The outcome of sexual conflict depends on the social environment.

Sexual conflict over reproduction is widespread, and can lead to the evolution of traits in males that enhance their reproductive success but harm the females they mate with. I addressed the broad question of whether the social environment, and in particular relatedness among competing males, is important for the outcome of sexual conflict. I found that male seed beetles plastically adjusted their harmfulness in response to changes in both competitor relatedness and chemical cues to kinship. The conditions that allow non-plastic divergences in harmfulness, however, are more restrictive. The social environment is therefore important for male harmfulness and female fitness.