The question of how new species arise is an old and difficult one. Despite decades of research, we still lack a clear understanding of what causes speciation. A long standing but little tested hypothesis is that sexual selection (male competition for mates and female mating preferences) can cause speciation as male mating signals and female preferences diversify. Yet, the causes of diversification in mating traits remain elusive. Without such diversification, sexual selection cannot contribute to speciation. Therefore, we cannot understand how sexual selection gives rise to new species without understanding what causes mating traits to diverge. This project will test the hypothesis that sexual selection differs when populations live in different habitats, and that this can lead to diversification of mating traits. It ties together ecology and behavior to understand how they interact to create new species. The project studies the threespine stickleback species complex because both ecology and behavior are implicated in their speciation. Using field and lab experiments, the project focuses on two mating traits that have been shown to be involved in both sexual selection and speciation. These traits are nuptial color and body size. Major goals are to explore how habitat differences influence sexual selection on these traits and to quantify differences between species in mating preferences and male competition. The project will provide training for a postdoctoral scientist, a graduate student, and several undergraduates. The work is timely because the study species are endangered. This work will assist in conservation efforts by helping to identify the critical ecological features that are necessary for the species to persist.
