Dissertation Research: Mechanisms Maintaining Sympatric Morphological Divergence in Ilyodon Furcidens

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A fundamental goal of evolutionary ecology is to understand the processes that maintain population-level diversity. Theoretical models suggest that the interaction between divergent natural selection and sexual selection can maintain within-species diversity, ultimately leading to speciation. This project seeks to identify the mode of divergent selection on trophic morphology and to test if sexual selection on the same trait also contributes to population divergence. The live-bearing fish Ilyodon furcidens vary in feeding morphology, and males have striking color variation that is correlated with morphology. Comparative analyses are used to test the hypothesis that variation in dentition and gill-raker number results from diet specialization and, when coupled with variation in mating success, causes population divergence. Additionally, mate choice experiments will identify female preferences and test the hypothesis that assortative mating maintains the resulting population variation. This research will improve understanding of adaptive evolution, particularly of how local processes lead to evolutionary diversification. By integrating the fields of animal form and function, population biology, and behavioral ecology, this work empirically explores the roles of natural and sexual selection in within-population divergence. Both U.S. and Mexican undergraduates will be trained in laboratory and field research techniques, and the results will be disseminated to the scientific and broader community via publication and a website.