Sea stars, sperm, and sexual selection: how mating systems affect adapative and neutral molecular evolution

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Sexual reproduction by animals can have a strong effect on their genetic variation, and the size of this effect often depends on exactly how sex happens. I study this relationship between sex and genetics in a group of sea stars (called asterinids or cushion stars) that have evolved an astounding variety of reproductive traits such as high-risk sexual behaviour involving the release of vast numbers of tiny eggs and sperm; brood protection and live birth; sibling cannibalism; sex-change; and self-fertilization. Some cushion stars have combinations of these traits that should allow them to avoid inbreeding (and its bad consequences for fitness), but might also subject them to intense sexual selection due to competition among males to fertilize the eggs of females. Other cushion stars have other combinations of these traits that should relax this kind of sexual selection (because males are also females, and fertilize their own eggs), but also predispose them to very strong inbreeding (because the parents mate with themselves, and their offspring rarely move between populations). My research is designed to understand how these sexual differences among species affect both inbreeding and sexual selection by looking at different classes of genes that are expected to mainly respond to one or the other process. Because both sexual selection and inbreeding can cause population differences that lead to the formation of new species, an understanding of the role of these two processes can help us understand speciation and the origins of biodiversity. The results are also interesting and important for other areas of research, including animal breeding and human population biology, in which both inbreeding and sexual selection are important (sometimes competing) evolutionary processes.