Males of many species use multiple ornamental traits and behaviors to compete for and attract mates. If these interact to determine mating success, selection may lead to the evolution of genetically integrated suites of sexual traits and behaviors, known as mating phenotypes. Because hormones can coordinate the expression of suites of traits, they may play a central role in stabilizing these mating phenotypes. This study examines the evolution of the mating phenotype in a common songbird, the dark-eyed junco. Correlations will be measured between morphology used in acquiring mates (size and plumage), the sexual hormone testosterone, and the sexual behaviors mediated by testosterone. The role of current selection in maintaining these correlations will be quantified by associating trait combinations with genetic measurements of mating success. Experiments will examine whether testosterone acts to stabilize the mating phenotype by direct developmental effects on morphology.
This research should lead to a greater understanding of the evolution of groups of functionally related traits and may suggest important roles for hormones in maintaining integration. All work will involve the extensive participation of undergraduates, both as research assistants and collaborators. Undergraduates will be encouraged to develop their own independent projects related to this work.
