You know when you just want to steal someone else's food, lay on their couch, and swear off men forever? Yeah, same. And the Cape honeybee gets it, too. This species has evolved a unique survival strategy that allows its female worker bees to squat in foreign nests and lay viable eggs without any help from males. In a study published Thursday in PLOS Genetics, researchers take the first steps in determining the evolutionary history of these reproductive quirks.
Most of the time, Apis mellifera capensis is a perfectly normal honeybee. It shares most of its genes in common with other South African honeybee species, and it carries out a typical lifestyle: Female workers do work, a queen lays loads of eggs, and male "drones" fertilize them. Any unfertilized eggs turn into drones, any fertilized eggs turn into workers, and so it goes.
But the life of the Cape honeybee — a sub-species that is usually fairly isolated — takes a dark turn when it has neighbors. When female worker bees encounter the hive of another subspecies, they sneak in and lay eggs of their own.
"Eventually those colonies will die out, because the Cape bees move in there and reproduce and feed off of the honey and they don't go out to forage, so it’s sort of a dead end in that way," study author Matthew Webster of Uppsala University told The Post. In fact, African beekeepers have unwittingly caused trouble for their peers by moving Cape honeybee colonies into new neighborhoods. The freeloading bees have a tendency to invade and destroy surrounding hives.
But their social parasitism isn't the most unique thing about them. The fact that their females can lay eggs solo means they're capable of asexual reproduction — something that's thought to be extremely rare among other honeybees.
In a type of parthenogenesis (birth without male input) called thelytoky, the female worker bee essentially clones herself. When her cells split in two to create egg cells — which lack half the genetic data you typically need to create a fertile bee, leaving room for male contribution — some of the leftover bits recombine with the sex cells and fertilize them.
"The female worker bees also develop their ovaries to a greater extent than we see in other honeybees," Webster said, which makes sense — most bees rely on the fertilized eggs of their queen to keep the population going, so worker bees don't need to devote energy to growing their reproductive organs. "And they can go in and lay these eggs without being detected," he added.
Those eggs hatch as fully-fledged worker bees, but the workers don't do much work. They leave most of the foraging to the natives of the colony they've infiltrated, and reap the rewards. They can keep laying their own eggs to compete with the ones laid by their unsuspecting step-mom, and eventually the glut of lazy invaders leads to the collapse of the colony.
Until now, most research suggested that a single gene might be the cause of this strange behavior. But in the new study, Webster and his colleagues identified several regions of the Cape bee genome that were markedly different from those of their close relatives, standing out in sharp contrast to the many, many genes they share in common. For now, the scientists aren't exactly sure how or why these genes change behavior so drastically — but finding their location is a crucial step in the right direction.
"We don’t know what these different genes are doing and how they cause this behavior, but we can see there are definitely strong signals of something different going on there," he said. Webster and his colleagues suspect that the genes involved play roles in hormone regulation, development, and cell division. Future research could help single out individual mutations that might drive the bees' unique lifestyle — and figure out why those mutations were beneficial enough to create a new subspecies.
"It's not really known," Webster said. But he suspects that location has something to do with it. Cape bees are only naturally found in one specific place known as the fynbos ecoregion. This tiny belt of shrubland has a rich diversity of plant species that the Cape bee pollinates, and the creature's natural population seems completely tied to that ecological niche.
"It's not really clear what aspect of the environment would cause them to act this way," he said, "but it seems sensible that it might have something to do with them living in this region."