Biologists have been debating the role that mixed genetic heritage plays in your beehive. As children, we learned that there are three castes of honey bees – queen, workers, and drones. [That’s wrong – it’s two castes (queen/worker) and two genders (male/female) – but, thanks to those grade-school teachers, I sometimes still mess this up sometimes!]
Queens are mothers (Happy Mother’s Day), drones are males, and workers do all the work. A genetic quandary grew out of the recognition that few animals willingly tend the offspring of others – it makes no sense from a purely evolutionary-biology perspective. Yet, worker bees are perpetual spinsters, devoting themselves to the care, feeding, training, and safety of their younger sisters. According to modern genetics theory, that probably shouldn’t be happening.
It wasn’t until the 1960s that the idea of eusociality (the social activity of the caste division in animals) was more generally understood and the odd behaviour was explained. Biologists have come to learn that sister creatures with haploid fathers (as drones are) are extremely closely related – each sister shares 75% of the same DNA. (In humans and most other animals, the relatedness between sisters is 50%). So, by caring for many sisters, a worker is assured that much of her own DNA is passed along for another generation.
But there is another aspect to the genetic success of the honey bee, and that’s the idea that the colony itself is a live organism – each bee is a tiny unit, each bee acts effectively like an individual cell. Groups of bees make up organs in a manner similar to cells making up organs – within the colony, there are groups of bees that work together to feed, clean, circulate air, build new tissue (wax), defend against intruders, and care for offspring. Unlike cells in a body, of course, bees are almost identical and can move from one organ-activity to another. Seen in this context, the colony represents an individual which reproduces by swarming. As a unit, the colony’s DNA is preserved and spread.
Relatedness and eusociality are fascinating parts of the honey bee’s natural history. Eusociality has been described by Suzanne Batra (1966), and later E.O. Wilson, to include the social structure of creatures such as ants, wasps, and bees (Hymenoptera) and termites (Isoptera) which practice communal living where (1) generations overlap, (2) there is a reproductive division of labour (sterile and non-sterile members), and (3) cooperative work occurs, including foraging and raising of brood. There is much more to this, including the idea of super-sisters, or blocks within the colony which are extremely closely related, and the controversial aspect of kin selection, but those stories will wait for a future posting. Until then, Happy Mothers’ Day to all the bees in the hive. (Except for those lazy, inept, and mostly useless drones, of course.)