Punctuated gradualism

@article{bé1979chamber,
    author = "Bé, Allan W. H. and Hemleben, Christoph and Anderson, O. Roger and Spindler, Michael and Be, Allan W. H.",
    title = "Chamber Formation in Planktonic Foraminifera",
    year = "1979",
    journal = "Micropaleontology",
    url = "https://doi.org/10.2307/1485304",
    doi = "10.2307/1485304",
    number = "3",
    pages = "294",
    volume = "25"
}

The warm-water planktonic foraminiferal Globorotalia tumida lineage has been studied in a 10-Myr-long stratigraphic sequence (Late Miocene through Recent) from the Indian Ocean to determine long-term evolutionary patterns through the lineage's history, and particularly to study in great detail the evolutionary transition from G. plesiotumida to G. tumida across the Miocene/Pliocene boundary. Sampling resolution was very good, between 5 × 10 3 and 15 × 10 3 yr across the Miocene/Pliocene boundary and about 2 × 10 5 yr otherwise. The test shape was analyzed in edge view, permitting determinations of variation in inflation and elongation of the test. Shape was analyzed quantitatively using eigenshape analysis. This method represents the greatest proportion of variation observed among a collection of shapes by the least number of different shapes. The Late Miocene (10.4-5.6 Myr B.P.) populations exhibited only minor fluctuations in shape that did not result in any net phyletic change. This period of stasis was followed by an 0.6-Myr-long period (between 5.6 and 5.0 Myr B.P.) of gradual transformation of the Late Miocene morphotype (G. plesiotumida) into the Early Pliocene morphotype (G. tumida). The populations were again more or less in stasis in the Pliocene and Pleistocene (5.0 Myr to the present day), so that no major modifications of the newly evolved Early Pliocene morphotype occurred during these 5 Myr. Thus it would appear that the G. tumida lineage, while remaining in relative stasis over a considerable part of its total duration underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching. This pattern does not conform to the gradualistic model of evolution, because that would assume gradual changes throughout the history of the lineage. It also does not conform to the punctuational model, because (1) there was no speciation (lineage branching) in this lineage and (2) the transition was not rapid enough (

@article{malmgren1983evidence,
    author = "Malmgren, Björn A. and Berggren, W. A. and Lohmann, G. P.",
    title = "Evidence for punctuated gradualism in the Late Neogene Globorotalia tumida lineage of planktonic foraminifera",
    year = "1983",
    journal = "Paleobiology",
    abstract = "The warm-water planktonic foraminiferal Globorotalia tumida lineage has been studied in a 10-Myr-long stratigraphic sequence (Late Miocene through Recent) from the Indian Ocean to determine long-term evolutionary patterns through the lineage's history, and particularly to study in great detail the evolutionary transition from G. plesiotumida to G. tumida across the Miocene/Pliocene boundary. Sampling resolution was very good, between 5 × 10 3 and 15 × 10 3 yr across the Miocene/Pliocene boundary and about 2 × 10 5 yr otherwise. The test shape was analyzed in edge view, permitting determinations of variation in inflation and elongation of the test. Shape was analyzed quantitatively using eigenshape analysis. This method represents the greatest proportion of variation observed among a collection of shapes by the least number of different shapes. The Late Miocene (10.4-5.6 Myr B.P.) populations exhibited only minor fluctuations in shape that did not result in any net phyletic change. This period of stasis was followed by an 0.6-Myr-long period (between 5.6 and 5.0 Myr B.P.) of gradual transformation of the Late Miocene morphotype (G. plesiotumida) into the Early Pliocene morphotype (G. tumida). The populations were again more or less in stasis in the Pliocene and Pleistocene (5.0 Myr to the present day), so that no major modifications of the newly evolved Early Pliocene morphotype occurred during these 5 Myr. Thus it would appear that the G. tumida lineage, while remaining in relative stasis over a considerable part of its total duration underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching. This pattern does not conform to the gradualistic model of evolution, because that would assume gradual changes throughout the history of the lineage. It also does not conform to the punctuational model, because (1) there was no speciation (lineage branching) in this lineage and (2) the transition was not rapid enough (",
    url = "https://doi.org/10.1017/s0094837300007843",
    doi = "10.1017/s0094837300007843",
    number = "4",
    pages = "377-389",
    volume = "9"
}

@article{penny1983charles,
    author = "Penny, D.",
    title = "Charles Darwin, Gradualism and Punctuated Equilibria",
    year = "1983",
    journal = "Systematic Biology",
    url = "https://doi.org/10.1093/sysbio/32.1.72",
    doi = "10.1093/sysbio/32.1.72",
    number = "1",
    pages = "72-74",
    volume = "32"
}

@article{rhodes1983gradualism,
    author = "Rhodes, Frank H.T.",
    title = "Gradualism, punctuated equilibrium and the Origin of Species",
    year = "1983",
    journal = "Nature",
    url = "https://doi.org/10.1038/305269a0",
    doi = "10.1038/305269a0",
    number = "5932",
    pages = "269-272",
    volume = "305"
}

Detailed analysis of evolutionary changes in a 10-million-year long Late Neogene lineage of planktonic foraminifera has revealed a pattern that is not consistent with either the gradualistic or the punctuational model of evolution. The lineage was in stasis over a considerable part of its total duration but underwent relatively rapid, but not geologically instantaneous, gradual morphologic change that did not lead to lineage splitting. The term punctuated gradualism is suggested for this evolutionary modality.

@article{doi101126science2254659317,
    author = "Malmgren, B A and Berggren, W A and Lohmann, G P",
    title = "Species formation through punctuated gradualism in planktonic foraminifera.",
    year = "1984",
    journal = "Science (New York, N.Y.)",
    abstract = "Detailed analysis of evolutionary changes in a 10-million-year long Late Neogene lineage of planktonic foraminifera has revealed a pattern that is not consistent with either the gradualistic or the punctuational model of evolution. The lineage was in stasis over a considerable part of its total duration but underwent relatively rapid, but not geologically instantaneous, gradual morphologic change that did not lead to lineage splitting. The term punctuated gradualism is suggested for this evolutionary modality.",
    url = "https://pubmed.ncbi.nlm.nih.gov/17749563/",
    doi = "10.1126/science.225.4659.317",
    pmid = "17749563"
}

Detailed analysis of evolutionary changes in a 10-million-year long Late Neogene lineage of planktonic foraminifera has revealed a pattern that is not consistent with either the gradualistic or the punctuational model of evolution. The lineage was in stasis over a considerable part of its total duration but underwent relatively rapid, but not geologically instantaneous, gradual morphologic change that did not lead to lineage splitting. The term punctuated gradualism is suggested for this evolutionary modality.

@article{malmgren1984species,
    author = "Malmgren, Björn A. and Berggren, W. A. and Lohmann, G. P.",
    title = "Species Formation Through Punctuated Gradualism in Planktonic Foraminifera",
    year = "1984",
    journal = "Science",
    abstract = "Detailed analysis of evolutionary changes in a 10-million-year long Late Neogene lineage of planktonic foraminifera has revealed a pattern that is not consistent with either the gradualistic or the punctuational model of evolution. The lineage was in stasis over a considerable part of its total duration but underwent relatively rapid, but not geologically instantaneous, gradual morphologic change that did not lead to lineage splitting. The term punctuated gradualism is suggested for this evolutionary modality.",
    url = "https://doi.org/10.1126/science.225.4659.317",
    doi = "10.1126/science.225.4659.317",
    number = "4659",
    pages = "317-319",
    volume = "225"
}

@misc{malmgren1984species1,
    author = "Malmgren, B. A. and Berggren, W. A. and Lohmann, G. P",
    title = "Species formation through punctuated gradualism in planktonic foraminifera",
    year = "1984",
    howpublished = "Science, p. 317- 319",
    note = "talkorigins\_source = {true}; raw\_reference = {Malmgren, B. A., Berggren, W. A., and Lohmann, G. P., 1984, Species formation through punctuated gradualism in planktonic foraminifera: Science, p. 317- 319.}"
}

@article{kieser1985a,
    author = "Kieser, J.A. and Groeneveld, H.T.",
    title = "A threshold model for punctuated gradualism",
    year = "1985",
    journal = "Medical Hypotheses",
    url = "https://doi.org/10.1016/0306-9877(85)90126-4",
    doi = "10.1016/0306-9877(85)90126-4",
    number = "3",
    pages = "219-225",
    volume = "17"
}

@incollection{barnosky1987punctuated,
    author = "Barnosky, Anthony D.",
    title = "Punctuated Equilibrium and Phyletic Gradualism",
    year = "1987",
    booktitle = "Current Mammalogy",
    url = "https://doi.org/10.1007/978-1-4757-9909-5\_4",
    doi = "10.1007/978-1-4757-9909-5\_4",
    pages = "109-147"
}

Substantial geographic coverage in paleontological study is essential in testing evolutionary models of phyletic gradualism and punctuated equilibrium. We present a multivariate morphometric study of the late Neogene planktonic foraminiferal clade Globoconella using specimens from four Deep Sea Drilling Project sites (DSDP 284, 207A, 208, and 588) along a latitudinal traverse in the southwest Pacific. During the Late Miocene (7 Ma to 5 Ma), populations of the ancestral species Globorotalia (Globoconella) conomiozea formed a geographic cline showing continuous morphological variation from the temperate sites (DSDP 284 and 207A) to the warm subtropical sites (DSDP 208 and 588). Populations living to the south had higher conical angle and fewer chambers in the final whorl compared to the northern populations. Nevertheless, populations across the entire cline exhibited a coherent, directional trend towards having larger conical angle and fewer chambers through time. At the Miocene/Pliocene boundary, the intensification of the Tasman Front (Subtropical Divergence) possibly isolated the peripheral populations in the warm subtropics from the central stocks of the temperate water masses. The evolutionary trends became decoupled: the central populations gradually lost their keel and transformed into G. (G.) sphericomiozea, while the peripheral populations in the warm subtropical areas retained their keel and evolved into a flattened species, G. (G.) pliozea. The gradual transformation of G. (G.) conomiozea terminalis (a form retaining a keel) into G. (G.) sphericomiozea (a form lacking a keel) occurred during an interval of about 0.2 m.y., with all measured morphologic variables showing continuous and steady changes. The evolution of the central populations follows the model of phyletic gradualism. In peripheral populations, the origin of the descendant species G. (G.) pliozea from the ancestor G. (G.) conomiozea terminalis occurred very rapidly within an interval of less than 0.01 m.y. The population size of G. (G.) pliozea was small at the incipient stage at about 5.05 Ma, but increased rapidly to become dominant during the next 0.2 m.y. when the ancestral species G. (G.) conomiozea terminalis became locally extinct. Following speciation, G. (G.) pliozea exhibited morphological stasis for about 0.6 m.y., until the central stock form G. (G.) puncticulata migrated back to the warm subtropics; during the next 0.5 m.y. of their sympatry, there is no sign of hybridization between these two sister species. The evolution of G. (G.) pliozea follows the model of punctuated equilibrium. The evolution of the Globoconella clade shows both phyletic gradualism and punctuated equilibrium. These two “alternative” evolutionary models complement each other rather than being mutually exclusive. Both models are indispensable towards providing a complete picture of the evolution of Globoconella.

@article{wei1988phyletic,
    author = "Wei, Kuo-Yen and Kennett, James P.",
    title = "Phyletic gradualism and punctuated equilibrium in the late Neogene planktonic foraminiferal clade Globoconella",
    year = "1988",
    journal = "Paleobiology",
    abstract = "Substantial geographic coverage in paleontological study is essential in testing evolutionary models of phyletic gradualism and punctuated equilibrium. We present a multivariate morphometric study of the late Neogene planktonic foraminiferal clade Globoconella using specimens from four Deep Sea Drilling Project sites (DSDP 284, 207A, 208, and 588) along a latitudinal traverse in the southwest Pacific. During the Late Miocene (7 Ma to 5 Ma), populations of the ancestral species Globorotalia (Globoconella) conomiozea formed a geographic cline showing continuous morphological variation from the temperate sites (DSDP 284 and 207A) to the warm subtropical sites (DSDP 208 and 588). Populations living to the south had higher conical angle and fewer chambers in the final whorl compared to the northern populations. Nevertheless, populations across the entire cline exhibited a coherent, directional trend towards having larger conical angle and fewer chambers through time. At the Miocene/Pliocene boundary, the intensification of the Tasman Front (Subtropical Divergence) possibly isolated the peripheral populations in the warm subtropics from the central stocks of the temperate water masses. The evolutionary trends became decoupled: the central populations gradually lost their keel and transformed into G. (G.) sphericomiozea, while the peripheral populations in the warm subtropical areas retained their keel and evolved into a flattened species, G. (G.) pliozea. The gradual transformation of G. (G.) conomiozea terminalis (a form retaining a keel) into G. (G.) sphericomiozea (a form lacking a keel) occurred during an interval of about 0.2 m.y., with all measured morphologic variables showing continuous and steady changes. The evolution of the central populations follows the model of phyletic gradualism. In peripheral populations, the origin of the descendant species G. (G.) pliozea from the ancestor G. (G.) conomiozea terminalis occurred very rapidly within an interval of less than 0.01 m.y. The population size of G. (G.) pliozea was small at the incipient stage at about 5.05 Ma, but increased rapidly to become dominant during the next 0.2 m.y. when the ancestral species G. (G.) conomiozea terminalis became locally extinct. Following speciation, G. (G.) pliozea exhibited morphological stasis for about 0.6 m.y., until the central stock form G. (G.) puncticulata migrated back to the warm subtropics; during the next 0.5 m.y. of their sympatry, there is no sign of hybridization between these two sister species. The evolution of G. (G.) pliozea follows the model of punctuated equilibrium. The evolution of the Globoconella clade shows both phyletic gradualism and punctuated equilibrium. These two “alternative” evolutionary models complement each other rather than being mutually exclusive. Both models are indispensable towards providing a complete picture of the evolution of Globoconella.",
    url = "https://doi.org/10.1017/s0094837300012094",
    doi = "10.1017/s0094837300012094",
    number = "4",
    pages = "345-363",
    volume = "14"
}

Punctuated equilibrium and phyletic gradualism are contrasting patterns of evolution among a spectrum of patterns found in the fossil record. In punctuated equilibrium, species tend to show morphological stasis between abrupt speciation events, whereas in phyletic gradualism species undergo more continuous change.

@misc{sheldon2001punctuated,
    author = "Sheldon, Peter R",
    title = "Punctuated Equilibrium and Phyletic Gradualism",
    year = "2001",
    booktitle = "Encyclopedia of Life Sciences",
    abstract = "Punctuated equilibrium and phyletic gradualism are contrasting patterns of evolution among a spectrum of patterns found in the fossil record. In punctuated equilibrium, species tend to show morphological stasis between abrupt speciation events, whereas in phyletic gradualism species undergo more continuous change.",
    url = "https://doi.org/10.1038/npg.els.0001774",
    doi = "10.1038/npg.els.0001774"
}