Queen mating frequencies and genetic relatedness between workers in the hornet Vespa ducalis (Hymenoptera: Vespidae)

Abstract

Vespa ducalis is a monogynous hornet with an annual life cycle. Its colonies are the smallest in the genus Vespa. Generally, it is thought that the number of queen matings and colony size are positively correlated, so we analyzed the queen mating number and genetic relatedness between workers of V. ducalis using microsatellite DNA markers. We examined foundress queens and 20 workers from each of 20 colonies. All colonies were found to have one queen inseminated by one male. The genetic relatedness between workers was 0.724±0.0029 (mean±SE), which is not significantly different from the expected value of 0.75 for full sisters. This result suggests a possible conflict in male production between queens and workers based on kin selection prediction. Therefore, we performed microsatellite analysis of 400 males from 20 colonies to verify whether males are derived from either queens or from workers. No males could be assigned to workers developed ovaries were not found in a total of 880 mature workers. These results strongly suggest that queens dominate production of males in V. ducalis colonies.