Dissertation Research: An Examination of Variations on the Theme of Livebearing

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The fish family Poeciliidae includes one species that lays eggs and approximately 200 that bear live young. The livebearers include many species with placentas, a trait commonly thought to exist only in mammals. Placental reproduction is a type of matrotrophy (mother feeding), or post-fertilization maternal provisioning. It has evolved multiple times in a diversity of organisms. Despite its many origins and apparent importance as a life history trait, there is no explanation for what shaped its evolution. The diversity in the Poeciliidae facilitates the study of factors that shape different modes of maternal provisioning. The proposed research includes laboratory, field, and data-mining techniques to examine several hypotheses for the evolution of matrotrophy and reproductive allocation. This work represents the first experimental test of predictions derived from the only theoretical model for the evolution of matrotrophy, examines several ad-hoc hypotheses, and has the potential to generate new, testable, hypotheses. It will facilitate broader studies on the evolution of matrotrophy. It includes collaborations with the theoreticians that developed this model, so that empirical research can inform and modify the current model and make it more biologically realistic. Numerous undergraduates will participate in this research.