33.4 Thursday, Jan. 5 Parallel evolution of shape divergence in the shells of freshwater turtles inhabiting different flow regimes RIVERA, G*; DAVIS, JN; GODWIN, JC; ADAMS, DC; Iowa State University; Tuskegee University; Alabama Natural Heritage Program; Iowa State University firstname.lastname@example.org
Parallel evolution, the process by which similar selection pressures produce repeatable effects across disparate taxa, is considered strong evidence for the generation of adaptive phenotypes. In aquatic habitats, the velocity of water flow is a major selection pressure and has been shown to influence morphology in a broad array of taxa. We tested whether three confamilial species of freshwater turtle (family Emydidae: Pseudemys concinna, Graptemys nigrinoda and Graptemys pseudogeographica) displayed similar patterns of phenotypic divergence in carapace shape between fast- and slow-flowing aquatic environments. We used (1) geometric morphometrics to quantify shell shape, (2) factorial MANOVA to test the effects of species, sex, and flow, and (3) phenotypic trajectory analysis (PTA) to examine patterns of divergence for the six species-sex groups. We found significant effects on shell shape for all factors. In general, ecomorphs from fast-flowing habitats had flatter shells than those from slow-flowing habitats. Furthermore, results of PTA indicate that the degree to which and way in which ecomorphs differed were concordant across all species. Our findings indicate that flow velocity plays an important role in adaptive divergence of turtle shell shape and also highlights the repeatability of the evolutionary process.