Single gene makes worker bees buzz off and conquer
Their nifty trick of producing false queens from unfertilised eggs can save their colony
A small change in the genetic make-up of the Cape bee turns a social creature into a fighting parasite with a nasty sting in its tail.
And remarkably, the evolution of the trait might be due to the southeasterly wind that ravages the Western Cape in summer.
The change ensures infertile worker bees begin to lay eggs and fight other colonies – a process often observed in African honeybee colonies in northeastern SA, where for decades beekeepers have suffered losses caused by the phenomenon.
Now its genetic basis has been described for the first time by entomologists at the universities of Stellenbosch and Pretoria who were part of a team led by Martin Luther University Halle-Wittenberg, in Germany.
Bees live in large colonies with a distinct social structure. In addition to male drones, numerous infertile female worker bees care for the nest and provide for the queen.
The queen produces the colony’s entire offspring, with male drones developing from her unfertilised eggs and female bees from the fertilised ones. New queens emerge only when the colony divides or when the previous queen has died or is too old to reproduce.
In the Cape bee, however, some worker bees are able to produce female offspring — known as false queens — from unfertilised eggs.
After the animals have been raised in their own colony, the false queens begin to reproduce more of their kind and can invade foreign bee colonies and ultimately take over their hives.
“The phenomenon whereby worker bees have fully developed ovaries and the ability to produce their own offspring from unfertilised eggs occasionally happens and is called parthenogenesis,” said biologist Eckart Stolle, who led the study published in Molecular Biology and Evolution.
Cape bees’ ability to produce females from unfertilised eggs is called thelytoky. Stolle’s colleague, Denise Aumer, said: “The syndrome is uncommon, but evolutionarily it makes sense. When a queen dies suddenly, this process is a way to save the colony.”
The researchers said: “This ability has been suggested as the reason for the evolution of thelytoky in [the Cape bee] as the endemic region of this subspecies is characterised by suddenly changing and very windy weather, which might make it difficult for queens to return to their colonies after mating flight.”
Scientists have spent several years looking for the genetic basis for thelytoky, and the Halle biologists found the explanation when they compared the genome of Cape bees that produce parasitic offspring with those that produce normal offspring.
The scientists discovered a special gene that is responsible for the development of the parasitic offspring. A tiny variation in the code of this gene sets thelytoky in motion.
The researchers also found this is a dominant genetic trait. “Over time, this should result in more and more bee colonies with this trait. However, this is not the case. Obviously, the underlying mechanism is more complex,” said Stolle.
The scientists suspect the thelytoky variant only works in combination with the normal variant or that the thelytoky variant on its own may even be lethal for the animals.
Thelytoky has only been witnessed in a handful of species, including several globally invasive ants.