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https://hdl.handle.net/1959.11/17799
Title: | Evolution of Cranial Shape in Caecilians (Amphibia: Gymnophiona) | Contributor(s): | Sherratt, Emma (author); Gower, David J (author); Klingenberg, Christian Peter (author); Wilkinson, Mark (author) | Publication Date: | 2014 | DOI: | 10.1007/s11692-014-9287-2 | Handle Link: | https://hdl.handle.net/1959.11/17799 | Abstract: | Insights into morphological diversification can be obtained from the ways the species of a clade occupy morphospace. Projecting a phylogeny into morphospace provides estimates of evolutionary trajectories as lineages diversified information that can be used to infer the dynamics of evolutionary processes that produced patterns of morphospace occupation. We present here a large-scale investigation into evolution of morphological variation in the skull of caecilian amphibians, a major clade of vertebrates. Because caecilians are limbless, predominantly fossorial animals, diversification of their skull has occurred within a framework imposed by the functional demands of head-first burrowing. We examined cranial shape in 141 species, over half of known species, using X-ray computed tomography and geometric morphometrics. Mapping an existing phylogeny into the cranial morphospace to estimate the history of morphological change (phylomorphospace), we find a striking pattern: most species occupy distinct clusters in cranial morphospace that closely correspond to the main caecilian clades, and each cluster is separated by unoccupied morphospace. The empty spaces in shape space are unlikely to be caused entirely by extinction or incomplete sampling. The main caecilian clades have different amounts of morphological disparity, but neither clade age nor number of species account for this variation. Cranial shape variation is clearly linked to phyletic divergence, but there is also homoplasy, which is attributed to extrinsic factors associated with head-first digging: features of caecilian crania that have been previously argued to correlate with differential microhabitat use and burrowing ability, such as subterminal and terminal mouths, degree of temporal fenestration (stegokrotaphy/zygokrotaphy), and eyes covered by bone, have evolved and many combinations occur in modern species. We find evidence of morphological convergence in cranial shape, among species that have eyes covered by bone, resulting in a narrow bullet-shaped head. These results reveal a complex history, including early expansion of morphospace and both divergent and convergent evolution resulting in the diversity we observe today. | Publication Type: | Journal Article | Source of Publication: | Evolutionary Biology, 41(4), p. 528-545 | Publisher: | Springer New York LLC | Place of Publication: | United States of America | ISSN: | 1934-2845 0071-3260 |
Fields of Research (FoR) 2008: | 060809 Vertebrate Biology 060309 Phylogeny and Comparative Analysis 060303 Biological Adaptation |
Fields of Research (FoR) 2020: | 310914 Vertebrate biology 310410 Phylogeny and comparative analysis 310403 Biological adaptation |
Socio-Economic Objective (SEO) 2008: | 970106 Expanding Knowledge in the Biological Sciences | Socio-Economic Objective (SEO) 2020: | 280102 Expanding knowledge in the biological sciences | Peer Reviewed: | Yes | HERDC Category Description: | C1 Refereed Article in a Scholarly Journal |
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Appears in Collections: | Journal Article |
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