Meeting Abstract
Reproduction is arguably the most critical component of an organism’s fitness, but mating success does not always translate to reproductive success. In species where females mate with multiple males within a reproductive cycle, males can continue to compete for fertilization after mating has occurred (within the female reproductive tract); this competition can be a powerful driver of reproductive trait evolution. Here we compare six species of Peromyscus mice that have evolved under divergent mating systems to examine the evolution of male and female traits shaped by post-mating sexual selection. We find that in species where females that mate multiply, males invest greater in sperm production than in monogamous species, and we predict that higher sperm production gives these males a competitive advantage. Female control of fertilization weakens as sperm competition increases, and this conflict between the sexes can drive the evolution of adaptive changes in female reproductive physiology, either to limit the frequency of polyspermy or to influence the genotype of the offspring resulting from multiple matings. Within females, we compared the oviduct length and changes in the cell population surrounding oocytes that may regulate fertilization. We suggest that increased oviduct length and cumulus cell density may be mechanisms that regulate access to ova during competitive mating events. Together, our study investigates the association between mating system and the reproductive physiology in closely related species with diverse reproductive strategies.
