Convergent evolution of worker policing by egg eating in the honeybee and common wasp

Kevin R. Foster, Francis L. W. Ratnieks

Abstract

Mutual policing, where group members suppress each others' reproduction, is hypothesized to be important in the origin and stabilization of biological complexity. Mutual policing among workers in social insects can reduce within–colony conflict. However, there are few examples. We tested for worker policing in the common wasp Vespula vulgaris. Workers rapidly removed worker–laid eggs but left most queen–laid eggs (four out of 120 worker eggs versus 106 out of 120 queen eggs remained after 1h). Ovary dissection (1150 workers from six colonies) revealed that a small but significant number of workers have active ovaries (4%) equivalent to approximately five to 25 workers per colony. Consistent with effective policing of worker reproduction, microsatellite analysis of males (270 individuals from nine colonies) detected no workers' sons. Worker policing by egg eating has convergently evolved in the common wasp and the honeybee suggesting that worker policing may have broad significance in social evolution. Unlike the honeybee, relatedness patterns in V.vulgaris do not explain selection for policing. Genetic analysis (340 workers in 17 nests) revealed that workers are equally related to the queen's and other workers' sons (worker–worker relatedness was 0.51 ± 0.04, 95% confidence interval).Worker policing in V.vulgaris may be selected due to the colony–level benefit of conflict suppression.