We investigated the role of nest predation in selecting for group living in the primitively eusocial wasp Polistes bellicosus. Predation rates were so high that most colonies had to build new nests at least once during the season. To determine the responses of females to nest predation we marked all females on 49 nests and then removed the nests without harming the adults. Larger groups of females were more successful at building new nests. There was a per capita advantage in nest success for females in groups as measured 44 d after the simulated predation event, and the advantage did not diminish with increasing group size. Reproductive competition among females was dependent on number of females on the nest and age of females, and not on whether the nest was original or rebuilt. Ovaries developed as females grew older and were more developed in females on nests with greater numbers of females. Group living may be maintained in this population of Polistes bellicosus because of the advantages larger groups have in recovering from nest predation.
Cyclical oligogyny appears to be the best hypothesis for the maintenance of high levels of relatedness among colony members in epiponine wasps, a tribe of Neotropical social wasps characterized by many queens per colony and reproduction by swarms that contain many queens and workers. The cyclical oligogyny hypothesis predicts that queen number declines as colonies age, so colonies about to fission have very few queens, which results in high relatedness among future queens. We investigate key features of this hypothesis by analyzing demographic characteristics of colonies and relatedness in a Venezuelan population of Polybia emaciata. These colonies averaged 30 queens, 276 workers, and 26 males. Relatedness among workers from the same colony of P. emaciata was 0.24 (SE = 0.076). This value can be reconciled with the high numbers of queens only if queens are highly related, as expected under cyclical oligogyny. We found substantial demographic evidence supporting the cyclical oligogyny hypothesis from an examination of numbers of queens, their ages, and eggs per queen. By contrast, we found no support for the hypotheses that relatedness is elevated in epiponine wasps because of inbreeding (f = 0.07) or because of reproductive dominance among queens.
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