How Sex Ratios Influence Pairing Duration in Hyalella Amphipods

Abstract

While sexual conflict research has exploded over the past few decades, we know relatively little about how demographics affect sexual conflict in nature. Sex ratio is a demographic parameter that can affect sexual conflict through male-female encounter rates, which will affect harassment levels experienced by females. The purpose of this study was to test the effects of sex ratios on pairing duration in a freshwater amphipod species in the genus Hyalella. We hypothesized that populations with male-biased sex ratio would experience longer pairing durations than populations with female-biased sex ratios. To test this hypothesis three habitats of replicated populations that vary in sex ratio will be set up: female-biased, male-biased, and equal sex ratios. Our hypothesis was formed because in a female-biased population females are more likely to resist male harassment, while in a male-biased population it becomes costlier in terms of energy to attempt to resist male harassment because more males will be harassing females. Therefore, females in the male-biased population may accept the costs of prolonged guarding periods over costly resistance to pairing. This study will serve to provide important insight into how changes in sex ratio change pairing behavior.