Honeybees on strike

The honey bee is often used as the poster species for altruistic behaviour, behaving in a way costly to itself in order to benefit others or a group. In the ultimate act of self-sacrifice, worker bees do not reproduce themselves but instead dedicate their lives to the care of the single reproducing Queen Bee and her hundreds of offspring. However, recent studies by researchers in Poland seem to suggest it’s not all happy families within the hive and that some workers may become ‘Rebel Bees’, reproducing themselves despite the negative consequences that has on the hive.

A hive usually consists of a single female Queen and thousands of male drones to reproduce with her, all supported by the Queen’s sterile daughters, who act as workers helping to raise their mother’s offspring. But why would an individual choose a life of sterility if natural selection is centred on the idea of getting your genes into the next generation?
The reason workers usually do not produce their own young can be explained by the concepts highlighted by W.D. Hamilton in the 1960s. Hamilton’s rule showed that a social trait such as altruism can evolve if the cost to the individual is outweighed by the benefit to a relative multiplied by the relatedness between the two.

Honeybees operate a haplodiploid sex-determination system, meaning that whilst females are produced by normal sexual reproduction, males develop from unfertilised eggs. This means that though females are diploid with two sets of chromosomes, males only receive half the amount so are haploid. Therefore it is probable that each worker is more related to any one of the queen’s daughters (her sisters) than to offspring the worker herself might produce. Considering the costs associated with reproducing, workers therefore maximise their inclusive fitness (i.e. the amount of their genes they help continue into the next generation) by rearing their sisters instead, rendering themselves sterile.

However, interesting new research from a team lead by Professor Woyciechowski at Jagiellonian University, Poland has shown that a slight loss in relatedness when the Queen Bee is replaced with a new one can lead to workers rebelling against the system and reproducing themselves. When the reigning Queen produces a daughter to replace her as Head of the Colony the workers suffer a switch in the relatedness of the offspring they are expected to help rear. This transition between Queens means workers change from rearing their brothers and sisters to nieces and nephews. The professor explained that “This drop in relatedness causes the old queen’s workers to lay their own eggs.”

The Polish research team tested this observation by splitting up a bee colony; replicating the temporary lack of a Queen that usually occurs after a swarm (when the queen and part of her colony leave the hive to find a new nest site). They compared their observations with the behaviours of the natural swarm and found the same result in both. Before a new Queen had developed the worker larvae themselves grew ovaries in place of the food-producing glands they normally have to nurse the Queen’s young. This ability to switch from nursing to rebel strategy shows that, although honeybees usually rely on an altruistic lifestyle, a slight change in situation can soon turn co-operation into conflict.