Swarm-founding in the polistine wasps: the importance of finding many microsatellite loci in studies of adaptation.

We developed 52 microsatellite loci for the wasp, Polybioides tabidus, for the purpose of studying the evolution and inclusive fitness consequences of swarm-founding. The large number of loci is important for three reasons that may apply to many other systems. Heterozygosity was low in our target species, yet we found enough polymorphic loci for accurate kinship studies in this species. Many monomorphic loci were polymorphic in other polistine wasps, making comparative studies possible. Finally, enough loci amplified over a broad range of species to add a historical dimension. We sequenced six loci in other polistine wasps and used the flanking sequences to construct a phylogeny. Based on this phylogeny, we infer that swarm-founding has evolved independently three times in the polistine wasps.

Unrelated helpers in a social insect.

High-resolution genetic markers have revolutionized our understanding of vertebrate mating systems, but have so far yielded few comparable surprises about kinship in social insects. Here we use microsatellite markers to reveal an unexpected and unique social system in what is probably the best-studied social wasp, Polistes dominulus. Social insect colonies are nearly always composed of close relatives; therefore, non-reproductive helping behaviour can be favoured by kin selection, because the helpers aid reproductives who share their genes. In P. dominulus, however, 35% of foundress nestmates are unrelated and gain no such advantage. The P. dominulus system is unlike all other cases of unrelated social insects, because one individual has nearly complete reproductive dominance over subordinates who could have chosen other reproductive options. The only significant advantage that subordinates obtain is a chance at later reproduction, particularly if the queen dies. Thus, P. dominulus societies are functionally unlike other social insects, but similar to certain vertebrate societies, in which the unrelated helpers gain through inheritance of a territory or a mate.