Queen Killing Is Linked to High Worker-Worker Relatedness in a Social Wasp

Social insect colonies are pinnacles of evolved altruism but also exhibit dramatic conflict among relatives. In many species, a colony's workers compete with the queen and each other over the production of males. Interspecific comparisons demonstrate the importance of within-colony relatedness in determining the outcome of such conflicts, but facultative responses to within-colony relatedness are rarely reported. Here, I report facultative matricide (worker killing of a colony's queen) in the social wasp Dolichovespula arenaria. Matricide is strongly associated with high worker-worker relatedness, as predicted by theory, because closely related workers value nephews more than brothers. This pattern is the result of variation in both paternity frequency and the paternity skew of colonies with multiple patrilines, implicating worker-worker relatedness rather than a direct effect of multiple mating on queen survival. Furthermore, occasional inbreeding can explain why some multiple-patriline colonies exhibit high paternity skew associated with matricide. In general, these results support the hypothesis that workers can facultatively respond to intracolony relatedness determined by queen mating behavior and demonstrate a novel benefit of polyandry in annual social insects. Facultative matricide shows dramatically how workers are evolutionary actors with interests that can diverge from the queen's, rather than being "extrasomatic projections of her personal genome".