My research investigates evolutionary, behavioral and ecological processes that contribute to the maintenance of variation in the natural environment. Current research projects include laboratory and field work focusing on aspects of how natural and sexual selection contribute to the evolution of morphological, physiological and behavioral traits. My current research program includes: Investigating how mate choice and predation affect the maintenance of genetic variation for age at sexual maturation and body size in the platyfish. Results thus far indicate that in populations with a high risk of predation, alleles for larger size and later maturation increase in frequency, while in low predation populations, alleles for early maturation at smaller sizes increase in frequency. Examining the evolution of the sword in swordtail fishes. This research includes broad phylogenetic comparisons as well as manipulative experiments, directed at determining the costs and benefits of the sword, including energetic costs, predation costs and mating benefits. Results this far indicate that a female preference favoring a male sword appears to have evolved prior to the sword and is shared with a number of species lacking swords, and that multiple sources of selection act on the sword. Investigating the evolutionary and ecological dynamics of a host/parasite system between hermit crabs and a parasitic castrator. This is a relatively new line of research, but results thus far indicate that the prevalence of the parasite varies both seasonally and spatially along the California coast.