INFECTION AND COLONY VARIABILITY IN SOCIAL INSECTS

The average relatedness among colony members in the social insects, such as bees, wasps and ants, is often low, contrary to the expectations of kin selection theory. Lower relatedness results from multiple mating by the queens (polyandry) or from the presence of more than one functional queen (polygyny). Among the proposed advantages for such mating systems, selection by parasites for within-colony genetic variability is discussed. Empirical studies of this problem are few, but several lines of evidence suggest a role for parasites, such that genetic diversity reduces the rate of within-group transmission. Theoretical considerations indicate that multiple mating is advantageous under conditions of low mating costs relative to parasite pressure and when intermediately sized colonies have a disproportionately large share of reproductive success in the population. In this view, mating strategies (as in polyandry) and strategies of female associations (as in polygyny) that lead to an increased genetic diversity among offspring are, at least in part, an instance of variance reduction in relation to parasitism.