Genotypic and kin discrimination in a solitary Hymenopterous parasitoid: Implications for speciation

In Hymenopterous parasitoids, host discrimination enables a female to avoid ovipositing in an already parasitized host. A female recognizes such hosts by the presence of external or internal pheromone markings that differ depending on whether the host has been parasitized by the same female, a conspecific or a female of another species. If the ability to recognize hosts parasitized by genetically distant females does exist and results in a change in acceptance, this behaviour would have an impact on sympatric speciation. We tested this hypothesis in Anaphes victus Huber (Hymenoptera: Mymaridae) by examining two special cases of intraspecific discrimination: the recognition of different biotypes (i.e. genotypic discrimination) and the recognition of close relatives (i.e. kin discrimination). Female A. victus had to choose between two categories of parasitized eggs in petri dishes. They were able to discriminate between biotypes and always preferred to oviposit in eggs parasitized by females of other biotypes rather than by females of their own biotype. Females were also able to discriminate between their sisters and unrelated conspecifics and preferred to oviposit in eggs parasitized by unrelated females, but did not discriminate between their sisters and themselves. These results suggest that there is a polymorphic genetic component in host discrimination and that such a preference could induce a reduction in gene flow between populations. That this discrimination system shares many analogies with the complex system of communication of social Hymenoptera is discussed.