Keep calm, we know each other: kin recognition affects aggressiveness and conflict resolution in a solitary parasitoid

Abstract

Intraspecific competition for indivisible resources can trigger the expression of agonistic behaviour in individuals of many animal species. Aggressiveness and conflict resolution may be influenced by the value individuals place on the resource (subjective resource value) but also by genetic relatedness between competitors. The ability to differentiate genetically related from unrelated individuals (i.e. kin recognition) can play a key role in the dynamics of agonistic interactions between individuals. In this context, the theory of kin selection predicts that competitors should display fewer aggressive behaviours towards closely related individuals. Recognition of kin can be driven by the perception of (1) genetically linked phenotypic cues (phenotypic matching) and/or (2) environmental cues (familiarity). In the hymenopteran solitary parasitoid Eupelmus vuilleti, individuals develop on larvae and pupae of their host, Callosobruchus maculatus, which infest cowpea seeds, Vigna unguiculata. Eupelmus vuilleti females can fight for the host on which they lay their eggs. Here, we investigated the effect of genetic relatedness (genotype) and familiarity (the seed containing the host on which they develop as juveniles) on aggressiveness and contest outcome over hosts in E. vuilleti females. We first demonstrated that the probability of a conflict escalating was affected by the interaction between genetic relatedness and familiarity among females. We then found that familiarity alone affected the likelihood of contest resolution. The occurrence of escalated conflicts was reduced between related and familiar females, and contests were more likely to be clearly resolved when occurring between familiar competitors. Our results highlight a parasitoid wasp's abilities to identify and discriminate kin, showing for the first time that two kin recognition components can interact in mediating competition avoidance for resource access in a solitary insect species.