One factor thought to play an important role in sex ratio evolution is mating pattern. In the 1930s, R. A. Fisher predicted that a 1:1 ratio would evolve in species with random mating. Later, W. D. Hamilton predicted that biased sex ratios would evolve in populations with non-random mating. While sex ratios correlate with mating patterns across many species, these predictions have not been tested directly. This can be done by allowing sex ratios to evolve, via natural selections, in experimental populations with differing mating patterns. The goals of the proposed research are (1) to follow the process of sex ratio evolution in genetically variable populations with random mating, (2) to determine the behavioral and genetic mechanisms by which sex ratios evolve in these populations, and (3) to assess the genetic correlations among facultative sex ratio responses to multiple environments. For the experiments, we will use a wasp species in which females exhibit complex behavioral control over the sex ratio among their offspring. These experiments represent a novel approach to the study of sex ratio and should provide a rich source of new insights into sex ratio evolution in a species with complex, facultative, variation in sex ratio behavior.
