Male parentage and queen mating frequency in the bumblebee Bombus ignitus (Hymenoptera: bombinae)
Kin selection theory predicts conflict between queens and workers in the social insect colony with respect to male production. This conflict arises from the haplodiploid system of sex determination in Hymenoptera that creates relatedness asymmetries in which workers are more closely related to the sons of other workers than to those of the queen. In annual hymenopteran societies that are headed by a single queen, the mating frequency of the queen is the only factor that affects the colony kin structure. Therefore, we examined the mating structure of queens and the parentage of males in a monogynous bumblebee, Bombus ignitus, using DNA microsatellites. In the seven colonies that were studied, B. ignitus queens mated once, thereby leading to the prediction of conflict between the queen and workers regarding male production. In each of the five queen-right colonies, the majority of the males (95%) were produced by the colony’s queen. In contrast, workers produced approximately 47% of all the males in two queenless colonies. These results suggest that male production in B. ignitus is a conflict between queen and workers.