Meeting Abstract
Sexual conflict over mating is common in nature and arises because males and females have clashing interests over whether, when, how often and for how long to mate. In some cases, these conflicts may result in significant costs to females, which can have negative consequences on the health of a population. One factor affecting sexual conflict is the intensity of male-male competition in the environment. We hypothesized that females are more harassed and thus harmed in more densely populated areas. We also hypothesized that females would be harassed more in populations composed of male-biased sex ratios. We used freshwater amphipods in the genus Hyalella to test these hypotheses. In amphipods, there is sexual conflict over the duration of pre-copulatory mate guarding. Males prefer to pair for a longer period than females. We set up populations of amphipods and manipulated the relative proportion of the two sexes. The sex ratio commonly found in nature (40% male) was used as a control. Other populations were either female or male biased. Separately, we also varied the size of the container to manipulate amphipod density. We used female survival as our response variable to assess the costs associated with sexual conflict. As the percentage of males increased from 40% to 60% in populations of the same density, female survival decreased from 82% to 15%. Contrary to our predictions, females survived better at the higher of the two densities. As number of females in a population decreases, the population has less genetic diversity and hence a greater risk of local extinction. It can be concluded that sexual conflict has a negative effect on population health.
