Secondary sexual traits are common in animals, and male traits are sometimes so strongly developed that they appear maladaptive. What causes a particular combination of male traits and female preferences in a given population, and why do populations evolve different combinations of traits? The investigators are addressing this question in the guppy at several levels: the mechanisms of female choice, the effects of female choice on the evolution of color patterns within populations, and testing the prediction (from sexual selection theory) of co-divergence of female choice criteria and male traits among populations. This is a collaborative effort with John A. Endler, University of California @ Santa Barbara. They propose to explicitly test two major predictions from sexual selection theory. First, they will investigate the reciprocal evolution of male traits and female choice. Second, they propose to explore the effects of the sensory drive process, and how this interacts with the evolution of male traits and female choice. In order to do this, they propose to carry out three long-term selection experiments which should lead to long term genetic changes in female preferences and male traits. One experiment selects for male traits and looks for evolution of female preferences. Another selects for female preferences (via selection on spectral sensitivity) and looks for evolution of male traits. The third modifies the perception of color patterns (to females and predators) by varying ambient light color and predator color vision, and looks for changes in male traits and female preferences. The proposed continuation of the investigators work will yield an unusually complete understanding of the processes which affect the long term joint genetic change of female choice and secondary male traits under the influence of sexual selection and predation.
