Western Honey Bee - Queen-Worker Conflict

Queen-Worker Conflict

In instances where a fertile female worker produces drones, a conflict arises between her interests and those of the queen. The worker shares half of her genes with the drone and a quarter with her brothers, favoring her own offspring over those of the queen. The queen, however, shares half of her genes with her sons and only a quarter with the sons of fertile female workers. This situation pits the interest of the worker against those of the queen and other workers, who will each try to maximize their reproductive fitness by rearing the offspring most related to them. This relationship leads to the phenomenon known as "worker policing". In these rare situations, other worker bees in the hive which are more genetically related to the queen's sons than those of the fertile workers and will actively patrol the hive and remove the worker-laid eggs. Another form of worker-based policing is aggression toward the fertile females. Some studies have suggested the presence of a queen pheromone that may aid workers in discrimination of worker and queen-laid eggs, whereas other studies claim that egg viability is the key difference in eliciting the behavior. Worker policing is an example of forced altruism, in which the benefits of worker reproduction are reduced and the benefit of rearing the queen's offspring are raised.

In very rare instances, workers can subvert the policing mechanisms of the hive and lay eggs that are removed at a lower rate by other workers, a condition termed the "anarchic syndrome". Anarchic workers can activate their ovaries at a higher rate and contribute a greater proportion of males to the hive. Although an increase in the number of drones would decrease the overall productivity of the hive, the reproductive fitness of the mother of the drones would greatly increase. Thus, the anarchic syndrome is an example of selection working at both the individual and group levels in opposite directions for hive stability.

Under ordinary circumstances, the death or removal of a queen is sufficient to increase reproduction in workers. A significant proportion of the workers will have active ovaries in the absence of a queen. The workers of the hive produce a last batch of drones before the hive eventually collapses. During this period, worker policing is noticeably absent. However, in certain groups of bees, worker policing continues.

According to kin selection theory, worker policing is not favored if a queen does not mate multiply. Workers would be related by three-quarters of their genes, and so the difference in relatedness between the sons of the queen and those of the other workers would decrease. Thus, the benefit obtained by policing is negated. Under these circumstances, policing is less favored. Experiments confirming this hypothesis have shown a correlation between higher mating rates and increased rates of worker policing in many species of social hymenoptera.