Genetic relatedness in colonies of tropical wasps with multiple queens.

The evolution of worker behavior in the social insects is usually explained by kin selection: although workers do not produce offspring, they do reproduce their genes by aiding the reproduction of relatives. The most difficult case for kin selection theory would be species in which workers are fully capable of reproducing but instead opt to rear brood of low relatedness. These conditions are perhaps best fulfilled by the swarm-founding wasps because they have little caste differentiation and their colonies usually have multiple queens, which should lower relatedness. Estimates of within-colony relatedness for three species in this group confirm that it is sometimes (but not always) very low. Inbreeding is negligible in these species, so the hypothesis that inbreeding may raise relatedness is not supported. The maintenance of worker behavior in such species is a significant challenge for kin selection theory.