Multiple mating of queens and the sterility of workers among eusocial hymenoptera

Abstract

If females of eusocial Hymenoptera in large nests, in which division of labor exists, mate with one male, there is no reason for workers to refrain from producing their own sons and taking care of the sons of other workers. It is of selective advantage for the workers to take care of their brothers if the queen mates with more than two males. This has been shown by comparing the coefficients of relatedness and by genetic models. Another genetic model, with two loci and two alleles which allows for genetic variation both in the workers' and queen's behaviour, shows that multiple mating cannot be an adaptation enabling the queen to control the behaviour of workers. This result is due to some feature of the haplo-diploid genetic model in which linkage disequilibrium is higher among males than among females. If workers are able to perceive the multiple mating of the queen, they can apply a conditional strategy: “take care of nephews if the queen mates with one male, take care of brothers if it mates with more than two males”. Such a conditional strategy allows multiple mating to be an adaptation enabling the queen to control the behaviour of the workers. This is a paradoxical result: the ability of workers to perceive multiple mating allows the queen to prevent them from producing their own male progeny. Other functions of multiple mating are not excluded by the models presented here.