Most honey bees are as busy as, well, a bee, tending to the queen and her young, guarding the hive, and generally buzzing and flitting around in near constant motion. But some bees just sit around and rarely interact with their comrades. A new study reveals that these antisocial insects share a genetic profile with people who have autism spectrum disorders, which can affect how well they respond to social situations.
The work speaks to how evolution may tap the same molecular pathways in very different animals, even for traits as complex as social behavior, says Hans Hofmann, an evolutionary neuroscientist at the University of Texas in Austin who was not involved with the study. The neural circuits underlying social behavior “must be very different for humans and honey bees, yet it appears at the molecular level, the genes are employed in a similar manner,” he says. “That’s kind of striking.”
To look for variation in honey bee social behavior, Hagai Shpigler, a postdoctoral fellow at the University of Illinois (UI) in Urbana, designed two tests where he and colleagues video recorded a group of bees and analyzed each individual’s reaction to a social situation. In one test, he stuck an unfamiliar bee in with the group. Bees instinctively “guard” and typically react by mobbing the stranger and sometimes harming it. In the second test, Shpigler put an immature queen larva in with the group. Queen larvae bring out mothering instincts, and worker bees tend to feed the larva. He subjected 245 groups of bees from seven different colonies, 10 bees per group, to these tests multiple times, then ranked how eagerly the bees responded to these situations.
Most bees reacted to at least one situation, but about 14% were unresponsive to both, he and his colleagues report today in the Proceedings of the National Academy of Sciences. The team sacrificed some of the bees and isolated the genes active in the insects’ mushroom bodies, a part of the brain responsible for complex actions such as social behavior. They found a distinctive subset of genes was active in the nonresponsive bees. Then they compared that set of genes to sets of genes implicated in autism spectrum disorder, schizophrenia, and depression. Even though bees and people are very different evolutionarily, they have many genes in common.
There was a good match only between the gene activity of the nonresponsive bees and genes associated with autism, the team reports. Some of the genes involved help regulate the flow of ions in and out of the cells, particularly nerve cells; others code for so-called heat shock proteins that are typically induced during stress.
The researchers don’t yet know how exactly these genes influence social behavior in either bees or people, but manipulating the genes in honey bees may shed light on what they do in humans, says Alan Packer, a geneticist at the Simons Foundation in New York City, which funds autism research, including this bee work. Packer was not involved with this project but has been compiling a list of genes implicated in autism spectrum disorders.
Claire Rittschof, an entomologist at the University of Kentucky in Lexington who was not involved with the work, cautions that the nonresponsive bees might prove to be responsive in a different social situation. “It’s difficult to separate social responsiveness from behavioral variation in general,” she notes. But she’s fascinated by the idea that similar genes shape social behavior in different species.
No one is drawing exact parallels between honey bee and human behaviors, Packer notes. “We do not want to give the impression that bees are little people or humans are big bees,” says team leader Gene Robinson, a behavioral genomicist and director of the UI Carl R. Woese Institute for Genomic Biology. But, says Packer, “if you want to understand how these genes interact, the honey bee might be a useful model.” He’s eager to know whether this same set of genes is involved in social responsiveness of other animals. “The more models that are available to study how these genes give rise to these behaviors, the better.”
It’s not clear why these asocial bees are tolerated by the rest of the hive. Rittschof thinks these individuals are considered part of the group despite their unusual behavior. Both human and bee societies “contain and accommodate a range of different personality types, strengths, and weaknesses,” she suggests.