Biological Sciences, School of


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Poster presented at Society for Integrative & Comparative Biology 2018 Annual Meeting. January 3-7, 2018, San Francisco, CA




Twenty-four species of crocodile populate the globe today, but this richness represents a minute fraction of the diversity and disparity of Crocodyliformes since their origin early in the Triassic. Across this clade, three major diversification events into the aquatic realm have occurred. Aquatic and terrestrial habitats impose differing selective pressures on body size. However, previous research on this topic in Crocodyliformes remains qualitative in nature. In this study, our goal was to quantify the influence of habitat (terrestrial versus aquatic) on the evolution of body size in Crocodyliformes. We find a history of repeated body size increase and convergence following shifts to an aquatic lifestyle, suggesting common selective pressures on life in water spanning multiple independent aquatic clades.

All three aquatic clades converge on greater optima, with shorter phylogenetic half-lives and smaller stationary variances • Lung volume, which has long been proposed as the main constraint on diving capacity, is only a constraint at sizes greater than 10 kg • The rate of cooling strongly constrains diving capacity at sizes smaller than 10 kg and may be the primary driver of larger body sizes in diving crocodyliformes