DISSERTATION RESEARCH: Linking population genetic patterns of introgressive hybridization to the breakdown of reproductive barriers in Darters (Percidae)

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Biodiversity depends on the interplay of maintenance and dissolution of reproductive isolating barriers between species. However, the completeness of reproductive barriers may not be uniform across a species' geographic range, resulting in a mosaic of hybridization and genetic exchange between species. A mosaic pattern of hybridization appears within the overlapping geographic ranges of Rainbow Darters (Etheostoma caeruleum) and Orangethroat darters (E. spectabile) in the southeastern United States. This project will investigate the formation of hybrids and the selection pressures that act against them, using experimental crosses within and between these darter species, and will determine geographic patterns in the strength and symmetry of post-mating barriers. Hybridization can be a serious threat to endangered species, but the relationship between human-mediated disturbance and breakdown of reproductive barriers is not understood. Nearly one third of the approximately 230 species of darters are considered vulnerable, threatened, or endangered, and this research will inform conservation and management of these and other species. This project also provides training in population genetics, reproductive biology, museum techniques, and field-based research to undergraduate students and contributes specimen and data to museum collections and public data bases.