Abstracts (first author)
The landscape of sexual selection
Rugged fitness landscapes are thought to promote speciation, as they provide multiple adaptive peaks for populations to occupy. However, they have been rarely characterized, especially for sexual selection. Sexually selected fitness landscapes play a critical role in divergence of mating traits that underpins sexual isolation. We characterized the fitness landscape generated by sexual selection through male competition in stickleback fish. We capitalized on the highly variable genotypic and phenotypic combinations generated in an F2 mapping population to fully characterize the fitness landscape. This approach also allows us to experimentally tease apart selection on multiple traits. We measured fitness through male competition in naturalized habitats, assessing ability of males to acquire territories and defend nests, both of which are essential for access to females. We also measured male mating success. The species we study mate at different densities, which are expected to affect the strength of sexual selection. Thus, we manipulated density to ask whether fitness landscapes at low and high density differ, altering the direction of selection or the trait combinations favored. We then compared these fitness landscapes to naturally occurring phenotypic distributions to assess how sexual selection would affect evolutionary divergence in natural populations, leading to reproductive isolation and speciation. We thus fill a critical gap in our understanding of speciation.