeia",
    url = "https://doi.org/10.2307/1437762",
    doi = "10.2307/1437762",
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An apparatus is described which facilitates the presentation of pairs of variable colors without variation of luminance. With this instrument, various criteria of visual sensitivity to color difference have been investigated. The standard deviation of color matching was finally adopted as the most reproducible criterion. The test field was two degrees in diameter, divided by a vertical biprism edge, and was viewed centrally with a surrounding field of forty-two degrees diameter uniformly illuminated so as to have a chromaticity similar to that of the I.C.I. Standard Illuminant C (average daylight). The luminance of the test field was maintained constant at 15 millilamberts, and the surrounding field was 7.5 millilamberts. These fields were viewed monocularly through an artificial pupil, 2.6 mm in diameter. Over twenty-five thousand trials at color matching have been recorded for a single observer, and the readings are analyzed in detail and compared with previously available data. The standard deviations of the trials are represented in terms of distance in the standard 1931 I.C.I. chromaticity diagram. These increments of distance are represented as functions of position alongstraight lines in the chromaticity diagram, and also as functions of direction of departure from points representing certain standard chromaticities. Such representations are simpler than the traditional representations of wave-length thresholds and purity thresholds as functions of wave-length, and the accuracy of the representations is improved by this simplicity. Chromaticity discrimination for non-spectral colors is represented simultaneously and on the same basis as for spectral colors. Small, equally noticeable chromaticity differences are represented for all chromaticities and for all kinds of variations by the lengths of the radii of a family of ellipses drawn on the standard chromaticity diagram. These ellipses cannot be transformed into equal-sized circles by any projective transformation of the standard chromaticity diagram. The consistency of these data with the results of other investigators is exhibited in terms of the noticeabilities of wave-length differences in the spectrum and of the noticeabilities of purity differences from a neutral stimulus, as functions of dominant wave-length.

@article{doi101364josa32000247,
    author = "MacAdam, David L.",
    title = "Visual Sensitivities to Color Differences in Daylight*",
    year = "1942",
    journal = "Journal of the Optical Society of America",
    abstract = "An apparatus is described which facilitates the presentation of pairs of variable colors without variation of luminance. With this instrument, various criteria of visual sensitivity to color difference have been investigated. The standard deviation of color matching was finally adopted as the most reproducible criterion. The test field was two degrees in diameter, divided by a vertical biprism edge, and was viewed centrally with a surrounding field of forty-two degrees diameter uniformly illuminated so as to have a chromaticity similar to that of the I.C.I. Standard Illuminant C (average daylight). The luminance of the test field was maintained constant at 15 millilamberts, and the surrounding field was 7.5 millilamberts. These fields were viewed monocularly through an artificial pupil, 2.6 mm in diameter. Over twenty-five thousand trials at color matching have been recorded for a single observer, and the readings are analyzed in detail and compared with previously available data. The standard deviations of the trials are represented in terms of distance in the standard 1931 I.C.I. chromaticity diagram. These increments of distance are represented as functions of position alongstraight lines in the chromaticity diagram, and also as functions of direction of departure from points representing certain standard chromaticities. Such representations are simpler than the traditional representations of wave-length thresholds and purity thresholds as functions of wave-length, and the accuracy of the representations is improved by this simplicity. Chromaticity discrimination for non-spectral colors is represented simultaneously and on the same basis as for spectral colors. Small, equally noticeable chromaticity differences are represented for all chromaticities and for all kinds of variations by the lengths of the radii of a family of ellipses drawn on the standard chromaticity diagram. These ellipses cannot be transformed into equal-sized circles by any projective transformation of the standard chromaticity diagram. The consistency of these data with the results of other investigators is exhibited in terms of the noticeabilities of wave-length differences in the spectrum and of the noticeabilities of purity differences from a neutral stimulus, as functions of dominant wave-length.",
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@article{doi1023071929864,
    author = "Cole, L. C.",
    title = "Experiments on Toleration of High Temperature in Lizards with Reference to Adaptive Coloration",
    year = "1943",
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This book is divided into three parts. Part I outlines the elementary principles of the eye as a sense organ and the basic facts of color vision, including types of color blindness and methods of testing. Part II deals with tools and techniques, such as spectrophotometry, standards in colorimetry, and the reproduction of pictures in color. Part III deals with physics and the psychophysics of colorant layers. The book will be useful for all who deal in colors, particularly the manufacturer. The book is a happy combination of science and common sense and is written by one of the outstanding scientists in this field.

@article{doi10106313050671,
    author = "Judd, Deane B. and Wyszecki, Günter and Wintringham, W. T.",
    title = "Color in Business, Science, and Industry",
    year = "1963",
    journal = "Physics Today",
    abstract = "This book is divided into three parts. Part I outlines the elementary principles of the eye as a sense organ and the basic facts of color vision, including types of color blindness and methods of testing. Part II deals with tools and techniques, such as spectrophotometry, standards in colorimetry, and the reproduction of pictures in color. Part III deals with physics and the psychophysics of colorant layers. The book will be useful for all who deal in colors, particularly the manufacturer. The book is a happy combination of science and common sense and is written by one of the outstanding scientists in this field.",
    url = "https://doi.org/10.1063/1.3050671",
    doi = "10.1063/1.3050671",
    openalex = "W2263099603"
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@book{openalexw605090603,
    author = "Bagnara, Joseph T. and Hadley, Mac E.",
    title = "Chromatophores and color change: the comparative physiology of animal pigmentation",
    year = "1973",
    booktitle = "Prentice Hall eBooks",
    openalex = "W605090603"
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Journal Article Adaptive Coloration in Peromyscus polionotus: Experimental Selection by Owls Get access Donald W. Kaufman Donald W. Kaufman Savannah River Ecology Laboratory, Aiken, South Carolina 29801 and Department of Zoology, University of Georgia, Athens, 30601 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 55, Issue 2, 22 May 1974, Pages 271–283, https://doi.org/10.2307/1378997 Published: 22 May 1974 Article history Received: 02 April 1973 Accepted: 28 June 1973 Published: 22 May 1974

@article{doi1023071378997,
    author = "Kaufman, D. W.",
    title = "Adaptive Coloration in Peromyscus polionotus: Experimental Selection by Owls",
    year = "1974",
    journal = "Journal of Mammalogy",
    abstract = "Journal Article Adaptive Coloration in Peromyscus polionotus: Experimental Selection by Owls Get access Donald W. Kaufman Donald W. Kaufman Savannah River Ecology Laboratory, Aiken, South Carolina 29801 and Department of Zoology, University of Georgia, Athens, 30601 Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 55, Issue 2, 22 May 1974, Pages 271–283, https://doi.org/10.2307/1378997 Published: 22 May 1974 Article history Received: 02 April 1973 Accepted: 28 June 1973 Published: 22 May 1974",
    url = "https://doi.org/10.2307/1378997",
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"Color in Business, Science and Industry." Optica Acta: International Journal of Optics, 23(4), p. 340

@article{doi101080713819265,
    author = "Tarrant, A.W.S.",
    title = "Color in Business, Science and Industry",
    year = "1976",
    journal = "Optica Acta International Journal of Optics",
    abstract = {"Color in Business, Science and Industry." Optica Acta: International Journal of Optics, 23(4), p. 340},
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We show how the processes of visual detection and of temporal and spatial summation may be analyzed in terms of parallel luminance (achromatic) and opponent-color systems; a test flash is detected if it exceeds the threshold of either system. The spectral sensitivity of the luminance system may be determined by a flicker method, and has a single broad peak near 555 nm; the spectral sensitivity of the opponent-color system corresponds to the color recognition threshold, and has three peaks at about 440, 530, and 600 nm (on a white background). The temporal and spatial integration of the opponent-color system are generally greater than for the luminance system; further, a white background selectively depresses the sensitivity of the luminance system relative to the opponent-color system. Thus relatively large (1 degree) and long (200 msec) spectral test flashes on a white background are detected by the opponent-color system except near 570 nm; the contribution of the luminance system becomes more prominent if the size or duration of the test flash is reduced, or if the white background is extinguished. The present analysis is discussed in relation to Stiles' model of independent eta mechanisms.

@article{doi101364josa66000709,
    author = "King‐Smith, P. Ewen and Carden, D. E.",
    title = "Luminance and opponent-color contributions to visual detection and adaptation and to temporal and spatial integration",
    year = "1976",
    journal = "Journal of the Optical Society of America",
    abstract = "We show how the processes of visual detection and of temporal and spatial summation may be analyzed in terms of parallel luminance (achromatic) and opponent-color systems; a test flash is detected if it exceeds the threshold of either system. The spectral sensitivity of the luminance system may be determined by a flicker method, and has a single broad peak near 555 nm; the spectral sensitivity of the opponent-color system corresponds to the color recognition threshold, and has three peaks at about 440, 530, and 600 nm (on a white background). The temporal and spatial integration of the opponent-color system are generally greater than for the luminance system; further, a white background selectively depresses the sensitivity of the luminance system relative to the opponent-color system. Thus relatively large (1 degree) and long (200 msec) spectral test flashes on a white background are detected by the opponent-color system except near 570 nm; the contribution of the luminance system becomes more prominent if the size or duration of the test flash is reduced, or if the white background is extinguished. The present analysis is discussed in relation to Stiles' model of independent eta mechanisms.",
    url = "https://doi.org/10.1364/josa.66.000709",
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    openalex = "W2056841914"
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@incollection{doi10100797814615695655,
    author = "Endler, John A.",
    title = "A Predator’s View of Animal Color Patterns",
    year = "1978",
    journal = "Evolutionary Biology",
    url = "https://doi.org/10.1007/978-1-4615-6956-5\_5",
    doi = "10.1007/978-1-4615-6956-5\_5",
    openalex = "W185003398",
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@article{doi1010160003347278901276,
    author = "Snowdon, Charles T.",
    title = "How animals communicate",
    year = "1978",
    journal = "Animal Behaviour",
    url = "https://doi.org/10.1016/0003-3472(78)90127-6",
    doi = "10.1016/0003-3472(78)90127-6",
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Digital control of color television monitors—in particular, via frame buffers—has added precise control of a large subset of human colorspace to the capabilities of computer graphics. This subset is the gamut of colors spanned by the red, green, and blue (RGB) electron guns exciting their respective phosphors. It is called the RGB monitor gamut. Full-blown color theory is a quite complex subject involving physics, psychology, and physiology, but restriction to the RGB monitor gamut simplifies matters substantially. It is linear, for example, and admits to familiar spatial representations. This paper presents a set of alternative models of the RGB monitor gamut based on the perceptual variables hue (H), saturation (S), and value (V) or brightness (L). Algorithms for transforming between these models are derived. Particular emphasis is placed on an RGB to HSV non-trigonometric pair of transforms which have been used successfully for about four years in frame buffer painting programs. These are fast, accurate, and adequate in many applications. Computationally more difficult transform pairs are sometimes necessary, however. Guidelines for choosing among the models are provided. Psychophysical corrections are described within the context of the definitions established by the NTSC (National Television Standards Committee).

@article{doi101145800248807361,
    author = "Smith, Alvy Ray",
    title = "Color gamut transform pairs",
    year = "1978",
    abstract = "Digital control of color television monitors—in particular, via frame buffers—has added precise control of a large subset of human colorspace to the capabilities of computer graphics. This subset is the gamut of colors spanned by the red, green, and blue (RGB) electron guns exciting their respective phosphors. It is called the RGB monitor gamut. Full-blown color theory is a quite complex subject involving physics, psychology, and physiology, but restriction to the RGB monitor gamut simplifies matters substantially. It is linear, for example, and admits to familiar spatial representations. This paper presents a set of alternative models of the RGB monitor gamut based on the perceptual variables hue (H), saturation (S), and value (V) or brightness (L). Algorithms for transforming between these models are derived. Particular emphasis is placed on an RGB to HSV non-trigonometric pair of transforms which have been used successfully for about four years in frame buffer painting programs. These are fast, accurate, and adequate in many applications. Computationally more difficult transform pairs are sometimes necessary, however. Guidelines for choosing among the models are provided. Psychophysical corrections are described within the context of the definitions established by the NTSC (National Television Standards Committee).",
    url = "https://doi.org/10.1145/800248.807361",
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@article{doi1010160003347279901416,
    author = "Clutton‐Brock, Tim and Albon, S. D. and Gibson, Robert M. and Guinness, F. E.",
    title = "The logical stag: Adaptive aspects of fighting in red deer (Cervus elaphus L.)",
    year = "1979",
    journal = "Animal Behaviour",
    url = "https://doi.org/10.1016/0003-3472(79)90141-6",
    doi = "10.1016/0003-3472(79)90141-6",
    openalex = "W2157684935",
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Under the auspices of the ISCC Committee on Color Difference Problems, an experiment was carried out in the visual scaling of small color differences involving six color microspaces. The object‐color samples were visually evaluated by ranking, by subjective estimation, and by acceptability judgments. Visual scales were calculated by traditional procedures. Correlations were calculated between the visual scales and four color‐difference formulas (CIELAB, C1ELUV, FMC‐2, and FCM), and ellipsoids were optimized to the visual data. No fundamental differences were found between the results of the perceptibility judgments and the acceptability judgments. Higher correlations than reported for earlier comparable experiments were obtained between visual and calculated color differences.

@article{doi101111j152063781979tb00094x,
    author = "Kuehni, Rolf G. and Marcus, Robert T.",
    title = "An Experiment in Visual Scaling of Small Color Differences*",
    year = "1979",
    journal = "Color Research \& Application",
    abstract = "Under the auspices of the ISCC Committee on Color Difference Problems, an experiment was carried out in the visual scaling of small color differences involving six color microspaces. The object‐color samples were visually evaluated by ranking, by subjective estimation, and by acceptability judgments. Visual scales were calculated by traditional procedures. Correlations were calculated between the visual scales and four color‐difference formulas (CIELAB, C1ELUV, FMC‐2, and FCM), and ellipsoids were optimized to the visual data. No fundamental differences were found between the results of the perceptibility judgments and the acceptability judgments. Higher correlations than reported for earlier comparable experiments were obtained between visual and calculated color differences.",
    url = "https://doi.org/10.1111/j.1520-6378.1979.tb00094.x",
    doi = "10.1111/j.1520-6378.1979.tb00094.x",
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NATURAL SELECTION ON COLOR PATTERNS IN POECILIA RETICULATA

@article{doi101111j155856461980tb04790x,
    author = "Endler, John A.",
    title = "NATURAL SELECTION ON COLOR PATTERNS IN POECILIA RETICULATA",
    year = "1980",
    journal = "Evolution",
    abstract = "NATURAL SELECTION ON COLOR PATTERNS IN POECILIA RETICULATA",
    url = "https://doi.org/10.1111/j.1558-5646.1980.tb04790.x",
    doi = "10.1111/j.1558-5646.1980.tb04790.x",
    openalex = "W2006099940",
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Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene, are proposed to reside in a head-to-tail tandem array within the X chromosome.

@article{doi101126science2937147,
    author = "Nathans, Jeremy and Thomas, Darcy and Hogness, David S.",
    title = "Molecular Genetics of Human Color Vision: The Genes Encoding Blue, Green, and Red Pigments",
    year = "1986",
    journal = "Science",
    abstract = "Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene, are proposed to reside in a head-to-tail tandem array within the X chromosome.",
    url = "https://doi.org/10.1126/science.2937147",
    doi = "10.1126/science.2937147",
    openalex = "W2019875735"
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Abstract Young Sepia officinalis (0-5 months) were studied in the laboratory and in the sea, and their appearance and behaviour compared with that of adult animals. Cuttlefish lay large eggs and the hatchlings are miniature replicas of the adults. From the moment of hatching they show body patterns as complex as those of adults and far more elaborate than those shown by most juvenile cephalopods. There are 13 body patterns: 6 of these are ‘chronic’ (lasting for minutes or hours) and 7 are ‘acute’ (lasting for seconds or minutes). The patterns are built up from no fewer than 34 chromatic, 6 textural, 8 postural and 6 locomotor components, used in varying combinations and intensities of expression. Nearly all these components occur in young animals: 26 of the chromatic, all the textural and locomotor, and 6 of the postural components. Nevertheless, patterning does change with age and we have recorded this and correlated the changes with behaviour. The components are built up from units, which themselves comprise four elements organized in precise relation to one another: chromatophores, iridophores, leucophores and skin muscles. The chromatophores are always especially important: they are muscular organs innervated directly from the brain and controlled ultimately by the highest centres (optic lobes). The areas in the Sepia brain that control patterning are already well developed at hatching, for the appearance of the skin is as much part of the brain’s motor program as is the attitude of the arms or fins, or the posture of the entire animal. The iridophores and leucophores develop later and are especially important constituents of many adult patterns, notably the Intense Zebra of the mature male. Experiments confirm that patterning is neurally controlled and apparently mediated exclusively by the visual system. Young cuttlefish use patterning primarily for concealment, utilizing such strategies as general colour resemblance, disruptive coloration, obliterative shading, shadow elimination, disguise and adaptive behaviour. Older animals also conceal themselves but increasingly use patterns for signalling, both interspecifically (warning or ‘deimatic’ displays) and intraspecifically (sexual signalling). Laboratory-reared cuttlefish were released in the sea and observed underwater. They quickly and effectively concealed themselves on the substrate; it was easy for the human observer to lose them and many passing fish behaved as if they were not there. One local predator, Serranus cabrilla, was observed to attack them and no fewer than 35 attacks were recorded, only six of which were successful. Laboratory-reared cuttlefish apparently distinguished between these predators and other, non-predatory, fish the first time they encountered them in nature.

@article{doi101098rstb19880087,
    author = "Hanlon, Roger T. and Messenger, J. B.",
    title = "Adaptive coloration in young cuttlefish (Sepia officinalis L.): the morphology and development of body patterns and their relation to behaviour",
    year = "1988",
    journal = "Philosophical transactions of the Royal Society of London. Series B, Biological sciences",
    abstract = "Abstract Young Sepia officinalis (0-5 months) were studied in the laboratory and in the sea, and their appearance and behaviour compared with that of adult animals. Cuttlefish lay large eggs and the hatchlings are miniature replicas of the adults. From the moment of hatching they show body patterns as complex as those of adults and far more elaborate than those shown by most juvenile cephalopods. There are 13 body patterns: 6 of these are ‘chronic’ (lasting for minutes or hours) and 7 are ‘acute’ (lasting for seconds or minutes). The patterns are built up from no fewer than 34 chromatic, 6 textural, 8 postural and 6 locomotor components, used in varying combinations and intensities of expression. Nearly all these components occur in young animals: 26 of the chromatic, all the textural and locomotor, and 6 of the postural components. Nevertheless, patterning does change with age and we have recorded this and correlated the changes with behaviour. The components are built up from units, which themselves comprise four elements organized in precise relation to one another: chromatophores, iridophores, leucophores and skin muscles. The chromatophores are always especially important: they are muscular organs innervated directly from the brain and controlled ultimately by the highest centres (optic lobes). The areas in the Sepia brain that control patterning are already well developed at hatching, for the appearance of the skin is as much part of the brain’s motor program as is the attitude of the arms or fins, or the posture of the entire animal. The iridophores and leucophores develop later and are especially important constituents of many adult patterns, notably the Intense Zebra of the mature male. Experiments confirm that patterning is neurally controlled and apparently mediated exclusively by the visual system. Young cuttlefish use patterning primarily for concealment, utilizing such strategies as general colour resemblance, disruptive coloration, obliterative shading, shadow elimination, disguise and adaptive behaviour. Older animals also conceal themselves but increasingly use patterns for signalling, both interspecifically (warning or ‘deimatic’ displays) and intraspecifically (sexual signalling). Laboratory-reared cuttlefish were released in the sea and observed underwater. They quickly and effectively concealed themselves on the substrate; it was easy for the human observer to lose them and many passing fish behaved as if they were not there. One local predator, Serranus cabrilla, was observed to attack them and no fewer than 35 attacks were recorded, only six of which were successful. Laboratory-reared cuttlefish apparently distinguished between these predators and other, non-predatory, fish the first time they encountered them in nature.",
    url = "https://doi.org/10.1098/rstb.1988.0087",
    doi = "10.1098/rstb.1988.0087",
    openalex = "W2039012144",
    references = "doi101002ar1090940210, doi101007bf00408216, doi1010160022098186900869, doi101098rspb19810056, doi101111j143904851983tb00299x, doi103354meps007067, openalexw2480470726, openalexw3208881761, openalexw605090603"
}

Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.

@article{doi101126science3283936,
    author = "Livingstone, Margaret S. and Hubel, David H.",
    title = "Segregation of Form, Color, Movement, and Depth: Anatomy, Physiology, and Perception",
    year = "1988",
    journal = "Science",
    abstract = "Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.",
    url = "https://doi.org/10.1126/science.3283936",
    doi = "10.1126/science.3283936",
    openalex = "W1979741733",
    references = "doi101001archopht195201700030123016"
}

Frequency-dependent selection on warning color can maintain narrow hybrid zones between unpalatable prey taxa. To measure such selection, we transferred marked Heliconius erato (Lepidoptera: Nymphalidae) in both directions across a 10-km-wide hybrid zone between Peruvian races differing in color pattern. These experimental H. erato were released at four sites, along with control H. erato of the phenotype native to each site. Survival of experimental butterflies was significantly lower than that of controls at two sites and overall. Most selection, measured as differences in survival, occurred soon after release. Selection against foreign morphs was 52% (confidence limits: 25-71 %) and was probably due to bird attacks on unusual warning-color morphs (more than 10% of the recaptures had beak marks). Since only three major loci determine the color-pattern differences, this suggests an average selection coefficient of 0.17 per locus, sufficient to maintain the narrow clines in H. erato.

@article{doi101111j155856461989tb04237x,
    author = "Mallet, James and Barton, Nick",
    title = "STRONG NATURAL SELECTION IN A WARNING-COLOR HYBRID ZONE",
    year = "1989",
    journal = "Evolution",
    abstract = "Frequency-dependent selection on warning color can maintain narrow hybrid zones between unpalatable prey taxa. To measure such selection, we transferred marked Heliconius erato (Lepidoptera: Nymphalidae) in both directions across a 10-km-wide hybrid zone between Peruvian races differing in color pattern. These experimental H. erato were released at four sites, along with control H. erato of the phenotype native to each site. Survival of experimental butterflies was significantly lower than that of controls at two sites and overall. Most selection, measured as differences in survival, occurred soon after release. Selection against foreign morphs was 52\% (confidence limits: 25-71 \%) and was probably due to bird attacks on unusual warning-color morphs (more than 10\% of the recaptures had beak marks). Since only three major loci determine the color-pattern differences, this suggests an average selection coefficient of 0.17 per locus, sufficient to maintain the narrow clines in H. erato.",
    url = "https://doi.org/10.1111/j.1558-5646.1989.tb04237.x",
    doi = "10.1111/j.1558-5646.1989.tb04237.x",
    openalex = "W2332616442",
    references = "benson1972natural, doi101007bf02986626, doi101038hdy196642, doi101038hdy197987, doi101086409995, doi101093biomet5212225, doi101093genetics754733, doi101098rstb19850066, doi101111j109583121986tb01772x, doi101111j109583121987tb00435x, doi101111j155856461967tb00126x, doi101111j155856461969tb03516x, doi101126science1443615183, doi101146annureves16110185000553, doi1023072407738, doi1023072989703, doi105962p203311, openalexw3133798068"
}

The CIELAB colorimetric system was used for the study of the relationship between measured color difference values and human observer responses. This study verified that a specific, visually meaningful and precise relationship exists between the magnitude and direction of the measurements and the average dental-observer responses. The results support the use of this system in dentistry as a means of evaluating color by differences. The further development of such systems for clinical use would be warranted and could serve as a valuable tool for material selection and restoration design, particularly in the area of aesthetic restorative dentistry.

@article{doi10117700220345890680120801,
    author = "Seghi, Robert R. and Hewlett, Edmond R. and Kim, J.",
    title = "Visual and Instrumental Colorimetric Assessments of Small Color Differences on Translucent Dental Porcelain",
    year = "1989",
    journal = "Journal of Dental Research",
    abstract = "The CIELAB colorimetric system was used for the study of the relationship between measured color difference values and human observer responses. This study verified that a specific, visually meaningful and precise relationship exists between the magnitude and direction of the measurements and the average dental-observer responses. The results support the use of this system in dentistry as a means of evaluating color by differences. The further development of such systems for clinical use would be warranted and could serve as a valuable tool for material selection and restoration design, particularly in the area of aesthetic restorative dentistry.",
    url = "https://doi.org/10.1177/00220345890680120801",
    doi = "10.1177/00220345890680120801",
    openalex = "W2031769431",
    references = "doi10106313050671"
}

In studies of animal colouration it is no longer necessary to rely on subjective assessments of colour and conspicuousness, nor on methods which rely upon human vision. This is important because animals vary greatly in colour vision and colour is context-dependent. New methods make it practical to measure the colour spectrum of pattern elements (patches) of animals and their visual backgrounds for the conditions under which patch spectra reach the conspecific's, predator's or prey's eyes. These methods can be used in both terrestrial and aquatic habitats. A patch's colour is dependent not only upon its reflectance spectrum, but also upon the ambient light spectrum, the transmission properties of air or water, and the veiling light spectrum. These factors change with time of day, weather, season and microhabitat, so colours must be measured under the conditions prevalent when colour patterns are normally used. Methods of measuring, classifying and comparing colours are presented, as well as techniques for assessing the conspicuousness of colour patterns as a whole. Some implications of the effect of environmental light and vision are also discussed.

@article{doi101111j109583121990tb00839x,
    author = "Endler, John A.",
    title = "On the measurement and classification of colour in studies of animal colour patterns",
    year = "1990",
    journal = "Biological Journal of the Linnean Society",
    abstract = "In studies of animal colouration it is no longer necessary to rely on subjective assessments of colour and conspicuousness, nor on methods which rely upon human vision. This is important because animals vary greatly in colour vision and colour is context-dependent. New methods make it practical to measure the colour spectrum of pattern elements (patches) of animals and their visual backgrounds for the conditions under which patch spectra reach the conspecific's, predator's or prey's eyes. These methods can be used in both terrestrial and aquatic habitats. A patch's colour is dependent not only upon its reflectance spectrum, but also upon the ambient light spectrum, the transmission properties of air or water, and the veiling light spectrum. These factors change with time of day, weather, season and microhabitat, so colours must be measured under the conditions prevalent when colour patterns are normally used. Methods of measuring, classifying and comparing colours are presented, as well as techniques for assessing the conspicuousness of colour patterns as a whole. Some implications of the effect of environmental light and vision are also discussed.",
    url = "https://doi.org/10.1111/j.1095-8312.1990.tb00839.x",
    doi = "10.1111/j.1095-8312.1990.tb00839.x",
    openalex = "W2014518833",
    references = "doi10100797814615695655, doi10100797894015768267, doi101111j109583121984tb01677x, doi101111j109583121986tb01772x, openalexw1594469865"
}

@article{doi101016s0003347205806001,
    author = "Guilford, Tim and Dawkins, Marian Stamp",
    title = "Receiver psychology and the evolution of animal signals",
    year = "1991",
    journal = "Animal Behaviour",
    url = "https://doi.org/10.1016/s0003-3472(05)80600-1",
    doi = "10.1016/s0003-3472(05)80600-1",
    openalex = "W2007031449",
    references = "doi10100797814615695655, doi1010160005791678900733, doi1010160022519375901113, doi101016s0022519305800888, doi101038343066a0, doi101111j109583121984tb01677x, doi10112111907229, doi101126science7123238, doi101537ase188722495, doi1023071421765, doi1023074581, doi1023075530"
}

@book{openalexw614507079,
    author = "Blaisdell, Muriel L.",
    title = "Darwinism and its data: the adaptive coloration of animals",
    year = "1992",
    url = "https://openalex.org/W614507079",
    openalex = "W614507079"
}

@article{s2658ec77b022ba8e3d9bb503979c24328c78cd70a,
    author = "Blaisdell, Muriel L.",
    title = "Darwinism and its data : the adaptive coloration of animals",
    year = "1992",
    url = "https://www.semanticscholar.org/paper/658ec77b022ba8e3d9bb503979c24328c78cd70a",
    is_oa = "true",
    openalex = "W614507079",
    semanticscholar_citation_count = "6",
    semanticscholar_id = "658ec77b022ba8e3d9bb503979c24328c78cd70a"
}

Animal communication systems have evolved so that individuals can make decisions based upon the behaviour, physiology or morphology of others. Receiving mechanisms probably evolve to increase the efficiency and reliability of information reception whereas signals probably evolve to increase the efficiency of communication and reliability of manipulation of the receiving individual to the benefit of the emitter. The minimum requirement for clear reception suggests that any study of the evolution and design of communication systems must consider the factors that affect the quality of the received and processed signal. Critical information is needed about how the signal is generated and emitted, how it fares during transmission through air, water or substrate, how it is received and processed by the receiver's sensory and cognitive systems, and the factors which affect the fitness consequences of alternative ways of reacting to the information contained in the signal. These should allow predictions about the kinds and forms of signals used by animals signalling under known conditions. Phylogenetic history, and the geological time a clade spends in different signalling environments, will also affect signal evolution, and hence the success of predictions about signal design. We need to use methods of many different biological fields to understand the design and evolution of signals and signalling systems.

@article{doi101098rstb19930060,
    author = "Endler, John A.",
    title = "Some general comments on the evolution and design of animal communication systems",
    year = "1993",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Animal communication systems have evolved so that individuals can make decisions based upon the behaviour, physiology or morphology of others. Receiving mechanisms probably evolve to increase the efficiency and reliability of information reception whereas signals probably evolve to increase the efficiency of communication and reliability of manipulation of the receiving individual to the benefit of the emitter. The minimum requirement for clear reception suggests that any study of the evolution and design of communication systems must consider the factors that affect the quality of the received and processed signal. Critical information is needed about how the signal is generated and emitted, how it fares during transmission through air, water or substrate, how it is received and processed by the receiver's sensory and cognitive systems, and the factors which affect the fitness consequences of alternative ways of reacting to the information contained in the signal. These should allow predictions about the kinds and forms of signals used by animals signalling under known conditions. Phylogenetic history, and the geological time a clade spends in different signalling environments, will also affect signal evolution, and hence the success of predictions about signal design. We need to use methods of many different biological fields to understand the design and evolution of signals and signalling systems.",
    url = "https://doi.org/10.1098/rstb.1993.0060",
    doi = "10.1098/rstb.1993.0060",
    openalex = "W2155528423",
    references = "doi10100797894015768267, doi1023072937121, openalexw63174745"
}

Forests exhibit much variation in light environments, and this can affect communication among animals, communication between animals and plants, photosynthesis, and plant morphogenesis. Light environments are caused by, and can be predicted from, the geometry of the light paths, the weather conditions, and the time of day. The structure of forests leads to four major light habitats when the sun is not blocked by clouds: forest shade, woodland shade, small gaps, and large gaps. These are characterized by yellow—green, blue—gray, reddish, and "white" ambient light spectra, respectively. When the sun is blocked by clouds, the spectra of these four habitats converge on that of large gaps and open areas, so the single light environment during cloudy weather will be called open/cloudy. An additional light environment (early/late) is associated with low sun angles (near dawn or dusk); it is purplish. Each light environment is well defined and was found in forests of Trinidad, Panama, Costa Rica, Australia, California, and Florida. Scattered literature references suggest similar patterns elsewhere in North America, Europe, and Java. Perceived colors of animals, flowers, and fruits depend upon the interaction between ambient light color and the reflectance color of the animal or plant parts. As a result, an animal or plant may have a different appearance in each environment, i.e., a color pattern may be relatively cryptic in some light environments while relatively conspicuous in others. This has strong implications for the joint evolution of visual signals and vision, as well as microhabitat choice. Plant growth and form may also be affected by variation in the color of forest light.

@article{doi1023072937121,
    author = "Endler, John A.",
    title = "The Color of Light in Forests and Its Implications",
    year = "1993",
    journal = "Ecological Monographs",
    abstract = {Forests exhibit much variation in light environments, and this can affect communication among animals, communication between animals and plants, photosynthesis, and plant morphogenesis. Light environments are caused by, and can be predicted from, the geometry of the light paths, the weather conditions, and the time of day. The structure of forests leads to four major light habitats when the sun is not blocked by clouds: forest shade, woodland shade, small gaps, and large gaps. These are characterized by yellow—green, blue—gray, reddish, and "white" ambient light spectra, respectively. When the sun is blocked by clouds, the spectra of these four habitats converge on that of large gaps and open areas, so the single light environment during cloudy weather will be called open/cloudy. An additional light environment (early/late) is associated with low sun angles (near dawn or dusk); it is purplish. Each light environment is well defined and was found in forests of Trinidad, Panama, Costa Rica, Australia, California, and Florida. Scattered literature references suggest similar patterns elsewhere in North America, Europe, and Java. Perceived colors of animals, flowers, and fruits depend upon the interaction between ambient light color and the reflectance color of the animal or plant parts. As a result, an animal or plant may have a different appearance in each environment, i.e., a color pattern may be relatively cryptic in some light environments while relatively conspicuous in others. This has strong implications for the joint evolution of visual signals and vision, as well as microhabitat choice. Plant growth and form may also be affected by variation in the color of forest light.},
    url = "https://doi.org/10.2307/2937121",
    doi = "10.2307/2937121",
    openalex = "W2044206835",
    references = "doi101017cbo9780511623370, doi101104pp475656, doi101111j109583121990tb00839x, doi10117515200493192452397satr20co2, doi101364ao4000011, doi1023071219834, doi1023072260066, doi1023072260471, openalexw1507653370, openalexw2154344098"
}

Many long-standing evolutionary hypotheses make predictions about trends in color patterns. Examples of these include crypsis, mimicry and warning coloration, fruit coloration, flower coloration, the handicap principle of honest advertisement, Fisher's runaway process, the parasite theory of sexual selection, and sensory drive theories of signaling. The majority of tests of these hypotheses, particularly with regard to sexual selection, have been conducted on objects that birds perceive visually, with human vision used to assess color. This assumes that birds see color patterns as humans do, an assumption that is seriously flawed. First, birds see very well parts of the spectrum that humans cannot. Second, birds have at least four dimensions to their color vision, compared to only three in humans. Third, birds have a complex system of oil droplets in their retinas, which may alter the number of hues they perceive. Thus, an object will not appear to have the same hues for a human and a bird, and maybe not even the same relative brightness or saturation. Despite this, human vision is routinely, and almost without exception, the method used for assessment of color patterns seen by birds. We argue that the error in this assumption may well be a major reason that support for various evolutionary hypotheses involving color is an area of controversy. We also suggest methods for overcoming the shortcomings of existing studies and suggest which previous approaches are likely to have been most erroneous. As part of this, it is apparent that a research program in color cognition is necessary, for if we wish to understand evolutionary hypotheses involving color we need to understand how animals perceive color. Color is not an inherent property of the object; it is a product of the brain of the animal perceiving the object. Humans can see hues seen by birds as much as knowledge of x and y coordinates can predict the position of a point in three-dimensional space.

@article{doi101086285711,
    author = "Bennett, Andrew T. D. and Cuthill, Innes C. and Norris, Ken",
    title = "Sexual Selection and the Mismeasure of Color",
    year = "1994",
    journal = "The American Naturalist",
    abstract = "Many long-standing evolutionary hypotheses make predictions about trends in color patterns. Examples of these include crypsis, mimicry and warning coloration, fruit coloration, flower coloration, the handicap principle of honest advertisement, Fisher's runaway process, the parasite theory of sexual selection, and sensory drive theories of signaling. The majority of tests of these hypotheses, particularly with regard to sexual selection, have been conducted on objects that birds perceive visually, with human vision used to assess color. This assumes that birds see color patterns as humans do, an assumption that is seriously flawed. First, birds see very well parts of the spectrum that humans cannot. Second, birds have at least four dimensions to their color vision, compared to only three in humans. Third, birds have a complex system of oil droplets in their retinas, which may alter the number of hues they perceive. Thus, an object will not appear to have the same hues for a human and a bird, and maybe not even the same relative brightness or saturation. Despite this, human vision is routinely, and almost without exception, the method used for assessment of color patterns seen by birds. We argue that the error in this assumption may well be a major reason that support for various evolutionary hypotheses involving color is an area of controversy. We also suggest methods for overcoming the shortcomings of existing studies and suggest which previous approaches are likely to have been most erroneous. As part of this, it is apparent that a research program in color cognition is necessary, for if we wish to understand evolutionary hypotheses involving color we need to understand how animals perceive color. Color is not an inherent property of the object; it is a product of the brain of the animal perceiving the object. Humans can see hues seen by birds as much as knowledge of x and y coordinates can predict the position of a point in three-dimensional space.",
    url = "https://doi.org/10.1086/285711",
    doi = "10.1086/285711",
    openalex = "W2028033258"
}

Phenotypic plasticity is an environmentally based change in the phenotype. Understanding the evolution of adaptive phenotypic plasticity has been hampered by dissenting opinions on the merits of different methods of description, on the underlying genetic mechanisms, and on the way that plasticity is affected by natural selection in a heterogeneous environment. During much of this debate, the authors of this article have held opposing views. Here, we attempt to lay out current issues and summarize the areas of consensus and controversy surrounding the evolution of plasticity and the reaction norm (the set of phenotypes produced by a genotype over a range of environments).

@article{doi101016s0169534700890618,
    author = "Via, Sara and Gomulkiewicz, Richard and de Jong, Gerdien and Scheiner, Samuel M. and Schlichting, Carl D. and van Tienderen, Peter H.",
    title = "Adaptive phenotypic plasticity: consensus and controversy",
    year = "1995",
    journal = "Trends in Ecology \& Evolution",
    abstract = "Phenotypic plasticity is an environmentally based change in the phenotype. Understanding the evolution of adaptive phenotypic plasticity has been hampered by dissenting opinions on the merits of different methods of description, on the underlying genetic mechanisms, and on the way that plasticity is affected by natural selection in a heterogeneous environment. During much of this debate, the authors of this article have held opposing views. Here, we attempt to lay out current issues and summarize the areas of consensus and controversy surrounding the evolution of plasticity and the reaction norm (the set of phenotypes produced by a genotype over a range of environments).",
    url = "https://doi.org/10.1016/s0169-5347(00)89061-8",
    doi = "10.1016/s0169-5347(00)89061-8",
    openalex = "W2122591605",
    references = "doi1023072408842"
}

Avian plumage has long been used to test theories of sexual selection, with humans assessing the colors. However, many birds see in the ultraviolet (<400 nm), to which humans are blind. Consequently, it is important to know whether natural variation in UV reflectance from plumage functions in sexual signaling. We show that female starlings rank males differently when UV wavelengths are present or absent. Principal component analysis of approximately 1300 reflectance spectra (300-700 nm) taken from sexually dimorphic plumage regions of males predicted preference under the UV+ treatment. Under UV- conditions, females ranked males in a different and nonrandom order, but plumage reflectance in the human visible spectrum did not predict choice. Natural variation in UV reflectance is thus important in avian mate assessment, and the prevailing light environment can have profound effects on observed mating preferences.

@article{doi101073pnas94168618,
    author = "Bennett, Andrew T. D. and Cuthill, Innes C. and Partridge, Julian C. and Lunau, Klaus",
    title = "Ultraviolet plumage colors predict mate preferences in starlings",
    year = "1997",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Avian plumage has long been used to test theories of sexual selection, with humans assessing the colors. However, many birds see in the ultraviolet (<400 nm), to which humans are blind. Consequently, it is important to know whether natural variation in UV reflectance from plumage functions in sexual signaling. We show that female starlings rank males differently when UV wavelengths are present or absent. Principal component analysis of approximately 1300 reflectance spectra (300-700 nm) taken from sexually dimorphic plumage regions of males predicted preference under the UV+ treatment. Under UV- conditions, females ranked males in a different and nonrandom order, but plumage reflectance in the human visible spectrum did not predict choice. Natural variation in UV reflectance is thus important in avian mate assessment, and the prevailing light environment can have profound effects on observed mating preferences.",
    url = "https://doi.org/10.1073/pnas.94.16.8618",
    doi = "10.1073/pnas.94.16.8618",
    openalex = "W2134425408"
}

This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented using vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided.

@article{doi10110983597268,
    author = "Sharma, Gaurav and Trussell, H.J.",
    title = "Digital color imaging",
    year = "1997",
    journal = "IEEE Transactions on Image Processing",
    abstract = "This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented using vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided.",
    url = "https://doi.org/10.1109/83.597268",
    doi = "10.1109/83.597268",
    openalex = "W2171678033",
    references = "doi101080713819265"
}

@article{doi101002sici15206378199808234248aidcol930co2o,
    author = "Brill, Michael H.",
    title = "Color appearance models",
    year = "1998",
    journal = "Color Research \& Application",
    url = "https://doi.org/10.1002/(sici)1520-6378(199808)23:4<248::aid-col9>3.0.co;2-o",
    doi = "10.1002/(sici)1520-6378(199808)23:4<248::aid-col9>3.0.co;2-o",
    openalex = "W2087401004"
}

It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight some of the more representative examples in the text, and discuss some ecological and evolutionary aspects of the use of chemosensory information for prey decision making. Curiously, only one example illustrates the ability of birds to detect predator odours and we have found no examples for terrestrial insects, suggesting a fruitful area for future study.

@article{doi10108011956860199811682468,
    author = "Kats, Lee B. and Dill, Lawrence M.",
    title = "The scent of death: Chemosensory assessment of predation risk by prey animals",
    year = "1998",
    journal = "Ecoscience",
    abstract = "It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight some of the more representative examples in the text, and discuss some ecological and evolutionary aspects of the use of chemosensory information for prey decision making. Curiously, only one example illustrates the ability of birds to detect predator odours and we have found no examples for terrestrial insects, suggesting a fruitful area for future study.",
    url = "https://doi.org/10.1080/11956860.1998.11682468",
    doi = "10.1080/11956860.1998.11682468",
    openalex = "W126353083",
    references = "doi101007978146848261412, doi101016s0149763405800387, doi101086416841, doi101126science2474945949, doi101126science25850861348, doi101139z90092, doi1023071437762, doi1023071941163, openalexw1480947368, openalexw1484524608"
}

Genetic color variation provides a tangible link between the external phenotype of an organism and its underlying genetic determination and thus furnishes a tractable system with which to explore fundamental evolutionary phenomena. Here we examine the basis of color variation in spiders and its evolutionary and ecological implications. Reversible color changes, resulting from several mechanisms, are surprisingly widespread in the group and must be distinguished from true genetic variation for color to be used as an evolutionary tool. Genetic polymorphism occurs in a large number of families and is frequently sex limited: Sex linkage has not yet been demonstrated, nor have the forces promoting sex limitation been elucidated. It is argued that the production of color is metabolically costly and is principally maintained by the action of sight-hunting predators. Key avenues for future research are suggested.

@article{doi101146annurevento431619,
    author = "Oxford, Geoff and Gillespie, Rosemary G.",
    title = "EVOLUTION AND ECOLOGY OF SPIDER COLORATION",
    year = "1998",
    journal = "Annual Review of Entomology",
    abstract = "Genetic color variation provides a tangible link between the external phenotype of an organism and its underlying genetic determination and thus furnishes a tractable system with which to explore fundamental evolutionary phenomena. Here we examine the basis of color variation in spiders and its evolutionary and ecological implications. Reversible color changes, resulting from several mechanisms, are surprisingly widespread in the group and must be distinguished from true genetic variation for color to be used as an evolutionary tool. Genetic polymorphism occurs in a large number of families and is frequently sex limited: Sex linkage has not yet been demonstrated, nor have the forces promoting sex limitation been elucidated. It is argued that the production of color is metabolically costly and is principally maintained by the action of sight-hunting predators. Key avenues for future research are suggested.",
    url = "https://doi.org/10.1146/annurev.ento.43.1.619",
    doi = "10.1146/annurev.ento.43.1.619",
    openalex = "W2103451480",
    references = "doi1010160047248480900779, doi101017cbo9780511623431, doi101146annureves22110191003025, doi101163036551660x00053, doi1023071437762, doi1023072420875, doi1023072529912, doi105860choice293876, eaton1940adaptive, openalexw2062594085, openalexw2242001249, seitz1987excretory"
}

▪ Abstract Mimicry and warning color are highly paradoxical adaptations. Color patterns in both Müllerian and Batesian mimicry are often determined by relatively few pattern-regulating loci with major effects. Many of these loci are “supergenes,” consisting of multiple, tightly linked epistatic elements. On the one hand, strong purifying selection on these genes must explain accurate resemblance (a reduction of morphological diversity between species), as well as monomorphic color patterns within species. On the other hand, mimicry has diversified at every taxonomic level; warning color has evolved from cryptic patterns, and there are mimetic polymorphisms within species, multiple color patterns in different geographic races of the same species, mimetic differences between sister species, and multiple mimicry rings within local communities. These contrasting patterns can be explained, in part, by the shape of a “number-dependent” selection function first modeled by Fritz Müller in 1879: Purifying selection against any warning-colored morph is very strong when that morph is rare, but becomes weak in a broad basin of intermediate frequencies, allowing opportunities for polymorphisms and genetic drift. This Müllerian explanation, however, makes unstated assumptions about predator learning and forgetting which have recently been challenged. Today's “receiver psychology” models predict that classical Müllerian mimicry could be much rarer than believed previously, and that “quasi-Batesian mimicry,” a new type of mimicry intermediate between Müllerian and Batesian, could be common. However, the new receiver psychology theory is untested, and indeed it seems to us unlikely; alternative assumptions could easily lead to a more traditional Müllerian/Batesian mimicry divide.

@article{doi101146annurevecolsys301201,
    author = "Mallet, James and Joron, Mathieu",
    title = "Evolution of Diversity in Warning Color and Mimicry: Polymorphisms, Shifting Balance, and Speciation",
    year = "1999",
    journal = "Annual Review of Ecology and Systematics",
    abstract = "▪ Abstract Mimicry and warning color are highly paradoxical adaptations. Color patterns in both Müllerian and Batesian mimicry are often determined by relatively few pattern-regulating loci with major effects. Many of these loci are “supergenes,” consisting of multiple, tightly linked epistatic elements. On the one hand, strong purifying selection on these genes must explain accurate resemblance (a reduction of morphological diversity between species), as well as monomorphic color patterns within species. On the other hand, mimicry has diversified at every taxonomic level; warning color has evolved from cryptic patterns, and there are mimetic polymorphisms within species, multiple color patterns in different geographic races of the same species, mimetic differences between sister species, and multiple mimicry rings within local communities. These contrasting patterns can be explained, in part, by the shape of a “number-dependent” selection function first modeled by Fritz Müller in 1879: Purifying selection against any warning-colored morph is very strong when that morph is rare, but becomes weak in a broad basin of intermediate frequencies, allowing opportunities for polymorphisms and genetic drift. This Müllerian explanation, however, makes unstated assumptions about predator learning and forgetting which have recently been challenged. Today's “receiver psychology” models predict that classical Müllerian mimicry could be much rarer than believed previously, and that “quasi-Batesian mimicry,” a new type of mimicry intermediate between Müllerian and Batesian, could be common. However, the new receiver psychology theory is untested, and indeed it seems to us unlikely; alternative assumptions could easily lead to a more traditional Müllerian/Batesian mimicry divide.",
    url = "https://doi.org/10.1146/annurev.ecolsys.30.1.201",
    doi = "10.1146/annurev.ecolsys.30.1.201",
    openalex = "W2155422373",
    references = "benson1972natural, doi1010160022519364900384, doi1010160022519371901895, doi101016s0022519384800041, doi10103712293000, doi101038384236a0, doi101086284581, doi101093oso97801985498330010001, doi101098rstb19850066, doi101098rstb19950033, doi101111j109583121984tb00143x, doi101111j109583121986tb01772x, doi101111j109583121987tb00435x, doi101111j109583121996tb01452x, doi101111j109636421860tb00146x, doi101111j155856461989tb04237x, doi101146annureven15010170000355, doi1015159780691207278, doi1023072411226, doi1023072420875, doi1023072531471, doi1023074510368, doi104159harvard9780674865327, doi105962bhltitle27468, eaton1940adaptive, openalexw1523652513, openalexw160989634, openalexw2151993477, openalexw2624262714, openalexw3133798068"
}

This paper presents the measurement of colored object reflectance, under different, general assumptions regarding the imaging conditions. We exploit the Gaussian scale-space paradigm for color images to define a framework for the robust measurement of object reflectance from color images. Object reflectance is derived from a physical reflectance model based on the Kubelka-Munk theory for colorant layers. Illumination and geometrical invariant properties are derived from the reflectance model. Invariance and discriminative power of the color invariants is experimentally investigated, showing the invariants to be successful in discounting shadow, illumination, highlights, and noise. Extensive experiments show the different invariants to be highly discriminative, while maintaining invariance properties. The presented framework for color measurement is well-founded in the physics of color as well as in measurement science. Hence, the proposed invariants are considered more adequate for the measurement of invariant color features than existing methods.

@article{doi10110934977559,
    author = "Geusebroek, Jan‐Mark and van den Boomgaard, R. and Smeulders, A.W.M. and Geerts, Hugo",
    title = "Color invariance",
    year = "2001",
    journal = "IEEE Transactions on Pattern Analysis and Machine Intelligence",
    abstract = "This paper presents the measurement of colored object reflectance, under different, general assumptions regarding the imaging conditions. We exploit the Gaussian scale-space paradigm for color images to define a framework for the robust measurement of object reflectance from color images. Object reflectance is derived from a physical reflectance model based on the Kubelka-Munk theory for colorant layers. Illumination and geometrical invariant properties are derived from the reflectance model. Invariance and discriminative power of the color invariants is experimentally investigated, showing the invariants to be successful in discounting shadow, illumination, highlights, and noise. Extensive experiments show the different invariants to be highly discriminative, while maintaining invariance properties. The presented framework for color measurement is well-founded in the physics of color as well as in measurement science. Hence, the proposed invariants are considered more adequate for the measurement of invariant color features than existing methods.",
    url = "https://doi.org/10.1109/34.977559",
    doi = "10.1109/34.977559",
    openalex = "W2296249689",
    references = "doi101080713819265"
}

Carotenoid pigments are a widespread source of ornamental coloration in vertebrates and expression of carotenoid-based colour displays has been shown to serve as an important criterion in female mate choice in birds and fishes. Unlike other integumentary pigments, carotenoids cannot be synthesized; they must be ingested. Carotenoid-based coloration is condition-dependent and has been shown to be affected by both parasites and nutritional condition. A controversial hypothesis is that the expression of carotenoid-based coloration in wild vertebrates is also affected by the amount and types of carotenoid pigments that are ingested. We tested this carotenoid-limitation hypothesis by sampling the gut contents of moulting house finches and comparing the concentration of carotenoid pigments in their gut contents with the colour of growing feathers. We found a positive association: males that ingested food with a higher concentration of carotenoid pigments grew brighter ornamental plumage. We also compared the concentration of carotenoids in the gut contents of males from two subspecies of house finches with small and large patches of carotenoid-based coloration. Consistent with the hypothesis that carotenoid access drives the evolution of carotenoid-based colour displays, males from the population with limited ornamentation had much lower concentrations of carotenoids in their gut contents than males from the population with extensive ornamentation. These observations support the idea that carotenoid intake plays a part in determining the plumage brightness of male house finches.

@article{doi101098rspb20021980,
    author = "Hill, Geoffrey E. and Inouye, Caron Y. and Montgomerie, Robert",
    title = "Dietary carotenoids predict plumage coloration in wild house finches",
    year = "2002",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Carotenoid pigments are a widespread source of ornamental coloration in vertebrates and expression of carotenoid-based colour displays has been shown to serve as an important criterion in female mate choice in birds and fishes. Unlike other integumentary pigments, carotenoids cannot be synthesized; they must be ingested. Carotenoid-based coloration is condition-dependent and has been shown to be affected by both parasites and nutritional condition. A controversial hypothesis is that the expression of carotenoid-based coloration in wild vertebrates is also affected by the amount and types of carotenoid pigments that are ingested. We tested this carotenoid-limitation hypothesis by sampling the gut contents of moulting house finches and comparing the concentration of carotenoid pigments in their gut contents with the colour of growing feathers. We found a positive association: males that ingested food with a higher concentration of carotenoid pigments grew brighter ornamental plumage. We also compared the concentration of carotenoids in the gut contents of males from two subspecies of house finches with small and large patches of carotenoid-based coloration. Consistent with the hypothesis that carotenoid access drives the evolution of carotenoid-based colour displays, males from the population with limited ornamentation had much lower concentrations of carotenoids in their gut contents than males from the population with extensive ornamentation. These observations support the idea that carotenoid intake plays a part in determining the plumage brightness of male house finches.",
    url = "https://doi.org/10.1098/rspb.2002.1980",
    doi = "10.1098/rspb.2002.1980",
    openalex = "W2100292625",
    references = "doi101093acprofoso97801951484800010001"
}

A photonic paper/ink system for color writing on and with colorless materials is described. The “paper” is a 3D crystal of polymer beads embedded in an elastomer matrix made of poly(dimethylsiloxane) (PDMS), and the “ink” is a liquid (e.g., a silicone fluid or organic solvent) capable of swelling the matrix, changing the lattice constant and hence wavelength of light diffracted (see Figure and cover).

@article{doi101002adma200304795,
    author = "Fudouzi, Hiroshi and Xia, Younan",
    title = "Photonic Papers and Inks: Color Writing with Colorless Materials",
    year = "2003",
    journal = "Advanced Materials",
    abstract = "A photonic paper/ink system for color writing on and with colorless materials is described. The “paper” is a 3D crystal of polymer beads embedded in an elastomer matrix made of poly(dimethylsiloxane) (PDMS), and the “ink” is a liquid (e.g., a silicone fluid or organic solvent) capable of swelling the matrix, changing the lattice constant and hence wavelength of light diffracted (see Figure and cover).",
    url = "https://doi.org/10.1002/adma.200304795",
    doi = "10.1002/adma.200304795",
    openalex = "W2094965297"
}

The target article is an attempt to make some progress on the problem of color realism. Are objects colored? And what is the nature of the color properties? We defend the view that physical objects (for instance, tomatoes, radishes, and rubies) are colored, and that colors are physical properties, specifically, types of reflectance. This is probably a minority opinion, at least among color scientists. Textbooks frequently claim that physical objects are not colored, and that the colors are "subjective" or "in the mind." The article has two other purposes: First, to introduce an interdisciplinary audience to some distinctively philosophical tools that are useful in tackling the problem of color realism and, second, to clarify the various positions and central arguments in the debate. The first part explains the problem of color realism and makes some useful distinctions. These distinctions are then used to expose various confusions that often prevent people from seeing that the issues are genuine and difficult, and that the problem of color realism ought to be of interest to anyone working in the field of color science. The second part explains the various leading answers to the problem of color realism, and (briefly) argues that all views other than our own have serious difficulties or are unmotivated. The third part explains and motivates our own view, that colors are types of reflectances and defends it against objections made in the recent literature that are often taken as fatal.

@article{doi101017s0140525x03000013,
    author = "Byrne, Alex and Hilbert, David",
    title = "Color realism and color science",
    year = "2003",
    journal = "Behavioral and Brain Sciences",
    abstract = {The target article is an attempt to make some progress on the problem of color realism. Are objects colored? And what is the nature of the color properties? We defend the view that physical objects (for instance, tomatoes, radishes, and rubies) are colored, and that colors are physical properties, specifically, types of reflectance. This is probably a minority opinion, at least among color scientists. Textbooks frequently claim that physical objects are not colored, and that the colors are "subjective" or "in the mind." The article has two other purposes: First, to introduce an interdisciplinary audience to some distinctively philosophical tools that are useful in tackling the problem of color realism and, second, to clarify the various positions and central arguments in the debate. The first part explains the problem of color realism and makes some useful distinctions. These distinctions are then used to expose various confusions that often prevent people from seeing that the issues are genuine and difficult, and that the problem of color realism ought to be of interest to anyone working in the field of color science. The second part explains the various leading answers to the problem of color realism, and (briefly) argues that all views other than our own have serious difficulties or are unmotivated. The third part explains and motivates our own view, that colors are types of reflectances and defends it against objections made in the recent literature that are often taken as fatal.},
    url = "https://doi.org/10.1017/s0140525x03000013",
    doi = "10.1017/s0140525x03000013",
    openalex = "W2124218959",
    references = "doi10106313050671, doi101080713819265, openalexw2041984916"
}

Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: 'what neural interactions underlie colour vision?' This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.

@article{doi101017s1464793102005985,
    author = "Kelber, Almut and Vorobyev, Misha and Osorio, Daniel",
    title = "Animal colour vision — behavioural tests and physiological concepts",
    year = "2003",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: 'what neural interactions underlie colour vision?' This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.",
    url = "https://doi.org/10.1017/s1464793102005985",
    doi = "10.1017/s1464793102005985",
    openalex = "W2164173165",
    references = "crossref1943the, doi101001jama194302840160064031, doi101007bf01708548, doi1010160042698975902035, doi101016s135094620100009x, doi101017s0952523800174036, doi101038236, doi101088003191121810010, doi101098rspb19980302, doi101146annurevento461471, doi101364josa69001183, doi105962bhltitle7369, doi105962p203427"
}

Identifying the genes underlying adaptation is a major challenge in evolutionary biology. Here, we describe the molecular changes underlying adaptive coat color variation in a natural population of rock pocket mice, Chaetodipus intermedius. Rock pocket mice are generally light-colored and live on light-colored rocks. However, populations of dark (melanic) mice are found on dark lava, and this concealing coloration provides protection from avian and mammalian predators. We conducted association studies by using markers in candidate pigmentation genes and discovered four mutations in the melanocortin-1-receptor gene, Mc1r, that seem to be responsible for adaptive melanism in one population of lava-dwelling pocket mice. Interestingly, another melanic population of these mice on a different lava flow shows no association with Mc1r mutations, indicating that adaptive dark color has evolved independently in this species through changes at different genes.

@article{doi101073pnas0431157100,
    author = "Nachman, Michael W. and Hoekstra, Hopi E. and D'Agostino, Susan L.",
    title = "The genetic basis of adaptive melanism in pocket mice",
    year = "2003",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Identifying the genes underlying adaptation is a major challenge in evolutionary biology. Here, we describe the molecular changes underlying adaptive coat color variation in a natural population of rock pocket mice, Chaetodipus intermedius. Rock pocket mice are generally light-colored and live on light-colored rocks. However, populations of dark (melanic) mice are found on dark lava, and this concealing coloration provides protection from avian and mammalian predators. We conducted association studies by using markers in candidate pigmentation genes and discovered four mutations in the melanocortin-1-receptor gene, Mc1r, that seem to be responsible for adaptive melanism in one population of lava-dwelling pocket mice. Interestingly, another melanic population of these mice on a different lava flow shows no association with Mc1r mutations, indicating that adaptive dark color has evolved independently in this species through changes at different genes.",
    url = "https://doi.org/10.1073/pnas.0431157100",
    doi = "10.1073/pnas.0431157100",
    openalex = "W2163529681",
    references = "doi101002sici109686441999031083375aidajpa1130co2g, doi101017s0016672300014634, doi101017s0016672308009579, doi101038351652a0, doi101046j14390388200200356x, doi101073pnas76105269, doi101073pnas86239365, doi101093genetics1161153, doi101093oso97801985498330010001, doi101111j155856461975tb00851x, doi1023072407274, openalexw1523652513, openalexw3217097258"
}

We report the mechanism of color production in peacock feathers. We find that the cortex in differently colored barbules, which contains a 2D photonic-crystal structure, is responsible for coloration. Simulations reveal that the photonic-crystal structure possesses a partial photonic bandgap along the direction normal to the cortex surface, for frequencies within which light is strongly reflected. Coloration strategies in peacock feathers are very ingenious and simple: controlling the lattice constant and the number of periods in the photonic-crystal structure. Varying the lattice constant produces diversified colors. The reduction of the number of periods brings additional colors, causing mixed coloration.

@article{doi101073pnas2133313100,
    author = "Zi, Jian and Yu, Xindi and Li, Yizhou and Hu, Xinhua and Xu, Chunxiang and Wang, Xingjun and Liu, Xiaohan and RONG-TANG, FU",
    title = "Coloration strategies in peacock feathers",
    year = "2003",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "We report the mechanism of color production in peacock feathers. We find that the cortex in differently colored barbules, which contains a 2D photonic-crystal structure, is responsible for coloration. Simulations reveal that the photonic-crystal structure possesses a partial photonic bandgap along the direction normal to the cortex surface, for frequencies within which light is strongly reflected. Coloration strategies in peacock feathers are very ingenious and simple: controlling the lattice constant and the number of periods in the photonic-crystal structure. Varying the lattice constant produces diversified colors. The reduction of the number of periods brings additional colors, causing mixed coloration.",
    url = "https://doi.org/10.1073/pnas.2133313100",
    doi = "10.1073/pnas.2133313100",
    openalex = "W1972533342",
    references = "doi1010881464425826201"
}

To gain insights into the evolution and ecology of visually acute animals such as birds, biologists often need to understand how these animals perceive colors. This poses a problem, since the human eye is of a different design than that of most other animals. The standard solution is to examine the spectral sensitivity properties of animal retinas through microspectophotometry-a procedure that is rather complicated and therefore only has allowed examinations of a limited number of species to date. We have developed a faster and simpler molecular method, which can be used to estimate the color sensitivities of a bird by sequencing a part of the gene coding for the ultraviolet or violet absorbing opsin in the avian retina. With our method, there is no need to sacrifice the animal, and it thereby facilitates large screenings, including rare and endangered species beyond the reach of microspectrophotometry. Color vision in birds may be categorized into two classes: one with a short-wavelength sensitivity biased toward violet (VS) and the other biased toward ultraviolet (UVS). Using our method on 45 species from 35 families, we demonstrate that the distribution of avian color vision is more complex than has previously been shown. Our data support VS as the ancestral state in birds and show that UVS has evolved independently at least four times. We found species with the UVS type of color vision in the orders Psittaciformes and Passeriformes, in agreement with previous findings. However, species within the families Corvidae and Tyrannidae did not share this character with other passeriforms. We also found UVS type species within the Laridae and Struthionidae families. Raptors (Accipitridae and Falconidae) are of the violet type, giving them a vision system different from their passeriform prey. Intriguing effects on the evolution of color signals can be expected from interactions between predators and prey. Such interactions may explain the presence of UVS in Laridae and Passeriformes.

@article{doi101093molbevmsg108,
    author = "Ödeen, Anders",
    title = "Complex Distribution of Avian Color Vision Systems Revealed by Sequencing the SWS1 Opsin from Total DNA",
    year = "2003",
    journal = "Molecular Biology and Evolution",
    abstract = "To gain insights into the evolution and ecology of visually acute animals such as birds, biologists often need to understand how these animals perceive colors. This poses a problem, since the human eye is of a different design than that of most other animals. The standard solution is to examine the spectral sensitivity properties of animal retinas through microspectophotometry-a procedure that is rather complicated and therefore only has allowed examinations of a limited number of species to date. We have developed a faster and simpler molecular method, which can be used to estimate the color sensitivities of a bird by sequencing a part of the gene coding for the ultraviolet or violet absorbing opsin in the avian retina. With our method, there is no need to sacrifice the animal, and it thereby facilitates large screenings, including rare and endangered species beyond the reach of microspectrophotometry. Color vision in birds may be categorized into two classes: one with a short-wavelength sensitivity biased toward violet (VS) and the other biased toward ultraviolet (UVS). Using our method on 45 species from 35 families, we demonstrate that the distribution of avian color vision is more complex than has previously been shown. Our data support VS as the ancestral state in birds and show that UVS has evolved independently at least four times. We found species with the UVS type of color vision in the orders Psittaciformes and Passeriformes, in agreement with previous findings. However, species within the families Corvidae and Tyrannidae did not share this character with other passeriforms. We also found UVS type species within the Laridae and Struthionidae families. Raptors (Accipitridae and Falconidae) are of the violet type, giving them a vision system different from their passeriform prey. Intriguing effects on the evolution of color signals can be expected from interactions between predators and prey. Such interactions may explain the presence of UVS in Laridae and Passeriformes.",
    url = "https://doi.org/10.1093/molbev/msg108",
    doi = "10.1093/molbev/msg108",
    openalex = "W1967738288",
    references = "doi101111j109586491999tb00848x"
}

Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions "exposed to" and "concealed from" visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of "exposed" body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of "concealed" body regions and ornament dimorphism were positively associated with sexual size dimorphism (SSD). When we examined male and female ornamentation separately, however, both were positively associated with habitat openness in addition to snout-vent length and head SSD. These results suggest that natural selection constrains the evolution of elaborate ornamentation in both sexes as well as sexual dichromatism of body regions exposed to visual predators. By contrast, dichromatism of "concealed" body regions and degree of ornament dimorphism appear to be driven to a greater degree by sexual selection.

@article{doi101098rspb20042802,
    author = "Stuart‐Fox, Devi and Ord, Terry J.",
    title = "Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards",
    year = "2004",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = {Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions "exposed to" and "concealed from" visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of "exposed" body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of "concealed" body regions and ornament dimorphism were positively associated with sexual size dimorphism (SSD). When we examined male and female ornamentation separately, however, both were positively associated with habitat openness in addition to snout-vent length and head SSD. These results suggest that natural selection constrains the evolution of elaborate ornamentation in both sexes as well as sexual dichromatism of body regions exposed to visual predators. By contrast, dichromatism of "concealed" body regions and degree of ornament dimorphism appear to be driven to a greater degree by sexual selection.},
    url = "https://doi.org/10.1098/rspb.2004.2802",
    doi = "10.1098/rspb.2004.2802",
    openalex = "W2121080541",
    references = "doi101006anbe20032235"
}

The wealth of information on the genetics of pigmentation and the clear fitness consequences of many pigmentation phenotypes provide an opportunity to study the molecular basis of an ecologically important trait. The melanocortin-1 receptor (Mc1r) is responsible for intraspecific color variation in mammals and birds. Here, we study the molecular evolution of Mc1r and investigate its role in adaptive intraspecific color differences in reptiles. We sequenced the complete Mc1r locus in seven phylogenetically diverse squamate species with melanic or blanched forms associated with different colored substrates or thermal environments. We found that patterns of amino acid substitution across different regions of the receptor are similar to the patterns seen in mammals, suggesting comparable levels of constraint and probably a conserved function for Mc1r in mammals and reptiles. We also found high levels of silent-site heterozygosity in all species, consistent with a high mutation rate or large long-term effective population size. Mc1r polymorphisms were strongly associated with color differences in Holbrookia maculata and Aspidoscelis inornata. In A. inornata, several observations suggest that Mc1r mutations may contribute to differences in color: (1) a strong association is observed between one Mc1r amino acid substitution and dorsal color; (2) no significant population structure was detected among individuals from these populations at the mitochondrial ND4 gene; (3) the distribution of allele frequencies at Mc1r deviates from neutral expectations; and (4) patterns of linkage disequilibrium at Mc1r are consistent with recent selection. This study provides comparative data on a nuclear gene in reptiles and highlights the utility of a candidate-gene approach for understanding the evolution of genes involved in vertebrate adaptation.

@article{doi101111j001438202004tb00462x,
    author = "Rosenblum, Erica Bree and Hoekstra, Hopi E. and Nachman, Michael W.",
    title = "ADAPTIVE REPTILE COLOR VARIATION AND THE EVOLUTION OF THE MCIR GENE",
    year = "2004",
    journal = "Evolution",
    abstract = "The wealth of information on the genetics of pigmentation and the clear fitness consequences of many pigmentation phenotypes provide an opportunity to study the molecular basis of an ecologically important trait. The melanocortin-1 receptor (Mc1r) is responsible for intraspecific color variation in mammals and birds. Here, we study the molecular evolution of Mc1r and investigate its role in adaptive intraspecific color differences in reptiles. We sequenced the complete Mc1r locus in seven phylogenetically diverse squamate species with melanic or blanched forms associated with different colored substrates or thermal environments. We found that patterns of amino acid substitution across different regions of the receptor are similar to the patterns seen in mammals, suggesting comparable levels of constraint and probably a conserved function for Mc1r in mammals and reptiles. We also found high levels of silent-site heterozygosity in all species, consistent with a high mutation rate or large long-term effective population size. Mc1r polymorphisms were strongly associated with color differences in Holbrookia maculata and Aspidoscelis inornata. In A. inornata, several observations suggest that Mc1r mutations may contribute to differences in color: (1) a strong association is observed between one Mc1r amino acid substitution and dorsal color; (2) no significant population structure was detected among individuals from these populations at the mitochondrial ND4 gene; (3) the distribution of allele frequencies at Mc1r deviates from neutral expectations; and (4) patterns of linkage disequilibrium at Mc1r are consistent with recent selection. This study provides comparative data on a nuclear gene in reptiles and highlights the utility of a candidate-gene approach for understanding the evolution of genes involved in vertebrate adaptation.",
    url = "https://doi.org/10.1111/j.0014-3820.2004.tb00462.x",
    doi = "10.1111/j.0014-3820.2004.tb00462.x",
    openalex = "W2177885391",
    references = "doi1010160040580975900209, doi101016b9781483232119500097, doi101038351652a0, doi101073pnas76105269, doi101093ajcp1511552b, doi101093bioinformatics149817, doi101093bioinformatics17121244, doi101093genetics1233585, doi101093oxfordjournalsmolbeva040410, doi101111j146918091949tb02451x, doi1023072420875, eaton1940adaptive, openalexw605090603"
}

SUMMARY Poison frogs in the anuran family Dendrobatidae use bright colors on their bodies to advertise toxicity. The species Dendrobates pumilio Schmidt 1858, the strawberry poison frog, shows extreme polymorphism in color and pattern in Panama. It is known that females of D. pumiliopreferentially choose mates of their own color morph. Nevertheless, potential predators must clearly see and recognize all color morphs if the aposematic signaling system is to function effectively. We examined the ability of conspecifics and a model predator to discriminate a diverse selection of D. pumilio colors from each other and from background colors. Microspectrophotometry of isolated rod and cone photoreceptors of D. pumilio revealed the presence of a trichromatic photopic visual system. A typical tetrachromatic bird system was used for the model predator. Reflectance spectra of frog and background colors were obtained, and discrimination among spectra in natural illuminants was mathematically modeled. The results revealed that both D. pumilio and the model predator discriminate most colors quite well, both from each other and from typical backgrounds, with the predator generally performing somewhat better than the conspecifics. Each color morph displayed at least one color signal that is highly visible against backgrounds to both visual systems. Our results indicate that the colors displayed by the various color morphs of D. pumilio are effective signals both to conspecifics and to a model predator.

@article{doi101242jeb01047,
    author = "Siddiqi, Afsheen and Cronin, Thomas W. and Loew, Ellis R. and Vorobyev, Misha and Summers, Kyle",
    title = "Interspecific and intraspecific views of color signals in the strawberry poison frog Dendrobates pumilio",
    year = "2004",
    journal = "Journal of Experimental Biology",
    abstract = "SUMMARY Poison frogs in the anuran family Dendrobatidae use bright colors on their bodies to advertise toxicity. The species Dendrobates pumilio Schmidt 1858, the strawberry poison frog, shows extreme polymorphism in color and pattern in Panama. It is known that females of D. pumiliopreferentially choose mates of their own color morph. Nevertheless, potential predators must clearly see and recognize all color morphs if the aposematic signaling system is to function effectively. We examined the ability of conspecifics and a model predator to discriminate a diverse selection of D. pumilio colors from each other and from background colors. Microspectrophotometry of isolated rod and cone photoreceptors of D. pumilio revealed the presence of a trichromatic photopic visual system. A typical tetrachromatic bird system was used for the model predator. Reflectance spectra of frog and background colors were obtained, and discrimination among spectra in natural illuminants was mathematically modeled. The results revealed that both D. pumilio and the model predator discriminate most colors quite well, both from each other and from typical backgrounds, with the predator generally performing somewhat better than the conspecifics. Each color morph displayed at least one color signal that is highly visible against backgrounds to both visual systems. Our results indicate that the colors displayed by the various color morphs of D. pumilio are effective signals both to conspecifics and to a model predator.",
    url = "https://doi.org/10.1242/jeb.01047",
    doi = "10.1242/jeb.01047",
    openalex = "W2044881674",
    references = "doi101016s135094620100009x, doi101098rspb19980302, doi101146annurevecolsys301201, doi10560219780801847806"
}

Coloring in nature mostly comes from the inherent colors of materials, but it sometimes has a purely physical origin, such as diffraction or interference of light. The latter, called structural color or iridescence, has long been a problem of scientific interest. Recently, structural colors have attracted great interest because their applications have been rapidly progressing in many fields related to vision, such as the paint, automobile, cosmetics, and textile industries. As the research progresses, however, it has become clear that these colors are due to the presence of surprisingly minute microstructures, which are hardly attainable even by ultramodern nanotechnology. Fundamentally, most of the structural colors originate from basic optical processes represented by thin-film interference, multilayer interference, a diffraction grating effect, photonic crystals, light scattering, and so on. However, to enhance the perception of the eyes, natural creatures have produced various designs, in the course of evolution, to fulfill simultaneously high reflectivity in a specific wavelength range and the generation of diffusive light in a wide angular range. At a glance, these two characteristics seem to contradict each other in the usual optical sense, but these seemingly conflicting requirements are realized by combining appropriate amounts of regularity and irregularity of the structure. In this Review, we first explain the fundamental optical properties underlying the structural colors, and then survey these mysteries of nature from the viewpoint of regularity and irregularity of the structure. Finally, we propose a general principle of structural colors based on structural hierarchy and show their up-to-date applications.

@article{doi101002cphc200500007,
    author = "Kinoshita, Shuichi and Yoshioka, Shinya",
    title = "Structural Colors in Nature: The Role of Regularity and Irregularity in the Structure",
    year = "2005",
    journal = "ChemPhysChem",
    abstract = "Coloring in nature mostly comes from the inherent colors of materials, but it sometimes has a purely physical origin, such as diffraction or interference of light. The latter, called structural color or iridescence, has long been a problem of scientific interest. Recently, structural colors have attracted great interest because their applications have been rapidly progressing in many fields related to vision, such as the paint, automobile, cosmetics, and textile industries. As the research progresses, however, it has become clear that these colors are due to the presence of surprisingly minute microstructures, which are hardly attainable even by ultramodern nanotechnology. Fundamentally, most of the structural colors originate from basic optical processes represented by thin-film interference, multilayer interference, a diffraction grating effect, photonic crystals, light scattering, and so on. However, to enhance the perception of the eyes, natural creatures have produced various designs, in the course of evolution, to fulfill simultaneously high reflectivity in a specific wavelength range and the generation of diffusive light in a wide angular range. At a glance, these two characteristics seem to contradict each other in the usual optical sense, but these seemingly conflicting requirements are realized by combining appropriate amounts of regularity and irregularity of the structure. In this Review, we first explain the fundamental optical properties underlying the structural colors, and then survey these mysteries of nature from the viewpoint of regularity and irregularity of the structure. Finally, we propose a general principle of structural colors based on structural hierarchy and show their up-to-date applications.",
    url = "https://doi.org/10.1002/cphc.200500007",
    doi = "10.1002/cphc.200500007",
    openalex = "W2154143283",
    references = "doi101038scientificamerican017164, doi1010881464425826201, doi101242jeb482227"
}

@article{doi101016janbehav200406022,
    author = "McGraw, Kevin J.",
    title = "The antioxidant function of many animal pigments: are there consistent health benefits of sexually selected colourants?",
    year = "2005",
    journal = "Animal Behaviour",
    url = "https://doi.org/10.1016/j.anbehav.2004.06.022",
    doi = "10.1016/j.anbehav.2004.06.022",
    openalex = "W1993184166",
    references = "openalexw605090603"
}

Sexual selection often favors brighter and exaggerated traits, which also increase the risk of detection by predators. Signals that are preferentially conspicuous to conspecifics would reduce the predation cost of signaling and, therefore, might facilitate the evolution of stronger sexual and social signals. This selective signaling is possible if predators and prey have differently tuned sensory systems. By using a retinal model to compare reflectance from the plumages of Swedish songbirds to the reflectance of their natural backgrounds, we found their color badges to be significantly more conspicuous to other songbirds (which have a UV-tuned visual system) than to raptors and corvids (which have a violet-tuned system) in both coniferous and deciduous forests, consistent with an adaptive private communication system.

@article{doi101073pnas0409228102,
    author = "Håstad, Olle and Victorsson, Jonas and Ödeen, Anders",
    title = "Differences in color vision make passerines less conspicuous in the eyes of their predators",
    year = "2005",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Sexual selection often favors brighter and exaggerated traits, which also increase the risk of detection by predators. Signals that are preferentially conspicuous to conspecifics would reduce the predation cost of signaling and, therefore, might facilitate the evolution of stronger sexual and social signals. This selective signaling is possible if predators and prey have differently tuned sensory systems. By using a retinal model to compare reflectance from the plumages of Swedish songbirds to the reflectance of their natural backgrounds, we found their color badges to be significantly more conspicuous to other songbirds (which have a UV-tuned visual system) than to raptors and corvids (which have a violet-tuned system) in both coniferous and deciduous forests, consistent with an adaptive private communication system.",
    url = "https://doi.org/10.1073/pnas.0409228102",
    doi = "10.1073/pnas.0409228102",
    openalex = "W2023112640",
    references = "doi101006anbe20032235"
}

Cryptic prey coloration typically bears a resemblance to the habitat the prey uses. It has been suggested that coloration which visually matches a random sample of the background maximizes background matching. We studied this previously untested hypothesis, as well as another, little studied principle of concealment, disruptive coloration, and whether it could, acting in addition to background matching, provide another plausible means of achieving camouflage. We presented great tits (Parus major) with artificial background-matching and disruptive prey (DP), and measured detection times. First, we studied whether any random sample of a background produces equally good crypsis. This turned out to not be the case. Next, we compared the DP and the best background-matching prey and found that they were equally cryptic. We repeated the tests using prey with all the coloration elements being whole, instead of some of them being broken by the prey outline, but this did not change the result. We conclude that resemblance of the background is an important aspect of concealment, but that coloration matching a random visual sample of the background is neither sufficient nor necessary to minimize the probability of detection. Further, our study lends empirical support to the principle of disruptive coloration.

@article{doi101098rspb20043000,
    author = "Merilaita, Sami and Lind, Johan",
    title = "Background-matching and disruptive coloration, and the evolution of cryptic coloration",
    year = "2005",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Cryptic prey coloration typically bears a resemblance to the habitat the prey uses. It has been suggested that coloration which visually matches a random sample of the background maximizes background matching. We studied this previously untested hypothesis, as well as another, little studied principle of concealment, disruptive coloration, and whether it could, acting in addition to background matching, provide another plausible means of achieving camouflage. We presented great tits (Parus major) with artificial background-matching and disruptive prey (DP), and measured detection times. First, we studied whether any random sample of a background produces equally good crypsis. This turned out to not be the case. Next, we compared the DP and the best background-matching prey and found that they were equally cryptic. We repeated the tests using prey with all the coloration elements being whole, instead of some of them being broken by the prey outline, but this did not change the result. We conclude that resemblance of the background is an important aspect of concealment, but that coloration matching a random visual sample of the background is neither sufficient nor necessary to minimize the probability of detection. Further, our study lends empirical support to the principle of disruptive coloration.",
    url = "https://doi.org/10.1098/rspb.2004.3000",
    doi = "10.1098/rspb.2004.3000",
    openalex = "W2133393886",
    references = "openalexw1493613979"
}

This review outlines how eyes of terrestrial vertebrates and insects meet the competing requirements of coding both spatial and spectral information. There is no unique solution to this problem. Thus, mammals and honeybees use their long-wavelength receptors for both achromatic (luminance) and colour vision, whereas flies and birds probably use separate sets of photoreceptors for the two purposes. In particular, we look at spectral tuning and diversification among 'long-wavelength' receptors (sensitivity maxima at greater than 500 nm), which play a primary role in luminance vision. Data on spectral sensitivities and phylogeny of visual photopigments can be incorporated into theoretical models to suggest how eyes are adapted to coding natural stimuli. Models indicate, for example, that animal colour vision--involving five or fewer broadly tuned receptors--is well matched to most natural spectra. We can also predict that the particular objects of interest and signal-to-noise ratios will affect the optimal eye design. Nonetheless, it remains difficult to account for the adaptive significance of features such as co-expression of photopigments in single receptors, variation in spectral sensitivities of mammalian L-cone pigments and the diversification of long-wavelength receptors that has occurred in several terrestrial lineages.

@article{doi101098rspb20053156,
    author = "Osorio, Daniel and Vorobyev, Misha",
    title = "Photoreceptor sectral sensitivities in terrestrial animals: adaptations for luminance and colour vision",
    year = "2005",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "This review outlines how eyes of terrestrial vertebrates and insects meet the competing requirements of coding both spatial and spectral information. There is no unique solution to this problem. Thus, mammals and honeybees use their long-wavelength receptors for both achromatic (luminance) and colour vision, whereas flies and birds probably use separate sets of photoreceptors for the two purposes. In particular, we look at spectral tuning and diversification among 'long-wavelength' receptors (sensitivity maxima at greater than 500 nm), which play a primary role in luminance vision. Data on spectral sensitivities and phylogeny of visual photopigments can be incorporated into theoretical models to suggest how eyes are adapted to coding natural stimuli. Models indicate, for example, that animal colour vision--involving five or fewer broadly tuned receptors--is well matched to most natural spectra. We can also predict that the particular objects of interest and signal-to-noise ratios will affect the optimal eye design. Nonetheless, it remains difficult to account for the adaptive significance of features such as co-expression of photopigments in single receptors, variation in spectral sensitivities of mammalian L-cone pigments and the diversification of long-wavelength receptors that has occurred in several terrestrial lineages.",
    url = "https://doi.org/10.1098/rspb.2005.3156",
    doi = "10.1098/rspb.2005.3156",
    openalex = "W2166452173",
    references = "doi101007bf00190398, doi101007s003590050286, doi101016s135094620100009x, doi101017s0952523800174036, doi101017s1464793102005985, doi101088003191121810010, doi101098rspb19980302, doi101126science3283936, doi101146annurevento461471, doi1023072937121, openalexw1507653370"
}

Animals that are brightly colored have intrigued scientists since the time of Darwin, because it seems surprising that prey should have evolved to be clearly visible to predators. Often this self-advertisement is explained by the prey being unprofitable in some way, with the conspicuous warning coloration helping to protect the prey because it signals to potential predators that the prey is unprofitable. However, such signals only work in this way once predators have learned to associate the conspicuous color with the unprofitability of the prey. The evolution of warning coloration is still widely considered to be a paradox, because it has traditionally been assumed that the very first brightly colored individuals would be at an immediate selective disadvantage because of their greater conspicuousness to predators that are naive to the meaning of the signal. As a result, it has been difficult to understand how a novel conspicuous color morph could ever avoid extinction for long enough for predators to become educated about the signal. Thus, the traditional view that the evolution of warning coloration is difficult to explain rests entirely on assumptions about the foraging behavior of predators. However, we review recent evidence from a range of studies of predator foraging decisions, which refute these established assumptions. These studies show that: (1) Many predators are so conservative in their food preferences that even very conspicuous novel prey morphs are not necessarily at a selective disadvantage. (2) The survival and spread of novel color morphs can be simulated in field and aviary experiments using real predators (birds) foraging on successive generations of artificial prey populations. This work demonstrates that the foraging preferences of predators can regularly (though not always) result in the increase to fixation of a novel morph appearing in a population of familiar-colored prey. Such fixation events occur even if both novel and familiar prey are fully palatable and despite the novel food being much more conspicuous than the familiar prey. These studies therefore provide strong empirical evidence that conspicuous coloration can evolve readily, and repeatedly, as a result of the conservative foraging decisions of predators.

@article{doi101111j001438202005tb01032x,
    author = "Marples, Nicola M. and Kelly, David and Thomas, Robert J.",
    title = "PERSPECTIVE: THE EVOLUTION OF WARNING COLORATION IS NOT PARADOXICAL",
    year = "2005",
    journal = "Evolution",
    abstract = "Animals that are brightly colored have intrigued scientists since the time of Darwin, because it seems surprising that prey should have evolved to be clearly visible to predators. Often this self-advertisement is explained by the prey being unprofitable in some way, with the conspicuous warning coloration helping to protect the prey because it signals to potential predators that the prey is unprofitable. However, such signals only work in this way once predators have learned to associate the conspicuous color with the unprofitability of the prey. The evolution of warning coloration is still widely considered to be a paradox, because it has traditionally been assumed that the very first brightly colored individuals would be at an immediate selective disadvantage because of their greater conspicuousness to predators that are naive to the meaning of the signal. As a result, it has been difficult to understand how a novel conspicuous color morph could ever avoid extinction for long enough for predators to become educated about the signal. Thus, the traditional view that the evolution of warning coloration is difficult to explain rests entirely on assumptions about the foraging behavior of predators. However, we review recent evidence from a range of studies of predator foraging decisions, which refute these established assumptions. These studies show that: (1) Many predators are so conservative in their food preferences that even very conspicuous novel prey morphs are not necessarily at a selective disadvantage. (2) The survival and spread of novel color morphs can be simulated in field and aviary experiments using real predators (birds) foraging on successive generations of artificial prey populations. This work demonstrates that the foraging preferences of predators can regularly (though not always) result in the increase to fixation of a novel morph appearing in a population of familiar-colored prey. Such fixation events occur even if both novel and familiar prey are fully palatable and despite the novel food being much more conspicuous than the familiar prey. These studies therefore provide strong empirical evidence that conspicuous coloration can evolve readily, and repeatedly, as a result of the conservative foraging decisions of predators.",
    url = "https://doi.org/10.1111/j.0014-3820.2005.tb01032.x",
    doi = "10.1111/j.0014-3820.2005.tb01032.x",
    openalex = "W2173902898",
    references = "doi101006anbe20032235, doi101093beheco141103"
}

Animal color pattern phenotypes evolve rapidly. What influences their evolution? Because color patterns are used in communication, selection for signal efficacy, relative to the intended receiver's visual system, may explain and predict the direction of evolution. We investigated this in bowerbirds, whose color patterns consist of plumage, bower structure, and ornaments and whose visual displays are presented under predictable visual conditions. We used data on avian vision, environmental conditions, color pattern properties, and an estimate of the bowerbird phylogeny to test hypotheses about evolutionary effects of visual processing. Different components of the color pattern evolve differently. Plumage sexual dimorphism increased and then decreased, while overall (plumage plus bower) visual contrast increased. The use of bowers allows relative crypsis of the bird but increased efficacy of the signal as a whole. Ornaments do not elaborate existing plumage features but instead are innovations (new color schemes) that increase signal efficacy. Isolation between species could be facilitated by plumage but not ornaments, because we observed character displacement only in plumage. Bowerbird color pattern evolution is at least partially predictable from the function of the visual system and from knowledge of different functions of different components of the color patterns. This provides clues to how more constrained visual signaling systems may evolve.

@article{doi101111j001438202005tb01827x,
    author = "Endler, John A. and Westcott, David A. and Madden, Joah R. and Robson, Tim",
    title = "ANIMAL VISUAL SYSTEMS AND THE EVOLUTION OF COLOR PATTERNS: SENSORY PROCESSING ILLUMINATES SIGNAL EVOLUTION",
    year = "2005",
    journal = "Evolution",
    abstract = "Animal color pattern phenotypes evolve rapidly. What influences their evolution? Because color patterns are used in communication, selection for signal efficacy, relative to the intended receiver's visual system, may explain and predict the direction of evolution. We investigated this in bowerbirds, whose color patterns consist of plumage, bower structure, and ornaments and whose visual displays are presented under predictable visual conditions. We used data on avian vision, environmental conditions, color pattern properties, and an estimate of the bowerbird phylogeny to test hypotheses about evolutionary effects of visual processing. Different components of the color pattern evolve differently. Plumage sexual dimorphism increased and then decreased, while overall (plumage plus bower) visual contrast increased. The use of bowers allows relative crypsis of the bird but increased efficacy of the signal as a whole. Ornaments do not elaborate existing plumage features but instead are innovations (new color schemes) that increase signal efficacy. Isolation between species could be facilitated by plumage but not ornaments, because we observed character displacement only in plumage. Bowerbird color pattern evolution is at least partially predictable from the function of the visual system and from knowledge of different functions of different components of the color patterns. This provides clues to how more constrained visual signaling systems may evolve.",
    url = "https://doi.org/10.1111/j.0014-3820.2005.tb01827.x",
    doi = "10.1111/j.0014-3820.2005.tb01827.x",
    openalex = "W2146693782",
    references = "doi101093acprofoso97801951484800010001"
}

Abstract Coloration is a diagnostic tool for identifying mammals, but inquiry into its function has lain dormant for almost a century. Recently, the topic has been revived and modern phylogenetic methods have been applied to large data sets, allowing researchers to assess, for the first time, the relative importance of three classic hypotheses for the function of coloration in mammals: concealment, communication, and regulation of physiological processes. Camouflage appears to be the single most important evolutionary force in explaining overall coloration in mammals, whereas patches of colored fur are used for intraspecific signaling. Sexual selection is associated with flamboyant ornamentation in a minority of primates and other restricted mammalian taxa, but to a far lesser extent than in birds. Interspecific signaling among mammals includes aposematic coloration, exaggeration of signals to deter pursuit, and lures for misdirecting predatory attack. Physiological causes of coloration, including melanism, are evident but poorly researched. The relative importance of evolutionary forces responsible for external coloration varies greatly between vertebrate taxa, but the reasons for this variation are not yet understood.

@article{doi1016410006356820050550125tasoci20co2,
    author = "Caro, Tim",
    title = "The Adaptive Significance of Coloration in Mammals",
    year = "2005",
    journal = "BioScience",
    abstract = "Abstract Coloration is a diagnostic tool for identifying mammals, but inquiry into its function has lain dormant for almost a century. Recently, the topic has been revived and modern phylogenetic methods have been applied to large data sets, allowing researchers to assess, for the first time, the relative importance of three classic hypotheses for the function of coloration in mammals: concealment, communication, and regulation of physiological processes. Camouflage appears to be the single most important evolutionary force in explaining overall coloration in mammals, whereas patches of colored fur are used for intraspecific signaling. Sexual selection is associated with flamboyant ornamentation in a minority of primates and other restricted mammalian taxa, but to a far lesser extent than in birds. Interspecific signaling among mammals includes aposematic coloration, exaggeration of signals to deter pursuit, and lures for misdirecting predatory attack. Physiological causes of coloration, including melanism, are evident but poorly researched. The relative importance of evolutionary forces responsible for external coloration varies greatly between vertebrate taxa, but the reasons for this variation are not yet understood.",
    url = "https://doi.org/10.1641/0006-3568(2005)055[0125:tasoci]2.0.co;2",
    doi = "10.1641/0006-3568(2005)055[0125:tasoci]2.0.co;2",
    openalex = "W2175719052",
    references = "doi101006anbe19991159, doi10100797814615695655, doi101016016953479290056h, doi101038375311a0, doi101111j109583121990tb00839x, doi101126science1073257, doi1023071378997, openalexw1487662794, openalexw1493613979, openalexw1696245089, openalexw2151993477, openalexw2276102674, openalexw614507079"
}

Sexual isolation is a critical form of reproductive isolation in the early stages of animal speciation, yet little is known about the genetic basis of divergent mate preferences and preference cues in young species. Heliconius butterflies, well known for their diversity of wing color patterns, mate assortatively as a result of divergence in male preference for wing patterns. Here we show that the specific cue used by Heliconius cydno and Heliconius pachinus males to recognize conspecific females is the color of patches on the wings. In addition, male mate preference segregates with forewing color in hybrids, indicating a genetic association between the loci responsible for preference and preference cue. Quantitative trait locus mapping places a preference locus coincident with the locus that determines forewing color, which itself is perfectly linked to the wing patterning candidate gene, wingless. Furthermore, yellow-colored males of the polymorphic race H. cydno alithea prefer to court yellow females, indicating that wing color and color preference are controlled by loci that are located in an inversion or are pleiotropic effects of a single locus. Tight genetic associations between preference and preference cue, although rare, make divergence and speciation particularly likely because the effects of natural and sexual selection on one trait are transferred to the other, leading to the coordinated evolution of mate recognition. This effect of linkage on divergence is especially important in Heliconius because differentiation of wing color patterns in the genus has been driven and maintained by natural selection for Müllerian mimicry.

@article{doi101073pnas0509685103,
    author = "Kronforst, Marcus R. and Young, Laura G. and Kapan, Durrell D. and McNeely, Camille and O’Neill, Rachel J. and Gilbert, Lawrence E.",
    title = "Linkage of butterfly mate preference and wing color preference cue at the genomic location of wingless",
    year = "2006",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Sexual isolation is a critical form of reproductive isolation in the early stages of animal speciation, yet little is known about the genetic basis of divergent mate preferences and preference cues in young species. Heliconius butterflies, well known for their diversity of wing color patterns, mate assortatively as a result of divergence in male preference for wing patterns. Here we show that the specific cue used by Heliconius cydno and Heliconius pachinus males to recognize conspecific females is the color of patches on the wings. In addition, male mate preference segregates with forewing color in hybrids, indicating a genetic association between the loci responsible for preference and preference cue. Quantitative trait locus mapping places a preference locus coincident with the locus that determines forewing color, which itself is perfectly linked to the wing patterning candidate gene, wingless. Furthermore, yellow-colored males of the polymorphic race H. cydno alithea prefer to court yellow females, indicating that wing color and color preference are controlled by loci that are located in an inversion or are pleiotropic effects of a single locus. Tight genetic associations between preference and preference cue, although rare, make divergence and speciation particularly likely because the effects of natural and sexual selection on one trait are transferred to the other, leading to the coordinated evolution of mate recognition. This effect of linkage on divergence is especially important in Heliconius because differentiation of wing color patterns in the genus has been driven and maintained by natural selection for Müllerian mimicry.",
    url = "https://doi.org/10.1073/pnas.0509685103",
    doi = "10.1073/pnas.0509685103",
    openalex = "W2014443275",
    references = "benson1972natural, doi101016s0065280608601307, doi101016s0169534701021875, doi10103835053066, doi101093aibsbulletin2214b, doi101093genetics1211185, doi101093genetics13741121, doi101093genetics1421285, doi101093jhered93177, doi101111j155856461989tb04233x, doi101146annurevento461471, openalexw1840956397, openalexw2612775479"
}

Understanding how animals achieve simultaneous conspicuousness to intended receivers and crypsis to unintended receivers requires investigating the distribution, size, and spectral characteristics of color patches. Here we characterize plumage patterns of 40 rainforest bird species living in understory or canopy. Visual signals maximizing (or minimizing) detection are expected to differ between these contrasted light habitats, making rainforests appropriate to test hypotheses of color signal evolution. Using spectrometry and comparative analyses, we show that canopy and understory act as distinct selective regimes that strongly influence bird coloration. Birds reduce detectability by displaying countershaded patterns, by matching background color and contrast, and by reducing in size the most conspicuous patches. More intense on males than on females, selection for conspicuousness acts on large patches by increasing contrast on ventral parts likely to be seen by conspecifics. It also operates on small patches by focusing visual contrast on chest, head, and tail in understory and on wing and tail in canopy, by increasing local brightness contrast compared to general contrast in canopy, and by exploiting different wavelengths for contrast (short in canopy and long in understory). These results are of general interest to understanding the evolution of color patterns for all organisms living in contrasted light environments.

@article{doi101086510138,
    author = "Gomez, Doris and Théry, Marc",
    title = "Simultaneous Crypsis and Conspicuousness in Color Patterns: Comparative Analysis of a Neotropical Rainforest Bird Community",
    year = "2006",
    journal = "The American Naturalist",
    abstract = "Understanding how animals achieve simultaneous conspicuousness to intended receivers and crypsis to unintended receivers requires investigating the distribution, size, and spectral characteristics of color patches. Here we characterize plumage patterns of 40 rainforest bird species living in understory or canopy. Visual signals maximizing (or minimizing) detection are expected to differ between these contrasted light habitats, making rainforests appropriate to test hypotheses of color signal evolution. Using spectrometry and comparative analyses, we show that canopy and understory act as distinct selective regimes that strongly influence bird coloration. Birds reduce detectability by displaying countershaded patterns, by matching background color and contrast, and by reducing in size the most conspicuous patches. More intense on males than on females, selection for conspicuousness acts on large patches by increasing contrast on ventral parts likely to be seen by conspecifics. It also operates on small patches by focusing visual contrast on chest, head, and tail in understory and on wing and tail in canopy, by increasing local brightness contrast compared to general contrast in canopy, and by exploiting different wavelengths for contrast (short in canopy and long in understory). These results are of general interest to understanding the evolution of color patterns for all organisms living in contrasted light environments.",
    url = "https://doi.org/10.1086/510138",
    doi = "10.1086/510138",
    openalex = "W2071830728",
    references = "doi101006anbe20032235, doi105962bhltitle19780"
}

Many animals use concealing markings to reduce the risk of predation. These include background pattern matching (crypsis), where the coloration matches a random sample of the background and disruptive patterns, whose effectiveness has been hypothesized to lie in breaking up the body into a series of apparently unrelated objects. We have previously established the effectiveness of disruptive coloration against avian predators, using artificial moth-like stimuli with colours designed to match natural backgrounds as perceived by birds. Here, we investigate the mechanism by which disruptive patterns reduce detectability, using a computational vision model of edge detection applied to photographs of our experimental stimuli, calibrated for bird colour vision. We show that, disruptive coloration is effective by exploiting edge detection algorithms that we use to model early visual processing. Thus, 'false' edges are detected within the body rather than at its periphery, so inhibiting successful detection of the animal's body outline.

@article{doi101098rspb20063556,
    author = "Stevens, Martin and Cuthill, Innes C.",
    title = "Disruptive coloration, crypsis and edge detection in early visual processing",
    year = "2006",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Many animals use concealing markings to reduce the risk of predation. These include background pattern matching (crypsis), where the coloration matches a random sample of the background and disruptive patterns, whose effectiveness has been hypothesized to lie in breaking up the body into a series of apparently unrelated objects. We have previously established the effectiveness of disruptive coloration against avian predators, using artificial moth-like stimuli with colours designed to match natural backgrounds as perceived by birds. Here, we investigate the mechanism by which disruptive patterns reduce detectability, using a computational vision model of edge detection applied to photographs of our experimental stimuli, calibrated for bird colour vision. We show that, disruptive coloration is effective by exploiting edge detection algorithms that we use to model early visual processing. Thus, 'false' edges are detected within the body rather than at its periphery, so inhibiting successful detection of the animal's body outline.",
    url = "https://doi.org/10.1098/rspb.2006.3556",
    doi = "10.1098/rspb.2006.3556",
    openalex = "W2125732494",
    references = "doi101093acprofoso97801985286090010001, doi101098rspb20053156, doi101111j10958312200700725x"
}

Abstract Animal color patterns are a compromise between sexual selection pressures that increase advantages accrued from conspicuousness, and natural selection pressures that decrease those advantages through reduced survivorship. Predation pressure, as a mode of natural selection, often is invoked as a counter‐selective force to sexual selection, yet few studies have demonstrated empirically that more conspicuous individuals experience higher rates of predation. We quantified predator attacks on models of collared lizards, Crotaphytus collaris, in three well‐studied populations (Oklahoma, USA). These populations differ in coloration and in visual backgrounds against which the lizards are viewed by conspecifics and predators. Attack frequencies varied considerably among study sites but at all sites the models exhibiting the strongest color contrast with local rocks were detected and attacked most often. By comparison, inconspicuous models of females were never attacked at any of the sites. These results suggest a survival cost of conspicuous coloration in collared lizards, and reiterate the importance of considering the visual environment as well as differences among populations when examining the influence of predation on the evolution of animal color patterns.

@article{doi101111j14390310200501189x,
    author = "Husak, Jerry F. and Macedonia, Joseph M. and Fox, Stanley F. and Sauceda, Richard C.",
    title = "Predation Cost of Conspicuous Male Coloration in Collared Lizards (Crotaphytus collaris): An Experimental Test Using Clay‐Covered Model Lizards",
    year = "2006",
    journal = "Ethology",
    abstract = "Abstract Animal color patterns are a compromise between sexual selection pressures that increase advantages accrued from conspicuousness, and natural selection pressures that decrease those advantages through reduced survivorship. Predation pressure, as a mode of natural selection, often is invoked as a counter‐selective force to sexual selection, yet few studies have demonstrated empirically that more conspicuous individuals experience higher rates of predation. We quantified predator attacks on models of collared lizards, Crotaphytus collaris, in three well‐studied populations (Oklahoma, USA). These populations differ in coloration and in visual backgrounds against which the lizards are viewed by conspecifics and predators. Attack frequencies varied considerably among study sites but at all sites the models exhibiting the strongest color contrast with local rocks were detected and attacked most often. By comparison, inconspicuous models of females were never attacked at any of the sites. These results suggest a survival cost of conspicuous coloration in collared lizards, and reiterate the importance of considering the visual environment as well as differences among populations when examining the influence of predation on the evolution of animal color patterns.",
    url = "https://doi.org/10.1111/j.1439-0310.2005.01189.x",
    doi = "10.1111/j.1439-0310.2005.01189.x",
    openalex = "W2118551402",
    references = "doi101006anbe20032235"
}

Natural populations of beach mice exhibit a characteristic color pattern, relative to their mainland conspecifics, driven by natural selection for crypsis. We identified a derived, charge-changing amino acid mutation in the melanocortin-1 receptor (Mc1r) in beach mice, which decreases receptor function. In genetic crosses, allelic variation at Mc1r explains 9.8% to 36.4% of the variation in seven pigmentation traits determining color pattern. The derived Mc1r allele is present in Florida's Gulf Coast beach mice but not in Atlantic coast mice with similar light coloration, suggesting that different molecular mechanisms are responsible for convergent phenotypic evolution. Here, we link a single mutation in the coding region of a pigmentation gene to adaptive quantitative variation in the wild.

@article{doi101126science1126121,
    author = "Hoekstra, Hopi E. and Hirschmann, Rachel J. and Bundey, Richard A. and Insel, Paul A. and Crossland, Janet P.",
    title = "A Single Amino Acid Mutation Contributes to Adaptive Beach Mouse Color Pattern",
    year = "2006",
    journal = "Science",
    abstract = "Natural populations of beach mice exhibit a characteristic color pattern, relative to their mainland conspecifics, driven by natural selection for crypsis. We identified a derived, charge-changing amino acid mutation in the melanocortin-1 receptor (Mc1r) in beach mice, which decreases receptor function. In genetic crosses, allelic variation at Mc1r explains 9.8\% to 36.4\% of the variation in seven pigmentation traits determining color pattern. The derived Mc1r allele is present in Florida's Gulf Coast beach mice but not in Atlantic coast mice with similar light coloration, suggesting that different molecular mechanisms are responsible for convergent phenotypic evolution. Here, we link a single mutation in the coding region of a pigmentation gene to adaptive quantitative variation in the wild.",
    url = "https://doi.org/10.1126/science.1126121",
    doi = "10.1126/science.1126121",
    openalex = "W2062935524",
    references = "doi101073pnas0431157100, doi1023071378997"
}

This research focuses on the relation between color and psychological functioning, specifically, that between red and performance attainment. Red is hypothesized to impair performance on achievement tasks, because red is associated with the danger of failure in achievement contexts and evokes avoidance motivation. Four experiments demonstrate that the brief perception of red prior to an important test (e.g., an IQ test) impairs performance, and this effect appears to take place outside of participants' conscious awareness. Two further experiments establish the link between red and avoidance motivation as indicated by behavioral (i.e., task choice) and psychophysiological (i.e., cortical activation) measures. The findings suggest that care must be taken in how red is used in achievement contexts and illustrate how color can act as a subtle environmental cue that has important influences on behavior.

@article{doi101037009634451361154,
    author = "Elliot, Andrew J. and Maier, Markus and Moller, Arlen C. and Friedman, Ron and Meinhardt, Jörg",
    title = "Color and psychological functioning: The effect of red on performance attainment.",
    year = "2007",
    journal = "Journal of Experimental Psychology General",
    abstract = "This research focuses on the relation between color and psychological functioning, specifically, that between red and performance attainment. Red is hypothesized to impair performance on achievement tasks, because red is associated with the danger of failure in achievement contexts and evokes avoidance motivation. Four experiments demonstrate that the brief perception of red prior to an important test (e.g., an IQ test) impairs performance, and this effect appears to take place outside of participants' conscious awareness. Two further experiments establish the link between red and avoidance motivation as indicated by behavioral (i.e., task choice) and psychophysiological (i.e., cortical activation) measures. The findings suggest that care must be taken in how red is used in achievement contexts and illustrate how color can act as a subtle environmental cue that has important influences on behavior.",
    url = "https://doi.org/10.1037/0096-3445.136.1.154",
    doi = "10.1037/0096-3445.136.1.154",
    openalex = "W2061915922"
}

Animals possess a range of defensive markings to reduce the risk of predation, including warning colours, camouflage, eyespots and mimicry. These different strategies are frequently considered independently, and with little regard towards predator vision, even though they may be linked in various ways and can be fully understood only in terms of predator perception. For example, camouflage and warning coloration need not be mutually exclusive, and may frequently exploit similar features of visual perception. This paper outlines how different forms of protective markings can be understood from predator perception and illustrates how this is fundamental in determining the mechanisms underlying, and the interrelation between, different strategies. Suggestions are made for future work, and potential mechanisms discussed in relation to various forms of defensive coloration, including disruptive coloration, eyespots, dazzle markings, motion camouflage, aposematism and mimicry.

@article{doi101098rspb20070220,
    author = "Stevens, Martin",
    title = "Predator perception and the interrelation between different forms of protective coloration",
    year = "2007",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Animals possess a range of defensive markings to reduce the risk of predation, including warning colours, camouflage, eyespots and mimicry. These different strategies are frequently considered independently, and with little regard towards predator vision, even though they may be linked in various ways and can be fully understood only in terms of predator perception. For example, camouflage and warning coloration need not be mutually exclusive, and may frequently exploit similar features of visual perception. This paper outlines how different forms of protective markings can be understood from predator perception and illustrates how this is fundamental in determining the mechanisms underlying, and the interrelation between, different strategies. Suggestions are made for future work, and potential mechanisms discussed in relation to various forms of defensive coloration, including disruptive coloration, eyespots, dazzle markings, motion camouflage, aposematism and mimicry.",
    url = "https://doi.org/10.1098/rspb.2007.0220",
    doi = "10.1098/rspb.2007.0220",
    openalex = "W2156084444",
    references = "doi10100797814615695655, doi101016jtree200507011, doi101016s0003347205806001, doi101038nature03312, doi101093acprofoso97801985286090010001, doi101098rspb20053156, doi101098rstb19880087, doi101111j10958312200700725x, doi101111j15585646200700054x, doi101113jphysiol1962sp006837, doi101113jphysiol1985sp015591, doi101364josaa2000284, doi1023071437762, doi1023074068693, doi105962bhltitle27468, doi107551mitpress97802625146200010001, openalexw1493613979, openalexw1507653370"
}

In understanding how visual signals function, quantifying the components of those patterns is vital. With the everincreasing power and availability of digital photography, many studies are utilizing this technique to study the content of animal colour signals. Digital photography has many advantages over other techniques, such as spectrometry, for measuring chromatic information, particularly in terms of the speed of data acquisition and its relatively cheap cost. Not only do digital photographs provide a method of quantifying the chromatic and achromatic content of spatially complex markings, but also they can be incorporated into powerful models of animal vision. Unfortunately, many studies utilizing digital photography appear to be unaware of several crucial issues involved in the acquisition of images, notably the nonlinearity of many cameras' responses to light intensity, and biases in a camera's processing of the images towards particular wavebands. In the present study, we set out step-by-step guidelines for the use of digital photography to obtain accurate data, either independent of any particular visual system (such as reflection values), or for particular models of nonhuman visual processing (such as that of a passerine bird). These guidelines include how to: (1) linearize the camera's response to changes in light intensity; (2) equalize the different colour channels to obtain reflectance information; and (3) produce a mapping from camera colour space to that of another colour space (such as photon catches for the cone types of a specific animal species).

@article{doi101111j10958312200700725x,
    author = "Stevens, Martin and Párraga, C. Alejandro and Cuthill, Innes C. and Partridge, Julian C. and Troscianko, Tom S.",
    title = "Using digital photography to study animal coloration",
    year = "2007",
    journal = "Biological Journal of the Linnean Society",
    abstract = "In understanding how visual signals function, quantifying the components of those patterns is vital. With the everincreasing power and availability of digital photography, many studies are utilizing this technique to study the content of animal colour signals. Digital photography has many advantages over other techniques, such as spectrometry, for measuring chromatic information, particularly in terms of the speed of data acquisition and its relatively cheap cost. Not only do digital photographs provide a method of quantifying the chromatic and achromatic content of spatially complex markings, but also they can be incorporated into powerful models of animal vision. Unfortunately, many studies utilizing digital photography appear to be unaware of several crucial issues involved in the acquisition of images, notably the nonlinearity of many cameras' responses to light intensity, and biases in a camera's processing of the images towards particular wavebands. In the present study, we set out step-by-step guidelines for the use of digital photography to obtain accurate data, either independent of any particular visual system (such as reflection values), or for particular models of nonhuman visual processing (such as that of a passerine bird). These guidelines include how to: (1) linearize the camera's response to changes in light intensity; (2) equalize the different colour channels to obtain reflectance information; and (3) produce a mapping from camera colour space to that of another colour space (such as photon catches for the cone types of a specific animal species).",
    url = "https://doi.org/10.1111/j.1095-8312.2007.00725.x",
    doi = "10.1111/j.1095-8312.2007.00725.x",
    openalex = "W1885077476",
    references = "doi101017s1464793102005985, doi101088003191121810010, doi101098rspb19800020, doi10110983650848, doi101111j109583121984tb01677x, doi101111j109583121990tb00839x, doi101111j10958312200500540x, doi1023074068693, doi105962bhltitle87588, openalexw1507653370, openalexw1533162639, openalexw2138825607, openalexw70084438"
}

Summary The role of phenotypic plasticity in evolution has historically been a contentious issue because of debate over whether plasticity shields genotypes from selection or generates novel opportunities for selection to act. Because plasticity encompasses diverse adaptive and non‐adaptive responses to environmental variation, no single conceptual framework adequately predicts the diverse roles of plasticity in evolutionary change. Different types of phenotypic plasticity can uniquely contribute to adaptive evolution when populations are faced with new or altered environments. Adaptive plasticity should promote establishment and persistence in a new environment, but depending on how close the plastic response is to the new favoured phenotypic optimum dictates whether directional selection will cause adaptive divergence between populations. Further, non‐adaptive plasticity in response to stressful environments can result in a mean phenotypic response being further away from the favoured optimum or alternatively increase the variance around the mean due to the expression of cryptic genetic variation. The expression of cryptic genetic variation can facilitate adaptive evolution if by chance it results in a fitter phenotype. We conclude that adaptive plasticity that places populations close enough to a new phenotypic optimum for directional selection to act is the only plasticity that predictably enhances fitness and is most likely to facilitate adaptive evolution on ecological time‐scales in new environments. However, this type of plasticity is likely to be the product of past selection on variation that may have been initially non‐adaptive. We end with suggestions on how future empirical studies can be designed to better test the importance of different kinds of plasticity to adaptive evolution.

@article{doi101111j13652435200701283x,
    author = "Ghalambor, Cameron K. and McKay, John and Carroll, Scott P. and Reznick, David N.",
    title = "Adaptive versus non‐adaptive phenotypic plasticity and the potential for contemporary adaptation in new environments",
    year = "2007",
    journal = "Functional Ecology",
    abstract = "Summary The role of phenotypic plasticity in evolution has historically been a contentious issue because of debate over whether plasticity shields genotypes from selection or generates novel opportunities for selection to act. Because plasticity encompasses diverse adaptive and non‐adaptive responses to environmental variation, no single conceptual framework adequately predicts the diverse roles of plasticity in evolutionary change. Different types of phenotypic plasticity can uniquely contribute to adaptive evolution when populations are faced with new or altered environments. Adaptive plasticity should promote establishment and persistence in a new environment, but depending on how close the plastic response is to the new favoured phenotypic optimum dictates whether directional selection will cause adaptive divergence between populations. Further, non‐adaptive plasticity in response to stressful environments can result in a mean phenotypic response being further away from the favoured optimum or alternatively increase the variance around the mean due to the expression of cryptic genetic variation. The expression of cryptic genetic variation can facilitate adaptive evolution if by chance it results in a fitter phenotype. We conclude that adaptive plasticity that places populations close enough to a new phenotypic optimum for directional selection to act is the only plasticity that predictably enhances fitness and is most likely to facilitate adaptive evolution on ecological time‐scales in new environments. However, this type of plasticity is likely to be the product of past selection on variation that may have been initially non‐adaptive. We end with suggestions on how future empirical studies can be designed to better test the importance of different kinds of plasticity to adaptive evolution.",
    url = "https://doi.org/10.1111/j.1365-2435.2007.01283.x",
    doi = "10.1111/j.1365-2435.2007.01283.x",
    openalex = "W2164403987",
    references = "doi10100797814615695655, doi101007bf02763457, doi101007bf02984069, doi101016s0065266008600486, doi101016s0169534702025545, doi101038150563a0, doi10103824550, doi101038nrg1041, doi101038scientificamerican117998, doi101086276408, doi101086346135, doi101093genetics16297, doi101093oso97801951223430010001, doi101111j13652435200701283x, doi101111j155856461985tb00391x, doi101111j155856461998tb01823x, doi1015159780691209418, doi1015159781400820108, doi1023072529912, doi105860choice364478, doi105962bhltitle27468"
}

The development and maintenance of color polymorphism in cryptic prey species is a source of enduring fascination, in part because it appears to result from selective processes operating across multiple levels of analysis, ranging from cognitive psychology to population ecology. Since the 1960s, prey species with diverse phenotypes have been viewed as the evolved reflection of the perceptual and cognitive characteristics of their predators. Because it is harder to search simultaneously for two or more cryptic prey types than to search for only one, visual predators should tend to focus on the most abundant forms and effectively overlook the others. The result should be frequency-dependent, apostatic selection, which will tend to stabilize the prey polymorphism. Validating this elegant hypothesis has been difficult, and many details have been established only relatively recently. This review clarifies the argument for a perceptual selective mechanism and examines the relevant experimental evidence.

@article{doi101146annurevecolsys38091206095728,
    author = "Bond, Alan B.",
    title = "The Evolution of Color Polymorphism: Crypticity, Searching Images, and Apostatic Selection",
    year = "2007",
    journal = "Annual Review of Ecology Evolution and Systematics",
    abstract = "The development and maintenance of color polymorphism in cryptic prey species is a source of enduring fascination, in part because it appears to result from selective processes operating across multiple levels of analysis, ranging from cognitive psychology to population ecology. Since the 1960s, prey species with diverse phenotypes have been viewed as the evolved reflection of the perceptual and cognitive characteristics of their predators. Because it is harder to search simultaneously for two or more cryptic prey types than to search for only one, visual predators should tend to focus on the most abundant forms and effectively overlook the others. The result should be frequency-dependent, apostatic selection, which will tend to stabilize the prey polymorphism. Validating this elegant hypothesis has been difficult, and many details have been established only relatively recently. This review clarifies the argument for a perceptual selective mechanism and examines the relevant experimental evidence.",
    url = "https://doi.org/10.1146/annurev.ecolsys.38.091206.095728",
    doi = "10.1146/annurev.ecolsys.38.091206.095728",
    openalex = "W2131480614",
    references = "doi101038415609a, doi101146annurevento431619"
}

Among the changeable camouflage patterns of cuttlefish, disruptive patterning is shown in response to certain features of light objects in the visual background. However, whether animals show disruptive patterns is dependent not only on object size but also on their body size. Here, we tested whether cuttlefish (Sepia officinalis) are able to match their disruptive body patterning with increasing size of background objects as they grow from hatchling to adult size (0.7 to 19.6 cm mantle length; factor of 28). Specifically, do cuttlefish have a single;visual sampling rule' that scales accurately during ontogeny? For each of seven size classes of cuttlefish, we created black and white checkerboards whose check sizes corresponded to 4, 12, 40, 120, 400 and 1200% of the area of the cuttlefish's White square, which is a neurophysiologically controlled component of the skin. Disruptive body patterns were evoked when, regardless of animal size, the check size measured either 40 or 120% of the area of the cuttlefish's White square, thus demonstrating a remarkable ontogenetic conformity to a single visual sampling rule. Cuttlefish have no known visual feedback loop with which to adjust their skin patterns. Since the area of a cuttlefish's White square skin component is a function of body size, our results indicate that cuttlefish are solving a visual scaling problem of camouflage presumably without visual confirmation of the size of their own skin component.

@article{doi101242jeb02741,
    author = "Barbosa, Alexandra and Mäthger, Lydia M. and Chubb, Charles and Florio, Christopher F. and Chiao, Chuan‐Chin and Hanlon, Roger T.",
    title = "Disruptive coloration in cuttlefish: a visual perception mechanism that regulates ontogenetic adjustment of skin patterning",
    year = "2007",
    journal = "Journal of Experimental Biology",
    abstract = "Among the changeable camouflage patterns of cuttlefish, disruptive patterning is shown in response to certain features of light objects in the visual background. However, whether animals show disruptive patterns is dependent not only on object size but also on their body size. Here, we tested whether cuttlefish (Sepia officinalis) are able to match their disruptive body patterning with increasing size of background objects as they grow from hatchling to adult size (0.7 to 19.6 cm mantle length; factor of 28). Specifically, do cuttlefish have a single;visual sampling rule' that scales accurately during ontogeny? For each of seven size classes of cuttlefish, we created black and white checkerboards whose check sizes corresponded to 4, 12, 40, 120, 400 and 1200\% of the area of the cuttlefish's White square, which is a neurophysiologically controlled component of the skin. Disruptive body patterns were evoked when, regardless of animal size, the check size measured either 40 or 120\% of the area of the cuttlefish's White square, thus demonstrating a remarkable ontogenetic conformity to a single visual sampling rule. Cuttlefish have no known visual feedback loop with which to adjust their skin patterns. Since the area of a cuttlefish's White square skin component is a function of body size, our results indicate that cuttlefish are solving a visual scaling problem of camouflage presumably without visual confirmation of the size of their own skin component.",
    url = "https://doi.org/10.1242/jeb.02741",
    doi = "10.1242/jeb.02741",
    openalex = "W2116757253"
}

Little is known about the genetic basis of ecologically important morphological variation such as the diverse color patterns of mammals. Here we identify genetic changes contributing to an adaptive difference in color pattern between two subspecies of oldfield mice (Peromyscus polionotus). One mainland subspecies has a cryptic dark brown dorsal coat, while a younger beach-dwelling subspecies has a lighter coat produced by natural selection for camouflage on pale coastal sand dunes. Using genome-wide linkage mapping, we identified three chromosomal regions (two of major and one of minor effect) associated with differences in pigmentation traits. Two candidate genes, the melanocortin-1 receptor (Mc1r) and its antagonist, the Agouti signaling protein (Agouti), map to independent regions that together are responsible for most of the difference in pigmentation between subspecies. A derived mutation in the coding region of Mc1r, rather than change in its expression level, contributes to light pigmentation. Conversely, beach mice have a derived increase in Agouti mRNA expression but no changes in protein sequence. These two genes also interact epistatically: the phenotypic effects of Mc1r are visible only in genetic backgrounds containing the derived Agouti allele. These results demonstrate that cryptic coloration can be based largely on a few interacting genes of major effect.

@article{doi101371journalpbio0050219,
    author = "Steiner, Cynthia and Weber, Jesse N. and Hoekstra, Hopi E.",
    title = "Adaptive Variation in Beach Mice Produced by Two Interacting Pigmentation Genes",
    year = "2007",
    journal = "PLoS Biology",
    abstract = "Little is known about the genetic basis of ecologically important morphological variation such as the diverse color patterns of mammals. Here we identify genetic changes contributing to an adaptive difference in color pattern between two subspecies of oldfield mice (Peromyscus polionotus). One mainland subspecies has a cryptic dark brown dorsal coat, while a younger beach-dwelling subspecies has a lighter coat produced by natural selection for camouflage on pale coastal sand dunes. Using genome-wide linkage mapping, we identified three chromosomal regions (two of major and one of minor effect) associated with differences in pigmentation traits. Two candidate genes, the melanocortin-1 receptor (Mc1r) and its antagonist, the Agouti signaling protein (Agouti), map to independent regions that together are responsible for most of the difference in pigmentation between subspecies. A derived mutation in the coding region of Mc1r, rather than change in its expression level, contributes to light pigmentation. Conversely, beach mice have a derived increase in Agouti mRNA expression but no changes in protein sequence. These two genes also interact epistatically: the phenotypic effects of Mc1r are visible only in genetic backgrounds containing the derived Agouti allele. These results demonstrate that cryptic coloration can be based largely on a few interacting genes of major effect.",
    url = "https://doi.org/10.1371/journal.pbio.0050219",
    doi = "10.1371/journal.pbio.0050219",
    openalex = "W2157240032",
    references = "doi1023071378997"
}

We use a tetrahedral color space to describe and analyze male plumage color variation and evolution in a clade of New World buntings--Cyanocompsa and Passerina (Aves: Cardinalidae). The Goldsmith color space models the relative stimulation of the four retinal cones, using the integrals of the product of plumage reflectance spectra and cone sensitivity functions. A color is represented as a vector defined by the relative stimulation of the four cone types--ultraviolet, blue, green, and red. Color vectors are plotted in a tetrahedral, or quaternary, plot with the achromatic point at the origin and the ultraviolet/violet channel along the Z-axis. Each color vector is specified by the spherical coordinates theta, phi, and r. Hue is given by the angles theta and phi. Chroma is given by the magnitude of r, the distance from the achromatic origin. Color vectors of all distinct patches in a plumage characterize the plumage color phenotype. We describe the variation in color space occupancy of male bunting plumages, using various measures of color contrast, hue contrast and diversity, and chroma. Comparative phylogenetic analyses using linear parsimony (in MacClade) and generalized least squares (GLS) models (in CONTINUOUS) with a molecular phylogeny of the group document that plumage color evolution in the clade has been very dynamic. The single best-fit GLS evolutionary model of plumage color variation over the entire clade is a directional change model with no phylogenetic correlation among species. However, phylogenetic innovations in feather color production mechanisms--derived pheomelanin and carotenoid expression in two lineages--created new opportunities to colonize novel areas of color space and fostered the explosive differentiation in plumage color. Comparison of the tetrahedral color space of Goldsmith with that of Endler and Mielke demonstrates that both provide essentially identical results. Evolution of avian ultraviolet/violet opsin sensitivity in relation to chromatic experience is discussed.

@article{doi101086587526,
    author = "Stoddard, Mary Caswell and Prum, Richard O.",
    title = "Evolution of Avian Plumage Color in a Tetrahedral Color Space: A Phylogenetic Analysis of New World Buntings",
    year = "2008",
    journal = "The American Naturalist",
    abstract = "We use a tetrahedral color space to describe and analyze male plumage color variation and evolution in a clade of New World buntings--Cyanocompsa and Passerina (Aves: Cardinalidae). The Goldsmith color space models the relative stimulation of the four retinal cones, using the integrals of the product of plumage reflectance spectra and cone sensitivity functions. A color is represented as a vector defined by the relative stimulation of the four cone types--ultraviolet, blue, green, and red. Color vectors are plotted in a tetrahedral, or quaternary, plot with the achromatic point at the origin and the ultraviolet/violet channel along the Z-axis. Each color vector is specified by the spherical coordinates theta, phi, and r. Hue is given by the angles theta and phi. Chroma is given by the magnitude of r, the distance from the achromatic origin. Color vectors of all distinct patches in a plumage characterize the plumage color phenotype. We describe the variation in color space occupancy of male bunting plumages, using various measures of color contrast, hue contrast and diversity, and chroma. Comparative phylogenetic analyses using linear parsimony (in MacClade) and generalized least squares (GLS) models (in CONTINUOUS) with a molecular phylogeny of the group document that plumage color evolution in the clade has been very dynamic. The single best-fit GLS evolutionary model of plumage color variation over the entire clade is a directional change model with no phylogenetic correlation among species. However, phylogenetic innovations in feather color production mechanisms--derived pheomelanin and carotenoid expression in two lineages--created new opportunities to colonize novel areas of color space and fostered the explosive differentiation in plumage color. Comparison of the tetrahedral color space of Goldsmith with that of Endler and Mielke demonstrates that both provide essentially identical results. Evolution of avian ultraviolet/violet opsin sensitivity in relation to chromatic experience is discussed.",
    url = "https://doi.org/10.1086/587526",
    doi = "10.1086/587526",
    openalex = "W1982586025",
    references = "doi101016s135094620100009x, doi101017s1464793102005985"
}

In recent years, structural colors have attracted great attention in a wide variety of research fields. This is because they are originated from complex interaction between light and sophisticated nanostructures generated in the natural world. In addition, their inherent regular structures are one of the most conspicuous examples of non-equilibrium order formation. Structural colors are deeply connected with recent rapidly growing fields of photonics and have been extensively studied to clarify their peculiar optical phenomena. Their mechanisms are, in principle, of a purely physical origin, which differs considerably from the ordinary coloration mechanisms such as in pigments, dyes and metals, where the colors are produced by virtue of the energy consumption of light. It is generally recognized that structural colors are mainly based on several elementary optical processes including thin-layer interference, diffraction grating, light scattering, photonic crystals and so on. However, in nature, these processes are somehow mixed together to produce complex optical phenomena. In many cases, they are combined with the irregularity of the structure to produce the diffusive nature of the reflected light, while in some cases they are accompanied by large-scale structures to generate the macroscopic effect on the coloration. Further, it is well known that structural colors cooperate with pigmentary colors to enhance or to reduce the brilliancy and to produce special effects. Thus, structure-based optical phenomena in nature appear to be quite multi-functional, the variety of which is far beyond our understanding. In this article, we overview these phenomena appearing particularly in the diversity of the animal world, to shed light on this rapidly developing research field.

@article{doi10108800344885717076401,
    author = "Kinoshita, S. and Yoshioka, Shinya and Miyazaki, Jun",
    title = "Physics of structural colors",
    year = "2008",
    journal = "Reports on Progress in Physics",
    abstract = "In recent years, structural colors have attracted great attention in a wide variety of research fields. This is because they are originated from complex interaction between light and sophisticated nanostructures generated in the natural world. In addition, their inherent regular structures are one of the most conspicuous examples of non-equilibrium order formation. Structural colors are deeply connected with recent rapidly growing fields of photonics and have been extensively studied to clarify their peculiar optical phenomena. Their mechanisms are, in principle, of a purely physical origin, which differs considerably from the ordinary coloration mechanisms such as in pigments, dyes and metals, where the colors are produced by virtue of the energy consumption of light. It is generally recognized that structural colors are mainly based on several elementary optical processes including thin-layer interference, diffraction grating, light scattering, photonic crystals and so on. However, in nature, these processes are somehow mixed together to produce complex optical phenomena. In many cases, they are combined with the irregularity of the structure to produce the diffusive nature of the reflected light, while in some cases they are accompanied by large-scale structures to generate the macroscopic effect on the coloration. Further, it is well known that structural colors cooperate with pigmentary colors to enhance or to reduce the brilliancy and to produce special effects. Thus, structure-based optical phenomena in nature appear to be quite multi-functional, the variety of which is far beyond our understanding. In this article, we overview these phenomena appearing particularly in the diversity of the animal world, to shed light on this rapidly developing research field.",
    url = "https://doi.org/10.1088/0034-4885/71/7/076401",
    doi = "10.1088/0034-4885/71/7/076401",
    openalex = "W1977675747",
    references = "denton1970review, doi101007b138376, doi1010160029558260903539, doi101038nature01941, doi10106311325200, doi1010881464425826201, doi101098rsif20080366focus, doi101098rsif20080395focus, doi101103physrevlett582486, doi101103physrevlett642953, doi101242jeb482227, doi101364josaa12001068, doi101364josaa12001077, doi101364oe8000173, openalexw659399033"
}

Octopus, squid and cuttlefish are renowned for rapid adaptive coloration that is used for a wide range of communication and camouflage. Structural coloration plays a key role in augmenting the skin patterning that is produced largely by neurally controlled pigmented chromatophore organs. While most iridescence and white scattering is produced by passive reflectance or diffusion, some iridophores in squid are actively controlled via a unique cholinergic, non-synaptic neural system. We review the recent anatomical and experimental evidence regarding the mechanisms of reflection and diffusion of light by the different cell types (iridophores and leucophores) of various cephalopod species. The structures that are responsible for the optical effects of some iridophores and leucophores have recently been shown to be proteins. Optical interactions with the overlying pigmented chromatophores are complex, and the recent measurements are presented and synthesized. Polarized light reflected from iridophores can be passed through the chromatophores, thus enabling the use of a discrete communication channel, because cephalopods are especially sensitive to polarized light. We illustrate how structural coloration contributes to the overall appearance of the cephalopods during intra- and interspecific behavioural interactions including camouflage.

@article{doi101098rsif20080366focus,
    author = "Mäthger, Lydia M. and Denton, E. J. and Marshall, N. Justin and Hanlon, Roger T.",
    title = "Mechanisms and behavioural functions of structural coloration in cephalopods",
    year = "2008",
    journal = "Journal of The Royal Society Interface",
    abstract = "Octopus, squid and cuttlefish are renowned for rapid adaptive coloration that is used for a wide range of communication and camouflage. Structural coloration plays a key role in augmenting the skin patterning that is produced largely by neurally controlled pigmented chromatophore organs. While most iridescence and white scattering is produced by passive reflectance or diffusion, some iridophores in squid are actively controlled via a unique cholinergic, non-synaptic neural system. We review the recent anatomical and experimental evidence regarding the mechanisms of reflection and diffusion of light by the different cell types (iridophores and leucophores) of various cephalopod species. The structures that are responsible for the optical effects of some iridophores and leucophores have recently been shown to be proteins. Optical interactions with the overlying pigmented chromatophores are complex, and the recent measurements are presented and synthesized. Polarized light reflected from iridophores can be passed through the chromatophores, thus enabling the use of a discrete communication channel, because cephalopods are especially sensitive to polarized light. We illustrate how structural coloration contributes to the overall appearance of the cephalopods during intra- and interspecific behavioural interactions including camouflage.",
    url = "https://doi.org/10.1098/rsif.2008.0366.focus",
    doi = "10.1098/rsif.2008.0366.focus",
    openalex = "W2143534808",
    references = "denton1970review, denton1972the, doi101007s003590050286, doi1010160079610772900041, doi101016jjmps200607007, doi101017s0025315400033439, doi101017s1464793101005772, doi101038nature01941, doi101073pnas2133313100, doi101098rspb19990794, doi101098rstb19880087, doi101098rstb20080270, doi101146annurevcellbio141197, doi101146annurevento431619, doi101242jeb482227, doi1023071437762, openalexw1486180449, young1980bioluminescence"
}

Disruptive coloration breaks up the shape and destroys the outline of an object, hindering detection. The principle was first suggested approximately a century ago, but, although research has significantly increased, the field remains conceptually unstructured and no unambiguous definition exists. This has resulted in variable use of the term, making it difficult to formulate testable hypotheses that are comparable between studies, slowing down advancement in this field. Related to this, a range of studies do not effectively distinguish between disruption and other forms of camouflage. Here, we give a formal definition of disruptive coloration, reorganize a range of sub-principles involved in camouflage and argue that five in particular are specifically related to disruption: differential blending; maximum disruptive contrast; disruption of surface through false edges; disruptive marginal patterns; and coincident disruptive coloration. We discuss how disruptive coloration can be optimized, how it can relate to other forms of camouflage markings and where future work is particularly needed.

@article{doi101098rstb20080216,
    author = "Stevens, Martin and Merilaita, Sami",
    title = "Defining disruptive coloration and distinguishing its functions",
    year = "2008",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Disruptive coloration breaks up the shape and destroys the outline of an object, hindering detection. The principle was first suggested approximately a century ago, but, although research has significantly increased, the field remains conceptually unstructured and no unambiguous definition exists. This has resulted in variable use of the term, making it difficult to formulate testable hypotheses that are comparable between studies, slowing down advancement in this field. Related to this, a range of studies do not effectively distinguish between disruption and other forms of camouflage. Here, we give a formal definition of disruptive coloration, reorganize a range of sub-principles involved in camouflage and argue that five in particular are specifically related to disruption: differential blending; maximum disruptive contrast; disruption of surface through false edges; disruptive marginal patterns; and coincident disruptive coloration. We discuss how disruptive coloration can be optimized, how it can relate to other forms of camouflage markings and where future work is particularly needed.",
    url = "https://doi.org/10.1098/rstb.2008.0216",
    doi = "10.1098/rstb.2008.0216",
    openalex = "W2131072062",
    references = "doi101016s0079612308612844, doi101038nature03312, doi101098rspb20043000, doi101098rspb20063556, doi101098rspb20070220, doi101098rstb19880087, doi101098rstb20080217, doi1023071437762, doi105962bhltitle17416, doi105962bhltitle69899, doi105962bhltitle87588"
}

Individual cuttlefish, octopus and squid have the versatile capability to use body patterns for background matching and disruptive coloration. We define--qualitatively and quantitatively--the chief characteristics of the three major body pattern types used for camouflage by cephalopods: uniform and mottle patterns for background matching, and disruptive patterns that primarily enhance disruptiveness but aid background matching as well. There is great variation within each of the three body pattern types, but by defining their chief characteristics we lay the groundwork to test camouflage concepts by correlating background statistics with those of the body pattern. We describe at least three ways in which background matching can be achieved in cephalopods. Disruptive patterns in cuttlefish possess all four of the basic components of 'disruptiveness', supporting Cott's hypotheses, and we provide field examples of disruptive coloration in which the body pattern contrast exceeds that of the immediate surrounds. Based upon laboratory testing as well as thousands of images of camouflaged cephalopods in the field (a sample is provided on a web archive), we note that size, contrast and edges of background objects are key visual cues that guide cephalopod camouflage patterning. Mottle and disruptive patterns are frequently mixed, suggesting that background matching and disruptive mechanisms are often used in the same pattern.

@article{doi101098rstb20080270,
    author = "Hanlon, Roger T. and Chiao, Chuan‐Chin and Mäthger, Lydia M. and Barbosa, Ana and Buresch, Kendra C. and Chubb, Charles",
    title = "Cephalopod dynamic camouflage: bridging the continuum between background matching and disruptive coloration",
    year = "2008",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Individual cuttlefish, octopus and squid have the versatile capability to use body patterns for background matching and disruptive coloration. We define--qualitatively and quantitatively--the chief characteristics of the three major body pattern types used for camouflage by cephalopods: uniform and mottle patterns for background matching, and disruptive patterns that primarily enhance disruptiveness but aid background matching as well. There is great variation within each of the three body pattern types, but by defining their chief characteristics we lay the groundwork to test camouflage concepts by correlating background statistics with those of the body pattern. We describe at least three ways in which background matching can be achieved in cephalopods. Disruptive patterns in cuttlefish possess all four of the basic components of 'disruptiveness', supporting Cott's hypotheses, and we provide field examples of disruptive coloration in which the body pattern contrast exceeds that of the immediate surrounds. Based upon laboratory testing as well as thousands of images of camouflaged cephalopods in the field (a sample is provided on a web archive), we note that size, contrast and edges of background objects are key visual cues that guide cephalopod camouflage patterning. Mottle and disruptive patterns are frequently mixed, suggesting that background matching and disruptive mechanisms are often used in the same pattern.",
    url = "https://doi.org/10.1098/rstb.2008.0270",
    doi = "10.1098/rstb.2008.0270",
    openalex = "W2146904805",
    references = "doi101016jcub200703034, doi101017s1464793101005772, doi101038nature03312, doi101093acprofoso97801985286090010001, doi101098rspb20070220, doi101098rstb19880087, doi101098rstb20080216, doi101098rstb20080217, doi101111j1469185x1972tb00975x, doi1023071437762, doi1023074068693, doi105962bhltitle69899, openalexw1493613979, openalexw1507653370, openalexw58525211"
}

There is an amazing amount of diversity in coloration patterns in nature. The ease of observing this diversity and the recent application of genetic and molecular techniques to model and nonmodel animals are allowing us to investigate the genetic basis and evolution of coloration in an ever-increasing variety of animals. It is now possible to ask questions about how many genes are responsible for any given pattern, what types of genetic changes have occurred to generate the diversity, and if the same underlying genetic changes occur repeatedly when coloration phenotypes arise through convergent evolution or parallel evolution.

@article{doi101146annurevcellbio24110707175302,
    author = "Protas, Meredith and Patel, Nipam H.",
    title = "Evolution of Coloration Patterns",
    year = "2008",
    journal = "Annual Review of Cell and Developmental Biology",
    abstract = "There is an amazing amount of diversity in coloration patterns in nature. The ease of observing this diversity and the recent application of genetic and molecular techniques to model and nonmodel animals are allowing us to investigate the genetic basis and evolution of coloration in an ever-increasing variety of animals. It is now possible to ask questions about how many genes are responsible for any given pattern, what types of genetic changes have occurred to generate the diversity, and if the same underlying genetic changes occur repeatedly when coloration phenotypes arise through convergent evolution or parallel evolution.",
    url = "https://doi.org/10.1146/annurev.cellbio.24.110707.175302",
    doi = "10.1146/annurev.cellbio.24.110707.175302",
    openalex = "W2100184629",
    references = "doi1016410006356820050550125tasoci20co2"
}

We summarize direct and indirect effects on fitness components of animal color pattern and present a synthesis of theories concerning the ecological and evolutionary dynamics of chromatic multiple niche polymorphisms. Previous endeavors have aimed primarily at identifying conditions that promote the evolution and maintenance of polymorphisms. We consider in a conceptual model also the reciprocal influence of color polymorphism on population processes and propose that polymorphism entails selective advantages that may promote the ecological success of polymorphic species. The model begins with an evolutionary branching event from mono- to polymorphic condition that, under the influence of correlational selection, is predicted to promote the evolution of physical integration of coloration and other traits (cf. multi-trait coevolution and complex phenotypes). We propose that the coexistence within a population of alternative ecomorphs with coadapted gene complexes promotes utilization of diverse environmental resources, population stability and persistence, colonization success, and range expansions, and enhances the evolutionary potential and speciation. Conversely, we predict polymorphic populations to be less vulnerable to environmental change and at lower risk of range contractions and extinctions compared with monomorphic populations. We offer brief suggestions as to how these falsifiable predictions may be tested.

@article{doi1018900705721,
    author = "Forsman, Anders and Ahnesjö, Jonas and Caesar, Sofia and Karlsson, Magnus",
    title = "A MODEL OF ECOLOGICAL AND EVOLUTIONARY CONSEQUENCES OF COLOR POLYMORPHISM",
    year = "2008",
    journal = "Ecology",
    abstract = "We summarize direct and indirect effects on fitness components of animal color pattern and present a synthesis of theories concerning the ecological and evolutionary dynamics of chromatic multiple niche polymorphisms. Previous endeavors have aimed primarily at identifying conditions that promote the evolution and maintenance of polymorphisms. We consider in a conceptual model also the reciprocal influence of color polymorphism on population processes and propose that polymorphism entails selective advantages that may promote the ecological success of polymorphic species. The model begins with an evolutionary branching event from mono- to polymorphic condition that, under the influence of correlational selection, is predicted to promote the evolution of physical integration of coloration and other traits (cf. multi-trait coevolution and complex phenotypes). We propose that the coexistence within a population of alternative ecomorphs with coadapted gene complexes promotes utilization of diverse environmental resources, population stability and persistence, colonization success, and range expansions, and enhances the evolutionary potential and speciation. Conversely, we predict polymorphic populations to be less vulnerable to environmental change and at lower risk of range contractions and extinctions compared with monomorphic populations. We offer brief suggestions as to how these falsifiable predictions may be tested.",
    url = "https://doi.org/10.1890/07-0572.1",
    doi = "10.1890/07-0572.1",
    openalex = "W2091140740",
    references = "openalexw58525211"
}

Existing research reports inconsistent findings with regard to the effect of color on cognitive task performances. Some research suggests that blue or green leads to better performances than red; other studies record the opposite. Current work reconciles this discrepancy. We demonstrate that red (versus blue) color induces primarily an avoidance (versus approach) motivation (study 1, n = 69) and that red enhances performance on a detail-oriented task, whereas blue enhances performance on a creative task (studies 2 and 3, n = 208 and 118). Further, we replicate these results in the domains of product design (study 4, n = 42) and persuasive message evaluation (study 5, n = 161) and show that these effects occur outside of individuals' consciousness (study 6, n = 68). We also provide process evidence suggesting that the activation of alternative motivations mediates the effect of color on cognitive task performances.

@article{doi101126science1169144,
    author = "Mehta, Ravi and Zhu, Rui",
    title = "Blue or Red? Exploring the Effect of Color on Cognitive Task Performances",
    year = "2009",
    journal = "Science",
    abstract = "Existing research reports inconsistent findings with regard to the effect of color on cognitive task performances. Some research suggests that blue or green leads to better performances than red; other studies record the opposite. Current work reconciles this discrepancy. We demonstrate that red (versus blue) color induces primarily an avoidance (versus approach) motivation (study 1, n = 69) and that red enhances performance on a detail-oriented task, whereas blue enhances performance on a creative task (studies 2 and 3, n = 208 and 118). Further, we replicate these results in the domains of product design (study 4, n = 42) and persuasive message evaluation (study 5, n = 161) and show that these effects occur outside of individuals' consciousness (study 6, n = 68). We also provide process evidence suggesting that the activation of alternative motivations mediates the effect of color on cognitive task performances.",
    url = "https://doi.org/10.1126/science.1169144",
    doi = "10.1126/science.1169144",
    openalex = "W2023425620"
}

Abstract Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close‐packed or non‐close‐packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed.

@article{doi101002adfm201000143,
    author = "Aguirre, Carlos I. and Reguera, E. and Stein, Andreas",
    title = "Tunable Colors in Opals and Inverse Opal Photonic Crystals",
    year = "2010",
    journal = "Advanced Functional Materials",
    abstract = "Abstract Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close‐packed or non‐close‐packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed.",
    url = "https://doi.org/10.1002/adfm.201000143",
    doi = "10.1002/adfm.201000143",
    openalex = "W2020923303",
    references = "doi101038nphoton2007140"
}

Ecological opportunity--through entry into a new environment, the origin of a key innovation or extinction of antagonists--is widely thought to link ecological population dynamics to evolutionary diversification. The population-level processes arising from ecological opportunity are well documented under the concept of ecological release. However, there is little consensus as to how these processes promote phenotypic diversification, rapid speciation and adaptive radiation. We propose that ecological opportunity could promote adaptive radiation by generating specific changes to the selective regimes acting on natural populations, both by relaxing effective stabilizing selection and by creating conditions that ultimately generate diversifying selection. We assess theoretical and empirical evidence for these effects of ecological opportunity and review emerging phylogenetic approaches that attempt to detect the signature of ecological opportunity across geological time. Finally, we evaluate the evidence for the evolutionary effects of ecological opportunity in the diversification of Caribbean Anolis lizards. Some of the processes that could link ecological opportunity to adaptive radiation are well documented, but others remain unsupported. We suggest that more study is required to characterize the form of natural selection acting on natural populations and to better describe the relationship between ecological opportunity and speciation rates.

@article{doi101111j14209101201002029x,
    author = "Yoder, Jeremy B. and Clancey, Erin and Roches, Simone Des and Eastman, Jonathan M. and Gentry, Lydia R. and Godsoe, William and Hagey, Travis J. and Jochimsen, Denim M. and Oswald, Benjamin P. and Robertson, Jeanne M. and Sarver, Brice A. J. and Schenk, John J. and Spear, Stephen F. and Harmon, Luke J.",
    title = "Ecological opportunity and the origin of adaptive radiations",
    year = "2010",
    journal = "Journal of Evolutionary Biology",
    abstract = "Ecological opportunity--through entry into a new environment, the origin of a key innovation or extinction of antagonists--is widely thought to link ecological population dynamics to evolutionary diversification. The population-level processes arising from ecological opportunity are well documented under the concept of ecological release. However, there is little consensus as to how these processes promote phenotypic diversification, rapid speciation and adaptive radiation. We propose that ecological opportunity could promote adaptive radiation by generating specific changes to the selective regimes acting on natural populations, both by relaxing effective stabilizing selection and by creating conditions that ultimately generate diversifying selection. We assess theoretical and empirical evidence for these effects of ecological opportunity and review emerging phylogenetic approaches that attempt to detect the signature of ecological opportunity across geological time. Finally, we evaluate the evidence for the evolutionary effects of ecological opportunity in the diversification of Caribbean Anolis lizards. Some of the processes that could link ecological opportunity to adaptive radiation are well documented, but others remain unsupported. We suggest that more study is required to characterize the form of natural selection acting on natural populations and to better describe the relationship between ecological opportunity and speciation rates.",
    url = "https://doi.org/10.1111/j.1420-9101.2010.02029.x",
    doi = "10.1111/j.1420-9101.2010.02029.x",
    openalex = "W1566874056",
    references = "crowell1962reduced, doi101007978940100585210, doi101016jtree200810011, doi101016s0169534702024990, doi101017s0094837300003778, doi101038303614a0, doi101086284196, doi101086285404, doi101086510633, doi101093molbevmsi103, doi101093oso97801985052350010001, doi101098rspb20080630, doi101111j001438202003tb00285x, doi101111j001438202004tb00462x, doi101111j109583121996tb01434x, doi101111j155856461964tb01674x, doi101111j155856461982tb05068x, doi101111j155856461983tb00236x, doi101126science1157966, doi101186147121487214, doi101722611310, doi1023071438156, doi1023071932042, doi1023071934090, doi1023073071998, doi1043249780203509104"
}

Color variation within populations of the pea aphid influences relative susceptibility to predators and parasites. We have discovered that infection with a facultative endosymbiont of the genus Rickettsiella changes the insects' body color from red to green in natural populations. Approximately 8% of pea aphids collected in Western Europe carried the Rickettsiella infection. The infection increased amounts of blue-green polycyclic quinones, whereas it had less of an effect on yellow-red carotenoid pigments. The effect of the endosymbiont on body color is expected to influence prey-predator interactions, as well as interactions with other endosymbionts.

@article{doi101126science1195463,
    author = "Tsuchida, Tsutomu and Koga, Ryuichi and Horikawa, Mitsuyo and Tsunoda, Tetsuto and Maoka, Takashi and Matsumoto, Shogo and Simon, Jean‐Christophe and Fukatsu, Takema",
    title = "Symbiotic Bacterium Modifies Aphid Body Color",
    year = "2010",
    journal = "Science",
    abstract = "Color variation within populations of the pea aphid influences relative susceptibility to predators and parasites. We have discovered that infection with a facultative endosymbiont of the genus Rickettsiella changes the insects' body color from red to green in natural populations. Approximately 8\% of pea aphids collected in Western Europe carried the Rickettsiella infection. The infection increased amounts of blue-green polycyclic quinones, whereas it had less of an effect on yellow-red carotenoid pigments. The effect of the endosymbiont on body color is expected to influence prey-predator interactions, as well as interactions with other endosymbionts.",
    url = "https://doi.org/10.1126/science.1195463",
    doi = "10.1126/science.1195463",
    openalex = "W2060834037",
    references = "doi101093acprofoso97801985286090010001, openalexw58525211"
}

Fish travel in schools, birds migrate in flocks, honeybees swarm, and ants build trails. How and why do these collective behaviors occur? Exploring how coordinated group patterns emerge from individual interactions, Collective Animal Behavior reveals why animals produce group behaviors and examines their evolution across a range of species. Providing a synthesis of mathematical modeling, theoretical biology, and experimental work, David Sumpter investigates how animals move and arrive together, how they transfer information, how they make decisions and synchronize their activities, and how they build collective structures. Sumpter constructs a unified appreciation of how different group-living species coordinate their behaviors and why natural selection has produced these groups. For the first time, the book combines traditional approaches to behavioral ecology with ideas about self-organization and complex systems from physics and mathematics. Sumpter offers a guide for working with key models in this area along with case studies of their application, and he shows how ideas about animal behavior can be applied to understanding human social behavior. Containing a wealth of accessible examples as well as qualitative and quantitative features, Collective Animal Behavior will interest behavioral ecologists and all scientists studying complex systems.

@book{doi1015159781400837106,
    author = "Sumpter, David J. T.",
    title = "Collective Animal Behavior",
    year = "2010",
    booktitle = "Princeton University Press eBooks",
    abstract = "Fish travel in schools, birds migrate in flocks, honeybees swarm, and ants build trails. How and why do these collective behaviors occur? Exploring how coordinated group patterns emerge from individual interactions, Collective Animal Behavior reveals why animals produce group behaviors and examines their evolution across a range of species. Providing a synthesis of mathematical modeling, theoretical biology, and experimental work, David Sumpter investigates how animals move and arrive together, how they transfer information, how they make decisions and synchronize their activities, and how they build collective structures. Sumpter constructs a unified appreciation of how different group-living species coordinate their behaviors and why natural selection has produced these groups. For the first time, the book combines traditional approaches to behavioral ecology with ideas about self-organization and complex systems from physics and mathematics. Sumpter offers a guide for working with key models in this area along with case studies of their application, and he shows how ideas about animal behavior can be applied to understanding human social behavior. Containing a wealth of accessible examples as well as qualitative and quantitative features, Collective Animal Behavior will interest behavioral ecologists and all scientists studying complex systems.",
    url = "https://doi.org/10.1515/9781400837106",
    doi = "10.1515/9781400837106",
    openalex = "W589337778",
    references = "doi1010079783642696893, doi101016jtics200402007, doi101016s0003347205806001, doi101016s0065345408603526, doi10103830918, doi10103835065725, doi101098rsif20071106, doi101098rstb19520012, doi101103physreve514282, doi101103physrevlett751226, doi101126science16238591243, doi101126science2865439509, doi101137s003614450342480, doi1023071913386, doi107551mitpress110680010001"
}

Antipredator defenses and warning signals typically evolve in concert. However, the extensive variation across taxa in both these components of predator deterrence and the relationship between them are poorly understood. Here we test whether there is a predictive relationship between visual conspicuousness and toxicity levels across 10 populations of the color-polymorphic strawberry poison frog, Dendrobates pumilio. Using a mouse-based toxicity assay, we find extreme variation in toxicity between frog populations. This variation is significantly positively correlated with frog coloration brightness, a viewer-independent measure of visual conspicuousness (i.e., total reflectance flux). We also examine conspicuousness from the view of three potential predator taxa, as well as conspecific frogs, using taxon-specific visual detection models and three natural background substrates. We find very strong positive relationships between frog toxicity and conspicuousness for bird-specific perceptual models. Weaker but still positive correlations are found for crab and D. pumilio conspecific visual perception, while frog coloration as viewed by snakes is not related to toxicity. These results suggest that poison frog colors can be honest signals of prey unpalatability to predators and that birds in particular may exert selection on aposematic signal design.

@article{doi101086663197,
    author = "Maan, Martine E. and Cummings, Molly E.",
    title = "Poison Frog Colors Are Honest Signals of Toxicity, Particularly for Bird Predators",
    year = "2011",
    journal = "The American Naturalist",
    abstract = "Antipredator defenses and warning signals typically evolve in concert. However, the extensive variation across taxa in both these components of predator deterrence and the relationship between them are poorly understood. Here we test whether there is a predictive relationship between visual conspicuousness and toxicity levels across 10 populations of the color-polymorphic strawberry poison frog, Dendrobates pumilio. Using a mouse-based toxicity assay, we find extreme variation in toxicity between frog populations. This variation is significantly positively correlated with frog coloration brightness, a viewer-independent measure of visual conspicuousness (i.e., total reflectance flux). We also examine conspicuousness from the view of three potential predator taxa, as well as conspecific frogs, using taxon-specific visual detection models and three natural background substrates. We find very strong positive relationships between frog toxicity and conspicuousness for bird-specific perceptual models. Weaker but still positive correlations are found for crab and D. pumilio conspecific visual perception, while frog coloration as viewed by snakes is not related to toxicity. These results suggest that poison frog colors can be honest signals of prey unpalatability to predators and that birds in particular may exert selection on aposematic signal design.",
    url = "https://doi.org/10.1086/663197",
    doi = "10.1086/663197",
    openalex = "W1980094530",
    references = "doi101016jtree200507011, doi101086284581, doi101086382662, doi101111j15585646200700054x"
}

Many animals are toxic or unpalatable and signal this to predators with warning signals (aposematism). Aposematic appearance has long been a classical system to study predator-prey interactions, communication and signalling, and animal behaviour and learning. The area has received considerable empirical and theoretical investigation. However, most research has centred on understanding the initial evolution of aposematism, despite the fact that these studies often tell us little about the form and diversity of real warning signals in nature. In contrast, less attention has been given to the mechanistic basis of aposematic markings; that is, 'what makes an effective warning signal?', and the efficacy of warning signals has been neglected. Furthermore, unlike other areas of adaptive coloration research (such as camouflage and mate choice), studies of warning coloration have often been slow to address predator vision and psychology. Here, we review the current understanding of warning signal form, with an aim to comprehend the diversity of warning signals in nature. We present hypotheses and suggestions for future work regarding our current understanding of several inter-related questions covering the form of warning signals and their relationship with predator vision, learning, and links to broader issues in evolutionary ecology such as mate choice and speciation.

@article{doi101098rspb20111932,
    author = "Stevens, Martin and Ruxton, Graeme D.",
    title = "Linking the evolution and form of warning coloration in nature",
    year = "2011",
    journal = "Proceedings of the Royal Society B Biological Sciences",
    abstract = "Many animals are toxic or unpalatable and signal this to predators with warning signals (aposematism). Aposematic appearance has long been a classical system to study predator-prey interactions, communication and signalling, and animal behaviour and learning. The area has received considerable empirical and theoretical investigation. However, most research has centred on understanding the initial evolution of aposematism, despite the fact that these studies often tell us little about the form and diversity of real warning signals in nature. In contrast, less attention has been given to the mechanistic basis of aposematic markings; that is, 'what makes an effective warning signal?', and the efficacy of warning signals has been neglected. Furthermore, unlike other areas of adaptive coloration research (such as camouflage and mate choice), studies of warning coloration have often been slow to address predator vision and psychology. Here, we review the current understanding of warning signal form, with an aim to comprehend the diversity of warning signals in nature. We present hypotheses and suggestions for future work regarding our current understanding of several inter-related questions covering the form of warning signals and their relationship with predator vision, learning, and links to broader issues in evolutionary ecology such as mate choice and speciation.",
    url = "https://doi.org/10.1098/rspb.2011.1932",
    doi = "10.1098/rspb.2011.1932",
    openalex = "W2162502965",
    references = "doi101016jtree200507011, doi101016s0003347205806001, doi10103835077075, doi101086284581, doi101086382662, doi101093acprofoso97801985286090010001, doi101098rspb20053156, doi101111j155856461989tb04237x, doi101111j15585646200700054x, doi101126science1208227, doi101146annurevecolsys301201, openalexw58525211"
}

Natural structural color materials, especially those that can undergo reversible changes, are attracting increasing interest in a wide variety of research fields. Inspired by the natural creatures, many elaborately nanostructured photonic materials with variable structural colors were developed. These materials have found important applications in switches, display devices, sensors, and so on. In this critical review, we will provide up-to-date research concerning the natural and bio-inspired photonic materials with variable structural colors. After introducing the variable structural colors in natural creatures, we will focus on the studies of artificial variable structural color photonic materials, including their bio-inspired designs, fabrications and applications. The prospects for the future development of these fantastic variable structural color materials will also be presented. We believe this review will promote the communications among biology, bionics, chemistry, optical physics, and material science (196 references).

@article{doi101039c2cs15267c,
    author = "Zhao, Yuanjin and Xie, Zhuoying and Gu, Hongcheng and Zhu, Cun and Gu, Zhongze",
    title = "Bio-inspired variable structural color materials",
    year = "2012",
    journal = "Chemical Society Reviews",
    abstract = "Natural structural color materials, especially those that can undergo reversible changes, are attracting increasing interest in a wide variety of research fields. Inspired by the natural creatures, many elaborately nanostructured photonic materials with variable structural colors were developed. These materials have found important applications in switches, display devices, sensors, and so on. In this critical review, we will provide up-to-date research concerning the natural and bio-inspired photonic materials with variable structural colors. After introducing the variable structural colors in natural creatures, we will focus on the studies of artificial variable structural color photonic materials, including their bio-inspired designs, fabrications and applications. The prospects for the future development of these fantastic variable structural color materials will also be presented. We believe this review will promote the communications among biology, bionics, chemistry, optical physics, and material science (196 references).",
    url = "https://doi.org/10.1039/c2cs15267c",
    doi = "10.1039/c2cs15267c",
    openalex = "W2036581304",
    references = "doi101002sici152140952000051210693aidadma69330co2j, doi101021cm990080, doi10103835003523, doi101038386143a0, doi10103839834, doi101038nature01775, doi101038nature01941, doi101038nmat2032, doi101038nphoton2007140, doi101039b717368g, doi10108800344885717076401, doi101103physrevlett582059, doi101103physrevlett582486, doi101126science28554331537"
}

Adaptive reflective surfaces have been a challenge for both electronic paper (e-paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology uses colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization and metrics used in synthetic reflective e-paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signaling.

@article{doi101098rsif20120601,
    author = "Kreit, Eric and Mäthger, Lydia M. and Hanlon, Roger T. and Dennis, Patrick B. and Naik, Rajesh R. and Forsythe, Eric and Heikenfeld, Jason",
    title = "Biological versus electronic adaptive coloration: how can one inform the other?",
    year = "2012",
    journal = "Journal of The Royal Society Interface",
    abstract = "Adaptive reflective surfaces have been a challenge for both electronic paper (e-paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology uses colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization and metrics used in synthetic reflective e-paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signaling.",
    url = "https://doi.org/10.1098/rsif.2012.0601",
    doi = "10.1098/rsif.2012.0601",
    openalex = "W2123457414",
    references = "doi101017s1464793102005985, doi10103828349, doi101038nature01941, doi101038nphoton2007140, doi10106313050671, doi101080713819265, doi101098rspb19980302, doi101126science1206157, doi101126science1222149, doi1023071437762"
}

Physiological color change is important for background matching, thermoregulation as well as signaling and is in vertebrates mediated by synchronous intracellular transport of pigmented organelles in chromatophores. We describe functions of and animal situations where color change occurs. A summary of endogenous and external factors that regulate this color change in fish and amphibians is provided, with special emphasis on extracellular stimuli. We describe not only color change in skin, but also highlight studies on color change that occurs using chromatophores in other areas such as iris and on the inside of the body. In addition, we discuss the growing field that applies melanophores and skin color in toxicology and as biosensors, and point out research areas with future potential.

@article{doi101111pcmr12040,
    author = "Sköld, Helén Nilsson and Aspengren, Sara and Wallin, Margareta",
    title = "Rapid color change in fish and amphibians – function, regulation, and emerging applications",
    year = "2012",
    journal = "Pigment Cell \& Melanoma Research",
    abstract = "Physiological color change is important for background matching, thermoregulation as well as signaling and is in vertebrates mediated by synchronous intracellular transport of pigmented organelles in chromatophores. We describe functions of and animal situations where color change occurs. A summary of endogenous and external factors that regulate this color change in fish and amphibians is provided, with special emphasis on extracellular stimuli. We describe not only color change in skin, but also highlight studies on color change that occurs using chromatophores in other areas such as iris and on the inside of the body. In addition, we discuss the growing field that applies melanophores and skin color in toxicology and as biosensors, and point out research areas with future potential.",
    url = "https://doi.org/10.1111/pcmr.12040",
    doi = "10.1111/pcmr.12040",
    openalex = "W2033127011",
    references = "doi101021jp071439h, doi101034j160007492000130502x, doi101038146144a0, doi101038nature11144, doi101111j1469185x200900118x, doi101111j155856461980tb04790x, doi101128cmr1845836072005, doi101242dev1231369, doi101371journalpgen1000326, doi1023071437762"
}

It is widely documented that hybridisation occurs between many closely related species, but the importance of introgression in adaptive evolution remains unclear, especially in animals. Here, we have examined the role of introgressive hybridisation in transferring adaptations between mimetic Heliconius butterflies, taking advantage of the recent identification of a gene regulating red wing patterns in this genus. By sequencing regions both linked and unlinked to the red colour locus, we found a region that displays an almost perfect genotype by phenotype association across four species, H. melpomene, H. cydno, H. timareta, and H. heurippa. This particular segment is located 70 kb downstream of the red colour specification gene optix, and coalescent analysis indicates repeated introgression of adaptive alleles from H. melpomene into the H. cydno species clade. Our analytical methods complement recent genome scale data for the same region and suggest adaptive introgression has a crucial role in generating adaptive wing colour diversity in this group of butterflies.

@article{doi101371journalpgen1002752,
    author = "Pardo‐Díaz, Carolina and Salazar, Camilo and Baxter, Simon W. and Mérot, Claire and Figueiredo-Ready, Wilsea M.B. and Joron, Mathieu and McMillan, W. Owen and Jiggins, Chris D.",
    title = "Adaptive Introgression across Species Boundaries in Heliconius Butterflies",
    year = "2012",
    journal = "PLoS Genetics",
    abstract = "It is widely documented that hybridisation occurs between many closely related species, but the importance of introgression in adaptive evolution remains unclear, especially in animals. Here, we have examined the role of introgressive hybridisation in transferring adaptations between mimetic Heliconius butterflies, taking advantage of the recent identification of a gene regulating red wing patterns in this genus. By sequencing regions both linked and unlinked to the red colour locus, we found a region that displays an almost perfect genotype by phenotype association across four species, H. melpomene, H. cydno, H. timareta, and H. heurippa. This particular segment is located 70 kb downstream of the red colour specification gene optix, and coalescent analysis indicates repeated introgression of adaptive alleles from H. melpomene into the H. cydno species clade. Our analytical methods complement recent genome scale data for the same region and suggest adaptive introgression has a crucial role in generating adaptive wing colour diversity in this group of butterflies.",
    url = "https://doi.org/10.1371/journal.pgen.1002752",
    doi = "10.1371/journal.pgen.1002752",
    openalex = "W1975533499",
    references = "doi101098rstb19850066, doi101126science1208227, doi101146annurevecolsys301201, doi101146annurevento50071803130447"
}

Nature's color has three main sources: pigments, structural colors and bioluminescence. Structural color is a special one, which is the color produced by micro- or nano-structures, and is bright and dazzling. The most common mechanisms of structural colors are film interference, diffraction grating, scattering and photonic crystals. Biological colors are mainly derived from film interference, which includes thin-film and multi-film interference. The diffraction grating mechanism is found in, for example, seed shrimp, mollusk Haliotis Glabra and the Hibiscus trionum flower. Scattering includes coherent and incoherent scattering. Well-known examples of coherent scattering include colors produced by brilliant iridescent butterfly wing scales and avian feather barbules, such as the peacock's tail. Examples of colors produced by photonic crystal structures include opal in beetles and iridescent spines in the sea mouse. Coloration changes occur through structural changes for camouflage, predation, signal communication and sex choice. This paper presents an overview of lessons from nature and various relevant mechanisms. Examples of bioinspired fabrication methods and applications are also presented in this paper.

@article{doi101039c3ra41096j,
    author = "Sun, Jiyu and Bhushan, Bharat and Tong, Jin",
    title = "Structural coloration in nature",
    year = "2013",
    journal = "RSC Advances",
    abstract = "Nature's color has three main sources: pigments, structural colors and bioluminescence. Structural color is a special one, which is the color produced by micro- or nano-structures, and is bright and dazzling. The most common mechanisms of structural colors are film interference, diffraction grating, scattering and photonic crystals. Biological colors are mainly derived from film interference, which includes thin-film and multi-film interference. The diffraction grating mechanism is found in, for example, seed shrimp, mollusk Haliotis Glabra and the Hibiscus trionum flower. Scattering includes coherent and incoherent scattering. Well-known examples of coherent scattering include colors produced by brilliant iridescent butterfly wing scales and avian feather barbules, such as the peacock's tail. Examples of colors produced by photonic crystal structures include opal in beetles and iridescent spines in the sea mouse. Coloration changes occur through structural changes for camouflage, predation, signal communication and sex choice. This paper presents an overview of lessons from nature and various relevant mechanisms. Examples of bioinspired fabrication methods and applications are also presented in this paper.",
    url = "https://doi.org/10.1039/c3ra41096j",
    doi = "10.1039/c3ra41096j",
    openalex = "W2072086579",
    references = "doi101002cphc200500007, doi10103835090573, doi101038nature01941, doi101038nphoton2007140, doi101038nphoton2009141, doi10108800344885717076401, doi1010881464425826201, doi101098rsif20080366focus, doi101098rsif20080395focus, doi101098rsif20120601, doi101098rsta20090011, doi101126science1112255, doi101126science1172051, doi101126science1222149"
}

Most examples of seasonal mismatches in phenology span multiple trophic levels, with timing of animal reproduction, hibernation, or migration becoming detached from peak food supply. The consequences of such mismatches are difficult to link to specific future climate change scenarios because the responses across trophic levels have complex underlying climate drivers often confounded by other stressors. In contrast, seasonal coat color polyphenism creating camouflage against snow is a direct and potentially severe type of seasonal mismatch if crypsis becomes compromised by the animal being white when snow is absent. It is unknown whether plasticity in the initiation or rate of coat color change will be able to reduce mismatch between the seasonal coat color and an increasingly snow-free background. We find that natural populations of snowshoe hares exposed to 3 y of widely varying snowpack have plasticity in the rate of the spring white-to-brown molt, but not in either the initiation dates of color change or the rate of the fall brown-to-white molt. Using an ensemble of locally downscaled climate projections, we also show that annual average duration of snowpack is forecast to decrease by 29-35 d by midcentury and 40-69 d by the end of the century. Without evolution in coat color phenology, the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century. This novel and visually compelling climate change-induced stressor likely applies to >9 widely distributed mammals with seasonal coat color.

@article{doi101073pnas1222724110,
    author = "Mills, L. Scott and Zímová, Markéta and Oyler, Jared W. and Running, Steven W. and Abatzoglou, John T. and Lukacs, Paul M.",
    title = "Camouflage mismatch in seasonal coat color due to decreased snow duration",
    year = "2013",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Most examples of seasonal mismatches in phenology span multiple trophic levels, with timing of animal reproduction, hibernation, or migration becoming detached from peak food supply. The consequences of such mismatches are difficult to link to specific future climate change scenarios because the responses across trophic levels have complex underlying climate drivers often confounded by other stressors. In contrast, seasonal coat color polyphenism creating camouflage against snow is a direct and potentially severe type of seasonal mismatch if crypsis becomes compromised by the animal being white when snow is absent. It is unknown whether plasticity in the initiation or rate of coat color change will be able to reduce mismatch between the seasonal coat color and an increasingly snow-free background. We find that natural populations of snowshoe hares exposed to 3 y of widely varying snowpack have plasticity in the rate of the spring white-to-brown molt, but not in either the initiation dates of color change or the rate of the fall brown-to-white molt. Using an ensemble of locally downscaled climate projections, we also show that annual average duration of snowpack is forecast to decrease by 29-35 d by midcentury and 40-69 d by the end of the century. Without evolution in coat color phenology, the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century. This novel and visually compelling climate change-induced stressor likely applies to >9 widely distributed mammals with seasonal coat color.",
    url = "https://doi.org/10.1073/pnas.1222724110",
    doi = "10.1073/pnas.1222724110",
    openalex = "W2016449118",
    references = "doi101038nature03312, doi1016410006356820050550125tasoci20co2"
}

Adaptive genetic variation has been thought to originate primarily from either new mutation or standing variation. Another potential source of adaptive variation is adaptive variants from other (donor) species that are introgressed into the (recipient) species, termed adaptive introgression. Here, the various attributes of these three potential sources of adaptive variation are compared. For example, the rate of adaptive change is generally thought to be faster from standing variation, slower from mutation and potentially intermediate from adaptive introgression. Additionally, the higher initial frequency of adaptive variation from standing variation and lower initial frequency from mutation might result in a higher probability of fixation of the adaptive variants for standing variation. Adaptive variation from introgression might have higher initial frequency than new adaptive mutations but lower than that from standing variation, again making the impact of adaptive introgression variation potentially intermediate. Adaptive introgressive variants might have multiple changes within a gene and affect multiple loci, an advantage also potentially found for adaptive standing variation but not for new adaptive mutants. The processes that might produce a common variant in two taxa, convergence, trans-species polymorphism from incomplete lineage sorting or from balancing selection and adaptive introgression, are also compared. Finally, potential examples of adaptive introgression in animals, including balancing selection for multiple alleles for major histocompatibility complex (MHC), S and csd genes, pesticide resistance in mice, black colour in wolves and white colour in coyotes, Neanderthal or Denisovan ancestry in humans, mimicry genes in Heliconius butterflies, beak traits in Darwin's finches, yellow skin in chickens and non-native ancestry in an endangered native salamander, are examined.

@article{doi101111mec12415,
    author = "Hedrick, Philip W.",
    title = "Adaptive introgression in animals: examples and comparison to new mutation and standing variation as sources of adaptive variation",
    year = "2013",
    journal = "Molecular Ecology",
    abstract = "Adaptive genetic variation has been thought to originate primarily from either new mutation or standing variation. Another potential source of adaptive variation is adaptive variants from other (donor) species that are introgressed into the (recipient) species, termed adaptive introgression. Here, the various attributes of these three potential sources of adaptive variation are compared. For example, the rate of adaptive change is generally thought to be faster from standing variation, slower from mutation and potentially intermediate from adaptive introgression. Additionally, the higher initial frequency of adaptive variation from standing variation and lower initial frequency from mutation might result in a higher probability of fixation of the adaptive variants for standing variation. Adaptive variation from introgression might have higher initial frequency than new adaptive mutations but lower than that from standing variation, again making the impact of adaptive introgression variation potentially intermediate. Adaptive introgressive variants might have multiple changes within a gene and affect multiple loci, an advantage also potentially found for adaptive standing variation but not for new adaptive mutants. The processes that might produce a common variant in two taxa, convergence, trans-species polymorphism from incomplete lineage sorting or from balancing selection and adaptive introgression, are also compared. Finally, potential examples of adaptive introgression in animals, including balancing selection for multiple alleles for major histocompatibility complex (MHC), S and csd genes, pesticide resistance in mice, black colour in wolves and white colour in coyotes, Neanderthal or Denisovan ancestry in humans, mimicry genes in Heliconius butterflies, beak traits in Darwin's finches, yellow skin in chickens and non-native ancestry in an endangered native salamander, are examined.",
    url = "https://doi.org/10.1111/mec.12415",
    doi = "10.1111/mec.12415",
    openalex = "W2021736445",
    references = "doi101016jtree200401003, doi101016jtree200502010, doi101016jtree200709008, doi101016jtree201206001, doi10103835077075, doi101038nature09710, doi101038nature10944, doi101038scientificamerican117998, doi101111j001438202006tb01143x, doi101111j14209101201202599x, doi101126science1188021, doi101126science1208227, doi101146annureves12110181000531, doi101146annurevgenet110711155557, doi104159harvard9780674865327, doi107208chicago97802268933340010001"
}

Color is a ubiquitous perceptual stimulus that is often considered in terms of aesthetics. Here we review theoretical and empirical work that looks beyond color aesthetics to the link between color and psychological functioning in humans. We begin by setting a historical context for research in this area, particularly highlighting methodological issues that hampered earlier empirical work. We proceed to overview theoretical and methodological advances during the past decade and conduct a review of emerging empirical findings. Our empirical review focuses especially on color in achievement and affiliation/attraction contexts, but it also covers work on consumer behavior as well as food and beverage evaluation and consumption. The review clearly shows that color can carry important meaning and can have an important impact on people's affect, cognition, and behavior. The literature remains at a nascent stage of development, however, and we note that considerable work on boundary conditions, moderators, and real-world generalizability is needed before strong conceptual statements and recommendations for application are warranted. We provide suggestions for future research and conclude by emphasizing the broad promise of research in this area.

@article{doi101146annurevpsych010213115035,
    author = "Elliot, Andrew J. and Maier, Markus",
    title = "Color Psychology: Effects of Perceiving Color on Psychological Functioning in Humans",
    year = "2013",
    journal = "Annual Review of Psychology",
    abstract = "Color is a ubiquitous perceptual stimulus that is often considered in terms of aesthetics. Here we review theoretical and empirical work that looks beyond color aesthetics to the link between color and psychological functioning in humans. We begin by setting a historical context for research in this area, particularly highlighting methodological issues that hampered earlier empirical work. We proceed to overview theoretical and methodological advances during the past decade and conduct a review of emerging empirical findings. Our empirical review focuses especially on color in achievement and affiliation/attraction contexts, but it also covers work on consumer behavior as well as food and beverage evaluation and consumption. The review clearly shows that color can carry important meaning and can have an important impact on people's affect, cognition, and behavior. The literature remains at a nascent stage of development, however, and we note that considerable work on boundary conditions, moderators, and real-world generalizability is needed before strong conceptual statements and recommendations for application are warranted. We provide suggestions for future research and conclude by emphasizing the broad promise of research in this area.",
    url = "https://doi.org/10.1146/annurev-psych-010213-115035",
    doi = "10.1146/annurev-psych-010213-115035",
    openalex = "W2164901293",
    references = "doi101002sici15206378199808234248aidcol930co2o, doi101007s117470100245y, doi101037003329091315763, doi101037009634451234394, doi101037009634451361154, doi10103710001000, doi10103821557, doi101098rspb20111932, doi101126science1169144, openalexw1784588679"
}

Click here for all previous articles in the History of the Ecological Sciences series by F. N. Egerton W. C. Allee (1949) and T. Park (1949) have surveyed the history of animal ecology before 1900, and 1900–1940, respectively. R. T. McIntosh (1985:61–68) also did so, more briefly. W. R. Thompson (1939) wrote a history of “Biological control and the theories of the interactions of populations” (1939: see 301–318). The scientific contributions of Charles Darwin, Henry W. Bates, Alfred R. Wallace, and Ernst Haeckel, discussed previously (Egerton 2010, 2011, 2012a, b, c, 2013c), contributed significantly to the ultimate emergence of animal ecology. Aspects of the history of animal ecology in the later 1800s were discussed in parts 45–46 (Egerton 2013a, b), on entomology and parasitology; those developments were absorbed into a separate science of animal ecology after it emerged. In this part 49, developments in Europe and North America are discussed separately; then, a formal synthesis in textbooks is discussed. Belgian zoologist Pierre-Joseph van Beneden (1809–1894) was most known for his parasitology studies (Florkin 1970). One of his books was Les commensaux et les parasites dans le règne animal (1875, English 1876). As a Catholic, he found Darwin's emphasis on the struggle for existence distasteful (Sapp 1994:7–8, 18–20). His book classified relations between species of animals as parasitism, commensalism, and mutualism. Commensals he defined as sharing the food of a neighbor without doing it harm, and mutualists as both benefiting (1876:1). Alfred Victor Espinas (1844–1922) published Des Sociétés Animales (1878), which tends toward what we call synecology, and drew upon van Beneden's book. Espinas was a controversial French philosopher, who nevertheless was liked by his students and colleagues (Brooks 1998:97–133). His introduction to evolution was from Herbert Spencer, whose Principles of Psychology Espinas and a colleague translated into French. He wrote Darwin two extant letters (March 1872, 1 July 1877), and Darwin responded (before 1 July 1877) that corals should not be considered social animals. In retrospect one might say that Espinas was a sort of precursor of ethology and sociobiology: he thought that human societies had evolved out of animal societies, and that humans could gain insights into cooperation from studying animal societies. Some controversy arose because Des Sociétés Animales seemed like a scientific treatise, yet was submitted successfully in Paris for a Ph.D. degree in philosophy. Since it was a philosophical treatise, French zoologists felt justified in ignoring it. In reality, it was a scientific work with philosophical implications. However, it was based on library research, not first-hand observations. His survey included: I: Accidental Societies among Animals of Different Species, Parasites, Commensals, Mutualists; II. Normal Societies among Animals of the Same Species; III. Function of Reproduction, chapter 1: Of the Family, Conjugal Society; chapter 2: Maternal Societies, Families of Insects; chapter 3: Paternal Societies, Families among Fish, Reptiles, Birds, and Mammals. Edward O. Wilson (1975:16) noted that William M. Wheeler's five basic kinds of societies (1930) were influenced by Espinas' book, and Allee (1949:32) acknowledged that although “Espinas' (1877) great work” had little contemporary influence, “more recently many have come to recognize the value of his work.” Carl Gottfried Semper (1832–1893), whom we met in part 47 as a hostile rival of Haeckel (Egerton 2013b:229), published Animal Life as Affected by the Natural Conditions of Existence in both German and English editions, which devotes 290 pages to what we call “autecology,” while 75 pages can be called “synecology” (two terms coined in 1896: Allee 1949:42). He attended the University of Würzburg and later was its Professor of Zoology and Director of its Zoological Institute (Beard 1893, Mayr 1975). His doctoral dissertation (1856) was on the anatomy and physiology of snails, and he continued studying invertebrates during his travels to Pacific islands, December 1858–May 1865. He spent 1862 on the Palau Islands and the rest of the time in the Philippines, and his five volumes of the 10-volume Reisen im Archipel der Philippinen (1868–1905) were on Holothuria (sea cucumbers), terrestrial mollusks, and Lepidoptera (Johnson 1969). As Semper's attacks on Haeckel in Animal Life (Semper 1881:v–vi, 461–463) make clear, he was quite familiar with Haeckel's works, but being averse to them (or him), he did not use Haeckel's term “oekologie” for the science on which he wrote his book. His alternative was “the natural conditions of existence” (in title of his book). Semper's occasion for writing Animal Life was an invitation to lecture at the Lowell Institute in Boston in 1877. That invitation enabled him to take a broad perspective on his life's work, but with the advantage that he had a wealth of illustrative Pacific research and discovery on which to draw. His “autecology” encompassed the influence of light, temperature, stagnant water, atmosphere, water currents, gravity, electricity, and water pressure. In less detail, he discussed the influence of living organisms on animals: reciprocal influences, parasitism, competition, mimicry, and more. In a discussion of the food of herbivores and carnivores, he pointed out that when herbivores transform vegetation into flesh, there is a loss of mass due to oxidation of organic material, and that the same is true when carnivores transform flesh of prey into their own flesh (Semper 1881:51–52). To illustrate this, he arbitrarily assumed a 10:1 ratio of food to flesh, a ratio that is in accord with a more recent estimate (Pequegnat 1958, Egerton 2007:53). Semper was a well-respected zoologist, and his book was read by other zoologists, but without serving as a Kuhnian paradigm that led others down paths which he had blazed. More focused and also significant for early animal ecology was a study by German zoologist Karl August Möbius (1825–1909) on oysters (Querner 1974, Kölmel 1981, König et al. 1981, Nyhart 2009:125–160). He was born into a poor family and worked his way up from teaching primary school in a small town to teaching high school in Hamburg. He soon worked at the Hamburg Museum of Natural History, co-founded the Hamburg Zoo, and planned Germany's first public aquarium. He studied under Johannes Müller at the University of Berlin and in 1853 became a teacher in a school in Kiel. He co-authored a treatise on three classes of Mollusca (sea slugs, marine snails, and clams) in Kiel Bay (Meyer and Möbius 1865–1872, two volumes) that had a general introduction in volume 1 that is ecological in scope and methodology, and used the term “Biocönose” to indicate forms of life having something in common (Querner 1974:432, Nyhart 2009:140–143). The introduction described five regions (zones) extending from sandy beach to mud at 10 fathoms. It also compared Kiel Bay's fauna with fauna in other parts of the North Sea. This treatise helped Möbius become Professor of Zoology at the University of Kiel in 1868. (a) Carl Gottfried Semper. From web site. (b) Karl August Möbius. From web site. If the dredge is thrown out and dragged over the sea-flats between the oyster-beds, fewer and also different animals will be found upon this muddy bottom than upon the sand. Every oyster-bed is thus, to a certain degree, a community of living beings, a collection of species, and a massing of individuals, which find here everything necessary for their growth and continuance, such as suitable soil, sufficient food, the requisite percentage of salt, and a temperature favorable to their development. Each species which lives here is represented by the greatest number of individuals which can grow to maturity subject to the conditions which surround them, for among all species the number of individuals which arrive at maturity at each breeding period is much smaller than the number of germs produced at that time. The individual number of cultivated plants and animals has been immensely increased because man has artificially extended their biocönotic territory; and this artificial increase in the number of plants and animals by means of cultivation is the foundation for the increased fecundity of the human species and the greater number of individuals which arrive at maturity—that is, for the extension of the biocönotic territory of Homo sapiens. Möbius' community concept was synthesized from three major lines of thought, popular at his time. Möbius combined Charles Darwin's theory of natural selection within the “web of life” with Alexander v. Humboldt's recurrent associations of plants as entities in our landscape, and added to these the ancient belief in natural harmony or balance of nature, called equilibrium in his mechanistic parlance. …causes of disequilibrium tend either to suppress each other, or an increased and to decrease one another alternately. The causes of disequilibrium produced by man in any animal group, such as deforestation, agriculture, etc., have many times insignificant effects because they are counterbalanced by other causes coming from the various groups of animals themselves The second of two food web diagrams. Camerano 1994:378. His paper stimulated neither controversy nor other studies to test his conclusions. With the works of Beneden, Espinas, Semper, and Möbius having displayed what a science of animal ecology might encompass, it seems surprising that afterwards the path grew dimmer rather than brighter. There was no well-defined tradition in zoology comparable to that in botany (Egerton 1976:340–342, 2013c), which spontaneously evolved into animal ecology. This lack of a well-defined animal ecology tradition is evident in a survey of relevant works published in Sweden, 1880s–1910s, showing no trend and no dominant leadership (Söderqvist 1986:58–69). Ecological traditions were developing in entomology and parasitology (Egerton 2013a, b), but without much broader influence. British plant ecologists organized the British Ecological Society in 1913—the world's first ecological society—and its of was toward plant ecology (Egerton published The Animal and of the Natural History of Animals that was ecological in but without the then, Charles was his but had not yet his plant ecology (Egerton animal ecology arose in the and being and for the same there were and could ecologists to their which students to ecology. whom we met in part (Egerton was a zoologist, who relations with the and the public Egerton see It was due to social societies, public a into a and his is a collection of articles and his He was first to make studies on the food of and and he was of his to ecological To who considered and in he the balance of should be after and should be evident to any one who the relations of living and the and of any in these (in His study of that the from by which he that their between and and The of any group, either in or various other and each of these the in or other of the in a extending is a natural later a concept which with his and its to a He Möbius' concept of but did not use that term he and other and “the and upon the and the and and the common did he a between plants and upon among different species of animals. of species in its and the family was common species were to they did not were poor in and in The species of and common He discussed in most the that were common both and the that it themselves and the second we find our into upon of animals in the of a between plant and animal was are plants that have of little that animals which it and with for food He that is in the of a The is that a species more than the individuals of its food it will in due to food (a) Alfred (b) In the for in and the in with serving as its entomology the studying a and a of He found a that was to and during the early he both and the to with he the on its own of work in for use in control of later in the In the University of of had a who increased for both the and the work in entomology increased In his of the on the and ecology as as a separate subject and entomology as of this science of W. that that found no between July of these and of is a not by was in In the to for a research on the The of that will be in part of this on as of the Ecological Society of America in As an the of in studying the fauna at in for the of Egerton He later studied other fauna and published of North with on the of the and of the His was on evolution but his work was also a for at a later time. C. was from a living on a at which spent in 1974, He grew up with a in In during the two terms in which his was a his him to with at the and had and his to have a in which was In 1872, for him to of the published a on the and of the studied zoology at University for three an degree from the of and in for In he became of a in to study and and there after which he continued research into was among two who organized the in as of the on the of Birds, for his work, he his in by of a in of to study and and there his studied life of species having and a control for had of which had ecological in his a survey of the and As of North America showing the life in the by the of and of this led to the belief that many of scientific and be to by a survey of a a of and a high were as is different and of animals and life one another from to was because of its great and to an The surveyed and territory was to make in all of which a has been The and he had studied the and he the of the life of North a in the primary and The he were on the of the at different and and of there were no without such one could see as one the that the vegetation with and many animal species were to and He in the from down to at and them on he defined these for that for the first the concept was and had been by in his of and in which did as as (Egerton is is that used his to a of North America the Life as his As he more from other he his of North Life in the same as of his published a of the and regions of the One might in the regions of and and there is but not the ecologists as his use of both animal and plant in his life which to be in the (a) Victor From web (b) web of animals. was a of who studying them with rather than with O. most at the and of were with In their Animals of Park he wrote on and on However, an in a on a of the in the and articles were by from published of a to (a) site. (b) Alfred site. The first book to use the term might be and Animal a of Zoology which was of animal is, of the relations of animals to their and their to these from was of University and was a there Victor from the University of in for studies Egerton He with an William at the and he worked as in the of the Zoology That to a to the University of in and with a in zoology in He continued in work under zoologists Charles and Charles and plant Henry was a for toward an animal He studied in the same that had studied vegetation He found that each species was with breeding and of vegetation could have become an ecological but he upon three studies on among in and and two on in all of which he into his Animal in as in the which drew upon both and It in the same as to the of Animal both books being by University of studies added an animal to studies on the vegetation of the (a) Charles (b) Charles In three R. and C. produced an of a food web of of in a Egerton was in the first of in in he his and at the University of and his Ph.D. at University in He worked at in was born in and studied at the University of and University and in became a at the of He worked on parasites of the and when that work he was work on in first of animal and was also the first to those His was a broad survey that encompassed a of and and and and in each the relations between the plant and animal it detail, as a general with a defined it was a have known him for more than a and been more with him than has as one of the in the the of animal ecology. The other who him was he liked was for time as an and one as at the of Natural the school in in not for but for colleague at C. Director of the had to a ecology He there between and him an to his and from to animal which he found more than of he for of and animal was in the of the Ecological Society of America in and as its first in Allee grew up on his and Park His family was and he his degree at and his and Ph.D. at the University of under Allee at other before at the University of he an school of animal He also in zoology at the He was a focused on social in social the three books which him during the they upon his during the doctoral students the Park and both of whom as of the Ecological Society of The second of the volume of was an Allee As they had from another two and Alfred at the same time that animal ecologists had not that could their The was an see he was the of the it was not that his in that was the same in which the in to and in published his of which was to found a of see However, it more than a book to a and had little with The had him to University on a in to his book, and had the of for his own responded to book, but no his to human with no of published his first to his in English in in in the of a species considered in continued on their during the and and their work did during the and However, there was much work to ecologists the these had before their could be and it to work those Charles C. from wrote the first book on animal to the of Animal He that it is a not a treatise like was among the first animal ecologists with an degree from and Ph.D. from The most in was the most early of animal the second most was the most of a later was a colleague of while he was in McIntosh see see The that and British plant ecologists (Egerton was not by animal Charles was by Animal an to animal and in two by and Park compared their books and found and more and born in a on the his and from the University of and his Ph.D. from University He a of before the University in He was of the Ecological Society of America in book was and have been more than it was it had not been by a Charles of an English at had been to natural history by his and Charles his degree at he studied under In while an was during the University He read book before the terrestrial and food were of each other, yet in was by of from to as to their He a food web showing this and from and Egerton two to in and and Charles The of in before his first with discussion of and focused on ecology However, his Animal to a not to the for to illustrate ecological In to the introduction of the book, there are but the influence was based on a animal food and and the of are to animal and chapter on also with be but each chapter with a and had been discussed the early (Egerton but in the of had could food and to both and of of the University of Museum of Zoology used the term in to as in of the in his history of animal compared and a general of and and classified animals to their major The was on the other was more with ecology and most of his the animal community and the natural he was not much in an animal was found in a or a but rather in the the of such a also the in with the number of animals that any community and the that these make on their He food as the most of the and his of this subject is In other book was much more than that it seems to see these as a of in of the two with being more and and being more has been the concept and concept However, this by five and he the between and were rather and that the significant is rather between and The of animal ecology with works of broad scope by Espinas and Semper and Möbius' treatise on but to the of Animal a to the The an ecological perspective in his studies on food of and and he on his in his as a He the term in Animal ecology as an arose at the University of in when as a and studied under two zoologists and wrote a doctoral dissertation on in the the scope of his research to and animals as a for his book, Animal which in the same as Animal ecologists in the Ecological Society of America and in was its first The Animal and was but without the animal ecology textbooks soon from in the and from in the of animal ecology. and did not upon the of animal ecology were who that animal ecologists had not the that could their and they and it to However, their contributions did not in the animal ecology of the their and University of

@article{doi1018900012962395159,
    author = "Egerton, Frank N.",
    title = "History of Ecological Sciences, Part 49: Formalizing Animal Ecology, 1870s to 1920s",
    year = "2013",
    journal = "Bulletin of the Ecological Society of America",
    abstract = "Click here for all previous articles in the History of the Ecological Sciences series by F. N. Egerton W. C. Allee (1949) and T. Park (1949) have surveyed the history of animal ecology before 1900, and 1900–1940, respectively. R. T. McIntosh (1985:61–68) also did so, more briefly. W. R. Thompson (1939) wrote a history of “Biological control and the theories of the interactions of populations” (1939: see 301–318). The scientific contributions of Charles Darwin, Henry W. Bates, Alfred R. Wallace, and Ernst Haeckel, discussed previously (Egerton 2010, 2011, 2012a, b, c, 2013c), contributed significantly to the ultimate emergence of animal ecology. Aspects of the history of animal ecology in the later 1800s were discussed in parts 45–46 (Egerton 2013a, b), on entomology and parasitology; those developments were absorbed into a separate science of animal ecology after it emerged. In this part 49, developments in Europe and North America are discussed separately; then, a formal synthesis in textbooks is discussed. Belgian zoologist Pierre-Joseph van Beneden (1809–1894) was most known for his parasitology studies (Florkin 1970). One of his books was Les commensaux et les parasites dans le règne animal (1875, English 1876). As a Catholic, he found Darwin's emphasis on the struggle for existence distasteful (Sapp 1994:7–8, 18–20). His book classified relations between species of animals as parasitism, commensalism, and mutualism. Commensals he defined as sharing the food of a neighbor without doing it harm, and mutualists as both benefiting (1876:1). Alfred Victor Espinas (1844–1922) published Des Sociétés Animales (1878), which tends toward what we call synecology, and drew upon van Beneden's book. Espinas was a controversial French philosopher, who nevertheless was liked by his students and colleagues (Brooks 1998:97–133). His introduction to evolution was from Herbert Spencer, whose Principles of Psychology Espinas and a colleague translated into French. He wrote Darwin two extant letters (March 1872, 1 July 1877), and Darwin responded (before 1 July 1877) that corals should not be considered social animals. In retrospect one might say that Espinas was a sort of precursor of ethology and sociobiology: he thought that human societies had evolved out of animal societies, and that humans could gain insights into cooperation from studying animal societies. Some controversy arose because Des Sociétés Animales seemed like a scientific treatise, yet was submitted successfully in Paris for a Ph.D. degree in philosophy. Since it was a philosophical treatise, French zoologists felt justified in ignoring it. In reality, it was a scientific work with philosophical implications. However, it was based on library research, not first-hand observations. His survey included: I: Accidental Societies among Animals of Different Species, Parasites, Commensals, Mutualists; II. Normal Societies among Animals of the Same Species; III. Function of Reproduction, chapter 1: Of the Family, Conjugal Society; chapter 2: Maternal Societies, Families of Insects; chapter 3: Paternal Societies, Families among Fish, Reptiles, Birds, and Mammals. Edward O. Wilson (1975:16) noted that William M. Wheeler's five basic kinds of societies (1930) were influenced by Espinas' book, and Allee (1949:32) acknowledged that although “Espinas' (1877) great work” had little contemporary influence, “more recently many have come to recognize the value of his work.” Carl Gottfried Semper (1832–1893), whom we met in part 47 as a hostile rival of Haeckel (Egerton 2013b:229), published Animal Life as Affected by the Natural Conditions of Existence in both German and English editions, which devotes 290 pages to what we call “autecology,” while 75 pages can be called “synecology” (two terms coined in 1896: Allee 1949:42). He attended the University of Würzburg and later was its Professor of Zoology and Director of its Zoological Institute (Beard 1893, Mayr 1975). His doctoral dissertation (1856) was on the anatomy and physiology of snails, and he continued studying invertebrates during his travels to Pacific islands, December 1858–May 1865. He spent 1862 on the Palau Islands and the rest of the time in the Philippines, and his five volumes of the 10-volume Reisen im Archipel der Philippinen (1868–1905) were on Holothuria (sea cucumbers), terrestrial mollusks, and Lepidoptera (Johnson 1969). As Semper's attacks on Haeckel in Animal Life (Semper 1881:v–vi, 461–463) make clear, he was quite familiar with Haeckel's works, but being averse to them (or him), he did not use Haeckel's term “oekologie” for the science on which he wrote his book. His alternative was “the natural conditions of existence” (in title of his book). Semper's occasion for writing Animal Life was an invitation to lecture at the Lowell Institute in Boston in 1877. That invitation enabled him to take a broad perspective on his life's work, but with the advantage that he had a wealth of illustrative Pacific research and discovery on which to draw. His “autecology” encompassed the influence of light, temperature, stagnant water, atmosphere, water currents, gravity, electricity, and water pressure. In less detail, he discussed the influence of living organisms on animals: reciprocal influences, parasitism, competition, mimicry, and more. In a discussion of the food of herbivores and carnivores, he pointed out that when herbivores transform vegetation into flesh, there is a loss of mass due to oxidation of organic material, and that the same is true when carnivores transform flesh of prey into their own flesh (Semper 1881:51–52). To illustrate this, he arbitrarily assumed a 10:1 ratio of food to flesh, a ratio that is in accord with a more recent estimate (Pequegnat 1958, Egerton 2007:53). Semper was a well-respected zoologist, and his book was read by other zoologists, but without serving as a Kuhnian paradigm that led others down paths which he had blazed. More focused and also significant for early animal ecology was a study by German zoologist Karl August Möbius (1825–1909) on oysters (Querner 1974, Kölmel 1981, König et al. 1981, Nyhart 2009:125–160). He was born into a poor family and worked his way up from teaching primary school in a small town to teaching high school in Hamburg. He soon worked at the Hamburg Museum of Natural History, co-founded the Hamburg Zoo, and planned Germany's first public aquarium. He studied under Johannes Müller at the University of Berlin and in 1853 became a teacher in a school in Kiel. He co-authored a treatise on three classes of Mollusca (sea slugs, marine snails, and clams) in Kiel Bay (Meyer and Möbius 1865–1872, two volumes) that had a general introduction in volume 1 that is ecological in scope and methodology, and used the term “Biocönose” to indicate forms of life having something in common (Querner 1974:432, Nyhart 2009:140–143). The introduction described five regions (zones) extending from sandy beach to mud at 10 fathoms. It also compared Kiel Bay's fauna with fauna in other parts of the North Sea. This treatise helped Möbius become Professor of Zoology at the University of Kiel in 1868. (a) Carl Gottfried Semper. From web site. (b) Karl August Möbius. From web site. If the dredge is thrown out and dragged over the sea-flats between the oyster-beds, fewer and also different animals will be found upon this muddy bottom than upon the sand. Every oyster-bed is thus, to a certain degree, a community of living beings, a collection of species, and a massing of individuals, which find here everything necessary for their growth and continuance, such as suitable soil, sufficient food, the requisite percentage of salt, and a temperature favorable to their development. Each species which lives here is represented by the greatest number of individuals which can grow to maturity subject to the conditions which surround them, for among all species the number of individuals which arrive at maturity at each breeding period is much smaller than the number of germs produced at that time. The individual number of cultivated plants and animals has been immensely increased because man has artificially extended their biocönotic territory; and this artificial increase in the number of plants and animals by means of cultivation is the foundation for the increased fecundity of the human species and the greater number of individuals which arrive at maturity—that is, for the extension of the biocönotic territory of Homo sapiens. Möbius' community concept was synthesized from three major lines of thought, popular at his time. Möbius combined Charles Darwin's theory of natural selection within the “web of life” with Alexander v. Humboldt's recurrent associations of plants as entities in our landscape, and added to these the ancient belief in natural harmony or balance of nature, called equilibrium in his mechanistic parlance. …causes of disequilibrium tend either to suppress each other, or an increased and to decrease one another alternately. The causes of disequilibrium produced by man in any animal group, such as deforestation, agriculture, etc., have many times insignificant effects because they are counterbalanced by other causes coming from the various groups of animals themselves The second of two food web diagrams. Camerano 1994:378. His paper stimulated neither controversy nor other studies to test his conclusions. With the works of Beneden, Espinas, Semper, and Möbius having displayed what a science of animal ecology might encompass, it seems surprising that afterwards the path grew dimmer rather than brighter. There was no well-defined tradition in zoology comparable to that in botany (Egerton 1976:340–342, 2013c), which spontaneously evolved into animal ecology. This lack of a well-defined animal ecology tradition is evident in a survey of relevant works published in Sweden, 1880s–1910s, showing no trend and no dominant leadership (Söderqvist 1986:58–69). Ecological traditions were developing in entomology and parasitology (Egerton 2013a, b), but without much broader influence. British plant ecologists organized the British Ecological Society in 1913—the world's first ecological society—and its of was toward plant ecology (Egerton published The Animal and of the Natural History of Animals that was ecological in but without the then, Charles was his but had not yet his plant ecology (Egerton animal ecology arose in the and being and for the same there were and could ecologists to their which students to ecology. whom we met in part (Egerton was a zoologist, who relations with the and the public Egerton see It was due to social societies, public a into a and his is a collection of articles and his He was first to make studies on the food of and and he was of his to ecological To who considered and in he the balance of should be after and should be evident to any one who the relations of living and the and of any in these (in His study of that the from by which he that their between and and The of any group, either in or various other and each of these the in or other of the in a extending is a natural later a concept which with his and its to a He Möbius' concept of but did not use that term he and other and “the and upon the and the and and the common did he a between plants and upon among different species of animals. of species in its and the family was common species were to they did not were poor in and in The species of and common He discussed in most the that were common both and the that it themselves and the second we find our into upon of animals in the of a between plant and animal was are plants that have of little that animals which it and with for food He that is in the of a The is that a species more than the individuals of its food it will in due to food (a) Alfred (b) In the for in and the in with serving as its entomology the studying a and a of He found a that was to and during the early he both and the to with he the on its own of work in for use in control of later in the In the University of of had a who increased for both the and the work in entomology increased In his of the on the and ecology as as a separate subject and entomology as of this science of W. that that found no between July of these and of is a not by was in In the to for a research on the The of that will be in part of this on as of the Ecological Society of America in As an the of in studying the fauna at in for the of Egerton He later studied other fauna and published of North with on the of the and of the His was on evolution but his work was also a for at a later time. C. was from a living on a at which spent in 1974, He grew up with a in In during the two terms in which his was a his him to with at the and had and his to have a in which was In 1872, for him to of the published a on the and of the studied zoology at University for three an degree from the of and in for In he became of a in to study and and there after which he continued research into was among two who organized the in as of the on the of Birds, for his work, he his in by of a in of to study and and there his studied life of species having and a control for had of which had ecological in his a survey of the and As of North America showing the life in the by the of and of this led to the belief that many of scientific and be to by a survey of a a of and a high were as is different and of animals and life one another from to was because of its great and to an The surveyed and territory was to make in all of which a has been The and he had studied the and he the of the life of North a in the primary and The he were on the of the at different and and of there were no without such one could see as one the that the vegetation with and many animal species were to and He in the from down to at and them on he defined these for that for the first the concept was and had been by in his of and in which did as as (Egerton is is that used his to a of North America the Life as his As he more from other he his of North Life in the same as of his published a of the and regions of the One might in the regions of and and there is but not the ecologists as his use of both animal and plant in his life which to be in the (a) Victor From web (b) web of animals. was a of who studying them with rather than with O. most at the and of were with In their Animals of Park he wrote on and on However, an in a on a of the in the and articles were by from published of a to (a) site. (b) Alfred site. The first book to use the term might be and Animal a of Zoology which was of animal is, of the relations of animals to their and their to these from was of University and was a there Victor from the University of in for studies Egerton He with an William at the and he worked as in the of the Zoology That to a to the University of in and with a in zoology in He continued in work under zoologists Charles and Charles and plant Henry was a for toward an animal He studied in the same that had studied vegetation He found that each species was with breeding and of vegetation could have become an ecological but he upon three studies on among in and and two on in all of which he into his Animal in as in the which drew upon both and It in the same as to the of Animal both books being by University of studies added an animal to studies on the vegetation of the (a) Charles (b) Charles In three R. and C. produced an of a food web of of in a Egerton was in the first of in in he his and at the University of and his Ph.D. at University in He worked at in was born in and studied at the University of and University and in became a at the of He worked on parasites of the and when that work he was work on in first of animal and was also the first to those His was a broad survey that encompassed a of and and and and in each the relations between the plant and animal it detail, as a general with a defined it was a have known him for more than a and been more with him than has as one of the in the the of animal ecology. The other who him was he liked was for time as an and one as at the of Natural the school in in not for but for colleague at C. Director of the had to a ecology He there between and him an to his and from to animal which he found more than of he for of and animal was in the of the Ecological Society of America in and as its first in Allee grew up on his and Park His family was and he his degree at and his and Ph.D. at the University of under Allee at other before at the University of he an school of animal He also in zoology at the He was a focused on social in social the three books which him during the they upon his during the doctoral students the Park and both of whom as of the Ecological Society of The second of the volume of was an Allee As they had from another two and Alfred at the same time that animal ecologists had not that could their The was an see he was the of the it was not that his in that was the same in which the in to and in published his of which was to found a of see However, it more than a book to a and had little with The had him to University on a in to his book, and had the of for his own responded to book, but no his to human with no of published his first to his in English in in in the of a species considered in continued on their during the and and their work did during the and However, there was much work to ecologists the these had before their could be and it to work those Charles C. from wrote the first book on animal to the of Animal He that it is a not a treatise like was among the first animal ecologists with an degree from and Ph.D. from The most in was the most early of animal the second most was the most of a later was a colleague of while he was in McIntosh see see The that and British plant ecologists (Egerton was not by animal Charles was by Animal an to animal and in two by and Park compared their books and found and more and born in a on the his and from the University of and his Ph.D. from University He a of before the University in He was of the Ecological Society of America in book was and have been more than it was it had not been by a Charles of an English at had been to natural history by his and Charles his degree at he studied under In while an was during the University He read book before the terrestrial and food were of each other, yet in was by of from to as to their He a food web showing this and from and Egerton two to in and and Charles The of in before his first with discussion of and focused on ecology However, his Animal to a not to the for to illustrate ecological In to the introduction of the book, there are but the influence was based on a animal food and and the of are to animal and chapter on also with be but each chapter with a and had been discussed the early (Egerton but in the of had could food and to both and of of the University of Museum of Zoology used the term in to as in of the in his history of animal compared and a general of and and classified animals to their major The was on the other was more with ecology and most of his the animal community and the natural he was not much in an animal was found in a or a but rather in the the of such a also the in with the number of animals that any community and the that these make on their He food as the most of the and his of this subject is In other book was much more than that it seems to see these as a of in of the two with being more and and being more has been the concept and concept However, this by five and he the between and were rather and that the significant is rather between and The of animal ecology with works of broad scope by Espinas and Semper and Möbius' treatise on but to the of Animal a to the The an ecological perspective in his studies on food of and and he on his in his as a He the term in Animal ecology as an arose at the University of in when as a and studied under two zoologists and wrote a doctoral dissertation on in the the scope of his research to and animals as a for his book, Animal which in the same as Animal ecologists in the Ecological Society of America and in was its first The Animal and was but without the animal ecology textbooks soon from in the and from in the of animal ecology. and did not upon the of animal ecology were who that animal ecologists had not the that could their and they and it to However, their contributions did not in the animal ecology of the their and University of",
    url = "https://doi.org/10.1890/0012-9623-95.1.59",
    doi = "10.1890/0012-9623-95.1.59",
    openalex = "W2025030839",
    references = "doi1018900012962393135, doi10189000129623932125, doi1018900012962394136"
}

Octopus, squid, cuttlefish, and other cephalopods exhibit exceptional capabilities for visually adapting to or differentiating from the coloration and texture of their surroundings, for the purpose of concealment, communication, predation, and reproduction. Long-standing interest in and emerging understanding of the underlying ultrastructure, physiological control, and photonic interactions has recently led to efforts in the construction of artificial systems that have key attributes found in the skins of these organisms. Despite several promising options in active materials for mimicking biological color tuning, existing routes to integrated systems do not include critical capabilities in distributed sensing and actuation. Research described here represents progress in this direction, demonstrated through the construction, experimental study, and computational modeling of materials, device elements, and integration schemes for cephalopod-inspired flexible sheets that can autonomously sense and adapt to the coloration of their surroundings. These systems combine high-performance, multiplexed arrays of actuators and photodetectors in laminated, multilayer configurations on flexible substrates, with overlaid arrangements of pixelated, color-changing elements. The concepts provide realistic routes to thin sheets that can be conformally wrapped onto solid objects to modulate their visual appearance, with potential relevance to consumer, industrial, and military applications.

@article{doi101073pnas1410494111,
    author = "Yu, Cunjiang and Li, Yuhang and Zhang, Xun and Huang, Xian and Malyarchuk, Viktor and Wang, Shuodao and Shi, Yan and Gao, Li and Su, Yewang and Zhang, Yihui and Xu, Hangxun and Hanlon, Roger T. and Huang, Yonggang and Rogers, John A.",
    title = "Adaptive optoelectronic camouflage systems with designs inspired by cephalopod skins",
    year = "2014",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Octopus, squid, cuttlefish, and other cephalopods exhibit exceptional capabilities for visually adapting to or differentiating from the coloration and texture of their surroundings, for the purpose of concealment, communication, predation, and reproduction. Long-standing interest in and emerging understanding of the underlying ultrastructure, physiological control, and photonic interactions has recently led to efforts in the construction of artificial systems that have key attributes found in the skins of these organisms. Despite several promising options in active materials for mimicking biological color tuning, existing routes to integrated systems do not include critical capabilities in distributed sensing and actuation. Research described here represents progress in this direction, demonstrated through the construction, experimental study, and computational modeling of materials, device elements, and integration schemes for cephalopod-inspired flexible sheets that can autonomously sense and adapt to the coloration of their surroundings. These systems combine high-performance, multiplexed arrays of actuators and photodetectors in laminated, multilayer configurations on flexible substrates, with overlaid arrangements of pixelated, color-changing elements. The concepts provide realistic routes to thin sheets that can be conformally wrapped onto solid objects to modulate their visual appearance, with potential relevance to consumer, industrial, and military applications.",
    url = "https://doi.org/10.1073/pnas.1410494111",
    doi = "10.1073/pnas.1410494111",
    openalex = "W2110230545",
    references = "doi101016jcub200703034, doi10103828349, doi101038nature01941, doi101038nature03932, doi101038nmat1588, doi101038nmat3711, doi101038nmat712, doi101038nphoton2009141, doi101098rstb19880087, doi101098rstb20080270, doi101126science1222149, doi101201b18971"
}

Animal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong, the adaptive role of these sequences seems clear (e.g. mate attraction and territorial defence). More often however, researchers have only begun to characterise - let alone understand - the significance and meaning of acoustic sequences. Hypotheses abound, but there is little agreement as to how sequences should be defined and analysed. Our review aims to outline suitable methods for testing these hypotheses, and to describe the major limitations to our current and near-future knowledge on questions of acoustic sequences. This review and prospectus is the result of a collaborative effort between 43 scientists from the fields of animal behaviour, ecology and evolution, signal processing, machine learning, quantitative linguistics, and information theory, who gathered for a 2013 workshop entitled, 'Analysing vocal sequences in animals'. Our goal is to present not just a review of the state of the art, but to propose a methodological framework that summarises what we suggest are the best practices for research in this field, across taxa and across disciplines. We also provide a tutorial-style introduction to some of the most promising algorithmic approaches for analysing sequences. We divide our review into three sections: identifying the distinct units of an acoustic sequence, describing the different ways that information can be contained within a sequence, and analysing the structure of that sequence. Each of these sections is further subdivided to address the key questions and approaches in that area. We propose a uniform, systematic, and comprehensive approach to studying sequences, with the goal of clarifying research terms used in different fields, and facilitating collaboration and comparative studies. Allowing greater interdisciplinary collaboration will facilitate the investigation of many important questions in the evolution of communication and sociality.

@article{doi101111brv12160,
    author = "Kershenbaum, Arik and Blumstein, Daniel T. and Roch, Marie A. and Akçay, Çağlar and Backus, Gregory A. and Bee, Mark A. and Bohn, Kirsten M. and Cao, Yan and Carter, Gerald G. and Cäsar, Cristiane and Coen, Michael H. and DeRuiter, Stacy L. and Doyle, Laurance R. and Edelman, Shimon and Ferrer‐i‐Cancho, Ramon and Freeberg, Todd M. and Garland, Ellen C. and Gustison, Morgan L. and Harley, Heidi E. and Huetz, Chloé and Hughes, Melissa and Bruno, Julia Hyland and Ilany, Amiyaal and Jin, Dezhe Z. and Johnson, Michael T. and Ju, Chenghui and Karnowski, Jeremy and Lohr, Bernard and Manser, Marta B. and McCowan, Brenda and Mercado, Eduardo and Narins, Peter M. and Piel, A. and Rice, Megan G. and Salmi, Roberta and Sasahara, Kazutoshi and Sayigh, Laela S. and Shiu, Yu and Taylor, Charles and Vallejo, Edgar E. and Waller, Sara and Zamora‐Gutierrez, Veronica",
    title = "Acoustic sequences in non‐human animals: a tutorial review and prospectus",
    year = "2014",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Animal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong, the adaptive role of these sequences seems clear (e.g. mate attraction and territorial defence). More often however, researchers have only begun to characterise - let alone understand - the significance and meaning of acoustic sequences. Hypotheses abound, but there is little agreement as to how sequences should be defined and analysed. Our review aims to outline suitable methods for testing these hypotheses, and to describe the major limitations to our current and near-future knowledge on questions of acoustic sequences. This review and prospectus is the result of a collaborative effort between 43 scientists from the fields of animal behaviour, ecology and evolution, signal processing, machine learning, quantitative linguistics, and information theory, who gathered for a 2013 workshop entitled, 'Analysing vocal sequences in animals'. Our goal is to present not just a review of the state of the art, but to propose a methodological framework that summarises what we suggest are the best practices for research in this field, across taxa and across disciplines. We also provide a tutorial-style introduction to some of the most promising algorithmic approaches for analysing sequences. We divide our review into three sections: identifying the distinct units of an acoustic sequence, describing the different ways that information can be contained within a sequence, and analysing the structure of that sequence. Each of these sections is further subdivided to address the key questions and approaches in that area. We propose a uniform, systematic, and comprehensive approach to studying sequences, with the goal of clarifying research terms used in different fields, and facilitating collaboration and comparative studies. Allowing greater interdisciplinary collaboration will facilitate the investigation of many important questions in the evolution of communication and sociality.",
    url = "https://doi.org/10.1111/brv.12160",
    doi = "10.1111/brv.12160",
    openalex = "W1514601846",
    references = "doi101007bf00132234, doi101007s0026500408657"
}

Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases, signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the interplay between relevant visual signals remains little explored. Here, we address this question in the aposematic passion-vine butterfly Heliconius erato by using color- and pattern-manipulated models to test the contributions of different visual features to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was correlated with its effectiveness at inducing mating behavior, and in both cases wing color was more predictive of presumptive fitness benefits than wing pattern. Overall, however, a combination of the natural (local) color and pattern was most successful for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern composition in predation and mate preference studies, we have shown how both natural and sexual selection may work in parallel to drive the evolution of specific animal color patterns.

@article{doi101111evo12524,
    author = "Finkbeiner, Susan D. and Briscoe, Adriana D. and Reed, Robert D.",
    title = "Warning signals are seductive: Relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies",
    year = "2014",
    journal = "Evolution",
    abstract = "Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases, signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the interplay between relevant visual signals remains little explored. Here, we address this question in the aposematic passion-vine butterfly Heliconius erato by using color- and pattern-manipulated models to test the contributions of different visual features to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was correlated with its effectiveness at inducing mating behavior, and in both cases wing color was more predictive of presumptive fitness benefits than wing pattern. Overall, however, a combination of the natural (local) color and pattern was most successful for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern composition in predation and mate preference studies, we have shown how both natural and sexual selection may work in parallel to drive the evolution of specific animal color patterns.",
    url = "https://doi.org/10.1111/evo.12524",
    doi = "10.1111/evo.12524",
    openalex = "W1873020453",
    references = "doi101007s1088600692078, doi1010160022519375901113, doi101017cbo9781139087759, doi10108000031305199810480559, doi10108001621459199510476572, doi101086285308, doi101098rspb20111932, doi1018637jssv027i08, doi1023071437762, doi1023072965438, openalexw68436435"
}

Adaptive camouflage in thermal imaging, a form of cloaking technology capable of blending naturally into the surrounding environment, has been a great challenge in the past decades. Emissivity engineering for thermal camouflage is regarded as a more promising way compared to merely temperature controlling that has to dissipate a large amount of excessive heat. However, practical devices with an active modulation of emissivity have yet to be well explored. In this letter we demonstrate an active cloaking device capable of efficient thermal radiance control, which consists of a vanadium dioxide (VO2) layer, with a negative differential thermal emissivity, coated on a graphene/carbon nanotube (CNT) thin film. A slight joule heating drastically changes the emissivity of the device, achieving rapid switchable thermal camouflage with a low power consumption and excellent reliability. It is believed that this device will find wide applications not only in artificial systems for infrared camouflage or cloaking but also in energy-saving smart windows and thermo-optical modulators.

@article{doi101021acsnanolett5b04090,
    author = "Xiao, Lin and Ma, He and Liu, Junku and Zhao, Wei and Jia, Yi and Zhao, Qiang and Liu, Kai and Wu, Yang and Wei, Yang and Fan, Shoushan and Jiang, Kaili",
    title = "Fast Adaptive Thermal Camouflage Based on Flexible VO 2 /Graphene/CNT Thin Films",
    year = "2015",
    journal = "Nano Letters",
    abstract = "Adaptive camouflage in thermal imaging, a form of cloaking technology capable of blending naturally into the surrounding environment, has been a great challenge in the past decades. Emissivity engineering for thermal camouflage is regarded as a more promising way compared to merely temperature controlling that has to dissipate a large amount of excessive heat. However, practical devices with an active modulation of emissivity have yet to be well explored. In this letter we demonstrate an active cloaking device capable of efficient thermal radiance control, which consists of a vanadium dioxide (VO2) layer, with a negative differential thermal emissivity, coated on a graphene/carbon nanotube (CNT) thin film. A slight joule heating drastically changes the emissivity of the device, achieving rapid switchable thermal camouflage with a low power consumption and excellent reliability. It is believed that this device will find wide applications not only in artificial systems for infrared camouflage or cloaking but also in energy-saving smart windows and thermo-optical modulators.",
    url = "https://doi.org/10.1021/acs.nanolett.5b04090",
    doi = "10.1021/acs.nanolett.5b04090",
    openalex = "W2180194198",
    references = "doi101002adma201003989, doi101016jcub200703034, doi101021nl802750z, doi101021nn404061g, doi101038146144a0, doi101103physrevlett171286, doi101103physrevlett334, doi101103revmodphys701039, doi101126science1150124, doi1023074068693, doi105962bhltitle69899"
}

The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.

@article{doi101086681021,
    author = "Kemp, Darrell J. and Herberstein, Marie E. and Fleishman, Leo J. and Endler, John A. and Bennett, Andrew T. D. and Dyer, Adrian G. and Hart, Nathan S. and Marshall, N. Justin and Whiting, Martin J.",
    title = "An Integrative Framework for the Appraisal of Coloration in Nature",
    year = "2015",
    journal = "The American Naturalist",
    abstract = "The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.",
    url = "https://doi.org/10.1086/681021",
    doi = "10.1086/681021",
    openalex = "W2024579982",
    references = "doi101098rspb20053156"
}

Anthropogenic sensory pollution is affecting ecosystems worldwide. Human actions generate acoustic noise, emanate artificial light and emit chemical substances. All of these pollutants are known to affect animals. Most studies on anthropogenic pollution address the impact of pollutants in unimodal sensory domains. High levels of anthropogenic noise, for example, have been shown to interfere with acoustic signals and cues. However, animals rely on multiple senses, and pollutants often co-occur. Thus, a full ecological assessment of the impact of anthropogenic activities requires a multimodal approach. We describe how sensory pollutants can co-occur and how covariance among pollutants may differ from natural situations. We review how animals combine information that arrives at their sensory systems through different modalities and outline how sensory conditions can interfere with multimodal perception. Finally, we describe how sensory pollutants can affect the perception, behaviour and endocrinology of animals within and across sensory modalities. We conclude that sensory pollution can affect animals in complex ways due to interactions among sensory stimuli, neural processing and behavioural and endocrinal feedback. We call for more empirical data on covariance among sensory conditions, for instance, data on correlated levels in noise and light pollution. Furthermore, we encourage researchers to test animal responses to a full-factorial set of sensory pollutants in the presence or the absence of ecologically important signals and cues. We realize that such approach is often time and energy consuming, but we think this is the only way to fully understand the multimodal impact of sensory pollution on animal performance and perception.

@article{doi101098rsbl20141051,
    author = "Halfwerk, Wouter and Slabbekoorn, Hans",
    title = "Pollution going multimodal: the complex impact of the human-altered sensory environment on animal perception and performance",
    year = "2015",
    journal = "Biology Letters",
    abstract = "Anthropogenic sensory pollution is affecting ecosystems worldwide. Human actions generate acoustic noise, emanate artificial light and emit chemical substances. All of these pollutants are known to affect animals. Most studies on anthropogenic pollution address the impact of pollutants in unimodal sensory domains. High levels of anthropogenic noise, for example, have been shown to interfere with acoustic signals and cues. However, animals rely on multiple senses, and pollutants often co-occur. Thus, a full ecological assessment of the impact of anthropogenic activities requires a multimodal approach. We describe how sensory pollutants can co-occur and how covariance among pollutants may differ from natural situations. We review how animals combine information that arrives at their sensory systems through different modalities and outline how sensory conditions can interfere with multimodal perception. Finally, we describe how sensory pollutants can affect the perception, behaviour and endocrinology of animals within and across sensory modalities. We conclude that sensory pollution can affect animals in complex ways due to interactions among sensory stimuli, neural processing and behavioural and endocrinal feedback. We call for more empirical data on covariance among sensory conditions, for instance, data on correlated levels in noise and light pollution. Furthermore, we encourage researchers to test animal responses to a full-factorial set of sensory pollutants in the presence or the absence of ecologically important signals and cues. We realize that such approach is often time and energy consuming, but we think this is the only way to fully understand the multimodal impact of sensory pollution on animal performance and perception.",
    url = "https://doi.org/10.1098/rsbl.2014.1051",
    doi = "10.1098/rsbl.2014.1051",
    openalex = "W2104041404",
    references = "doi101007s0026500408657"
}

Modern population ecology began during the period 1860 to the 1920s, along with early formal development of animal ecology (Kingsland 1985:9–112, Price 2003:9–13, Egerton 2014a). Population ecology advanced on three fronts, sometimes linked: field studies, laboratory studies, and mathematical–theoretical studies (Cole 1954:106, 1958:6). It seems desirable to briefly treat here two special cases: invasive species and rare and extinct species, with bibliographic guides at these topics. There is helpful literature on the history of population ecology; yet its authors were often unaware of each other's contributions. William Thompson wrote a 26-page historical introduction to his “Biological Control and the Theories of the Interactions of Populations” (1939:301–327). Thomas Park's “Some Observations on the History and Scope of Population Ecology” (1946) has such general comments it has limited current interest. LaMont Cole (1954:105–117, 1958:2–11) set an excellent example by surveying the history of human and animal demography, observational and mathematical. David Lack's Natural Regulation of Animal Numbers (1954) encompassed animals in general; although his Population Studies of Birds (1966) in its Animal animals in Egerton has on animal to in Egerton of in Population Ecology” is a historical and History of Ecology” an on the history of and and were in population to a and history of population to Population began with a historical and historical comments and the and it in an of his the population a Population Regulation and and of two by and by were the in Population is a Thompson Cole and and and to the is of a bibliographic to ecology history a of of and has a a bibliographic and on of and wrote in the population studies in and Egerton and and in and and an to and in of of on a of his the history of and of each on and Population is an Thompson the by and by is a in the historical and and a in history of on population studies, the David and is is the in and and and history of population ecology to is briefly by Cole (1954:105–117, in by Egerton by and is the of the of population ecology in a and the of is the of of it a and in the early to the were the and were in of the species on to and to such early the of of and species of at the the the of the in in and and his with the of his and in with to these to a to were an in at the at to the of a of the in the the and an to and of to and in a on and a the were and the were of often sometimes the were a to population the three by a on by of and at the and at on the population of a and its a period of three in a it of It is to a in often in his laboratory and in his and the of three with in the a in of to in population in to to and to a by in his wrote in of the of the and and of in and Egerton in an of the the it of and the to the and of a of the and of the of and a the of in two and to a of the of the to a the and the in Population Regulation is and in the of a in population at a of three of the of to and in it in a the and in Egerton on and Egerton with studies on were studies on human the population of a of the in began to and species to a of on of the population studies of human in of in of the and in were to the of the on began in in were the to and in the to and a with the of to a began with in the and his of on and a of and the of the of to to human the a to human population (Kingsland unaware the the in three a and his the of of the Population of the and of population a the to the to his a a of (Kingsland of and a and a of population (Kingsland of the 1920s, animal were in and two and in and of to animal population and to his laboratory two wrote of in population by the of his the of the of his population studies in with in is in two a of and of and the in a the the to the in and wrote a to with a of the a to and in the of were by wrote to and to and three and wrote his in and in wrote his in and the a of his at the of a in by it on the a in to and a William William and the of of and with began with a and in with of three of the population with were and and two of by wrote to wrote on a in early and a to in and by to a by on and to on animals interest. with his a of a and and by wrote in and of and in and with of in to the of and the of and formal the an the and a the in population two of to with in and a with in a general in in and his in population Population is an on the a general of his an of population an excellent of and the of population in the 1920s, a of ecology in to by and wrote to to to (Kingsland a the to to with of his a of in the and a to the species and in in the field of and to the of the and it it to these in the and to in the general in of and and in in an with a seems to of a of wrote to of his and of and and the of two species the to the of species at the of to in in of the and by and by it such in the population and special the a in with the on the two species a in the with the of species with the of the of It is to in in at an of the of a and of in in it to in the to in it to to a and in William Thompson and were to and Thompson his at the of at the and in the to to a to and to to to the to and the and an in a to and studies of and a an and his at Thompson in and in of a at and Thompson to to the to and the and to of the of in and Thompson wrote to is in and wrote in in his Thompson a of of his and in a of in his and his of were were and Thompson a of and to in a on Thompson wrote to a of Thompson a of his and his at the of a in “Biological Control and the Theories of the Interactions of Populations” with a historical with and his and of field is and is a to its and to it a of in a and an of by (Kingsland and of and of Thompson in of and were and and of were population and a and Price is at and at William his and at his and his at to the of a and an ecology at and field his of two of a to wrote to on his and to his and his and to wrote and wrote on and of population in in his of and a yet wrote of a is in and is a of in with a species, and the of the two species the and Animal 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the to and in and these to a the of of It the of of the and is to the of the by a and with of and in and is with and is by a a and of on the the to the the to to were these and of the by the early in these species of by the in in to and were in and in is in species is the is has two on during the a and of on an History is an the of human of the in is to on these is to and of a of and of on the to species to to of a of Animal population ecology a development of it a history history began with of by and is a historical literature its and began in the and the and on the population of two invasive in and population the 1920s, and in and in began to of population and a of in a and and of and were to in his of and were and in a (1954) the of of and Population ecology in with studies by by by by and and by and of a a on animal and human demography, in a of of by and and Price the of population ecology during the and the a of and were and by the a history with and by population in three in by 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@article{doi10189000129623964560,
    author = "Egerton, Frank N.",
    title = "History of Ecological Sciences, Part 55: Animal Population Ecology",
    year = "2015",
    journal = "Bulletin of the Ecological Society of America",
    abstract = "Modern population ecology began during the period 1860 to the 1920s, along with early formal development of animal ecology (Kingsland 1985:9–112, Price 2003:9–13, Egerton 2014a). Population ecology advanced on three fronts, sometimes linked: field studies, laboratory studies, and mathematical–theoretical studies (Cole 1954:106, 1958:6). It seems desirable to briefly treat here two special cases: invasive species and rare and extinct species, with bibliographic guides at these topics. There is helpful literature on the history of population ecology; yet its authors were often unaware of each other's contributions. William Thompson wrote a 26-page historical introduction to his “Biological Control and the Theories of the Interactions of Populations” (1939:301–327). Thomas Park's “Some Observations on the History and Scope of Population Ecology” (1946) has such general comments it has limited current interest. LaMont Cole (1954:105–117, 1958:2–11) set an excellent example by surveying the history of human and animal demography, observational and mathematical. David Lack's Natural Regulation of Animal Numbers (1954) encompassed animals in general; although his Population Studies of Birds (1966) in its Animal animals in Egerton has on animal to in Egerton of in Population Ecology” is a historical and History of Ecology” an on the history of and and were in population to a and history of population to Population began with a historical and historical comments and the and it in an of his the population a Population Regulation and and of two by and by were the in Population is a Thompson Cole and and and to the is of a bibliographic to ecology history a of of and has a a bibliographic and on of and wrote in the population studies in and Egerton and and in and and an to and in of of on a of his the history of and of each on and Population is an Thompson the by and by is a in the historical and and a in history of on population studies, the David and is is the in and and and history of population ecology to is briefly by Cole (1954:105–117, in by Egerton by and is the of the of population ecology in a and the of is the of of it a and in the early to the were the and were in of the species on to and to such early the of of and species of at the the the of the in in and and his with the of his and in with to these to a to were an in at the at to the of a of the in the the and an to and of to and in a on and a the were and the were of often sometimes the were a to population the three by a on by of and at the and at on the population of a and its a period of three in a it of It is to a in often in his laboratory and in his and the of three with in the a in of to in population in to to and to a by in his wrote in of the of the and and of in and Egerton in an of the the it of and the to the and of a of the and of the of and a the of in two and to a of the of the to a the and the in Population Regulation is and in the of a in population at a of three of the of to and in it in a the and in Egerton on and Egerton with studies on were studies on human the population of a of the in began to and species to a of on of the population studies of human in of in of the and in were to the of the on began in in were the to and in the to and a with the of to a began with in the and his of on and a of and the of the of to to human the a to human population (Kingsland unaware the the in three a and his the of of the Population of the and of population a the to the to his a a of (Kingsland of and a and a of population (Kingsland of the 1920s, animal were in and two and in and of to animal population and to his laboratory two wrote of in population by the of his the of the of his population studies in with in is in two a of and of and the in a the the to the in and wrote a to with a of the a to and in the of were by wrote to and to and three and wrote his in and in wrote his in and the a of his at the of a in by it on the a in to and a William William and the of of and with began with a and in with of three of the population with were and and two of by wrote to wrote on a in early and a to in and by to a by on and to on animals interest. with his a of a and and by wrote in and of and in and with of in to the of and the of and formal the an the and a the in population two of to with in and a with in a general in in and his in population Population is an on the a general of his an of population an excellent of and the of population in the 1920s, a of ecology in to by and wrote to to to (Kingsland a the to to with of his a of in the and a to the species and in in the field of and to the of the and it it to these in the and to in the general in of and and in in an with a seems to of a of wrote to of his and of and and the of two species the to the of species at the of to in in of the and by and by it such in the population and special the a in with the on the two species a in the with the of species with the of the of It is to in in at an of the of a and of in in it to in the to in it to to a and in William Thompson and were to and Thompson his at the of at the and in the to to a to and to to to the to and the and an in a to and studies of and a an and his at Thompson in and in of a at and Thompson to to the to and the and to of the of in and Thompson wrote to is in and wrote in in his Thompson a of of his and in a of in his and his of were were and Thompson a of and to in a on Thompson wrote to a of Thompson a of his and his at the of a in “Biological Control and the Theories of the Interactions of Populations” with a historical with and his and of field is and is a to its and to it a of in a and an of by (Kingsland and of and of Thompson in of and were and and of were population and a and Price is at and at William his and at his and his at to the of a and an ecology at and field his of two of a to wrote to on his and to his and his and to wrote and wrote on and of population in in his of and a yet wrote of a is in and is a of in with a species, and the of the two species the and Animal with to an an of a by and of the of in animal species and the to an of to an and and unaware of its in to to and the and in the during a to and a on at the of and the an in the in of a species its and (Kingsland the of the and and and an of population and and its of Animal is the on population the in special it to a of population although his and has his and with of and a with the of Animal Populations” and the the the the of and to of at by a species its population and its population his of the of the in in his his of such the of a in it in the and with a population by the his and by an of population the of and of on the of and the the to the to an of a to were in in a with the and to each began animal a of to in a to a and to and two the of of Animal in and began on and his and the to to to and and species in species by and and an on population and (1954) each has of an it the Price the such a of an literature at and at and the of animal ecology in three to of and of two with the of a of a by it animals and Egerton in the Numbers of and in to example of in to the and and the were of the the the period is with the and in of with population field on an with during the animal ecology in two on population ecology and the of to its and to its of to the an population on in his and in Population field in and on the population of species in the Animal were to population by and of of David on each were and of with Egerton the in of in of population and his of Animal and in three at the of an of of Animal a Animal and animal to on Regulation of in the of and has in Egerton his the of and of and to the of in the on in the and the of the a to a of Animal Population at in of the is to of in of with special to and in at to to it in his of its in the to its of Animal with of Animal Population of the the of animal of and it to a (Kingsland a of his on the and in and wrote the of to in two and to to laboratory and to on (Kingsland the in and wrote to a in the and a on each at it in to of and in Population the and his and during It and a to is on historical and the on in of and in and in and and on in and a along with his to to his David a of a and a to on and in the Natural History field Lack's in and a interest. the with Birds of on and species the of the by the the of with on of and of David David his and at by of the and in during the of two on a and a a Birds of a at of his an in to a on at to to a to the in were the a a to the and with with it a to the of the of at It a of and an it the and in were to a a Lack's on a his on the species of of and Lack's of Lack's of Animal in his ecology and the of in of the Lack's Natural Regulation of Animal Numbers (1954) and wrote two the in of and on population and Price a of and Thompson the of a of population in the and of population Thompson to and of his and a with a on population in studies, and to the of of and to There to his in a Price and development of the were to were of human to set a animal population studies, and Thomas and of and of of Animal species in at two at Thomas laboratory at the of the of Thomas Park's Thomas the in population ecology and and Park's studies of of the and it studies of Price of in population ecology in the and in the these studies three and and and to two by Cole and two by these studies the the of in a of to his Natural Regulation of Animal Numbers of the population and at by in a of an during the and a and in of each species, is in the of to his in animals the the in an the and and in species, is in a to in his Population Studies of Birds of an on Animal an on his of and to such the is a the general of in to the of and it to the of the of and its of in Populations” on of to and and of the of Animal Populations” a his by and his and and to by Thompson and of his with a in and of Price and and a of to to Lack's and population and were in and and in to and a of animal LaMont Cole his and at the of at the of Population of History and and Cole of Natural of 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the in a at a of the of on were with the in and introduction to the and the history of population studies to population and of and History of the of the of the to Population of the of of of by in on at the in of in and the on to of in his were of population and each of and of to each and to the of three to on to these and the of and the of an were the the and were and of at the of in and by the and to an and in the a in in is the of each to a of three with each by and and of the of in the and in to a of wrote two the of the in the and in and the with these to in the of during the to the the of the three and the of in of the of the and early a in population William a of in Population and wrote a Population a Population Population Control on animal and human Natural Regulation of Animal and the of two of and the at the on of Numbers in at an and and and a by an of and and an of at of the of and in wrote his to Population two of his on his and the of his Animal Population and of his historical and it population to It and the in the and his a and and of the on general the studies of the is is a of is to to the of by to in and to it on on by and a on ecology a the of to population a and the of and a and with the of population and population with the of ecology is it is and the by and in in with a and is of the of and is to the of his on the population and the of his on ecology during the of and these at the on in the of the of the at the the the to the development of a of and and the of on population in set a of a of a animal species, began in during a period in of in the to an in to on in a in to and and of of in an animal and population the in a in his to a at on his at Lack's on his a on and Lack's to it in at on and a with a on a at Lack's the a and the of the and of and his to to his Population of of the his species on and and field on of Birds has by the at of his of and in Population in Birds and of his and in of Birds and and wrote in and during the (Kingsland laboratory in of a an of at the in to There is of on in and were on its and the population in the population to and a in of the a in were in were in a a of a a in the of the and and a to to a and the at a with in and and two his David in and in the of his in ecology at in a the at in and of in by and of of on the a in and a in ecology with a on and of of and on the Population of and of and on Population of and is the is and the of to a of the has on and an and of the of on the of to the of the on and of the population to with the at the early to an of to an to to the of a a and a it of the in the such and and on to a on to it to at a the it the to the to in sometimes and were three in the and population and the of of a species in a of interest. the in on in population by an population of the of ecology in the with the of on the population of of the a of in population of the on history to began to were and each other's William of in a Regulation in and were in in and and its to the of in a and to a to laboratory and studies to briefly of the history of population ecology and of population by often at these of the of the of population is the of by a in the the to of a to to and his Population population ecology a of population and an at his at the and the in population by and a of population by it by a the of and population of of population of on is an on in population the of on a of to species during the and early were in the were and were these the of the its and of by and the and and a a on and of and a in on (1966) in in in in and and Animal the of in and and with a Natural History of in in in the in the in in in and in the and a in and example of in of a by and and the to to these such by a of a in has a of an of the on of It is a species with limited in by is an of and at along the of the and the of in the to during the were to is a a an introduction of the and and in the Natural History of a such a of in the it in the a is with an and extinct and species and in a the and and and on with on and and on (1966) on on on on the and on and in these studies is the population of species human to a early example the the of of the in and extinct by and a species by species and the general of the and of the of the of by on to species in and the of during the by the species on the to with the at the in often to and in the early were species to by in studies on and Egerton a to and to and the is the extinct the rare extinct and by and extinct and the at the of the has with William were were in the in at the on in and and to early two at and to the a to to in to species, with the of to the in is David his on a of in on and on animal in were and were to It a and to the in and in the David the of of in with David to and in the in the to by and animals of a It three it rare and at to and were to were each in is the of of and in the the of the is and the population of rare species in the of it were of species with and wrote an It is of a rare the to and in and these to a the of of It the of of the and is to the of the by a and with of and in and is with and is by a a and of on the the to the the to to were these and of the by the early in these species of by the in in to and were in and in is in species is the is has two on during the a and of on an History is an the of human of the in is to on these is to and of a of and of on the to species to to of a of Animal population ecology a development of it a history history began with of by and is a historical literature its and began in the and the and on the population of two invasive in and population the 1920s, and in and in began to of population and a of in a and and of and were to in his of and were and in a (1954) the of of and Population ecology in with studies by by by by and and by and of a a on animal and human demography, in a of of by and and Price the of population ecology during the and the a of and were and by the a history with and by population in three in by by and by and were in an limited in were Animal population ecology of field and laboratory studies on the of species and of species and rare species often population of the helpful of and",
    url = "https://doi.org/10.1890/0012-9623-96.4.560",
    doi = "10.1890/0012-9623-96.4.560",
    openalex = "W2190647748",
    references = "doi1018900012962394136"
}

In the past decade there has been increased interest in research on color and psychological functioning. Important advances have been made in theoretical work and empirical work, but there are also important weaknesses in both areas that must be addressed for the literature to continue to develop apace. In this article, I provide brief theoretical and empirical reviews of research in this area, in each instance beginning with a historical background and recent advancements, and proceeding to an evaluation focused on weaknesses that provide guidelines for future research. I conclude by reiterating that the literature on color and psychological functioning is at a nascent stage of development, and by recommending patience and prudence regarding conclusions about theory, findings, and real-world application.

@article{doi103389fpsyg201500368,
    author = "Elliot, Andrew J.",
    title = "Color and psychological functioning: a review of theoretical and empirical work",
    year = "2015",
    journal = "Frontiers in Psychology",
    abstract = "In the past decade there has been increased interest in research on color and psychological functioning. Important advances have been made in theoretical work and empirical work, but there are also important weaknesses in both areas that must be addressed for the literature to continue to develop apace. In this article, I provide brief theoretical and empirical reviews of research in this area, in each instance beginning with a historical background and recent advancements, and proceeding to an evaluation focused on weaknesses that provide guidelines for future research. I conclude by reiterating that the literature on color and psychological functioning is at a nascent stage of development, and by recommending patience and prudence regarding conclusions about theory, findings, and real-world application.",
    url = "https://doi.org/10.3389/fpsyg.2015.00368",
    doi = "10.3389/fpsyg.2015.00368",
    openalex = "W2013475641",
    references = "doi101146annurevpsych010213115035"
}

The fundamental unit of rapid, physiological color change in vertebrates is the dermal chromatophore unit. This unit, comprised of cellular associations between different chromatophore types, is relatively conserved across the fish, amphibian, and reptilian species capable of physiological color change and numerous attempts have been made to understand the nature of the four major chromatophore types (melanophores, erythrophores, xanthophores, and iridophores) and their biochemical regulation. In this review, we attempt to describe the current state of knowledge regarding what classifies a pigment cell as a dynamic chromatophore, the unique characteristics of each chromatophore type, and how different hormones, neurotransmitters, or other signals direct pigment reorganization in a variety of vertebrate taxa.

@article{doi101093czzow051,
    author = "Ligon, Russell A. and McCartney, Kristen L",
    title = "Biochemical regulation of pigment motility in vertebrate chromatophores: a review of physiological color change mechanisms",
    year = "2016",
    journal = "Current Zoology",
    abstract = "The fundamental unit of rapid, physiological color change in vertebrates is the dermal chromatophore unit. This unit, comprised of cellular associations between different chromatophore types, is relatively conserved across the fish, amphibian, and reptilian species capable of physiological color change and numerous attempts have been made to understand the nature of the four major chromatophore types (melanophores, erythrophores, xanthophores, and iridophores) and their biochemical regulation. In this review, we attempt to describe the current state of knowledge regarding what classifies a pigment cell as a dynamic chromatophore, the unique characteristics of each chromatophore type, and how different hormones, neurotransmitters, or other signals direct pigment reorganization in a variety of vertebrate taxa.",
    url = "https://doi.org/10.1093/cz/zow051",
    doi = "10.1093/cz/zow051",
    openalex = "W2401730015",
    references = "doi101111pcmr12040"
}

The process of adaptive radiation—the proliferation of species from a single ancestor and diversification into many ecologically different forms—has been of great interest to evolutionary biologists since Darwin. Since the middle of the last century, ecological opportunity has been invoked as a potential key to understanding when and how adaptive radiation occurs. Interest in the topic of ecological opportunity has accelerated as research on adaptive radiation has experienced a resurgence, fueled in part by advances in phylogenetic approaches to studying evolutionary diversification. Nonetheless, what the term actually means, much less how it mechanistically leads to adaptive diversification, is currently debated; whether the term has any predictive value or is a heuristic useful only for post hoc explanation also remains unclear. Recent recognition that evolutionary change can occur rapidly and on a timescale commensurate with ecological processes suggests that it is time to synthesize ecological and evolutionary approaches to the study of community assembly and evolutionary diversification.

@article{doi101146annurevecolsys121415032254,
    author = "Stroud, James T. and Losos, Jonathan B.",
    title = "Ecological Opportunity and Adaptive Radiation",
    year = "2016",
    journal = "Annual Review of Ecology Evolution and Systematics",
    abstract = "The process of adaptive radiation—the proliferation of species from a single ancestor and diversification into many ecologically different forms—has been of great interest to evolutionary biologists since Darwin. Since the middle of the last century, ecological opportunity has been invoked as a potential key to understanding when and how adaptive radiation occurs. Interest in the topic of ecological opportunity has accelerated as research on adaptive radiation has experienced a resurgence, fueled in part by advances in phylogenetic approaches to studying evolutionary diversification. Nonetheless, what the term actually means, much less how it mechanistically leads to adaptive diversification, is currently debated; whether the term has any predictive value or is a heuristic useful only for post hoc explanation also remains unclear. Recent recognition that evolutionary change can occur rapidly and on a timescale commensurate with ecological processes suggests that it is time to synthesize ecological and evolutionary approaches to the study of community assembly and evolutionary diversification.",
    url = "https://doi.org/10.1146/annurev-ecolsys-121415-032254",
    doi = "10.1146/annurev-ecolsys-121415-032254",
    openalex = "W2327977699",
    references = "doi101007978146124018114, doi101016jcub201311063, doi101016jearscirev201004001, doi101038nature13726, doi101038ncomms5087, doi101038ngeo1475, doi101073pnas1302642110, doi101086282505, doi101086284196, doi101093behecoart058, doi101093oso97801951223430010001, doi101093oso97801985052350010001, doi101093sysbiosyt050, doi101098rspb20080630, doi101111j14209101201002029x, doi101111j14698137200601864x, doi101111j155856461964tb01674x, doi101111j15585646200800317x, doi101111j15585646201001026x, doi101111nph13230, doi101126sciadv1400253, doi101126science1161833, doi101146annurevearth271463, doi101146annurevecolsys281129, doi101146annurevecolsys33010802150448, doi101146annurevecolsys39110707173447, doi101371journalpone0089543, doi1015159780691224244, doi1015159781400847266, doi1023072412953, doi1023073545850, doi104159harvard9780674865327, doi105860choice485062"
}

Abstract An effective approach to develop a novel macroscopic anisotropic bilayer hydrogel actuator with on–off switchable fluorescent color‐changing function is reported. Through combining a collapsed thermoresponsive graphene oxide‐poly(N ‐isopropylacrylamide) (GO‐PNIPAM) hydrogel layer with a pH‐responsive perylene bisimide‐functionalized hyperbranched polyethylenimine (PBI‐HPEI) hydrogel layer via macroscopic supramolecular assembly, a bilayer hydrogel is obtained that can be tailored and reswells to form a 3D hydrogel actuator. The actuator can undergo complex shape deformation caused by the PNIPAM outside layer, then the PBI‐HPEI hydrogel inside layer can be unfolded to trigger the on–off switch of the pH‐responsive fluorescence under the green light irradiation. This work will inspire the design and fabrication of novel biomimetic smart materials with synergistic functions.

@article{doi101002adfm201704568,
    author = "Ma, Chunxin and Lü, Wei and Yang, Xuxu and He, Jiang and Le, Xiaoxia and Wang, Li and Zhang, Jiawei and Serpe, Michael J. and Huang, Youju and Chen, Tao",
    title = "Bioinspired Anisotropic Hydrogel Actuators with On–Off Switchable and Color‐Tunable Fluorescence Behaviors",
    year = "2017",
    journal = "Advanced Functional Materials",
    abstract = "Abstract An effective approach to develop a novel macroscopic anisotropic bilayer hydrogel actuator with on–off switchable fluorescent color‐changing function is reported. Through combining a collapsed thermoresponsive graphene oxide‐poly(N ‐isopropylacrylamide) (GO‐PNIPAM) hydrogel layer with a pH‐responsive perylene bisimide‐functionalized hyperbranched polyethylenimine (PBI‐HPEI) hydrogel layer via macroscopic supramolecular assembly, a bilayer hydrogel is obtained that can be tailored and reswells to form a 3D hydrogel actuator. The actuator can undergo complex shape deformation caused by the PNIPAM outside layer, then the PBI‐HPEI hydrogel inside layer can be unfolded to trigger the on–off switch of the pH‐responsive fluorescence under the green light irradiation. This work will inspire the design and fabrication of novel biomimetic smart materials with synergistic functions.",
    url = "https://doi.org/10.1002/adfm.201704568",
    doi = "10.1002/adfm.201704568",
    openalex = "W2773783903",
    references = "doi101038ncomms7368"
}

The fabrication of responsive photonic structures from cellulose nanocrystals (CNCs) that can operate in the entire visible spectrum is challenging due to the requirements of precise periodic modulation of the pitch size of the self-assembled multilayer structures at the length scale within the wavelength of the visible light. The surface charge density of CNCs is an important factor in controlling the pitch size of the chiral nematic structure of the dried solid CNC films. The assembly of poly(ethylene glycol) (PEG) together with CNCs into smaller chiral nematic domains results in solid films with uniform helical structure upon slow drying. Large, flexible, and flat photonic composite films with uniform structure colors from blue to red are prepared by changing the composition of CNCs and PEG. The CNC/PEG(80/20) composite film demonstrates a reversible and smooth structural color change between green and transparent in response to an increase and decrease of relative humidity between 50% and 100% owing to the reversible swelling and dehydration of the chiral nematic structure. The composite also shows excellent mechanical and thermal properties, complementing the multifunctional property profile.

@article{doi101002adma201701323,
    author = "Yao, Kun and Meng, Qijun and Bulone, Vincent and Zhou, Qi",
    title = "Flexible and Responsive Chiral Nematic Cellulose Nanocrystal/Poly(ethylene glycol) Composite Films with Uniform and Tunable Structural Color",
    year = "2017",
    journal = "Advanced Materials",
    abstract = "The fabrication of responsive photonic structures from cellulose nanocrystals (CNCs) that can operate in the entire visible spectrum is challenging due to the requirements of precise periodic modulation of the pitch size of the self-assembled multilayer structures at the length scale within the wavelength of the visible light. The surface charge density of CNCs is an important factor in controlling the pitch size of the chiral nematic structure of the dried solid CNC films. The assembly of poly(ethylene glycol) (PEG) together with CNCs into smaller chiral nematic domains results in solid films with uniform helical structure upon slow drying. Large, flexible, and flat photonic composite films with uniform structure colors from blue to red are prepared by changing the composition of CNCs and PEG. The CNC/PEG(80/20) composite film demonstrates a reversible and smooth structural color change between green and transparent in response to an increase and decrease of relative humidity between 50\% and 100\% owing to the reversible swelling and dehydration of the chiral nematic structure. The composite also shows excellent mechanical and thermal properties, complementing the multifunctional property profile.",
    url = "https://doi.org/10.1002/adma.201701323",
    doi = "10.1002/adma.201701323",
    openalex = "W2619486586",
    references = "doi101039b717368g, doi101039c2cs15267c"
}

Bioinspired out-of-equilibrium systems will set the scene for the next generation of molecular materials with active, adaptive, autonomous, emergent and intelligent behavior. Indeed life provides the best demonstrations of complex and functional out-of-equilibrium systems: cells keep track of time, communicate, move, adapt, evolve and replicate continuously. Stirred by the understanding of biological principles, artificial out-of-equilibrium systems are emerging in many fields of soft matter science. Here we put in perspective the molecular mechanisms driving biological functions with the ones driving synthetic molecular systems. Focusing on principles that enable new levels of functionalities (temporal control, autonomous structures, motion and work generation, information processing) rather than on specific material classes, we outline key cross-disciplinary concepts that emerge in this challenging field. Ultimately, the goal is to inspire and support new generations of autonomous and adaptive molecular devices fueled by self-regulating chemistry.

@article{doi101039c6cs00738d,
    author = "Merindol, Rémi and Walther, Andreas",
    title = "Materials learning from life: concepts for active, adaptive and autonomous molecular systems",
    year = "2017",
    journal = "Chemical Society Reviews",
    abstract = "Bioinspired out-of-equilibrium systems will set the scene for the next generation of molecular materials with active, adaptive, autonomous, emergent and intelligent behavior. Indeed life provides the best demonstrations of complex and functional out-of-equilibrium systems: cells keep track of time, communicate, move, adapt, evolve and replicate continuously. Stirred by the understanding of biological principles, artificial out-of-equilibrium systems are emerging in many fields of soft matter science. Here we put in perspective the molecular mechanisms driving biological functions with the ones driving synthetic molecular systems. Focusing on principles that enable new levels of functionalities (temporal control, autonomous structures, motion and work generation, information processing) rather than on specific material classes, we outline key cross-disciplinary concepts that emerge in this challenging field. Ultimately, the goal is to inspire and support new generations of autonomous and adaptive molecular devices fueled by self-regulating chemistry.",
    url = "https://doi.org/10.1039/c6cs00738d",
    doi = "10.1039/c6cs00738d",
    openalex = "W2581826111",
    references = "doi101021acschemrev5b00344, doi101038nature11223, doi101038nchem2511"
}

This research demonstrates a visual phenomenon with broad implications for consumers: the perceived size of products depends on the saturation of their color. Results from six experiments, employing objects and products with various shapes and hues, show that increasing color saturation increases size perceptions. This influence is explained by the tendency for saturated color to capture attention, which, in turn, is explained by the arousal that saturated color stimulates. This research also demonstrates several downstream outcomes of the effect of saturation on size perceptions: evaluations are more favorable—and willingness to pay is higher—for products with high (low) saturation when usage goals call for large (small) size. Additionally, participants choose more of a product to fill a container with higher saturation. Further, the saturation of an object’s color affects the perceived size of its surroundings, such that when a product with high (vs. low) saturation is used as a benchmark, the environment is perceived to be comparatively smaller (vs. larger). Implications for aesthetics, design, sensory marketing, and related topics are discussed. Lastly, to aid future color research, appendix A outlines general challenges and recommendations in connection with the conceptualization, manipulation, and measurement of color.

@article{doi101093jcrucx039,
    author = "Hagtvedt, Henrik and Bräsel, Sylvia",
    title = "Color Saturation Increases Perceived Product Size",
    year = "2017",
    journal = "Journal of Consumer Research",
    abstract = "This research demonstrates a visual phenomenon with broad implications for consumers: the perceived size of products depends on the saturation of their color. Results from six experiments, employing objects and products with various shapes and hues, show that increasing color saturation increases size perceptions. This influence is explained by the tendency for saturated color to capture attention, which, in turn, is explained by the arousal that saturated color stimulates. This research also demonstrates several downstream outcomes of the effect of saturation on size perceptions: evaluations are more favorable—and willingness to pay is higher—for products with high (low) saturation when usage goals call for large (small) size. Additionally, participants choose more of a product to fill a container with higher saturation. Further, the saturation of an object’s color affects the perceived size of its surroundings, such that when a product with high (vs. low) saturation is used as a benchmark, the environment is perceived to be comparatively smaller (vs. larger). Implications for aesthetics, design, sensory marketing, and related topics are discussed. Lastly, to aid future color research, appendix A outlines general challenges and recommendations in connection with the conceptualization, manipulation, and measurement of color.",
    url = "https://doi.org/10.1093/jcr/ucx039",
    doi = "10.1093/jcr/ucx039",
    openalex = "W2582349261",
    references = "doi101146annurevpsych010213115035"
}

Animals from a wide range of taxonomic groups are capable of colour change, of which camouflage is one of the main functions. A considerable amount of past work on this subject has investigated species capable of extremely rapid colour change (in seconds). However, relatively slow colour change (over hours, days, weeks and months), as well as changes arising via developmental plasticity are probably more common than rapid changes, yet less studied. We discuss three key areas of colour change and camouflage. First, we review the mechanisms underpinning colour change and developmental plasticity for camouflage, including cellular processes, visual feedback, hormonal control and dietary factors. Second, we discuss the adaptive value of colour change for camouflage, including the use of different camouflage types. Third, we discuss the evolutionary-ecological implications of colour change for concealment, including what it can tell us about intraspecific colour diversity, morph-specific strategies, and matching to different environments and microhabitats. Throughout, we discuss key unresolved questions and present directions for future work, and highlight how colour change facilitates camouflage among habitats and arises when animals are faced with environmental changes occurring over a range of spatial and temporal scales.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.

@article{doi101098rstb20160342,
    author = "Duarte, Rafael C. and Flores, Augusto A. V. and Stevens, Martin",
    title = "Camouflage through colour change: mechanisms, adaptive value and ecological significance",
    year = "2017",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Animals from a wide range of taxonomic groups are capable of colour change, of which camouflage is one of the main functions. A considerable amount of past work on this subject has investigated species capable of extremely rapid colour change (in seconds). However, relatively slow colour change (over hours, days, weeks and months), as well as changes arising via developmental plasticity are probably more common than rapid changes, yet less studied. We discuss three key areas of colour change and camouflage. First, we review the mechanisms underpinning colour change and developmental plasticity for camouflage, including cellular processes, visual feedback, hormonal control and dietary factors. Second, we discuss the adaptive value of colour change for camouflage, including the use of different camouflage types. Third, we discuss the evolutionary-ecological implications of colour change for concealment, including what it can tell us about intraspecific colour diversity, morph-specific strategies, and matching to different environments and microhabitats. Throughout, we discuss key unresolved questions and present directions for future work, and highlight how colour change facilitates camouflage among habitats and arises when animals are faced with environmental changes occurring over a range of spatial and temporal scales.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.",
    url = "https://doi.org/10.1098/rstb.2016.0342",
    doi = "10.1098/rstb.2016.0342",
    openalex = "W2620453139",
    references = "doi101007s1068201698543, doi101098rstb20080270"
}

Animal colour patterns are a model system for understanding evolution because they are unusually accessible for study and experimental manipulation. This is possible because their functions are readily identifiable. In this final paper of the symposium we provide a diagram of the processes affecting colour patterns and use this to summarize their functions and put the other papers in a broad context. This allows us to identify significant 'holes' in the field that only become obvious when we see the processes affecting colour patterns, and their interactions, as a whole. We make suggestions about new directions of research that will enhance our understanding of both the evolution of colour patterns and visual signalling but also illuminate how the evolution of multiple interacting traits works.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.

@article{doi101098rstb20160352,
    author = "Endler, John A. and Mappes, Johanna",
    title = "The current and future state of animal coloration research",
    year = "2017",
    journal = "Philosophical Transactions of the Royal Society B Biological Sciences",
    abstract = "Animal colour patterns are a model system for understanding evolution because they are unusually accessible for study and experimental manipulation. This is possible because their functions are readily identifiable. In this final paper of the symposium we provide a diagram of the processes affecting colour patterns and use this to summarize their functions and put the other papers in a broad context. This allows us to identify significant 'holes' in the field that only become obvious when we see the processes affecting colour patterns, and their interactions, as a whole. We make suggestions about new directions of research that will enhance our understanding of both the evolution of colour patterns and visual signalling but also illuminate how the evolution of multiple interacting traits works.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.",
    url = "https://doi.org/10.1098/rstb.2016.0352",
    doi = "10.1098/rstb.2016.0352",
    openalex = "W2618842291",
    references = "doi101093behecoarw009, doi101146annurevmarine010213135018"
}

Warning coloration is a widespread strategy to alert predators about prey unprofitability. The success of this strategy partly depends on predators being able to learn and recognize certain signals as indicators of toxicity, and theory predicts that this is easier if signals converge on similar colours. However, the diversity in warning signal form is astonishing, contradicting predictions. Here, we quantified ladybird signal diversity with respect to avian vision, measuring how unique and discernible each signal is from one another. In addition, we measured signal conspicuousness against a series of backgrounds, namely an average green, average brown, and where we collected each species, to determine whether signals are more contrasting against the ladybirds' local substrates than compared to average ones. This allowed us to establish whether there are local adaptations in conspicuousness that promote signal diversity. We found that while ladybird signals are unique and recognizable, specialist species are more contrasting against the background they are most commonly found on. However, overall our study suggests that warning signals have evolved to be effective against a wide range of natural backgrounds, partly explaining the success of this strategy in nature.

@article{doi101111jeb13074,
    author = "Arenas, Lina María and Stevens, Martin",
    title = "Diversity in warning coloration is easily recognized by avian predators",
    year = "2017",
    journal = "Journal of Evolutionary Biology",
    abstract = "Warning coloration is a widespread strategy to alert predators about prey unprofitability. The success of this strategy partly depends on predators being able to learn and recognize certain signals as indicators of toxicity, and theory predicts that this is easier if signals converge on similar colours. However, the diversity in warning signal form is astonishing, contradicting predictions. Here, we quantified ladybird signal diversity with respect to avian vision, measuring how unique and discernible each signal is from one another. In addition, we measured signal conspicuousness against a series of backgrounds, namely an average green, average brown, and where we collected each species, to determine whether signals are more contrasting against the ladybirds' local substrates than compared to average ones. This allowed us to establish whether there are local adaptations in conspicuousness that promote signal diversity. We found that while ladybird signals are unique and recognizable, specialist species are more contrasting against the background they are most commonly found on. However, overall our study suggests that warning signals have evolved to be effective against a wide range of natural backgrounds, partly explaining the success of this strategy in nature.",
    url = "https://doi.org/10.1111/jeb.13074",
    doi = "10.1111/jeb.13074",
    openalex = "W2602912663",
    references = "doi101038srep11021"
}

Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.

@article{doi101126scienceaan0221,
    author = "Cuthill, Innes C. and Allen, William L. and Arbuckle, Kevin and Caspers, Barbara A. and Chaplin, George and Hauber, Márk E. and Hill, Geoffrey E. and Jablonski, Nina G. and Jiggins, Chris D. and Kelber, Almut and Mappes, Johanna and Marshall, N. Justin and Merrill, Richard M. and Osorio, Daniel and Prum, Richard O. and Roberts, Nicholas W. and Roulin, Alexandre and Rowland, Hannah M. and Sherratt, Thomas N. and Skelhorn, John and Speed, Michael P. and Stevens, Martin and Stoddard, Mary Caswell and Stuart‐Fox, Devi and Tálas, László and Tibbetts, Elizabeth A. and Caro, Tim",
    title = "The biology of color",
    year = "2017",
    journal = "Science",
    abstract = "Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.",
    url = "https://doi.org/10.1126/science.aan0221",
    doi = "10.1126/science.aan0221",
    openalex = "W2745089499",
    references = "doi101007s1068201698543, doi101016jcub201606065, doi101016jisprsjprs201309014, doi101016jtree200806001, doi101017s1464793102005985, doi101038nature10341, doi101038ng3443, doi101073pnas0914628107, doi101086285308, doi101093behecoarr088, doi101093behecoarw009, doi101093molbevmsv037, doi101098rstb20080270, doi101111j109636421860tb00146x, doi101126science1187113, doi105962bhltitle17416"
}

Communicating the right affect, a feeling, experience or emotion, is critical in creating engaging visual communication. We carried out three studies examining how different color properties (lightness, chroma and hue) and different palette properties (combinations and distribution of colors) contribute to different affective interpretations in information visualization where the numbers of colors is typically smaller than the rich palettes used in design. Our results show how color and palette properties can be manipulated to achieve affective expressiveness even in the small sets of colors used for data encoding in information visualization.

@article{doi10114530254533026041,
    author = "Bartram, Lyn and Patra, Abhisekh and Stone, Maureen",
    title = "Affective Color in Visualization",
    year = "2017",
    abstract = "Communicating the right affect, a feeling, experience or emotion, is critical in creating engaging visual communication. We carried out three studies examining how different color properties (lightness, chroma and hue) and different palette properties (combinations and distribution of colors) contribute to different affective interpretations in information visualization where the numbers of colors is typically smaller than the rich palettes used in design. Our results show how color and palette properties can be manipulated to achieve affective expressiveness even in the small sets of colors used for data encoding in information visualization.",
    url = "https://doi.org/10.1145/3025453.3026041",
    doi = "10.1145/3025453.3026041",
    openalex = "W2611374796",
    references = "doi101146annurevpsych010213115035"
}

Abstract To add more functionalities and overcome the limitation in conventional soft robots, highly anisotropic soft actuators with color shifting function during actuation is demonstrated for the first time. The electrothermally operating soft actuators with installed transparent metal nanowire percolation network heater allow easy programming of their actuation direction and instantaneous visualization of temperature changes through color change. Due to the unique direction dependent coefficient of thermal expansion mismatch, the suggested actuator demonstrates a highly anisotropic and reversible behavior with very large bending curvature (2.5 cm −1) at considerably low temperature (≈40 °C) compared to the previously reported electrothermal soft actuators. The mild operating heat condition required for the maximum curvature enables the superior long‐term stability during more than 10 000 operating cycles. Also, the optical transparency of the polymer bilayer and metal nanowire percolation network heater allow the incorporation of the thermochromic pigments to fabricate color‐shifting actuators. As a proof‐of‐concept, various color‐shifting biomimetic soft robots such as color‐shifting blooming flower, fluttering butterfly, and color‐shifting twining tendril are demonstrated. The developed color‐shifting anisotropic soft actuator is expected to open new application fields and functionalities overcoming the limitation of current soft robots.

@article{doi101002adfm201801847,
    author = "Kim, Hyeonseok and Lee, Habeom and Ha, Inho and Jung, Jinwook and Won, Phillip and Cho, Hyunmin and Yeo, Junyeob and Hong, Sukjoon and Han, Seungyong and Kwon, Jinhyeong and Cho, Kyu‐Jin and Ko, Seung Hwan",
    title = "Biomimetic Color Changing Anisotropic Soft Actuators with Integrated Metal Nanowire Percolation Network Transparent Heaters for Soft Robotics",
    year = "2018",
    journal = "Advanced Functional Materials",
    abstract = "Abstract To add more functionalities and overcome the limitation in conventional soft robots, highly anisotropic soft actuators with color shifting function during actuation is demonstrated for the first time. The electrothermally operating soft actuators with installed transparent metal nanowire percolation network heater allow easy programming of their actuation direction and instantaneous visualization of temperature changes through color change. Due to the unique direction dependent coefficient of thermal expansion mismatch, the suggested actuator demonstrates a highly anisotropic and reversible behavior with very large bending curvature (2.5 cm −1) at considerably low temperature (≈40 °C) compared to the previously reported electrothermal soft actuators. The mild operating heat condition required for the maximum curvature enables the superior long‐term stability during more than 10 000 operating cycles. Also, the optical transparency of the polymer bilayer and metal nanowire percolation network heater allow the incorporation of the thermochromic pigments to fabricate color‐shifting actuators. As a proof‐of‐concept, various color‐shifting biomimetic soft robots such as color‐shifting blooming flower, fluttering butterfly, and color‐shifting twining tendril are demonstrated. The developed color‐shifting anisotropic soft actuator is expected to open new application fields and functionalities overcoming the limitation of current soft robots.",
    url = "https://doi.org/10.1002/adfm.201801847",
    doi = "10.1002/adfm.201801847",
    openalex = "W2805956980",
    references = "doi101098rstb20080254"
}

Stimuli-responsive colors are a unique characteristic of certain animals, evolved as either a method to hide from enemies and prey or to communicate their presence to rivals or mates. From a material science perspective, the solutions developed by Mother Nature to achieve these effects are a source of inspiration to scientists for decades. Here, an updated overview of the literature on bioinspired stimuli-responsive color-changing systems is provided. Starting from natural systems, which are the source of inspiration, a classification of the different solutions proposed is given, based on the stimuli used to trigger the color-changing effect.

@article{doi101002adma201707069,
    author = "Isapour, Golnaz and Lattuada, Marco",
    title = "Bioinspired Stimuli‐Responsive Color‐Changing Systems",
    year = "2018",
    journal = "Advanced Materials",
    abstract = "Stimuli-responsive colors are a unique characteristic of certain animals, evolved as either a method to hide from enemies and prey or to communicate their presence to rivals or mates. From a material science perspective, the solutions developed by Mother Nature to achieve these effects are a source of inspiration to scientists for decades. Here, an updated overview of the literature on bioinspired stimuli-responsive color-changing systems is provided. Starting from natural systems, which are the source of inspiration, a classification of the different solutions proposed is given, based on the stimuli used to trigger the color-changing effect.",
    url = "https://doi.org/10.1002/adma.201707069",
    doi = "10.1002/adma.201707069",
    openalex = "W2799767557",
    references = "doi101002adma200904059, doi101002anie200602866, doi1010160166662286802748, doi101016jaddr201005006, doi101038ncomms7368, doi101038ncomms9011, doi101038nphoton2007140, doi101039c2cs35191a, doi101039c3ra41096j, doi10108800344885717076401, doi101098rsif20120601, doi101111pcmr12040, doi101126scienceaaf3627"
}

Living organisms ubiquitously display colors that adapt to environmental changes, relying on the soft layer of cells or proteins. Adoption of soft materials into an artificial adaptive color system has promoted the development of material systems for environmental and health monitoring, anti-counterfeiting, and stealth technologies. Here, a hydrogel interferometer based on a single hydrogel thin film covalently bonded to a reflective substrate is reported as a simple and universal adaptive color platform. Similar to the cell or protein soft layer of color-changing animals, the soft hydrogel layer rapidly changes its thickness in response to external stimuli, resulting in instant color change. Such interference colors provide a visual and quantifiable means of revealing rich environmental metrics. Computational model is established and captures the key features of hydrogel stimuli-responsive swelling, which elucidates the mechanism and design principle for the broad-based platform. The single material-based platform has advantages of remarkable color uniformity, fast response, high robustness, and facile fabrication. Its versatility is demonstrated by diverse applications: a volatile-vapor sensor with highly accurate quantitative detection, a colorimetric sensor array for multianalyte recognition, breath-controlled information encryption, and a colorimetric humidity indicator. Portable and easy-to-use sensing systems are demonstrated with smartphone-based colorimetric analysis.

@article{doi101002adma201800468,
    author = "Qin, Meng and Sun, Mo and Bai, Ruobing and Mao, Yiqi and Qian, Xiaoshi and Sikka, Dipika and Zhao, Yuan and Qi, H. Jerry and Suo, Zhigang and He, Ximin",
    title = "Bioinspired Hydrogel Interferometer for Adaptive Coloration and Chemical Sensing",
    year = "2018",
    journal = "Advanced Materials",
    abstract = "Living organisms ubiquitously display colors that adapt to environmental changes, relying on the soft layer of cells or proteins. Adoption of soft materials into an artificial adaptive color system has promoted the development of material systems for environmental and health monitoring, anti-counterfeiting, and stealth technologies. Here, a hydrogel interferometer based on a single hydrogel thin film covalently bonded to a reflective substrate is reported as a simple and universal adaptive color platform. Similar to the cell or protein soft layer of color-changing animals, the soft hydrogel layer rapidly changes its thickness in response to external stimuli, resulting in instant color change. Such interference colors provide a visual and quantifiable means of revealing rich environmental metrics. Computational model is established and captures the key features of hydrogel stimuli-responsive swelling, which elucidates the mechanism and design principle for the broad-based platform. The single material-based platform has advantages of remarkable color uniformity, fast response, high robustness, and facile fabrication. Its versatility is demonstrated by diverse applications: a volatile-vapor sensor with highly accurate quantitative detection, a colorimetric sensor array for multianalyte recognition, breath-controlled information encryption, and a colorimetric humidity indicator. Portable and easy-to-use sensing systems are demonstrated with smartphone-based colorimetric analysis.",
    url = "https://doi.org/10.1002/adma.201800468",
    doi = "10.1002/adma.201800468",
    openalex = "W2799737397",
    references = "doi101002adma201504152, doi101002anie201603417, doi101016jcub200703034, doi101016jijsolstr200904022, doi101016jprogpolymsci201209001, doi101021ac030021m, doi101038nature11223, doi101038nmat2032, doi101039b717368g, doi101039c3cs60031a"
}

In nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many artificial systems for mimicking adaptive coloration to match the visual appearance to their surroundings. Thermal camouflage, however, has been an outstanding challenge which requires an ability to control the emitted thermal radiation from the surface. Here we report a new class of active thermal surfaces capable of efficient real-time electrical-control of thermal emission over the full infrared (IR) spectrum without changing the temperature of the surface. Our approach relies on electro-modulation of IR absorptivity and emissivity of multilayer graphene via reversible intercalation of nonvolatile ionic liquids. The demonstrated devices are light (30 g/m 2), thin (<50 μm), and ultraflexible, which can conformably coat their environment. In addition, by combining active thermal surfaces with a feedback mechanism, we demonstrate realization of an adaptive thermal camouflage system which can reconfigure its thermal appearance and blend itself with the varying thermal background in a few seconds. Furthermore, we show that these devices can disguise hot objects as cold and cold ones as hot in a thermal imaging system. We anticipate that, the electrical control of thermal radiation would impact on a variety of new technologies ranging from adaptive IR optics to heat management for outer space applications.

@article{doi101021acsnanolett8b01746,
    author = "Salihoglu, Ömer and Uzlu, Hasan Burkay and Yakar, Ozan and Aas, Shahnaz and Balcı, Osman and Kakenov, Nurbek and Balci, Sinan and Olçum, Selim and Süzer, Şefik and Kocabaş, Coşkun",
    title = "Graphene-Based Adaptive Thermal Camouflage",
    year = "2018",
    journal = "Nano Letters",
    abstract = "In nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many artificial systems for mimicking adaptive coloration to match the visual appearance to their surroundings. Thermal camouflage, however, has been an outstanding challenge which requires an ability to control the emitted thermal radiation from the surface. Here we report a new class of active thermal surfaces capable of efficient real-time electrical-control of thermal emission over the full infrared (IR) spectrum without changing the temperature of the surface. Our approach relies on electro-modulation of IR absorptivity and emissivity of multilayer graphene via reversible intercalation of nonvolatile ionic liquids. The demonstrated devices are light (30 g/m 2), thin (<50 μm), and ultraflexible, which can conformably coat their environment. In addition, by combining active thermal surfaces with a feedback mechanism, we demonstrate realization of an adaptive thermal camouflage system which can reconfigure its thermal appearance and blend itself with the varying thermal background in a few seconds. Furthermore, we show that these devices can disguise hot objects as cold and cold ones as hot in a thermal imaging system. We anticipate that, the electrical control of thermal radiation would impact on a variety of new technologies ranging from adaptive IR optics to heat management for outer space applications.",
    url = "https://doi.org/10.1021/acs.nanolett.8b01746",
    doi = "10.1021/acs.nanolett.8b01746",
    openalex = "W2798907066",
    references = "doi101038nature10067, doi101038nature13883, doi101038ncomms1787, doi101038ncomms7628, doi101038nmat2448, doi101073pnas0900155106, doi101073pnas1410494111, doi10108000018738100101367, doi101098rsif20120601, doi101103physrev138a197, doi101103physrevlett110195901, doi101126science1222149"
}

Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to materials science. Most work focuses on the role of animal morphology per se, and its interactions with the background in affecting detection and recognition. However, the behaviour of organisms is likely to be crucial in affecting camouflage too, through background choice, body orientation and positioning; and strategies of camouflage that require movement. A wealth of potential mechanisms may affect such behaviours, from imprinting and self-assessment to genetics, and operate at several levels (species, morph, and individual). Over many years there have been numerous studies investigating the role of behaviour in camouflage, but to date, no effort to synthesise these studies and ideas into a coherent framework. Here, we review key work on behaviour and camouflage, highlight the mechanisms involved and implications of behaviour, discuss the importance of this in a changing world, and offer suggestions for addressing the many important gaps in our understanding of this subject.

@article{doi101111brv12438,
    author = "Stevens, Martin and Ruxton, Graeme D.",
    title = "The key role of behaviour in animal camouflage",
    year = "2018",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to materials science. Most work focuses on the role of animal morphology per se, and its interactions with the background in affecting detection and recognition. However, the behaviour of organisms is likely to be crucial in affecting camouflage too, through background choice, body orientation and positioning; and strategies of camouflage that require movement. A wealth of potential mechanisms may affect such behaviours, from imprinting and self-assessment to genetics, and operate at several levels (species, morph, and individual). Over many years there have been numerous studies investigating the role of behaviour in camouflage, but to date, no effort to synthesise these studies and ideas into a coherent framework. Here, we review key work on behaviour and camouflage, highlight the mechanisms involved and implications of behaviour, discuss the importance of this in a changing world, and offer suggestions for addressing the many important gaps in our understanding of this subject.",
    url = "https://doi.org/10.1111/brv.12438",
    doi = "10.1111/brv.12438",
    openalex = "W2808725022",
    references = "doi101038s415590170256x, doi101093behecoart058, doi101098rspb20070220, doi101098rstb20080215"
}

Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency-dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator-prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once-paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.

@article{doi101111brv12460,
    author = "Briolat, Emmanuelle S. and Burdfield‐Steel, Emily and Paul, Sarah Catherine and Rönkä, Katja and Seymoure, Brett and Stankowich, Theodore and Stuckert, Adam M. M.",
    title = "Diversity in warning coloration: selective paradox or the norm?",
    year = "2018",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency-dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator-prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once-paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.",
    url = "https://doi.org/10.1111/brv.12460",
    doi = "10.1111/brv.12460",
    openalex = "W2889524965",
    references = "doi101038nature11041, doi101038ncomms4460, doi101038srep11021, doi101093behecoarw009, doi101098rspb20111932, doi101111j00221112200400433x, doi101111j14610248200801258x, doi101111j15585646200700054x, doi101111j15585646201101334x, doi101139z90092, doi1023072937121, doi1023075403, doi105860choice285664, openalexw1840956397, openalexw2145250129"
}

Materials and systems that statically reflect radiation in the infrared region of the electromagnetic spectrum underpin the performance of many entrenched technologies, including building insulation, energy-conserving windows, spacecraft components, electronics shielding, container packaging, protective clothing, and camouflage platforms. The development of their adaptive variants, in which the infrared-reflecting properties dynamically change in response to external stimuli, has emerged as an important unmet scientific challenge. By drawing inspiration from cephalopod skin, we developed adaptive infrared-reflecting platforms that feature a simple actuation mechanism, low working temperature, tunable spectral range, weak angular dependence, fast response, stability to repeated cycling, amenability to patterning and multiplexing, autonomous operation, robust mechanical properties, and straightforward manufacturability. Our findings may open opportunities for infrared camouflage and other technologies that regulate infrared radiation.

@article{doi101126scienceaar5191,
    author = "Xu, Chengyi and Ştiubianu, George and Gorodetsky, Alon A.",
    title = "Adaptive infrared-reflecting systems inspired by cephalopods",
    year = "2018",
    journal = "Science",
    abstract = "Materials and systems that statically reflect radiation in the infrared region of the electromagnetic spectrum underpin the performance of many entrenched technologies, including building insulation, energy-conserving windows, spacecraft components, electronics shielding, container packaging, protective clothing, and camouflage platforms. The development of their adaptive variants, in which the infrared-reflecting properties dynamically change in response to external stimuli, has emerged as an important unmet scientific challenge. By drawing inspiration from cephalopod skin, we developed adaptive infrared-reflecting platforms that feature a simple actuation mechanism, low working temperature, tunable spectral range, weak angular dependence, fast response, stability to repeated cycling, amenability to patterning and multiplexing, autonomous operation, robust mechanical properties, and straightforward manufacturability. Our findings may open opportunities for infrared camouflage and other technologies that regulate infrared radiation.",
    url = "https://doi.org/10.1126/science.aar5191",
    doi = "10.1126/science.aar5191",
    openalex = "W2795296306",
    references = "doi101002adma201304448, doi101002app29812, doi101007s0033901274028, doi101016jcub200703034, doi101017s1464793101005772, doi101021acsnanolett5b04090, doi101073pnas1410494111, doi101098rsif20080366focus, doi101098rsif20120601, doi101103physrevlett110195901, doi101126science1222149, doi101126scienceaac5082"
}

Active camouflage is widely recognized as a soft-tissue feature, and yet the ability to integrate adaptive coloration and tissuelike mechanical properties into synthetic materials remains elusive. We provide a solution to this problem by uniting these functions in moldable elastomers through the self-assembly of linear-bottlebrush-linear triblock copolymers. Microphase separation of the architecturally distinct blocks results in physically cross-linked networks that display vibrant color, extreme softness, and intense strain stiffening on par with that of skin tissue. Each of these functional properties is regulated by the structure of one macromolecule, without the need for chemical cross-linking or additives. These materials remain stable under conditions characteristic of internal bodily environments and under ambient conditions, neither swelling in bodily fluids nor drying when exposed to air.

@article{doi101126scienceaar5308,
    author = "Vatankhah‐Varnosfaderani, Mohammad and Keith, Andrew N. and Cong, Yidan and Liang, Heyi and Rosenthal, Martin and Sztucki, Michael and Clair, Charles and Magonov, Sergei and Ivanov, Dimitri A. and Dobrynin, Andrey V. and Sheiko, Sergei S.",
    title = "Chameleon-like elastomers with molecularly encoded strain-adaptive stiffening and coloration",
    year = "2018",
    journal = "Science",
    abstract = "Active camouflage is widely recognized as a soft-tissue feature, and yet the ability to integrate adaptive coloration and tissuelike mechanical properties into synthetic materials remains elusive. We provide a solution to this problem by uniting these functions in moldable elastomers through the self-assembly of linear-bottlebrush-linear triblock copolymers. Microphase separation of the architecturally distinct blocks results in physically cross-linked networks that display vibrant color, extreme softness, and intense strain stiffening on par with that of skin tissue. Each of these functional properties is regulated by the structure of one macromolecule, without the need for chemical cross-linking or additives. These materials remain stable under conditions characteristic of internal bodily environments and under ambient conditions, neither swelling in bodily fluids nor drying when exposed to air.",
    url = "https://doi.org/10.1126/science.aar5308",
    doi = "10.1126/science.aar5308",
    openalex = "W2794989242",
    references = "doi101038nature03521, doi101038ncomms7368, doi101039b811392k, doi101039c2cs15267c, doi10108809601317243035017, doi101098rsif20080366focus, doi101107s0021889806035059, doi101126science1222149, doi101126science1248494, doi101126scienceaan0221, doi101146annurevpc41100190002521"
}

Structural color materials from existing natural organisms have been widely studied to enable artificial manufacture. Variable iridescence has attracted particular interest because of the displays of various brilliant examples. Existing synthetic, variable, structural color materials require external stimuli to provide changing displays, despite autonomous regulation being widespread among natural organisms, and therefore suffer from inherent limitations. Inspired by the structural color regulation mechanism of chameleons, we present a conceptually different structural color material that has autonomic regulation capability by assembling engineered cardiomyocyte tissues on synthetic inverse opal hydrogel films. The cell elongation and contraction in the beating processes of the cardiomyocytes caused the inverse opal structure of the substrate film to follow the same cycle of volume or morphology changes. This was observed as the synchronous shifting of its photonic band gap and structural colors. Such biohybrid structural color hydrogels can be used to construct a variety of living materials, such as two-dimensional self-regulating structural color patterns and three-dimensional dynamic Morpho butterflies. These examples indicated that the stratagem could provide an intrinsic color-sensing feedback to modify the system behavior/action for future biohybrid robots. In addition, by integrating the biohybrid structural color hydrogels into microfluidics, we developed a "heart-on-a-chip" platform featuring microphysiological visuality for biological research and drug screening. This biohybrid, living, structural color hydrogel may be widely used in the design of a variety of intelligent actuators and soft robotic devices.

@article{doi101126sciroboticsaar8580,
    author = "Fu, Fanfan and Shang, Luoran and Chen, Zhuoyue and Yu, Yunru and Zhao, Yuanjin",
    title = "Bioinspired living structural color hydrogels",
    year = "2018",
    journal = "Science Robotics",
    abstract = {Structural color materials from existing natural organisms have been widely studied to enable artificial manufacture. Variable iridescence has attracted particular interest because of the displays of various brilliant examples. Existing synthetic, variable, structural color materials require external stimuli to provide changing displays, despite autonomous regulation being widespread among natural organisms, and therefore suffer from inherent limitations. Inspired by the structural color regulation mechanism of chameleons, we present a conceptually different structural color material that has autonomic regulation capability by assembling engineered cardiomyocyte tissues on synthetic inverse opal hydrogel films. The cell elongation and contraction in the beating processes of the cardiomyocytes caused the inverse opal structure of the substrate film to follow the same cycle of volume or morphology changes. This was observed as the synchronous shifting of its photonic band gap and structural colors. Such biohybrid structural color hydrogels can be used to construct a variety of living materials, such as two-dimensional self-regulating structural color patterns and three-dimensional dynamic Morpho butterflies. These examples indicated that the stratagem could provide an intrinsic color-sensing feedback to modify the system behavior/action for future biohybrid robots. In addition, by integrating the biohybrid structural color hydrogels into microfluidics, we developed a "heart-on-a-chip" platform featuring microphysiological visuality for biological research and drug screening. This biohybrid, living, structural color hydrogel may be widely used in the design of a variety of intelligent actuators and soft robotic devices.},
    url = "https://doi.org/10.1126/scirobotics.aar8580",
    doi = "10.1126/scirobotics.aar8580",
    openalex = "W2794678235",
    references = "doi101038ncomms7368, doi101038nmat2032, doi101039c2cs15267c"
}

Many visual animals exploit spectral information for seeking food and mates, for identifying preys and predators, and for navigation. Animals use chromatic information in two ways. "True color vision," the ability to discriminate visual stimuli on the basis of their spectral content independent of brightness, is thought to play an important role in object identification. In contrast, "wavelength-specific behavior," which is strongly dependent on brightness, often associates with foraging, navigation, and other species-specific needs. Among animals capable of chromatic vision, insects, with their diverse habitats, stereotyped behaviors, well-characterized anatomy and powerful genetic tools, are attractive systems for studying chromatic information processing. In this review, we first discuss insect photoreceptors and the relationship between their spectral sensitivity and animals' color vision and ecology. Second, we review recent studies that dissect chromatic circuits and explore neural mechanisms of chromatic information processing. Finally, we review insect behaviors involving "true color vision" and "wavelength-specific behaviors," especially in bees, butterflies, and flies. We include examples of high-order color vision, such as color contrast and constancy, which are shared by vertebrates. We focus on Drosophila studies that identified neuronal correlates of color vision and innate spectral preferences. We also discuss the electrophysiological studies in bees that reveal color encoding. Despite structural differences between insects' and vertebrates' visual systems, their chromatic vision appears to employ the same processing principles, such as color opponency, suggesting convergent solutions of neural computation to common problems.

@article{doi103389fncir201800016,
    author = "Song, Bomi and Lee, Chi‐Hon",
    title = "Toward a Mechanistic Understanding of Color Vision in Insects",
    year = "2018",
    journal = "Frontiers in Neural Circuits",
    abstract = {Many visual animals exploit spectral information for seeking food and mates, for identifying preys and predators, and for navigation. Animals use chromatic information in two ways. "True color vision," the ability to discriminate visual stimuli on the basis of their spectral content independent of brightness, is thought to play an important role in object identification. In contrast, "wavelength-specific behavior," which is strongly dependent on brightness, often associates with foraging, navigation, and other species-specific needs. Among animals capable of chromatic vision, insects, with their diverse habitats, stereotyped behaviors, well-characterized anatomy and powerful genetic tools, are attractive systems for studying chromatic information processing. In this review, we first discuss insect photoreceptors and the relationship between their spectral sensitivity and animals' color vision and ecology. Second, we review recent studies that dissect chromatic circuits and explore neural mechanisms of chromatic information processing. Finally, we review insect behaviors involving "true color vision" and "wavelength-specific behaviors," especially in bees, butterflies, and flies. We include examples of high-order color vision, such as color contrast and constancy, which are shared by vertebrates. We focus on Drosophila studies that identified neuronal correlates of color vision and innate spectral preferences. We also discuss the electrophysiological studies in bees that reveal color encoding. Despite structural differences between insects' and vertebrates' visual systems, their chromatic vision appears to employ the same processing principles, such as color opponency, suggesting convergent solutions of neural computation to common problems.},
    url = "https://doi.org/10.3389/fncir.2018.00016",
    doi = "10.3389/fncir.2018.00016",
    openalex = "W2790230962",
    references = "doi101111evo12524"
}

Soft matter systems and materials are moving toward adaptive and interactive behavior, which holds outstanding promise to make the next generation of intelligent soft materials systems inspired from the dynamics and behavior of living systems. But what is an adaptive material? What is an interactive material? How should classical responsiveness or smart materials be delineated? At present, the literature lacks a comprehensive discussion on these topics, which is however of profound importance in order to identify landmark advances, keep a correct and noninflating terminology, and most importantly educate young scientists going into this direction. By comparing different levels of complex behavior in biological systems, this Viewpoint strives to give some definition of the various different materials systems characteristics. In particular, the importance of thinking in the direction of training and learning materials, and metabolic or behavioral materials is highlighted, as well as communication and information-processing systems. This Viewpoint aims to also serve as a switchboard to further connect the important fields of systems chemistry, synthetic biology, supramolecular chemistry and nano- and microfabrication/3D printing with advanced soft materials research. A convergence of these disciplines will be at the heart of empowering future adaptive and interactive materials systems with increasingly complex and emergent life-like behavior.

@article{doi101002adma201905111,
    author = "Walther, Andreas",
    title = "Viewpoint: From Responsive to Adaptive and Interactive Materials and Materials Systems: A Roadmap",
    year = "2019",
    journal = "Advanced Materials",
    abstract = "Soft matter systems and materials are moving toward adaptive and interactive behavior, which holds outstanding promise to make the next generation of intelligent soft materials systems inspired from the dynamics and behavior of living systems. But what is an adaptive material? What is an interactive material? How should classical responsiveness or smart materials be delineated? At present, the literature lacks a comprehensive discussion on these topics, which is however of profound importance in order to identify landmark advances, keep a correct and noninflating terminology, and most importantly educate young scientists going into this direction. By comparing different levels of complex behavior in biological systems, this Viewpoint strives to give some definition of the various different materials systems characteristics. In particular, the importance of thinking in the direction of training and learning materials, and metabolic or behavioral materials is highlighted, as well as communication and information-processing systems. This Viewpoint aims to also serve as a switchboard to further connect the important fields of systems chemistry, synthetic biology, supramolecular chemistry and nano- and microfabrication/3D printing with advanced soft materials research. A convergence of these disciplines will be at the heart of empowering future adaptive and interactive materials systems with increasingly complex and emergent life-like behavior.",
    url = "https://doi.org/10.1002/adma.201905111",
    doi = "10.1002/adma.201905111",
    openalex = "W2989982684",
    references = "doi101021acschemrev5b00146, doi101038nature22987, doi101038nmat2614, doi101038nrm2017108, doi101038s4192801801033, doi101039c7cs00245a, doi101098rsif20120601, doi101126science1230020, doi101126scienceaac6103, doi101126scienceaau9533, doi101146annurevcellbio21012704131001"
}

Visual perception plays a key role in the selection of nutritious and healthy foods. Color, as one of the most important senses of vision, can be used as an indicator of food quality/defects and grade. It is recommended consumers include various colors in their plate to obtain various vitamins and minerals. Color is also thought to be related to antioxidant capacity. Within this regard, this study investigated the relationship between color and antioxidant capacity in various fruits and vegetables. The results indicate the color hues analyzed by computer vision based image analysis can be related with TAC of fruits and vegetables, but with some limitations and can be used as a guide for food selection to increase daily antioxidant intake. Most of fruits and vegetables having hue values above 180° and below 20°, have high antioxidant capacity (>10 mmol TE/kg fresh weight). The results also emphasized the importance of the serving size of fruits and vegetables in terms of their contribution to daily antioxidant intake. Based on these results, fruits and vegetables could be categorized into low-, medium-, and high-antioxidant groups according to their TAC and potential contributions to fulfill the recommended daily antioxidant intake. Finally, daily antioxidant intake was evaluated with a healthier scenario created by doubling vegetable portion and reducing fruit portion by half in the meal.

@article{doi101016jcrfs201911001,
    author = "Cömert, Ezgi Doğan and Mogol, Burçe Ataç and Gökmen, Vural",
    title = "Relationship between color and antioxidant capacity of fruits and vegetables",
    year = "2019",
    journal = "Current Research in Food Science",
    abstract = "Visual perception plays a key role in the selection of nutritious and healthy foods. Color, as one of the most important senses of vision, can be used as an indicator of food quality/defects and grade. It is recommended consumers include various colors in their plate to obtain various vitamins and minerals. Color is also thought to be related to antioxidant capacity. Within this regard, this study investigated the relationship between color and antioxidant capacity in various fruits and vegetables. The results indicate the color hues analyzed by computer vision based image analysis can be related with TAC of fruits and vegetables, but with some limitations and can be used as a guide for food selection to increase daily antioxidant intake. Most of fruits and vegetables having hue values above 180° and below 20°, have high antioxidant capacity (>10 mmol TE/kg fresh weight). The results also emphasized the importance of the serving size of fruits and vegetables in terms of their contribution to daily antioxidant intake. Based on these results, fruits and vegetables could be categorized into low-, medium-, and high-antioxidant groups according to their TAC and potential contributions to fulfill the recommended daily antioxidant intake. Finally, daily antioxidant intake was evaluated with a healthier scenario created by doubling vegetable portion and reducing fruit portion by half in the meal.",
    url = "https://doi.org/10.1016/j.crfs.2019.11.001",
    doi = "10.1016/j.crfs.2019.11.001",
    openalex = "W2990684933",
    references = "doi101016jbandc201508006"
}

Camouflage is a key defence across taxa and frequently critical to survival. A common strategy is background matching, resembling the colour and pattern of the environment. This approach, however, may be ineffective in complex habitats where matching one patch may lead to increased visibility in other patches. In contrast, disruptive coloration, which disguises body outlines, may be effective against complex backgrounds. These ideas have rarely been tested and previous work focuses on artificial systems. Here, we test the camouflage strategies of the shore crab (Carcinus maenas) in two habitats, being a species that is highly variable, capable of plastic changes in appearance, and lives in multiple environments. Using predator (bird and fish) vision modelling and image analysis, we quantified background matching and disruption in crabs from rock pools and mudflats, predicting that disruption would dominate in visually complex rock pools but background matching in more uniform mudflats. As expected, rock pool individuals had significantly higher edge disruption than mudflat crabs, whereas mudflat crabs more closely matched the substrate than rock pool crabs for colour, luminance, and pattern. Our study demonstrates facultative expression of camouflage strategies dependent on the visual environment, with implications for the evolution and interrelatedness of defensive strategies.

@article{doi101038s41598019443492,
    author = "Price, Natasha and Green, Samuel D. and Troscianko, Jolyon and Tregenza, Tom and Stevens, Martin",
    title = "Background matching and disruptive coloration as habitat-specific strategies for camouflage",
    year = "2019",
    journal = "Scientific Reports",
    abstract = "Camouflage is a key defence across taxa and frequently critical to survival. A common strategy is background matching, resembling the colour and pattern of the environment. This approach, however, may be ineffective in complex habitats where matching one patch may lead to increased visibility in other patches. In contrast, disruptive coloration, which disguises body outlines, may be effective against complex backgrounds. These ideas have rarely been tested and previous work focuses on artificial systems. Here, we test the camouflage strategies of the shore crab (Carcinus maenas) in two habitats, being a species that is highly variable, capable of plastic changes in appearance, and lives in multiple environments. Using predator (bird and fish) vision modelling and image analysis, we quantified background matching and disruption in crabs from rock pools and mudflats, predicting that disruption would dominate in visually complex rock pools but background matching in more uniform mudflats. As expected, rock pool individuals had significantly higher edge disruption than mudflat crabs, whereas mudflat crabs more closely matched the substrate than rock pool crabs for colour, luminance, and pattern. Our study demonstrates facultative expression of camouflage strategies dependent on the visual environment, with implications for the evolution and interrelatedness of defensive strategies.",
    url = "https://doi.org/10.1038/s41598-019-44349-2",
    doi = "10.1038/s41598-019-44349-2",
    openalex = "W2945469194",
    references = "doi10100797814615695655, doi101038415609a, doi101038hdy195536, doi101038nature03312, doi101073pnas0431157100, doi101098rspb19980302, doi101098rstb20080217, doi1011112041210x12439, doi101111j10958312200700725x, doi1023071437762"
}

Structural color materials with bioinspired functions are being introduced into real-life applications.

@article{doi101039c9mh00101h,
    author = "Shang, Luoran and Zhang, Weixia and Xu, Ke and Zhao, Yuanjin",
    title = "Bio-inspired intelligent structural color materials",
    year = "2019",
    journal = "Materials Horizons",
    abstract = "Structural color materials with bioinspired functions are being introduced into real-life applications.",
    url = "https://doi.org/10.1039/c9mh00101h",
    doi = "10.1039/c9mh00101h",
    openalex = "W2917443313",
    references = "doi101021acschemrev7b00153, doi101021acsnano5b01298, doi101126scienceaan0221"
}

Naturalists have been fascinated for centuries by animal colors and color patterns. While widely studied at the adult stage, we know little about color patterns in the embryo. Here, we study a trait consisting of coloration that is specific to the embryo and absent from postembryonic stages in water striders (Gerromorpha). By combining developmental genetics with chemical and phylogenetic analyses across a broad sample of species, we uncovered the mechanisms underlying the emergence and diversification of embryonic colors in this group of insects. We show that the pteridine biosynthesis pathway, which ancestrally produces red pigment in the eyes, has been recruited during embryogenesis in various extraocular tissues including antennae and legs. In addition, we discovered that this cooption is common to all water striders and initially resulted in the production of yellow extraocular color. Subsequently, 6 lineages evolved bright red color and 2 lineages lost the color independently. Despite the high diversity in colors and color patterns, we show that the underlying biosynthesis pathway remained stable throughout the 200 million years of Gerromorpha evolutionary time. Finally, we identified erythropterin and xanthopterin as the pigments responsible for these colors in the embryo of various species. These findings demonstrate how traits can emerge through the activation of a biosynthesis pathway in new developmental contexts.

@article{doi101073pnas1908316116,
    author = "Vargas-Lowman, Aïdamalia and Armisén, David and Floriano, Carla Fernanda Burguez and da Rocha Silva Cordeiro, Isabelle and Viala, Séverine and Bouchet, Mathilde and Bernard, Marie Alix and Bouquin, Augustin Le and Santos, M. Emília and Berlioz‐Barbier, Alexandra and Salvador, Arnaud and Moreira, Felipe Ferraz Figueiredo and Bonneton, François and Khila, Abderrahman",
    title = "Cooption of the pteridine biosynthesis pathway underlies the diversification of embryonic colors in water striders",
    year = "2019",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Naturalists have been fascinated for centuries by animal colors and color patterns. While widely studied at the adult stage, we know little about color patterns in the embryo. Here, we study a trait consisting of coloration that is specific to the embryo and absent from postembryonic stages in water striders (Gerromorpha). By combining developmental genetics with chemical and phylogenetic analyses across a broad sample of species, we uncovered the mechanisms underlying the emergence and diversification of embryonic colors in this group of insects. We show that the pteridine biosynthesis pathway, which ancestrally produces red pigment in the eyes, has been recruited during embryogenesis in various extraocular tissues including antennae and legs. In addition, we discovered that this cooption is common to all water striders and initially resulted in the production of yellow extraocular color. Subsequently, 6 lineages evolved bright red color and 2 lineages lost the color independently. Despite the high diversity in colors and color patterns, we show that the underlying biosynthesis pathway remained stable throughout the 200 million years of Gerromorpha evolutionary time. Finally, we identified erythropterin and xanthopterin as the pigments responsible for these colors in the embryo of various species. These findings demonstrate how traits can emerge through the activation of a biosynthesis pathway in new developmental contexts.",
    url = "https://doi.org/10.1073/pnas.1908316116",
    doi = "10.1073/pnas.1908316116",
    openalex = "W2972242328",
    references = "doi101111brv12460"
}

Abstract This chapter explores how Darwin’s theory of sexual selection has structured research on primate coloration. Darwin was fascinated by the conspicuous colors displayed by many animals and pointed to primates as a particularly colorful and interesting group. The chapter provides an overview of Darwin’s theory of sexual selection, highlighting how different selective mechanisms can lead to the extravagant colors found in many primate species. The chapter then overviews both modern and historical studies of primate coloration, emphasizing how methodological advances and a resurgence of interest in sexual selection has led to a modern revival of Darwin’s ideas regarding primate coloration. Finally, the chapter concludes with a discussion of future questions and possible directions of this research. Darwin’s collected works clearly show that he was captivated by the bright colors displayed by many primates, and his theory of sexual selection remains the key to understanding the evolution of many of these impressive traits.

@incollection{doi101093oso97801906249650030006,
    author = "Winters, Sandra and Petersdorf, Megan and Higham, James P.",
    title = "Charles Darwin and Selection in Relation to Sex in the Colors of Monkeys",
    year = "2019",
    abstract = "Abstract This chapter explores how Darwin’s theory of sexual selection has structured research on primate coloration. Darwin was fascinated by the conspicuous colors displayed by many animals and pointed to primates as a particularly colorful and interesting group. The chapter provides an overview of Darwin’s theory of sexual selection, highlighting how different selective mechanisms can lead to the extravagant colors found in many primate species. The chapter then overviews both modern and historical studies of primate coloration, emphasizing how methodological advances and a resurgence of interest in sexual selection has led to a modern revival of Darwin’s ideas regarding primate coloration. Finally, the chapter concludes with a discussion of future questions and possible directions of this research. Darwin’s collected works clearly show that he was captivated by the bright colors displayed by many primates, and his theory of sexual selection remains the key to understanding the evolution of many of these impressive traits.",
    url = "https://doi.org/10.1093/oso/9780190624965.003.0006",
    doi = "10.1093/oso/9780190624965.003.0006",
    openalex = "W2735733776",
    references = "doi101038hdy194821, doi101086285346, doi1011112041210x12439, doi101111j10958312200700725x, doi101111j109636421932tb01553x, doi101126science7123238, doi1016410006356820050550125tasoci20co2, doi10432497813151292667, eaton1940adaptive, openalexw58525211, openalexw614507079"
}

Adaptive mechanisms performing at different levels of organization of living matter play an important role in theoretical biology. One of the important cases of such mechanisms is the protective coloration of animals, that masks them on the ground. The article aims at building mathematical models of the performance of the protective coloration of animals, depending on the specific situations of their adaptation to a particular area. The results of the study can be used to create remote technologies for detecting animals of certain species at a considerable distance.

@article{doi101101822999,
    author = "Nosov, K. and Bespalov, Y. and Levchenko, O. and Grigoriev, O. and Hnoievyi, I.",
    title = "Mathematical modeling the protective coloration of animals with usage of parameters of diversity and evenness",
    year = "2019",
    journal = "bioRxiv",
    abstract = "Adaptive mechanisms performing at different levels of organization of living matter play an important role in theoretical biology. One of the important cases of such mechanisms is the protective coloration of animals, that masks them on the ground. The article aims at building mathematical models of the performance of the protective coloration of animals, depending on the specific situations of their adaptation to a particular area. The results of the study can be used to create remote technologies for detecting animals of certain species at a considerable distance.",
    url = "https://doi.org/10.1101/822999",
    doi = "10.1101/822999",
    is_oa = "true",
    semanticscholar_citation_count = "2",
    semanticscholar_id = "a7bfff4408f1c285f1e8102a5188501f93a47ff6"
}

Color and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa. Overall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrp1, lef1, leo1, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgap1, arfgap2, airc, and gart). Our results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog.

@article{doi101186s1286201914107,
    author = "Stuckert, Adam M. M. and Moore, Emily C. and Coyle, Kaitlin P. and Davison, Ian G. and MacManes, Matthew D. and Roberts, Reade B. and Summers, Kyle",
    title = "Variation in pigmentation gene expression is associated with distinct aposematic color morphs in the poison frog Dendrobates auratus",
    year = "2019",
    journal = "BMC Evolutionary Biology",
    abstract = "Color and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa. Overall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrp1, lef1, leo1, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgap1, arfgap2, airc, and gart). Our results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog.",
    url = "https://doi.org/10.1186/s12862-019-1410-7",
    doi = "10.1186/s12862-019-1410-7",
    openalex = "W2952006011",
    references = "doi101111brv12460"
}

Development of stimuli-responsive materials with complex practical functions is significant for achieving bioinspired artificial intelligence. It is challenging to fabricate stimuli-responsive hydrogels showing simultaneous changes in fluorescence color, brightness, and shape in response to a single stimulus. Herein, a bilayer hydrogel strategy is designed by utilizing an aggregation-induced emission luminogen, tetra-(4-pyridylphenyl)ethylene (TPE-4Py), to fabricate hydrogels with the above capabilities. Bilayer hydrogel actuators with the ionomer of poly(acrylamide-r-sodium 4-styrenesulfonate) (PAS) as a matrix of both active and passive layers and TPE-4Py as the core function element in the active layer are prepared. At acidic pH, the protonation of TPE-4Py leads to fluorescence color and brightness changes of the actuators and the electrostatic interactions between the protonated TPE-4Py and benzenesulfonate groups of the PAS chains in the active layer cause the actuators to deform. The proposed TPE-4Py/PAS-based bilayer hydrogel actuators with such responsiveness to stimulus provide insights in the design of intelligent systems and are highly attractive material candidates in the fields of 3D/4D printing, soft robots, and smart wearable devices.

@article{doi101002adma201906493,
    author = "Li, Zhao and Liu, Pengchao and Ji, Xiaofan and Gong, Junyi and Hu, Yubing and Wu, Wenjie and Wang, Xinnan and Peng, Hui‐Qing and Kwok, Ryan T. K. and Lam, Jacky W. Y. and Lü, Jian and Tang, Ben Zhong",
    title = "Bioinspired Simultaneous Changes in Fluorescence Color, Brightness, and Shape of Hydrogels Enabled by AIEgens",
    year = "2020",
    journal = "Advanced Materials",
    abstract = "Development of stimuli-responsive materials with complex practical functions is significant for achieving bioinspired artificial intelligence. It is challenging to fabricate stimuli-responsive hydrogels showing simultaneous changes in fluorescence color, brightness, and shape in response to a single stimulus. Herein, a bilayer hydrogel strategy is designed by utilizing an aggregation-induced emission luminogen, tetra-(4-pyridylphenyl)ethylene (TPE-4Py), to fabricate hydrogels with the above capabilities. Bilayer hydrogel actuators with the ionomer of poly(acrylamide-r-sodium 4-styrenesulfonate) (PAS) as a matrix of both active and passive layers and TPE-4Py as the core function element in the active layer are prepared. At acidic pH, the protonation of TPE-4Py leads to fluorescence color and brightness changes of the actuators and the electrostatic interactions between the protonated TPE-4Py and benzenesulfonate groups of the PAS chains in the active layer cause the actuators to deform. The proposed TPE-4Py/PAS-based bilayer hydrogel actuators with such responsiveness to stimulus provide insights in the design of intelligent systems and are highly attractive material candidates in the fields of 3D/4D printing, soft robots, and smart wearable devices.",
    url = "https://doi.org/10.1002/adma.201906493",
    doi = "10.1002/adma.201906493",
    openalex = "W3004728746",
    references = "doi101002adma201804540"
}

Abstract Structural colors widespread in nature have been theoretically in‐depth studied and manufactured through the artificial approaches such as self‐assembly and nanolithography thanks to the rapidly developing nanotechnology. Structural colors based on elastomers and hydrogels can be readily modulated upon mechanical stimuli, via adjusting the structural parameters such as interplanar spacing and diffractive angle. Recent breakthroughs in mechanochromic structural‐colored materials has not only enriched their varieties but also strengthened their competences remarkably. The emerging mechanoresponsive materials have been applied in various fields such as sensors, displays, anti‐counterfeiting, and healthcare. This review focuses on the recent progresses in mechanochromic structural‐colored materials with different architectures including photonic crystals, liquid crystals, and photonic glasses. A discussion on their structures and fabrications are presented, along with their merits and demerits by comparison. Special attention is given to the application potentials of these mechanochromic materials in diverse domains, followed by detailed discussion of their mechanism. Last but not least, the current challenges as well as the trends of structural‐colored mechanochromic materials are proposed.

@article{doi101002adom202000984,
    author = "Chen, Guojian and Hong, Wei",
    title = "Mechanochromism of Structural‐Colored Materials",
    year = "2020",
    journal = "Advanced Optical Materials",
    abstract = "Abstract Structural colors widespread in nature have been theoretically in‐depth studied and manufactured through the artificial approaches such as self‐assembly and nanolithography thanks to the rapidly developing nanotechnology. Structural colors based on elastomers and hydrogels can be readily modulated upon mechanical stimuli, via adjusting the structural parameters such as interplanar spacing and diffractive angle. Recent breakthroughs in mechanochromic structural‐colored materials has not only enriched their varieties but also strengthened their competences remarkably. The emerging mechanoresponsive materials have been applied in various fields such as sensors, displays, anti‐counterfeiting, and healthcare. This review focuses on the recent progresses in mechanochromic structural‐colored materials with different architectures including photonic crystals, liquid crystals, and photonic glasses. A discussion on their structures and fabrications are presented, along with their merits and demerits by comparison. Special attention is given to the application potentials of these mechanochromic materials in diverse domains, followed by detailed discussion of their mechanism. Last but not least, the current challenges as well as the trends of structural‐colored mechanochromic materials are proposed.",
    url = "https://doi.org/10.1002/adom.202000984",
    doi = "10.1002/adom.202000984",
    openalex = "W3049493807",
    references = "doi101002smll201907626"
}

Abstract The counterfeiting of goods is growing worldwide, affecting practically any marketable item ranging from consumer goods to human health. Anticounterfeiting is essential for authentication, currency, and security. Anticounterfeiting tags based on structural color materials have enjoyed worldwide and long‐term commercial success due to their inexpensive production and exceptional ease of percept. However, conventional anticounterfeiting tags of holographic gratings can be readily copied or imitated. Much progress has been made recently to overcome this limitation by employing sufficient complexity and stimuli‐responsive ability into the structural color materials. Moreover, traditional processing methods of structural color tags are mainly based on photolithography and nanoimprinting, while new processing methods such as the inkless printing and additive manufacturing have been developed, enabling massive scale up fabrication of novel structural color security engineering. This review presents recent breakthroughs in structural color materials, and their applications in optical encryption and anticounterfeiting are discussed in detail. Special attention is given to the unique structures for optical anticounterfeiting techniques and their optical aspects for encryption. Finally, emerging research directions and current challenges in optical encryption technologies using structural color materials is presented.

@article{doi101002smll201907626,
    author = "Hong, Wei and Yuan, Zhongke and Chen, Xudong",
    title = "Structural Color Materials for Optical Anticounterfeiting",
    year = "2020",
    journal = "Small",
    abstract = "Abstract The counterfeiting of goods is growing worldwide, affecting practically any marketable item ranging from consumer goods to human health. Anticounterfeiting is essential for authentication, currency, and security. Anticounterfeiting tags based on structural color materials have enjoyed worldwide and long‐term commercial success due to their inexpensive production and exceptional ease of percept. However, conventional anticounterfeiting tags of holographic gratings can be readily copied or imitated. Much progress has been made recently to overcome this limitation by employing sufficient complexity and stimuli‐responsive ability into the structural color materials. Moreover, traditional processing methods of structural color tags are mainly based on photolithography and nanoimprinting, while new processing methods such as the inkless printing and additive manufacturing have been developed, enabling massive scale up fabrication of novel structural color security engineering. This review presents recent breakthroughs in structural color materials, and their applications in optical encryption and anticounterfeiting are discussed in detail. Special attention is given to the unique structures for optical anticounterfeiting techniques and their optical aspects for encryption. Finally, emerging research directions and current challenges in optical encryption technologies using structural color materials is presented.",
    url = "https://doi.org/10.1002/smll.201907626",
    doi = "10.1002/smll.201907626",
    openalex = "W3011818791",
    references = "doi101002adma201800468, doi101002anie201307828, doi101021acschemrev7b00153, doi101021acsnano5b01298, doi10103839834, doi101038nature02772, doi101038nature09540, doi101038ncomms7368, doi101103physrevlett672295, doi101107s0365110x51000751, doi101109jproc20142320516, doi101126science1074376, doi101126science1172051"
}

How does consciousness vary across the animal kingdom? Are some animals 'more conscious' than others? This article presents a multidimensional framework for understanding interspecies variation in states of consciousness. The framework distinguishes five key dimensions of variation: perceptual richness, evaluative richness, integration at a time, integration across time, and self-consciousness. For each dimension, existing experiments that bear on it are reviewed and future experiments are suggested. By assessing a given species against each dimension, we can construct a consciousness profile for that species. On this framework, there is no single scale along which species can be ranked as more or less conscious. Rather, each species has its own distinctive consciousness profile.

@article{doi101016jtics202007007,
    author = "Birch, Jonathan and Schnell, Alexandra K. and Clayton, Nicola S.",
    title = "Dimensions of Animal Consciousness",
    year = "2020",
    journal = "Trends in Cognitive Sciences",
    abstract = "How does consciousness vary across the animal kingdom? Are some animals 'more conscious' than others? This article presents a multidimensional framework for understanding interspecies variation in states of consciousness. The framework distinguishes five key dimensions of variation: perceptual richness, evaluative richness, integration at a time, integration across time, and self-consciousness. For each dimension, existing experiments that bear on it are reviewed and future experiments are suggested. By assessing a given species against each dimension, we can construct a consciousness profile for that species. On this framework, there is no single scale along which species can be ranked as more or less conscious. Rather, each species has its own distinctive consciousness profile.",
    url = "https://doi.org/10.1016/j.tics.2020.07.007",
    doi = "10.1016/j.tics.2020.07.007",
    openalex = "W3081489731",
    references = "doi101016jbbr200911044, doi101016jcub200703034, doi101073pnas0608062103"
}

Structural colors traditionally refer to colors arising from the interaction of light with structures with periodicities on the order of the wavelength. Recently, the definition has been broadened to include colors arising from individual resonators that can be subwavelength in dimension, for example, plasmonic and dielectric nanoantennas. For instance, diverse metallic and dielectric nanostructure designs have been utilized to generate structural colors based on various physical phenomena, such as localized surface plasmon resonances (LSPRs), Mie resonances, thin-film Fabry–Pérot interference, and Rayleigh–Wood diffraction anomalies from 2D periodic lattices and photonic crystals. Here, we provide our perspective of the key application areas where structural colors really shine and other areas where more work is needed. We review major classes of materials and structures employed to generate structural coloration and highlight the main physical resonances involved. We discuss mechanisms to tune structural colors and review recent advances in dynamic structural colors. In the end, we propose the concept of a universal pixel that could be crucial in realizing next-generation displays based on nanophotonic structural colors.

@article{doi101021acsphotonics0c00947,
    author = "Rezaei, Soroosh Daqiqeh and Dong, Zhaogang and Chan, John You En and Trisno, Jonathan and Ng, Ray Jia Hong and Ruan, Qifeng and Qiu, Cheng‐Wei and Mortensen, N. Asger and Yang, Joel K. W.",
    title = "Nanophotonic Structural Colors",
    year = "2020",
    journal = "ACS Photonics",
    abstract = "Structural colors traditionally refer to colors arising from the interaction of light with structures with periodicities on the order of the wavelength. Recently, the definition has been broadened to include colors arising from individual resonators that can be subwavelength in dimension, for example, plasmonic and dielectric nanoantennas. For instance, diverse metallic and dielectric nanostructure designs have been utilized to generate structural colors based on various physical phenomena, such as localized surface plasmon resonances (LSPRs), Mie resonances, thin-film Fabry–Pérot interference, and Rayleigh–Wood diffraction anomalies from 2D periodic lattices and photonic crystals. Here, we provide our perspective of the key application areas where structural colors really shine and other areas where more work is needed. We review major classes of materials and structures employed to generate structural coloration and highlight the main physical resonances involved. We discuss mechanisms to tune structural colors and review recent advances in dynamic structural colors. In the end, we propose the concept of a universal pixel that could be crucial in realizing next-generation displays based on nanophotonic structural colors.",
    url = "https://doi.org/10.1021/acsphotonics.0c00947",
    doi = "10.1021/acsphotonics.0c00947",
    openalex = "W3045998919",
    references = "doi101002adma201800468, doi101002andp19083300302, doi1010070387378251, doi101021jp026731y, doi101038nmat3443, doi101080716099663, doi101103physrevlett334, doi101103physrevlett98266802, doi101126science1198258, doi101126scienceaag2472, openalexw1768994003"
}

The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.

@article{doi101111brv12670,
    author = "Caro, Tim and Koneru, Manisha",
    title = "Towards an ecology of protective coloration",
    year = "2020",
    journal = "Biological reviews/Biological reviews of the Cambridge Philosophical Society",
    abstract = "The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.",
    url = "https://doi.org/10.1111/brv.12670",
    doi = "10.1111/brv.12670",
    openalex = "W3107287993",
    references = "doi10100797814615695655, doi101007s1068201698543, doi101016jcub201110014, doi101038nature03312, doi101038s41598019443492, doi101093oso97801996886780010001, doi101098rstb20080217, doi101111brv12460, doi101111brv12612, doi101111j1469185x200700027x, doi101111jzo12682, doi101126scienceaan0221, doi101146annurevmarine010213135018, doi1023071437762, doi1023072937121, doi105860choice432800, openalexw1486180449, openalexw2764433274"
}

Death feigning is considered to be an adaptive antipredator behaviour. Previous studies on Tribolium castaneum have shown that prey which death feign have a fitness advantage over those that do not when using a jumping spider as the predator. Whether these effects are repeatable across species or whether they can be seen in nature is, however, unknown. Therefore, the present study involved two experiments: (a) divergent artificial selection for the duration of death feigning using a related species T. freemani as prey and a predatory bug as predator, demonstrating that previous results are repeatable across both prey and predator species, and (b) comparison of the death-feigning duration of T. castaneum populations collected from field sites with and without predatory bugs. In the first experiment, T. freemani adults from established selection regimes with longer durations of death feigning had higher survival rates and longer latency to being preyed on when they were placed with predatory bugs than the adults from regimes selected for shorter durations of death feigning. As a result, the adaptive significance of death-feigning behaviour was demonstrated in another prey-predator system. In the second experiment, wild T. castaneum beetles from populations with predators feigned death longer than wild beetles from predator-free populations. Combining the results from these two experiments with those from previous studies provided strong evidence that predators drive the evolution of longer death feigning.

@article{doi101111jeb13641,
    author = "Konishi, Kana and Matsumura, Kentarou and Sakuno, Wataru and Miyatake, Takahisa",
    title = "Death feigning as an adaptive anti‐predator behaviour: Further evidence for its evolution from artificial selection and natural populations",
    year = "2020",
    journal = "Journal of Evolutionary Biology",
    abstract = "Death feigning is considered to be an adaptive antipredator behaviour. Previous studies on Tribolium castaneum have shown that prey which death feign have a fitness advantage over those that do not when using a jumping spider as the predator. Whether these effects are repeatable across species or whether they can be seen in nature is, however, unknown. Therefore, the present study involved two experiments: (a) divergent artificial selection for the duration of death feigning using a related species T. freemani as prey and a predatory bug as predator, demonstrating that previous results are repeatable across both prey and predator species, and (b) comparison of the death-feigning duration of T. castaneum populations collected from field sites with and without predatory bugs. In the first experiment, T. freemani adults from established selection regimes with longer durations of death feigning had higher survival rates and longer latency to being preyed on when they were placed with predatory bugs than the adults from regimes selected for shorter durations of death feigning. As a result, the adaptive significance of death-feigning behaviour was demonstrated in another prey-predator system. In the second experiment, wild T. castaneum beetles from populations with predators feigned death longer than wild beetles from predator-free populations. Combining the results from these two experiments with those from previous studies provided strong evidence that predators drive the evolution of longer death feigning.",
    url = "https://doi.org/10.1111/jeb.13641",
    doi = "10.1111/jeb.13641",
    openalex = "W3028377846",
    references = "doi101093oso97801996886780010001"
}

Structural color materials have been studied for decades because of their fascinating properties. Effects in this area are the trend to develop functional structural color materials with new components, structures, or morphologies for different applications. In this study, we found that the coassembled graphene oxide (GO) and colloid nanoparticles in droplets could form component phase separations, and thus, previously unknown anisotropic structural color particles (SCPs) with hemispherical colloidal crystal cluster and oblate GO component could be achieved. The anisotropic SCPs, as well as their inverse opal hydrogel derivatives, were endowed with brilliant structural colors and controllable capabilities of fixation, location, orientation, and even responsiveness due to their specific structure, morphology, and components. We have also demonstrated that the anisotropic hydrogel SCPs with these features were ideal candidates for dynamic cell monitoring and sensing. These properties indicate that the anisotropic SCPs and their derivatives have huge potential values in biomedical areas.

@article{doi101126sciadvaay1438,
    author = "Wang, Huan and Liu, Yuxiao and Chen, Zhuoyue and Sun, Lingyu and Zhao, Yuanjin",
    title = "Anisotropic structural color particles from colloidal phase separation",
    year = "2020",
    journal = "Science Advances",
    abstract = "Structural color materials have been studied for decades because of their fascinating properties. Effects in this area are the trend to develop functional structural color materials with new components, structures, or morphologies for different applications. In this study, we found that the coassembled graphene oxide (GO) and colloid nanoparticles in droplets could form component phase separations, and thus, previously unknown anisotropic structural color particles (SCPs) with hemispherical colloidal crystal cluster and oblate GO component could be achieved. The anisotropic SCPs, as well as their inverse opal hydrogel derivatives, were endowed with brilliant structural colors and controllable capabilities of fixation, location, orientation, and even responsiveness due to their specific structure, morphology, and components. We have also demonstrated that the anisotropic hydrogel SCPs with these features were ideal candidates for dynamic cell monitoring and sensing. These properties indicate that the anisotropic SCPs and their derivatives have huge potential values in biomedical areas.",
    url = "https://doi.org/10.1126/sciadv.aay1438",
    doi = "10.1126/sciadv.aay1438",
    openalex = "W3000570919",
    references = "doi101002adma201707069"
}

Many species in nature have evolved remarkable strategies to visually adapt to the surroundings for the purpose of protection and predation. Similarly, acquiring the capabilities of adaptively camouflaging in the infrared (IR) spectrum has emerged as an intriguing but highly challenging technology in recent years. Here, we report adaptive thermal camouflage devices by bridging the optical and radiative properties of nanoscopic platinum (Pt) films and silver (Ag) electrodeposited Pt films. Specifically, these metal-based devices have large, uniform, and consistent IR tunabilities in mid-wave IR (MWIR) and long-wave IR (LWIR) atmospheric transmission windows (ATWs). Furthermore, these devices can be easily multiplexed, enlarged, applied to rough and flexible substrates, or colored, demonstrating their multiple adaptive camouflaging capabilities. We believe that this technology will be advantageous not only in various adaptive camouflage platforms but also in many thermal radiation management-related technologies.

@article{doi101126sciadvaba3494,
    author = "Li, Mingyang and Liu, Dongqing and Cheng, Haifeng and Peng, Liang and Zu, Mei",
    title = "Manipulating metals for adaptive thermal camouflage",
    year = "2020",
    journal = "Science Advances",
    abstract = "Many species in nature have evolved remarkable strategies to visually adapt to the surroundings for the purpose of protection and predation. Similarly, acquiring the capabilities of adaptively camouflaging in the infrared (IR) spectrum has emerged as an intriguing but highly challenging technology in recent years. Here, we report adaptive thermal camouflage devices by bridging the optical and radiative properties of nanoscopic platinum (Pt) films and silver (Ag) electrodeposited Pt films. Specifically, these metal-based devices have large, uniform, and consistent IR tunabilities in mid-wave IR (MWIR) and long-wave IR (LWIR) atmospheric transmission windows (ATWs). Furthermore, these devices can be easily multiplexed, enlarged, applied to rough and flexible substrates, or colored, demonstrating their multiple adaptive camouflaging capabilities. We believe that this technology will be advantageous not only in various adaptive camouflage platforms but also in many thermal radiation management-related technologies.",
    url = "https://doi.org/10.1126/sciadv.aba3494",
    doi = "10.1126/sciadv.aba3494",
    openalex = "W3031865987",
    references = "doi101002adom201801006, doi101021acsnanolett8b01746, doi101126scienceaar5191"
}

Color vision is widespread among insects but varies among species, depending on the spectral sensitivities and interplay of the participating photoreceptors. The spectral sensitivity of a photoreceptor is principally determined by the absorption spectrum of the expressed visual pigment, but it can be modified by various optical and electrophysiological factors. For example, screening and filtering pigments, rhabdom waveguide properties, retinal structure, and neural processing all influence the perceived color signal. We review the diversity in compound eye structure, visual pigments, photoreceptor physiology, and visual ecology of insects. Based on an overview of the current information about the spectral sensitivities of insect photoreceptors, covering 221 species in 13 insect orders, we discuss the evolution of color vision and highlight present knowledge gaps and promising future research directions in the field.

@article{doi101146annurevento061720071644,
    author = "van der Kooi, Casper J. and Stavenga, Doekele G. and Arikawa, Kentaro and Belušič, Gregor and Kelber, Almut",
    title = "Evolution of Insect Color Vision: From Spectral Sensitivity to Visual Ecology",
    year = "2020",
    journal = "Annual Review of Entomology",
    abstract = "Color vision is widespread among insects but varies among species, depending on the spectral sensitivities and interplay of the participating photoreceptors. The spectral sensitivity of a photoreceptor is principally determined by the absorption spectrum of the expressed visual pigment, but it can be modified by various optical and electrophysiological factors. For example, screening and filtering pigments, rhabdom waveguide properties, retinal structure, and neural processing all influence the perceived color signal. We review the diversity in compound eye structure, visual pigments, photoreceptor physiology, and visual ecology of insects. Based on an overview of the current information about the spectral sensitivities of insect photoreceptors, covering 221 species in 13 insect orders, we discuss the evolution of color vision and highlight present knowledge gaps and promising future research directions in the field.",
    url = "https://doi.org/10.1146/annurev-ento-061720-071644",
    doi = "10.1146/annurev-ento-061720-071644",
    openalex = "W3089077729",
    references = "doi101017s1464793102005985"
}

Infrared (IR) adaptation phenomena are ubiquitous in nature and biological systems. Taking inspiration from natural creatures, researchers have devoted extensive efforts for developing advanced IR adaptive materials and exploring their applications in areas of smart camouflage, thermal energy management, biomedical science, and many other IR-related technological fields. Herein, an up-to-date review is provided on the recent advancements of bioinspired IR adaptive materials and their promising applications. First an overview of IR adaptation in nature and advanced artificial IR technologies is presented. Recent endeavors are then introduced toward developing bioinspired adaptive materials for IR camouflage and IR radiative cooling. According to the Stefan-Boltzmann law, IR camouflage can be realized by either emissivity engineering or thermal cloaks. IR radiative cooling can maximize the thermal radiation of an object through an IR atmospheric transparency window, and thus holds great potential for use in energy-efficient green buildings and smart personal thermal management systems. Recent advances in bioinspired adaptive materials for emerging near-IR (NIR) applications are also discussed, including NIR-triggered biological technologies, NIR light-fueled soft robotics, and NIR light-driven supramolecular nanosystems. This review concludes with a perspective on the challenges and opportunities for the future development of bioinspired IR adaptive materials.

@article{doi101002adma202004754,
    author = "Yang, Jiajia and Zhang, Xinfang and Zhang, Xuan and Wang, Ling and Feng, Wei and Li, Quan",
    title = "Beyond the Visible: Bioinspired Infrared Adaptive Materials",
    year = "2021",
    journal = "Advanced Materials",
    abstract = "Infrared (IR) adaptation phenomena are ubiquitous in nature and biological systems. Taking inspiration from natural creatures, researchers have devoted extensive efforts for developing advanced IR adaptive materials and exploring their applications in areas of smart camouflage, thermal energy management, biomedical science, and many other IR-related technological fields. Herein, an up-to-date review is provided on the recent advancements of bioinspired IR adaptive materials and their promising applications. First an overview of IR adaptation in nature and advanced artificial IR technologies is presented. Recent endeavors are then introduced toward developing bioinspired adaptive materials for IR camouflage and IR radiative cooling. According to the Stefan-Boltzmann law, IR camouflage can be realized by either emissivity engineering or thermal cloaks. IR radiative cooling can maximize the thermal radiation of an object through an IR atmospheric transparency window, and thus holds great potential for use in energy-efficient green buildings and smart personal thermal management systems. Recent advances in bioinspired adaptive materials for emerging near-IR (NIR) applications are also discussed, including NIR-triggered biological technologies, NIR light-fueled soft robotics, and NIR light-driven supramolecular nanosystems. This review concludes with a perspective on the challenges and opportunities for the future development of bioinspired IR adaptive materials.",
    url = "https://doi.org/10.1002/adma.202004754",
    doi = "10.1002/adma.202004754",
    openalex = "W3132026474",
    references = "doi101002adma201905111, doi101002adom201801006, doi101016jnanoen2020104449, doi101021acschemrev5b00344, doi101021acsnanolett8b01746, doi101021cr900300p, doi101038nature14543, doi101038nmat3064, doi101038nmat708, doi101038s4137702003005, doi101038s41467017026788, doi101073pnas1410494111, doi101086305772, doi101126science1125907, doi101126science1133628, doi101126science1244693, doi101126scienceaai7899, doi101126scienceaar5191, doi1015159780691185507"
}

Development of an artificial camouflage at a complete device level remains a vastly challenging task, especially under the aim of achieving more advanced and natural camouflage characteristics via high-resolution camouflage patterns. Our strategy is to integrate a thermochromic liquid crystal layer with the vertically stacked, patterned silver nanowire heaters in a multilayer structure to overcome the limitations of the conventional lateral pixelated scheme through the superposition of the heater-induced temperature profiles. At the same time, the weaknesses of thermochromic camouflage schemes are resolved in this study by utilizing the temperature-dependent resistance of the silver nanowire network as the process variable of the active control system. Combined with the active control system and sensing units, the complete device chameleon model successfully retrieves the local background color and matches its surface color instantaneously with natural transition characteristics to be a competent option for a next-generation artificial camouflage.

@article{doi101038s4146702124916w,
    author = "Kim, Hyeonseok and Choi, Joonhwa and Kim, Kyun Kyu and Won, Phillip and Hong, Sukjoon and Ko, Seung Hwan",
    title = "Biomimetic chameleon soft robot with artificial crypsis and disruptive coloration skin",
    year = "2021",
    journal = "Nature Communications",
    abstract = "Development of an artificial camouflage at a complete device level remains a vastly challenging task, especially under the aim of achieving more advanced and natural camouflage characteristics via high-resolution camouflage patterns. Our strategy is to integrate a thermochromic liquid crystal layer with the vertically stacked, patterned silver nanowire heaters in a multilayer structure to overcome the limitations of the conventional lateral pixelated scheme through the superposition of the heater-induced temperature profiles. At the same time, the weaknesses of thermochromic camouflage schemes are resolved in this study by utilizing the temperature-dependent resistance of the silver nanowire network as the process variable of the active control system. Combined with the active control system and sensing units, the complete device chameleon model successfully retrieves the local background color and matches its surface color instantaneously with natural transition characteristics to be a competent option for a next-generation artificial camouflage.",
    url = "https://doi.org/10.1038/s41467-021-24916-w",
    doi = "10.1038/s41467-021-24916-w",
    openalex = "W3189885260",
    references = "doi101002adma201200359, doi101002adma201400633, doi101002adma201500917, doi101021acsaccounts8b00500, doi101038ncomms7368, doi101038s41598019443492, doi101039c2nr31254a, doi101098rstb20080216, doi101098rstb20080217, doi101126science1222149, doi101126scienceaac5082, doi101126sciroboticsaah3690"
}

This study aims to investigate the relationship between the diversity and uniformity of the protective coloration of animals. The protective coloration of animals is the result of the formation of adaptation strategies. The aim of this study is to identify the colorimetric parameters that characterize the adaptive properties of the protective coloration of animals in relation to their natural habitat. The relevance of this study is related to the importance of the tasks of remote collection of information about various biological species; in particular, animals that carry dangerous infections. This is all the more important in light of the current epidemic problems facing humanity. The revealed colorimetric characteristics can be used to describe digital images and their further recognition. They can be classifying features in machine learning algorithms. We give an example of digital image processing of a duck (Anas platyrhynchos). The analysis of the distribution of the found colorimetric parameter makes it possible to identify the image segments corresponding to the Anas platyrhynchos. The results thus obtained are also of interest from the point of view of the problem of the adaptive role of the diversity of biological systems in relation to the problem of the mechanisms of functioning of the protective coloration of animals.

@article{doi10110120210506441914,
    author = "Bespalov, Y. and Kabalyants, P. and Zuev, S.",
    title = "Relationships of diversity and evenness in adaptation strategies of the effect of protective coloration of animals",
    year = "2021",
    journal = "bioRxiv",
    abstract = "This study aims to investigate the relationship between the diversity and uniformity of the protective coloration of animals. The protective coloration of animals is the result of the formation of adaptation strategies. The aim of this study is to identify the colorimetric parameters that characterize the adaptive properties of the protective coloration of animals in relation to their natural habitat. The relevance of this study is related to the importance of the tasks of remote collection of information about various biological species; in particular, animals that carry dangerous infections. This is all the more important in light of the current epidemic problems facing humanity. The revealed colorimetric characteristics can be used to describe digital images and their further recognition. They can be classifying features in machine learning algorithms. We give an example of digital image processing of a duck (Anas platyrhynchos). The analysis of the distribution of the found colorimetric parameter makes it possible to identify the image segments corresponding to the Anas platyrhynchos. The results thus obtained are also of interest from the point of view of the problem of the adaptive role of the diversity of biological systems in relation to the problem of the mechanisms of functioning of the protective coloration of animals.",
    url = "https://www.biorxiv.org/content/biorxiv/early/2021/05/07/2021.05.06.441914.full.pdf",
    doi = "10.1101/2021.05.06.441914",
    is_oa = "true",
    semanticscholar_citation_count = "1",
    semanticscholar_id = "d4847f6f86e97700a3c83920b3e096e226c3c70a"
}

Abstract Fish coloration, evolved from selection and adaptation, is a prominent feature of remarkable aquaculture merits. Fish possess more pigment cell types than any other vertebrates and are an excellent model for the study of mechanisms underlying skin coloration and pigmentation at levels from molecular genetics to system biology. How to effectively improve skin colour in ornamental and aquaculture fish has long been a focus on selective breeding programmes. In this review article, we introduce different types of chromatophore and early development of pigmentation, describe cellular mechanisms related to morphological and physiological changes of body colour and demonstrate applications of single‐sex control and molecular marker–assisted breeding in body colour selection. We also reviewed genes that have been found involving in neural crest migration and development, as well as those involved in melanin‐based coloration and other types of pigmentation, and explored how to use transgenic technology for enhancing fish body colour. The applications of genome editing and other omics technologies in relation to fish coloration are also illustrated. Finally, we present our perspectives about future fish coloration research and practice in aquaculture. Taken together, this review is expected to provide an update on cellular and molecular mechanisms in fish coloration and pigmentation, which will likely promote body colour–based molecular breeding programmes in aquaculture.

@article{doi101111raq12583,
    author = "Luo, Mingkun and Lu, Guoqing and Yin, Haoran and Wang, Lanmei and Atuganile, Malambugi and Dong, Zaijie",
    title = "Fish pigmentation and coloration: Molecular mechanisms and aquaculture perspectives",
    year = "2021",
    journal = "Reviews in Aquaculture",
    abstract = "Abstract Fish coloration, evolved from selection and adaptation, is a prominent feature of remarkable aquaculture merits. Fish possess more pigment cell types than any other vertebrates and are an excellent model for the study of mechanisms underlying skin coloration and pigmentation at levels from molecular genetics to system biology. How to effectively improve skin colour in ornamental and aquaculture fish has long been a focus on selective breeding programmes. In this review article, we introduce different types of chromatophore and early development of pigmentation, describe cellular mechanisms related to morphological and physiological changes of body colour and demonstrate applications of single‐sex control and molecular marker–assisted breeding in body colour selection. We also reviewed genes that have been found involving in neural crest migration and development, as well as those involved in melanin‐based coloration and other types of pigmentation, and explored how to use transgenic technology for enhancing fish body colour. The applications of genome editing and other omics technologies in relation to fish coloration are also illustrated. Finally, we present our perspectives about future fish coloration research and practice in aquaculture. Taken together, this review is expected to provide an update on cellular and molecular mechanisms in fish coloration and pigmentation, which will likely promote body colour–based molecular breeding programmes in aquaculture.",
    url = "https://doi.org/10.1111/raq.12583",
    doi = "10.1111/raq.12583",
    openalex = "W3172652410",
    references = "doi101111pcmr12040"
}

Abstract Endowing artificial advanced materials and systems with biomimetic self‐regulatory intelligence is of paramount significance for the development of somatosensory soft robotics and adaptive optoelectronics. Herein, a bioinspired phototropic MXene‐reinforced soft tubular actuator is reported that exhibits omnidirectional self‐orienting ability and is capable of quickly sensing, continuously tracking, and adaptively interacting with incident light in all zenithal and azimuthal angles of 3D space. The novelty of the soft tubular actuator lies in three aspects: 1) the new polymerizable MXene nanomonomer shows high compatibility with liquid crystal elastomer (LCE) matrices and can be in situ photopolymerized into the polymer networks, thus enhancing the mechanical and photoactuation properties; 2) the distinct hollow and radially symmetrical structure facilitates the actuator with fast photoresponsiveness and phototropic performance through retarding the heat conduction along the radial direction; 3) the MXene‐LCE soft tubular actuator simultaneously integrates sensing, actuation, and built‐in feedback loop, thus leading to a high light‐tracking accuracy and adaptive phototropism like a hollow stem of plants in nature. As a proof‐of‐concept demonstration, an adaptive photovoltaic system with solar energy harvesting maximization is illustrated. This work can provide insights into the development of artificial intelligent materials toward adaptive optoelectronics, intelligent soft robotics, and beyond.

@article{doi101002adfm202201884,
    author = "Yang, Mengyuan and Xu, Yiyi and Zhang, Xuan and Bisoyi, Hari Krishna and Xue, Pan and Yang, Jiajia and Yang, Xiao and Valenzuela, Cristian and Chen, Yuanhao and Wang, Ling and Feng, Wei and Li, Quan",
    title = "Bioinspired Phototropic MXene‐Reinforced Soft Tubular Actuators for Omnidirectional Light‐Tracking and Adaptive Photovoltaics",
    year = "2022",
    journal = "Advanced Functional Materials",
    abstract = "Abstract Endowing artificial advanced materials and systems with biomimetic self‐regulatory intelligence is of paramount significance for the development of somatosensory soft robotics and adaptive optoelectronics. Herein, a bioinspired phototropic MXene‐reinforced soft tubular actuator is reported that exhibits omnidirectional self‐orienting ability and is capable of quickly sensing, continuously tracking, and adaptively interacting with incident light in all zenithal and azimuthal angles of 3D space. The novelty of the soft tubular actuator lies in three aspects: 1) the new polymerizable MXene nanomonomer shows high compatibility with liquid crystal elastomer (LCE) matrices and can be in situ photopolymerized into the polymer networks, thus enhancing the mechanical and photoactuation properties; 2) the distinct hollow and radially symmetrical structure facilitates the actuator with fast photoresponsiveness and phototropic performance through retarding the heat conduction along the radial direction; 3) the MXene‐LCE soft tubular actuator simultaneously integrates sensing, actuation, and built‐in feedback loop, thus leading to a high light‐tracking accuracy and adaptive phototropism like a hollow stem of plants in nature. As a proof‐of‐concept demonstration, an adaptive photovoltaic system with solar energy harvesting maximization is illustrated. This work can provide insights into the development of artificial intelligent materials toward adaptive optoelectronics, intelligent soft robotics, and beyond.",
    url = "https://doi.org/10.1002/adfm.202201884",
    doi = "10.1002/adfm.202201884",
    openalex = "W4214877580",
    references = "doi101002adma201905111, doi101002adma202004754"
}

Taking inspiration from beautiful colors in nature, structural colors produced from nanostructured metasurfaces have shown great promise as a platform for bright, highly saturated, and high-resolution colors. Both plasmonic and dielectric materials have been employed to produce static colors that fulfil the required criteria for high-performance color printing, however, for practical applications in dynamic situations, a form of tunability is desirable. Combinations of the additive color palette of red, green, and blue enable the expression of further colors beyond the three primary colors, while the simultaneous intensity modulation allows access to the full color gamut. Here, we demonstrate an electrically tunable metasurface that can represent saturated red, green, and blue pixels that can be dynamically and continuously controlled between on and off states using liquid crystals. We use this to experimentally realize ultrahigh-resolution color printing, active multicolor cryptographic applications, and tunable pixels toward high-performance full-color reflective displays.

@article{doi101038s41377022008068,
    author = "Badloe, Trevon and Kim, Joohoon and Kim, Inki and Kim, Wonsik and Kim, Wook Sung and Kim, Young‐Ki and Rho, Junsuk",
    title = "Liquid crystal-powered Mie resonators for electrically tunable photorealistic color gradients and dark blacks",
    year = "2022",
    journal = "Light Science \& Applications",
    abstract = "Taking inspiration from beautiful colors in nature, structural colors produced from nanostructured metasurfaces have shown great promise as a platform for bright, highly saturated, and high-resolution colors. Both plasmonic and dielectric materials have been employed to produce static colors that fulfil the required criteria for high-performance color printing, however, for practical applications in dynamic situations, a form of tunability is desirable. Combinations of the additive color palette of red, green, and blue enable the expression of further colors beyond the three primary colors, while the simultaneous intensity modulation allows access to the full color gamut. Here, we demonstrate an electrically tunable metasurface that can represent saturated red, green, and blue pixels that can be dynamically and continuously controlled between on and off states using liquid crystals. We use this to experimentally realize ultrahigh-resolution color printing, active multicolor cryptographic applications, and tunable pixels toward high-performance full-color reflective displays.",
    url = "https://doi.org/10.1038/s41377-022-00806-8",
    doi = "10.1038/s41377-022-00806-8",
    openalex = "W4225091459",
    references = "doi101021acsphotonics0c00947"
}

Abstract Behavioral ecologists have long studied the role of coloration as a defense against natural enemies. Recent reviews of defensive coloration have emphasized that these visual signals are rarely selected by single predatory receivers. Complex interactions between signaler, receiver, and environmental pressures produce a striking array of color strategies—many of which must serve multiple, sometimes conflicting, functions. In this review, we describe six common conflicts in selection pressures that produce multifunctional color patterns, and three key strategies of multifunctionality. Six general scenarios that produce conflicting selection pressures on defensive coloration are: (1) multiple antagonists, (2) conspecific communication, (3) hunting while being hunted, (4) variation in transmission environment, (5) ontogenetic changes, and (6) abiotic/physiological factors. Organisms resolve these apparent conflicts via (1) intermediate, (2) simultaneous, and/or (3) plastic color strategies. These strategies apply across the full spectrum of color defenses, from aposematism to crypsis, and reflect how complexity in sets of selection pressures can produce and maintain the diversity of animal color patterns we see in nature. Finally, we discuss how best to approach studies of multifunctionality in animal color, with specific examples of unresolved questions in the field.

@article{doi101093behecoarac056,
    author = "Postema, Elizabeth and Lippey, Mia K. and Armstrong-Ingram, Tiernan",
    title = "Color under pressure: how multiple factors shape defensive coloration",
    year = "2022",
    journal = "Behavioral Ecology",
    abstract = "Abstract Behavioral ecologists have long studied the role of coloration as a defense against natural enemies. Recent reviews of defensive coloration have emphasized that these visual signals are rarely selected by single predatory receivers. Complex interactions between signaler, receiver, and environmental pressures produce a striking array of color strategies—many of which must serve multiple, sometimes conflicting, functions. In this review, we describe six common conflicts in selection pressures that produce multifunctional color patterns, and three key strategies of multifunctionality. Six general scenarios that produce conflicting selection pressures on defensive coloration are: (1) multiple antagonists, (2) conspecific communication, (3) hunting while being hunted, (4) variation in transmission environment, (5) ontogenetic changes, and (6) abiotic/physiological factors. Organisms resolve these apparent conflicts via (1) intermediate, (2) simultaneous, and/or (3) plastic color strategies. These strategies apply across the full spectrum of color defenses, from aposematism to crypsis, and reflect how complexity in sets of selection pressures can produce and maintain the diversity of animal color patterns we see in nature. Finally, we discuss how best to approach studies of multifunctionality in animal color, with specific examples of unresolved questions in the field.",
    url = "https://doi.org/10.1093/beheco/arac056",
    doi = "10.1093/beheco/arac056",
    openalex = "W4285292250",
    references = "doi101007s1068201698543"
}

Although single-function camouflage under infrared/visible bands has made great advances, it is still difficult for camouflage materials to cope with the synergy detection spanning both visible and infrared spectra and adapt to complex and variable scenarios. Herein, a trilayer composite integrating thermal insulation, heat absorption, solar/electro-thermal conversions, and thermochromism is fabricated for visible and infrared dual camouflages by combining anisotropic MXene/reduced graphene oxide hybrid aerogel with the n-octadecane phase change material in its bottom and a thermochromic coating on its upper surface. Benefiting from the synergetic heat-transfer suppression derived from the thermal insulation of the porous aerogel layer and the heat absorption of the n-octadecane phase-change layer, the composite can serve as a cloak to hide the target signatures from the infrared images of its ambient surroundings during the day in the jungle and at night in all scenes and can assist the target in escaping visual surveillance by virtue of its green appearance. For desert scenarios, the composite can spontaneously increase its surface temperature via its solar-thermal energy conversion, merging infrared images of the targets into the high-temperature surroundings; meanwhile, it can vary the surface color from the original green to yellow, enabling the target to visually disappear from ambient sands and hills. This work provides a promising strategy for designing adaptive and adjustable integrated camouflage materials to counter multiband surveillance in complicated environments.

@article{doi101021acsnano3c00573,
    author = "Li, Baixue and Luo, Zhuo and Yang, Wei‐Guang and Sun, Hao and Ding, Yun and Yu, Zhong‐Zhen and Yang, Dongzhi",
    title = "Adaptive and Adjustable MXene/Reduced Graphene Oxide Hybrid Aerogel Composites Integrated with Phase-Change Material and Thermochromic Coating for Synchronous Visible/Infrared Camouflages",
    year = "2023",
    journal = "ACS Nano",
    abstract = "Although single-function camouflage under infrared/visible bands has made great advances, it is still difficult for camouflage materials to cope with the synergy detection spanning both visible and infrared spectra and adapt to complex and variable scenarios. Herein, a trilayer composite integrating thermal insulation, heat absorption, solar/electro-thermal conversions, and thermochromism is fabricated for visible and infrared dual camouflages by combining anisotropic MXene/reduced graphene oxide hybrid aerogel with the n-octadecane phase change material in its bottom and a thermochromic coating on its upper surface. Benefiting from the synergetic heat-transfer suppression derived from the thermal insulation of the porous aerogel layer and the heat absorption of the n-octadecane phase-change layer, the composite can serve as a cloak to hide the target signatures from the infrared images of its ambient surroundings during the day in the jungle and at night in all scenes and can assist the target in escaping visual surveillance by virtue of its green appearance. For desert scenarios, the composite can spontaneously increase its surface temperature via its solar-thermal energy conversion, merging infrared images of the targets into the high-temperature surroundings; meanwhile, it can vary the surface color from the original green to yellow, enabling the target to visually disappear from ambient sands and hills. This work provides a promising strategy for designing adaptive and adjustable integrated camouflage materials to counter multiband surveillance in complicated environments.",
    url = "https://doi.org/10.1021/acsnano.3c00573",
    doi = "10.1021/acsnano.3c00573",
    openalex = "W4361266474",
    references = "doi101002adfm202008006, doi101002adma201706807, doi101016jcej2019122622, doi101021acsnano5b02781, doi101021acsnano7b08889, doi101021acsnano8b05739, doi101021acsnano8b08913, doi101021ja01539a017, doi101038ncomms2251, doi101038ncomms7368, doi101038s4146702124916w, doi101038s41598019443492, doi101111pcmr12040"
}

Color plays an important role in human visual perception, reflecting the spectrum of objects. However, the existing infrared and visible image fusion methods rarely explore how to handle multi-spectral/channel data directly and achieve high color fidelity. This paper addresses the above issue by proposing a novel method with diffusion models, termed as Dif-Fusion, to generate the distribution of the multi-channel input data, which increases the ability of multi-source information aggregation and the fidelity of colors. In specific, instead of converting multi-channel images into single-channel data in existing fusion methods, we create the multi-channel data distribution with a denoising network in a latent space with forward and reverse diffusion process. Then, we use the the denoising network to extract the multi-channel diffusion features with both visible and infrared information. Finally, we feed the multi-channel diffusion features to the multi-channel fusion module to directly generate the three-channel fused image. To retain the texture and intensity information, we propose multi-channel gradient loss and intensity loss. Along with the current evaluation metrics for measuring texture and intensity fidelity, we introduce Delta E as a new evaluation metric to quantify color fidelity. Extensive experiments indicate that our method is more effective than other state-of-the-art image fusion methods, especially in color fidelity. The source code is available at https://github.com/GeoVectorMatrix/Dif-Fusion.

@article{doi101109tip20233322046,
    author = "Yue, Jun and Fang, Leyuan and Xia, Shaobo and Deng, Yue and Ma, Jiayi",
    title = "Dif-Fusion: Toward High Color Fidelity in Infrared and Visible Image Fusion With Diffusion Models",
    year = "2023",
    journal = "IEEE Transactions on Image Processing",
    abstract = "Color plays an important role in human visual perception, reflecting the spectrum of objects. However, the existing infrared and visible image fusion methods rarely explore how to handle multi-spectral/channel data directly and achieve high color fidelity. This paper addresses the above issue by proposing a novel method with diffusion models, termed as Dif-Fusion, to generate the distribution of the multi-channel input data, which increases the ability of multi-source information aggregation and the fidelity of colors. In specific, instead of converting multi-channel images into single-channel data in existing fusion methods, we create the multi-channel data distribution with a denoising network in a latent space with forward and reverse diffusion process. Then, we use the the denoising network to extract the multi-channel diffusion features with both visible and infrared information. Finally, we feed the multi-channel diffusion features to the multi-channel fusion module to directly generate the three-channel fused image. To retain the texture and intensity information, we propose multi-channel gradient loss and intensity loss. Along with the current evaluation metrics for measuring texture and intensity fidelity, we introduce Delta E as a new evaluation metric to quantify color fidelity. Extensive experiments indicate that our method is more effective than other state-of-the-art image fusion methods, especially in color fidelity. The source code is available at https://github.com/GeoVectorMatrix/Dif-Fusion.",
    url = "https://doi.org/10.1109/tip.2023.3322046",
    doi = "10.1109/tip.2023.3322046",
    openalex = "W4387682254",
    references = "doi101146annurevpsych010213115035"
}

Recent years have witnessed a rapid development in the field of structural coloration, colors generated from the interaction of nanostructures with light. Compared to conventional color generation based on pigments and dyes, structural color generation exhibits unique advantages in terms of spatial resolution, operational stability, environmental friendliness, and multiple functionality. Here, we discuss recent development in structural coloration based on layered thin films and optical metasurfaces. This review first presents fundamentals of color science and introduces a few popular color spaces used for color evaluation. Then, it elaborates on representative physical mechanisms for structural color generation, including Fabry-Pérot resonance, photonic crystal resonance, guided mode resonance, plasmon resonance, and Mie resonance. Optimization methods for efficient structure parameter searching, fabrication techniques for large-scale and low-cost manufacturing, as well as device designs for dynamic displaying are discussed subsequently. In the end, the review surveys diverse applications of structural colors in various areas such as printing, sensing, and advanced photovoltaics.

@article{doi101515nanoph20220063,
    author = "Wang, Danyan and Liu, Zeyang and Wang, Haozhu and Li, Moxin and Guo, L. Jay and Zhang, Cheng",
    title = "Structural color generation: from layered thin films to optical metasurfaces",
    year = "2023",
    journal = "Nanophotonics",
    abstract = "Recent years have witnessed a rapid development in the field of structural coloration, colors generated from the interaction of nanostructures with light. Compared to conventional color generation based on pigments and dyes, structural color generation exhibits unique advantages in terms of spatial resolution, operational stability, environmental friendliness, and multiple functionality. Here, we discuss recent development in structural coloration based on layered thin films and optical metasurfaces. This review first presents fundamentals of color science and introduces a few popular color spaces used for color evaluation. Then, it elaborates on representative physical mechanisms for structural color generation, including Fabry-Pérot resonance, photonic crystal resonance, guided mode resonance, plasmon resonance, and Mie resonance. Optimization methods for efficient structure parameter searching, fabrication techniques for large-scale and low-cost manufacturing, as well as device designs for dynamic displaying are discussed subsequently. In the end, the review surveys diverse applications of structural colors in various areas such as printing, sensing, and advanced photovoltaics.",
    url = "https://doi.org/10.1515/nanoph-2022-0063",
    doi = "10.1515/nanoph-2022-0063",
    openalex = "W4321435242",
    references = "doi101002smll201907626"
}

The adaptationist dogma among research on animal colors has recently come into question, as several studies have suggested that bright, conspicuous colors in animals are not always adaptive, but evolutionarily neutral. However, demonstrating that a color trait is evolutionarily neutral is complicated—there is no consensus as to what qualifies as sufficient evidence for a color trait to be considered neutral. Our study discusses these issues while investigating the function of coloration in a conspicuously colored blue crayfish, Cambarus monongalensis, which inhabits semi-terrestrial burrows and rarely interacts with the surface. By correlating sex and size with color variables, we found that three body regions of C. monongalensis do not vary in color with respect to sex or size, thereby rejecting two of our adaptive hypotheses. Additionally, visual models of crayfish and predators suggest that crayfish may not be able to distinguish body colors across the body and against backgrounds, but that predators can distinguish these colors. By integrating these results with prior studies, we discuss how bright colors in crayfish may are an ideal system to investigate the neutral theory of color evolution. Ultimately, such research may challenge the adaptationist dogma amongst research on animal color and other phenotypes.

@article{doi101093behecoaraf063,
    author = "Graham, Z. and Avery, Julian",
    title = "Color Variation and Visual Modeling Provide No Support for Adaptive Coloration in a Blue Crayfish",
    year = "2025",
    journal = "Behavioral Ecology",
    abstract = "The adaptationist dogma among research on animal colors has recently come into question, as several studies have suggested that bright, conspicuous colors in animals are not always adaptive, but evolutionarily neutral. However, demonstrating that a color trait is evolutionarily neutral is complicated—there is no consensus as to what qualifies as sufficient evidence for a color trait to be considered neutral. Our study discusses these issues while investigating the function of coloration in a conspicuously colored blue crayfish, Cambarus monongalensis, which inhabits semi-terrestrial burrows and rarely interacts with the surface. By correlating sex and size with color variables, we found that three body regions of C. monongalensis do not vary in color with respect to sex or size, thereby rejecting two of our adaptive hypotheses. Additionally, visual models of crayfish and predators suggest that crayfish may not be able to distinguish body colors across the body and against backgrounds, but that predators can distinguish these colors. By integrating these results with prior studies, we discuss how bright colors in crayfish may are an ideal system to investigate the neutral theory of color evolution. Ultimately, such research may challenge the adaptationist dogma amongst research on animal color and other phenotypes.",
    url = "https://www.semanticscholar.org/paper/257126e5159679ad321d61b91757bf04855bf499",
    doi = "10.1093/beheco/araf063",
    is_oa = "true",
    number = "4",
    semanticscholar_citation_count = "1",
    semanticscholar_id = "257126e5159679ad321d61b91757bf04855bf499",
    volume = "36"
}

In recent decades, there has been a marked surge in the development of marine-by-product-derived ingredients for cosmetic applications, driven by the increasing demand for natural, sustainable, and high-performance formulations. Marine animal by-products, particularly those from fish, crustaceans, and mollusks, represent an abundant yet underutilized source of bioactive compounds with notable potential in cosmeceutical innovation. Generated as waste from the fishery and seafood-processing industries, these materials are rich in valuable bioactives, such as chitosan, collagen, peptides, amino acids, fatty acids, polar lipids, lipid-soluble vitamins, carotenoids, pigments, phenolics, and mineral-based substrates like hydroxyapatite. Marine by-product bioactives can be isolated via several extraction methods, and most importantly, green ones. These compounds exhibit a broad spectrum of skin-health-promoting effects, including antioxidant, anti-aging, anti-inflammatory, antitumor, anti-wrinkle, anti-hyperpigmentation, and wound-healing properties. Moreover, applications extend beyond skincare to include hair, nail, and oral care. The present review provides a comprehensive analysis of bioactives obtained from marine mollusks, crustaceans, and fish by-products, emphasizing modern extraction technologies with a focus on green and sustainable approaches. It further explores their mechanisms of action and documented efficacy in cosmetic formulations. Finally, the review outlines current limitations and offers future perspectives for the industrial valorization of marine by-products in functional and environmentally-conscious cosmetic development.

@article{doi103390md23080299,
    author = "Papadopoulou, Sofia Neonilli A. and Adamantidi, Theodora and Kranas, Dimitrios and Cholidis, Paschalis and Anastasiadou, Chryssa and Τσούπρας, Αλέξανδρος",
    title = "A Comprehensive Review on the Valorization of Bioactives from Marine Animal By-Products for Health-Promoting, Biofunctional Cosmetics",
    year = "2025",
    journal = "Marine Drugs",
    abstract = "In recent decades, there has been a marked surge in the development of marine-by-product-derived ingredients for cosmetic applications, driven by the increasing demand for natural, sustainable, and high-performance formulations. Marine animal by-products, particularly those from fish, crustaceans, and mollusks, represent an abundant yet underutilized source of bioactive compounds with notable potential in cosmeceutical innovation. Generated as waste from the fishery and seafood-processing industries, these materials are rich in valuable bioactives, such as chitosan, collagen, peptides, amino acids, fatty acids, polar lipids, lipid-soluble vitamins, carotenoids, pigments, phenolics, and mineral-based substrates like hydroxyapatite. Marine by-product bioactives can be isolated via several extraction methods, and most importantly, green ones. These compounds exhibit a broad spectrum of skin-health-promoting effects, including antioxidant, anti-aging, anti-inflammatory, antitumor, anti-wrinkle, anti-hyperpigmentation, and wound-healing properties. Moreover, applications extend beyond skincare to include hair, nail, and oral care. The present review provides a comprehensive analysis of bioactives obtained from marine mollusks, crustaceans, and fish by-products, emphasizing modern extraction technologies with a focus on green and sustainable approaches. It further explores their mechanisms of action and documented efficacy in cosmetic formulations. Finally, the review outlines current limitations and offers future perspectives for the industrial valorization of marine by-products in functional and environmentally-conscious cosmetic development.",
    url = "https://doi.org/10.3390/md23080299",
    doi = "10.3390/md23080299",
    openalex = "W4412885657",
    references = "doi103390md21100514"
}