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The Influence of Modularity on Cranial Morphological Disparity in Carnivora and Primates (Mammalia)

Goswami, A; Polly, PD; (2010) The Influence of Modularity on Cranial Morphological Disparity in Carnivora and Primates (Mammalia). PLOS ONE , 5 (3) , Article e9517. 10.1371/journal.pone.0009517. Green open access

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Abstract

Background: Although variation provides the raw material for natural selection and evolution, few empirical data exist about the factors controlling morphological variation. Because developmental constraints on variation are expected to act by influencing trait correlations, studies of modularity offer promising approaches that quantify and summarize patterns of trait relationships. Modules, highly-correlated and semi-autonomous sets of traits, are observed at many levels of biological organization, from genes to colonies. The evolutionary significance of modularity is considerable, with potential effects including constraining the variation of individual traits, circumventing pleiotropy and canalization, and facilitating the transformation of functional structures. Despite these important consequences, there has been little empirical study of how modularity influences morphological evolution on a macroevolutionary scale. Here, we conduct the first morphometric analysis of modularity and disparity in two clades of placental mammals, Primates and Carnivora, and test if trait integration within modules constrains or facilitates morphological evolution.Principal Findings: We used both randomization methods and direct comparisons of landmark variance to compare disparity in the six cranial modules identified in previous studies. The cranial base, a highly-integrated module, showed significantly low disparity in Primates and low landmark variance in both Primates and Carnivora. The vault, zygomatic-pterygoid and orbit modules, characterized by low trait integration, displayed significantly high disparity within Carnivora. 14 of 24 results from analyses of disparity show no significant relationship between module integration and morphological disparity. Of the ten significant or marginally significant results, eight support the hypothesis that integration within modules constrains morphological evolution in the placental skull. Only the molar module, a highly-integrated and functionally important module, showed significantly high disparity in Carnivora, in support of the facilitation hypothesis.Conclusions: This analysis of within-module disparity suggested that strong integration of traits had little influence on morphological evolution over large time scales. However, where significant results were found, the primary effect of strong integration of traits was to constrain morphological variation. Thus, within Primates and Carnivora, there was some support for the hypothesis that integration of traits within cranial modules limits morphological evolution, presumably by limiting the variation of individual traits.

Type: Article
Title: The Influence of Modularity on Cranial Morphological Disparity in Carnivora and Primates (Mammalia)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1371/journal.pone.0009517
Publisher version: http://dx.doi.org/10.1371/journal.pone.0009517
Language: English
Additional information: © 2010 Goswami, Polly. 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. This study is based upon research supported by the U.S. National Science Foundation International Research Fellowship OISE #0502186 (to AG). Morphometric data was collected during AG's doctoral research, supported by U.S. National Science Foundation DDIG #0308765, the Field Museum Women-in-Science Fellowship, the Society of Vertebrate Paleontology Predoctoral Fellowship, the American Museum of Natural History Collections Study Grant, the University of California Samuel P. and Doris Welles Fund, and the University of Chicago Hinds Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Keywords: NEW-WORLD MONKEYS, QUANTITATIVE GENETICS, DEVELOPMENTAL INTEGRATION, MANDIBULAR MORPHOLOGY, ONTOGENETIC VARIATION, SIGMODON-FULVIVENTER, VARIATION PATTERNS, GEOMETRIC SHAPE, SAKIS PITHECIA, EVOLUTION
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Genetics, Evolution and Environment
URI: https://discovery.ucl.ac.uk/id/eprint/123928
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