Queen killing is linked to high worker-worker relatedness in a social wasp

Social insect colonies are pinnacles of evolved altruism, but also contain dramatic conflict among relatives [1, 2]. 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 this conflict [3, 4], but facultative responses to within-colony relatedness are rarely reported [5-7]. 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 [8]. 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 expla...