37.3 Thursday, Jan. 5 Snake Sex in the City or the Country? Different mating aggregation densities generate asymmetry in postcopulatory sexual selection in two populations of red-sided garter snakes FRIESEN, Chris/R*; ESTES, Suzanne; MASON, Robert/T; Oregon State Univ.; Oregon State Univ.; Portland State Univ. email@example.com
Models show that reproductive traits may quickly diverge via a coevolutionary arms race due to sexual conflict and sperm competition. The density of mating aggregations of garter snakes at spring emergence varies among populations which may lead to divergence because of sexual conflict and sexual selection within different social contexts. We found evidence of asymmetrical behavioral and postcopulatory prezygotic sexual isolation between two populations of Red-sided Garter Snakes (Thamnophis sirtalis parietalis). Asymmetry in reproductive isolation has been modeled as the transitory effect of rapid divergence of sexually selected traits facilitated by drift along the stable line of equilibria. Our study populations differ in several respects the most salient of which is low versus high density mating aggregations. The population with high density aggregations, and probably with the highest level of sexual conflict over mating, was also the population that exhibited homotypic mate preference and sperm precedence.