Sexual conflict promotes species coexistence through negative frequency dependence

A major challenge in community ecology is to understand the mechanisms promoting stable local coexistence. A necessary feature of local coexistence is that species show negative frequency dependence, rescuing rare species from exclusion. However, most studies have focused on ecological differences driving negative frequency dependence, ignoring non-ecological mechanisms such as reproductive interactions. Here, we combined field studies with behavioural and mesocosm experiments to investigate how reproductive interactions within and between species promote coexistence. Our results indicate that the intensity of male mating harassment and sexual conflict increases as species become more common, reducing female productivity and leading to negative frequency dependence. Moreover, field surveys reveal that negative frequency dependence operates in natural settings, consistent with our experimental results. These results suggest that sexual conflict can promote local coexistence and highlights the importance of studying reproductive interactions together with ecological differences to better understand the mechanisms promoting species coexistence.