GROUP NESTING AND REPRODUCTIVE CONFLICT IN PRIMITIVELY EUSOCIAL WASPS
HUGHES, COLIN ROBERT
Doctor of Philosophy
Group living is intriguing because animals that live together incur automatic costs but gain no automatic benefits. Chief among these costs are increased competition for opportunities to reproduce, and increased parasite and disease transmission. I investigate some factors that favor group living in Polistes wasps in the face of these costs, and two arenas of competition to reproduce within groups. Reviewing my own work and the literature, I show that groups withstand predation better than single females, suggesting that predation is a fundamental cause of group nesting. Group nesting females are shown to have emerged from the same nest and to nest near their natal-nest site. This suggests that relatedness and dispersal are important factors. On balance, the evidence indicates that queens do not manipulate their progeny to predispose some of them to becoming subordinate group members. Reproductive conflict is expected among females that have cooperated in starting a new nest since the queen lays most of the eggs. During the period in which the first workers emerge, subordinate nest foundresses of P. exclamans did not change their behavior in ways which would increase their chances of laying eggs. They continued to work for the colony and suffered higher mortality after worker emergence than they had before. This continued altruism may be favored because it increases the otherwise low probability that nests of this species have of producing offspring. Intense reproductive conflict is also expected when a queen dies and workers vie to become the new queen. I simulated queen death by removing queens from 20 nests of P. instabilis. The result was consistent among the 3 study sites which ranged from tropical to temperate; one of the oldest workers became the new queen. All new queens had ranked second in the dominance hierarchy to the original queens. Age was more important than size in determining dominance, and the identity of the new queen. Large females that probably could win high rank by fighting may be prevented from doing so by the likelihood that this would cause widespread fighting among nestmates thereby greatly lowering the fitness of the new queen.