Evolution of reproductive proteins in deer mice (Peromyscus)

This dissertation describes evolutionary patterns of female and male reproductive proteins and their potential contribution to speciation in deer mice (Peromyscus). Proteins involved in reproduction are among the most rapidly evolving genes in many taxa. This striking pattern is of particular interest because reproductive proteins mediate species-specific fertilization, and thus changes in these proteins have the potential to contribute to reproductive isolation. In internally fertilized taxa, knowledge of the evolutionary dynamics of reproductive proteins in closely related species is limited primarily to seminal proteins expressed in accessory glands of Drosophila. Investigation of additional taxa and functional classes of proteins is necessary to determine if there is a general pattern of adaptive evolution of reproductive proteins between recently diverged species. In mammals, positive selection has been documented in male and female reproductive proteins among divergent species. The research presented here extends this work by investigating reproductive protein evolution within a mammalian genus. Chapter 1 reports evidence that two egg- coat proteins, ZP2 and ZP3, have evolved under positive selection during diversification of the genus Peromyscus and identifies specific amino acid sites within these proteins that have been targets of selection. Chapter 2 describes patterns of sequence variation of ZP3 within two sister species of Peromyscus. High levels of amino acid polymorphism in both species suggest that balancing selection might promote sequence divergence in ZP3 in these species. Chapter 3 is a comparative analysis of testis protein evolution in three lineages of Muroid rodents: Peromyscus and the genetic model organisms Mus and Rattus. In each lineage, testis-expressed proteins evolve more rapidly, on average, than genes with highest expression in another tissue. Genes with the highest rates of evolution serve a variety of functions. Five of eleven of these genes sequenced in six Peromyscus species show evidence for positive selection. Together, these findings demonstrate that reproductive proteins evolve adaptively between closely related mammalian species, where reproductive isolation has evolved recently. Further, I identify positively selected egg and testis genes and specific amino acid sites that are targets of selection and are promising targets for future functional assays of allelic differences in fertilization potentia