Female dispersal in response to sexual conflict in a water strider species (#687)
In water striders, there is sexual conflict over mating rate: males frequently harass females to gain matings, and females resist mating attempts. It is generally admitted that females stop resisting and accept superfluous copulations when male harassment is too intense. However, evidence for convenience polyandry comes from experiments using few individuals confined to a small area. Moreover, convenience polyandry has rarely been observed in nature, where females likely have the opportunity to disperse away from harsh conditions imposed by male harassment. We performed an experiment with Gerris buenoi to investigate the effect of sexual conflict on dispersal behaviour. We hypothesized that dispersal can serve to attenuate sexual conflict and predicted that 1) females should disperse more than males, 2) female dispersal should increase with sexual conflict intensity, and 3) males should have a similar but weaker response than females. Three sex ratios were used to create three different sexual conflict intensities in semi-natural populations. Dispersal was monitored daily for 15 days. Additionally, we made behavioural observations to investigate if dispersal was influenced by individual traits (mating rate, harassment rate, body size). As expected, females dispersed more than males under all intensities of sexual conflict. Also, female dispersal increased with sexual conflict. Males dispersed significantly more when sexual conflict was most intense (under male-biased sex ratio). Our results indicate that dispersal allows escaping from sexual conflict in G. buenoi. Females disperse to avoid intense male harassment, showing that convenience polyandry is not the only means to escape from sexual conflict. Male dispersal in the male-biased sex ratio can be explained tentatively by male-male competition and/or sexual conflict avoidance.