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      On the Relationship between the Macroevolutionary Trajectories of Morphological Integration and Morphological Disparity

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      PLoS ONE
      Public Library of Science

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          Abstract

          How does the organization of phenotypes relate to their propensity to vary? How do evolutionary changes in this organization affect large-scale phenotypic evolution? Over the last decade, studies of morphological integration and modularity have renewed our understanding of the organizational and variational properties of complex phenotypes. Much effort has been made to unravel the connections among the genetic, developmental, and functional contexts leading to differential integration among morphological traits and individuation of variational modules. Yet, their macroevolutionary consequences on the dynamics of morphological disparity–the large-scale variety of organismal designs–are still largely unknown. Here, I investigate the relationship between morphological integration and morphological disparity throughout the entire evolutionary history of crinoids (echinoderms). Quantitative analyses of interspecific patterns of variation and covariation among characters describing the stem, cup, arm, and tegmen of the crinoid body do not show any significant concordance between the temporal trajectories of disparity and overall integration. Nevertheless, the results reveal marked differences in the patterns of integration for Palaeozoic and post-Palaeozoic crinoids. Post-Palaeozoic crinoids have a higher degree of integration and occupy a different region of the space of integration patterns, corresponding to more heterogeneously structured matrices of correlation among traits. Particularly, increased covariation is observed between subsets of characters from the dorsal cup and from the arms. These analyses show that morphological disparity is not dependent on the overall degree of evolutionary integration but rather on the way integration is distributed among traits. Hence, temporal changes in disparity dynamics are likely constrained by reorganizations of the modularity of the crinoid morphology and not by changes in the variability of individual traits. The differences in integration patterns explain the more stereotyped morphologies of post-Palaeozoic crinoids and, from a broader macroevolutionary perspective, call for a greater attention to the distributional heterogeneities of constraints in morphospace.

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          Author and article information

          Contributors
          Role: Editor
          Journal
          PLoS One
          PLoS ONE
          plos
          plosone
          PLoS ONE
          Public Library of Science (San Francisco, USA )
          1932-6203
          2013
          17 May 2013
          : 8
          : 5
          Affiliations
          [1]Department of Biology and Biochemistry, University of Bath, Bath, England
          Ludwig-Maximilians-Universität München, Germany
          Author notes

          Competing Interests: The author has declared that no competing interests exist.

          Conceived and designed the experiments: SG. Performed the experiments: SG. Analyzed the data: SG. Contributed reagents/materials/analysis tools: SG. Wrote the paper: SG.

          Article
          PONE-D-12-32311
          10.1371/journal.pone.0063913
          3656834
          23691115
          483b26f9-0e42-482e-8c59-14f97d7b08fb

          This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

          Page count
          Pages: 8
          Funding
          This research was supported by a Leverhulme Trust research grant (Grant F/00 351/Z). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
          Categories
          Research Article
          Biology
          Computational Biology
          Evolutionary Biology
          Forms of Evolution
          Macroevolution
          Organismal Evolution
          Animal Evolution
          Paleontology
          Invertebrate Paleontology
          Paleobiology
          Evolutionary Developmental Biology
          Evolutionary Theory
          Computer Science
          Computer Modeling

          Uncategorized
          Uncategorized

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