Population structure mediates sexual conflict in water striders.

Sexual conflict occurs when males and females act against each others' interest, typically resulting in selection favoring harmful males. We performed laboratory experiments on sexual conflict that both confined individuals in isolated groups, which prevents selection acting counter to this conflict, and provided more naturalistic multigroup population structures. We show that in water striders, aggressive male mating behavior was strongly favored within groups but not favored in a multigroup population when individuals can freely disperse among groups. These observations explain the persistence of less-aggressive males within natural populations.