In many species, females exhibit a localized immune response to male seminal proteins that helps defend against sexually transmitted diseases passed by the male. However, this immune response may also kill sperm. Therefore, in species where females mate with multiple males, the females immune response may reduce a males reproductive potential by limiting the number of sperm available for insemination. Preliminary work in several animal systems has suggested that males pass proteins along with their sperm that enhance sperm survival by inhibiting an effective immune response. As a consequence, females may experience a higher risk of pathogenic infection with each mating, leading to a conflict of interest between the sexes over the females immune response to insemination. The main focus of this proposal is to investigate the role this antagonistic relationship between the sexes plays in (1) the evolution of reproductive and immunological proteins and (2) speciation. With regard to the first objective, male reproductive success will be assessed when they are mated with immune suppressed females in the fruit fly, Drosophila melanogaster (e.g. more viable sperm are stored in the immune suppressed females reproductive tract). The proposal will also investigate which female immune pathways are being compromised, as well as which male proteins are involved in immune suppression. The second objective will examine the potential for the sexually antagonistic relationship to maintain species boundaries among several hybridizing species of crickets in the genus Allonemobius. In short, the objectives outlined in this proposal will elucidate the potential for sexual antagonism to contribute to the evolution of immunity and reproduction, and how the co-evolution between these systems contributes to speciation. The proposed research will involve an educational outreach program in local K-12 classrooms and will involve undergraduate and graduate students from various ethnic backgrounds. Research results will be disseminated in the scientific literature as well as in more popular media and through a public access website.
