Free and open to the public.
Abstract: How distinct species persist in the face of gene flow is a long-standing and central question in evolutionary biology, reinvigorated by the recent realization that hybridization is surprisingly common. Though it is now appreciated that gene flow often occurs before, during, and after speciation, little about the evolutionary impact of hybridization is understood, from the ecological and behavioral forces driving hybridization to the ways in which selection acts on hybrid genomes. My research addresses these questions using replicate, recently formed hybrid populations of swordtail fish. Combining field studies, behavioral observations, and genomic analyses, I find evidence for a crucial role of behavior and sexual selection in shaping the evolution of natural hybrid populations of swordtail fish. I further show that following hybridization, selection on hybrid ancestry has a dramatic impact on genomic patterns and that this effect is strongly modulated by local recombination rates. Together, this work reveals a set of mechanisms that shape hybridization on a population and genetic level.