Sex and Tragedy

In evolution, exploitative strategies often create a paradox in which the most successful individual strategy within the group is also the most detrimental strategy for the group, potentially resulting in extinction. With regards to sexual conflict, the overexploitation of females by harmful males can yield similar consequences. Despite these evolutionary implications, little research has addressed why sexual conflict does not ultimately drive populations to extinction. One possibility is that groups experiencing less sexual conflict are more productive than groups with greater conflict. However, most studies of sexual conflict are conducted in a single isolated group, disregarding the potential for selection among groups. We observed how mating aggression in Aquarius remigis water striders performs in isolated group environments as well as within naturalistic multigroup pools in which individuals could freely disperse amongst groups. The free movement of individuals generated variation in aggression and sex-ratio among groups, thereby increasing the importance of between-group selection compared to within-group selection. Females dispersed away from local aggression, creating more favorable mating environments for less-aggressive males. Individual male aggression positively predicted fitness while aggression at the group level negatively predicted fitness, empirically demonstrating the conflict between multiple levels of selection acting on mating aggression