Reproductive compatibility proteins have been shown to evolve rapidly under positive selection leading to reproductive isolation, despite the potential homogenizing effects of gene flow. I characterize the gene that encodes the gamete compatibility protein, bindin, for three broadcast spawning sea star species in the genus Pisaster, in a species-level comparison of bindin gene structure and molecular evolution. I then use phylogeographic patterns and variation in life history characteristics between P. ochraceus and P. brevispinus to test predictions about selection acting on bindin divergence among conspecific populations. I discover that divergence in the repetitive bindin domain structure may be partly influenced by concerted evolution within species. I find modest evidence of positive selection acting on P. ochraceus bindin alleles that is consistent with sexual conflict favoring selection for intraspecific bindin polymorphism, and can be explained in a demographic context of recent population expansions, coupled with the homogenizing effects of concerted evolution.
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Thesis advisor: Hart, Michael
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