Sex-specific Effects of Hybridization in a Species Lacking Degenerate Sex Chromosomes

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Most progress in understanding the genetics of speciation has come through work on model systems like Drosophila, with particular emphasis on the special role of their sex chromosomes. A more comprehensive understanding will require studies of alternative systems, including the vast diversity of species lacking sex chromosomes (most plants, mollusks, marine invertebrates and reptiles). This study uses a combination of breeding and molecular assays in a tidepool invertebrate, the copepod Tigriopus californicus, to examine how speciation occurs when there are no sex chromosomes. Predictions will be tested that address the role of genetic incompatibilities, conflict between nuclear and cytoplasmic genes, and the degree to which incompatibilities are masked by other genes. The genetic underpinnings of sterility vs. viability vs. morphological differences will be examined, as well as the possibility that mild sex-specific second-generation patterns in this species are driven by mechanisms similar to those underlying the strong sex-specific first-generation patterns commonly found in species bearing sex chromosomes.This work will develop genetic resources (single nucleotide polymorphisms, a linkage map) that should prove valuable for a range of future studies by the growing community of researchers focusing on Tigriopus. The research also has conservation implications: it addresses how biodiversity is generated in organisms lacking sex chromosomes. Lastly, this research will enhance outreach to diverse communities and will provide professional training for one postdoctoral associate, one graduate student, and numerous undergraduates, including individuals of underrepresented groups.