Group Colony Foundation in Polistes Annularis (Hymenoptera: Vespidae)

Foundresses of primitively eusocial insects have been the focus of many studies ofthe evolution of altruism because these females have a solitary or a social option. Comparing the costs and benefits of these options is one way of gaining insight into the circumstances that originally increased the fitness of individuals pursuing social options. Previous studies have indicated that altruists in small groups may pass on more genes than do solitary individuals (Noonan 198 l; Gibo 1978; Metcalf& Whitt 1977). Variation around an optimum number of foundresses is usually ascribed to a shortage of potential nestmates, especially at locations far from the natal nest site since only natal nestmates begin nests together (Noonan 1981). The current study differs from previous studies because foundress associations are especially large in Polistes annularis, making it likely that benefits to group nesting will be pronounced. It also has several advantages because of the nature of the study site. It is an exposed limestone cliff where all nests including small ones are readily visible, so the complete cohort of sibling nests can be observed, and reproductive success can be assessed without missing any nests. This cliff is a natural site where costs and benefits are unlikely to have been changed because of human alterations to the environment. Since I followed nesting success for several years it is unlikely that the aberrant climate of one year will unduly influence the results. I expect that nests with multiple foundresses on them will suffer lower rates of predation, parasitism and usurpation, since they will be better defended. Nests with multiple foundresses are also less likely to fail because all adults die, since there are multiple females tending the brood on these nests. The constraints of location and available females may limit foundress association size. Since nests are begun by females emerging from the same natal nest, the number of such females available will put an upper limit on foundress associations. In general females that do not disperse far from