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Cited by 94Evolution and Paleontology StudiesPaleontology and Stratigraphy of FossilsPaleontology and Evolutionary Biology

Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

Open access
Bapst, David W., Bullock, Peter C., Melchin, Michael J., Sheets, H. David, Mitchell, Charles E.·2012·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.1113870109PMC PMC3295294
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Abstract

The morphological study of extinct taxa allows for analysis of a diverse set of macroevolutionary hypotheses, including testing for change in the magnitude of morphological divergence, extinction selectivity on form, and the ecological context of radiations. Late Ordovician graptoloids experienced a phylogenetic bottleneck at the Hirnantian mass extinction (∼445 Ma), when a major clade of graptoloids was driven to extinction while another clade simultaneously radiated. In this study, we developed a dataset of 49 ecologically relevant characters for 183 species with which we tested two main hypotheses: ( i ) could the biased survival of one graptoloid clade over another have resulted from morphological selectivity alone and ( ii ) are the temporal patterns of morphological disparity and innovation during the recovery consistent with an interpretation as an adaptive radiation resulting from ecological release? We find that a general model of morphological selectivity has a low probability of producing the observed pattern of taxonomic selectivity. Contrary to predictions from theory on adaptive radiations and ecological speciation, changes in disparity and species richness are uncoupled. We also find that the early recovery is unexpectedly characterized by relatively low morphological disparity and innovation, despite also being an interval of elevated speciation. Because it is necessary to invoke factors other than ecology to explain the graptoloid recovery, more complex models may be needed to explain recovery dynamics after mass extinctions.

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Crossref · 10.1073/pnas.1113870109

Cites

43 of 43 references verified0 citation errors · 0 not checkable

Statistics

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Claims the paper makes

0 of 35 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Early recovery is characterized by relatively low morphological disparity and innovation despite elevated speciation.

    “We also find that the early recovery is unexpectedly characterized by relatively low morphological disparity and innovation, despite also being an interval of elevated speciation.”
    Quote in the paperSubstantial claim
  • Findingown data

    Species richness and morphological disparity, measured as mean pairwise distance, share a superficially similar pattern over the entire study interval.

    “Species richness and morphological disparity, measured as mean pair-wise distance (Materials and Methods), do share a superficially similar pattern over our entire study interval (Fig. 2).”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    A general model of morphological selectivity has a low probability of producing the observed pattern of taxonomic selectivity.

    “We find that a general model of morphological selectivity has a low probability of producing the observed pattern of taxonomic selectivity.”
    Quote in the paperSubstantial claim
  • Findingown data

    The joint probability for the observed survivorship at both extinction episodes under morphological selectivity is very low (P < 0.006).

    “The joint probability for the observed survivorship patterns at both extinction episodes under a model of morphological selectivity is very low (P < 0.006).”
    Quote in the paperSubstantial claim
  • Findingown data

    Both richness and disparity decrease prominently after the first extinction episode of the HME.

    “Both richness and disparity decrease prominently after the first extinction episode of the HME.”
    Quote in the paperSubstantial claim
  • May combine two claims. 24
  • Classified as probably not a substantial claim. 17

  • May combine two claims.

    Findingown data

    The drop in disparity lags behind the decline in species richness, and disparity falls farther than richness relative to their preceding maxima before the HME.

    “However, the drop in disparity lags behind the decline in species richness, and disparity falls farther than species richness compared with their respective preceding maxima before the HME.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Under direct selection for neograptine morphology, resampling simulations had a small probability of producing the observed neograptine survivorship patterns: P < 0.09 for Katian-Hirnantian and P < 0.06 for Hirnantian-Llandovery, each with 10,000 simulations.

    “Our resampling analyses for both extinction episodes found that, under a scenario of direct selection for neograptine morphology, there was a small but tangible probability of producing the observed neograptine survivorship patterns (for the Katian-Hirnantian extinction, P < 0.09; for the Hirnantian-Llandovery extinction, P < 0.06; each with 10,000 simulations).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Changes in disparity and species richness are uncoupled, contrary to predictions from adaptive radiation and ecological speciation theory.

    “Contrary to predictions from theory on adaptive radiations and ecological speciation, changes in disparity and species richness are uncoupled.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Graptoloid colony morphology is a good predictor of functional ecology, and morphological diversity can serve as a proxy for ecological diversity.

  • May combine two claims.

    Findingown data

    Mean NND and the NND-based innovation metric decrease with species richness.

    “We find the opposite trend, with mean NND and the NND-based innovation metric decreasing with species richness.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    In the Hirnantian, speciation accelerated among graptoloids while morphological innovation stayed low.

    “Any such explanation must account for both the observed increase in speciation rate and the depressed level of morphological innovation during the Hirnantian.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingnone given

    Changes in morphological innovation and morphological diversity appear to be correlated, though this is not a necessary expectation.

    “In addition, changes in morphological innovation and morphological diversity appear to be correlated, although this is not a necessary expectation based on first principles.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    By all three estimates, morphological change was relatively high during the late Katian but decreased sharply at the onset of the HME.

    “By all three estimates of morphological innovation, the magnitude of morphological change was relatively high during the late Katian but decreased sharply at the onset of the HME (Fig. 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The AZE extinction event also marks an increase in morphological disparity, though this shift is not statistically significant.

    “Surprisingly, this extinction event also marks an increase in morphological disparity, although this shift is not statistically significant (Fig. 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The NND pattern is very similar to the disparity pattern, with a decrease in the Hirnantian and an increase after the AZE.

    “We found NND to be very similar to the pattern shown for disparity in Fig. 2, with a decrease in the Hirnantian and an increase after the AZE (Fig. S1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    All three metrics indicate a decrease in morphological innovation of new species during the HME, though early Silurian dynamics are uncertain.

    “Although dynamics in the early Silurian are somewhat uncertain, all three metrics indicate a decrease in the morphological innovation of new species during the HME.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Mean innovation decreased in response to the mass extinction and remained low for millions of years, despite increased speciation rates for Neograptina.

    “Instead, mean innovation actually decreased in response to the mass extinction and remained at low levels for millions of years, despite the Hirnantian being an interval of increased speciation rates for the Neograptina (7).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [7] source

      Not checked in the free run.

  • May combine two claims.

    Findingreasoning

    In intervals after the AZE, species richness, disparity, and innovation all increased.

    “In the intervals after the AZE, species richness, disparity, and innovation all increased.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Late Ordovician graptoloids underwent a phylogenetic bottleneck at the Hirnantian mass extinction around 445 Ma, with one major clade going extinct while another radiated simultaneously.

    “Late Ordovician graptoloids experienced a phylogenetic bottleneck at the Hirnantian mass extinction (∼445 Ma), when a major clade of graptoloids was driven to extinction while another clade simultaneously radiated.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] source

      Not checked in the free run.

    • cites [15]

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  • May combine two claims.

    Study design and conductcitation

    Mean pairwise distance was selected to measure morphological disparity because it resists sample-size effects and is therefore suitable given large shifts in observed species richness.

    “We chose mean pair-wise distance as our measure of morphological disparity, which is notably robust to changes in number of species sampled (41) and thus well-suited for this study given the large changes in observed species richness.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The spread of variance across many PCO axes implies a highly mosaic pattern of graptoloid evolution in this interval, with few well-developed character complexes.

    “Although this finding precludes a simple discussion or illustration of the morphospace, this spreading of variance across a wide number of PCO axes implies that graptoloid evolution in our study interval was highly mosaic, with few well-developed character complexes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Previous work demonstrated links between graptoloid form, hydrodynamics, and overall ecology, supporting the claim that variation in graptoloid morphology reflects real ecological differences.

    “Previous work has demonstrated links between graptoloid form, hydrodynamics, and overall ecology (31)(32)(33), supporting our claim that variation in graptoloid morphology reflects real ecological differences.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites (31)(32)(33)

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Theory on adaptive radiations predicts that morphological variation should accumulate early in the radiation of the neograptines and that the rate should subsequently slow down.

    “Theory on adaptive radiations also predicts that morphological variation should accumulate early in the radiation of the neograptines and the rate should subsequently slow down (24,25).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [24] source

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    • cites [25]

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  • May combine two claims.

    Interpretationreasoning

    The tests do not reject the possibility that selective extinction favored specific morphological characters among Neograptina, but it is not clear that any uniquely neograptine traits could be the basis for their survival.

    “Although these tests do not reject the possibility that selective extinction may have favored specific morphological characters found among the Neograptina, it is not clear that any of the uniquely neograptine traits could be the basis for their unlikely survival.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S4 (based).

    Premisenone given
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Under a model of adaptive radiation where ecological opportunity promotes diversification, morphological and taxonomic diversity should correlate from interval to interval as new species fill the available ecospace.

    “Under a model of adaptive radiation where ecological opportunity promotes diversification, morphological and taxonomic diversity should correlate from interval to interval as new species fill the available ecospace.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Graptoloids experienced some of the highest extinction intensities among marine invertebrates during the HME, and the surviving taxa were a limited sample of pre-HME lineages.

    “The graptoloids experienced some of the highest extinction intensities among marine invertebrates during the HME (12), and the surviving taxa were a limited sample of pre-HME lineages.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [12]

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisereasoning
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Any evidence of a shift in the rate of morphological change should be in the Early Hirnantian when the neograptines first begin to diversify.

    “Thus, any evidence of a shift in the rate of morphological change should be in the Early Hirnantian when the neograptines first begin to diversify (Fig. 1).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    The inability to find strong correlations may partly result from the small number of intervals analyzed.

    “Our inability to find strong correlations may result in part from the small number of intervals analyzed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    If the intrinsic constraint model were true, no shift to pre-HME innovation levels would be observed, yet a shift to an adaptive radiation-like pattern occurs after the AZE.

    “If this model were true, no shift to pre-HME levels of morphological innovation would be observed, yet there is a shift to an adaptive radiation-like pattern of morphological diversification after the AZE.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Some recent work has shown that functional diversity and morphological diversity can be discordant.

    “However, some recent work has shown that functional diversity and morphological diversity can be discordant (34,35).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [34] source

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    • cites [35] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The small number of neograptine taxa known before the HME makes it difficult to quantitatively assess their characteristic level of morphological divergence.

    “However, the small number of neograptine taxa known before the HME makes it difficult to quantitatively assess their characteristic level of morphological divergence.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The expected bias from variable species richness reinforces the conclusion that Neograptina radiated in the early Hirnantian but new species were less morphologically divergent and all taxa were more clustered.

    “Therefore, the expected bias attributable to variable species richness only reinforces our conclusion that, although the Neograptina radiated in the early Hirnantian, new species were less morphologically divergent, and all taxa present were more clustered in morphospace.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Mitchell demonstrated that the Silurian Neograptina evolved a number of morphologies that converged upon pre-Hirnantian diplograptine forms.

    “Mitchell (18) demonstrated that the Silurian Neograptina evolved a number of morphologies that converged upon pre-Hirnantian diplograptine forms.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mitchell (18)

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    The Diplograptina were much more species-rich and morphologically disparate before the HME but were driven extinct during the Hirnantian glaciation.

    “Although the Diplograptina were much more species-rich and morphologically disparate before the HME (Fig. 1), they were driven to extinction during the Hirnantian glaciation (7,15).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] source

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    • cites [15]

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  • Probably not a substantial claim: may not pass S1 (asserted), S4 (based).

    Premisereasoning
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    If the graptoloid recovery was primarily driven by ecological opportunity, there should be a close relationship between species richness and morphological disparity as the neograptines diversify.

    “If the graptoloid recovery was primarily driven by ecological opportunity, there should be a close relationship between species richness and morphological disparity as the neograptines diversify.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Previous work suggests that only a single morphotype survived the HME and that the number of morphotypes recovered in the Silurian.

    “Previous work suggests that only a single morphotype survived the HME (16,17) and that the number of morphotypes recovered in the Silurian.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [16]

      Not checked in the free run.

    • cites [17] source

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  • May combine two claims.

    Interpretationreasoning

    These trends match theoretical expectations for an adaptive radiation driven by ecological opportunity, but this condition did not develop until several million years after neograptines began rapidly diversifying.

    “These trends match our theoretical expectations for an adaptive radiation driven by ecological opportunity, yet this condition did not develop until several million years after the neograptines began to rapidly diversify.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Graptoloid colony morphology is a good predictor of functional ecology, and morphological diversity can serve as a proxy for ecological diversity.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Only 3% of all possible species-by-trait entries were missing from the data matrix.

    “The resulting data matrix was only missing data for 3% of all possible species/ trait entries.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

    Chen et al. established that the survival and proliferation of the Neograptina during the Hirnantian cannot be explained by stochastic nonselective processes.

    “Chen et al. (7) established that the survival and proliferation of the Neograptina during the Hirnantian cannot be explained by stochastic nonselective processes”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Chen et al. (7)

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The NND-based metric may estimate morphological divergence more accurately than the others, since ancestral forms are likely to lie near their descendants in morphospace.

    “Given that ancestors are more likely to be close in morphospace to their descendants than not, the NND-based metric may be the more accurate estimate of morphological divergence.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Ancestors are more likely than not to lie close to their descendants in morphospace.

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    Together the three innovation metrics bracket the likely range of morphological divergence, although each alone is not a precise estimate of trait change.

    “These individual measures of innovation cannot be considered precise estimates of the degree of trait change, but together they effectively bracket the expected range of possibilities.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The graptolite zones are dated using the time scale of Sadler et al.

    “Absolute time scale for the zones is taken from Sadler et al.(39).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Sadler et al.(39)

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    The analysis adopts phylogenetic relationships from earlier cladistic studies.

    “Phylogenetic relationships are taken from previous cladistic analyses (13, 40).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [13]

      Not checked in the free run.

    • cites [40] source

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  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Disparity shifts were deemed significant using resampling tests with 1,000 bootstraps and a Bonferroni-corrected P < 0.05.

    “Asterisks represent significant shifts in disparity, based on resampling tests with 1,000 bootstraps (P < 0.05, Bonferroni-corrected)(46).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [46]

      Not checked in the free run.

38 of 38

  • The paper relies on this without support.

    The changes in morphological diversity during this interval had not been quantitatively studied before.

    “The changes in morphological diversity during this interval have not been studied quantitatively.”

  • The authors state this as an assumption.

    Graptoloid colony morphology is a good predictor of functional ecology, and morphological diversity can serve as a proxy for ecological diversity.

    “It is possible that this mismatch results from a failure of our assumption that the morphology of graptoloid colonies is a good predictor of their functional ecology and, thus, that morphological diversity can be used as a proxy for ecological diversity.”

  • The authors state this as an assumption.

    The morphological selectivity analysis assumes a linear-selection model favoring species with more neograptine-like colony forms.

    “This calculation assumes a model of linear selection for species with more neograptine-like colony forms.”

  • The authors state this as an assumption.

    The innovation metrics assume that species from the previous zone accurately represent the ancestral stock.

    “assuming that the species in the previous zone represent an accurate estimate of the ancestral stock.”

  • The paper relies on this without support.

    No theoretical explanation exists for why a nonadaptive radiation would later shift to high morphological differentiation, as happened in the early Silurian.

    “There is no theoretical explanation for why a nonadaptive radiation would later shift to high levels of morphological differentiation, however, as occurs in the early Silurian.”

  • The paper relies on this without support.

    Ancestors are more likely than not to lie close to their descendants in morphospace.

    “Given that ancestors are more likely to be close in morphospace to their descendants than not, the NND-based metric may be the more accurate estimate of morphological divergence.”
6 of 6

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Many recent studies followed similar protocols, and the authors adopted these methods as a unifying approach.

    “Many studies have recently followed similar protocols (27,(36)(37)(38), and we adopted these methods here as a unifying approach.”

    From Clades reach highest morphological disparity early in their evolution (2013) · cites this paper as [37]

Cites

Flagged first, then by citations

Research works printed but not linked: 4

  1. SM Stanley Macroevolution: Patterns and Process (Freeman, San Francisco, 1979).
  2. CE Mitchell, et al., Phylogeny of the Ordovician Diplograptoidea. Acta Palaeontologica Sin 46, 332–339 (2007).
  3. NV Sennikov, Manifestations of the global Ordovician-Silurian biotal crisis in the Central Siberian graptolite communities. Russ Geol Geophys 39, 565–574 (1998).
  4. CE Mitchell, Evolution and phylogenetic classification of the Diplograptacea. Palaeontology 30, 353–405 (1987).

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Related

Authors
Bapst, D. W., Bullock, P. C., Melchin, M. J., Sheets, H. D., & Mitchell, C. E.
Affiliations
  • University of Chicago (US)
  • St. Francis Xavier University (CA)
  • Canisius College (US)
  • University at Buffalo, State University of New York (US)
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2012-02-13
Volume
109
Issue
9
Pages
3428-3433
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.1113870109
PMC
PMC3295294
OpenAlex
W1994390563
Cited by
94
References
43
Citations by year
2026: 5 · 2025: 4 · 2024: 5 · 2023: 10 · 2022: 3 · 2021: 4 · 2020: 9 · 2019: 6 · 2018: 6 · 2017: 7 · 2016: 7 · 2015: 2 · 2014: 7 · 2013: 14 · 2012: 5
FWCI
6.63
Type
journal article
Language
en
Open access
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Science Foundation (0418790, 0418794)
  • Natural Sciences and Engineering Research Council of Canada
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
Keywords
morphological disparity, adaptive radiation, ecological release, post-extinction recovery, speciation, macroevolution, extinction selectivity
MeSH terms
Animals, Chordata, Nonvertebrate, Fossils, Models, Biological, Phylogeny, Species Specificity, Zooplankton, Ecosystem, Geologic Sediments, Biodiversity, Genetic Speciation, Extinction, Biological

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