Researchers have pieced together the genetic blueprint for the famously social honeybee, uncovering clues that point to an African origin and to a remarkable evolutionary transformation in an insect known for its memory, symbolic language and hierarchical caste system.
Featured in folk art and cave paintings alike, the honeybee has long enjoyed a reputation as a master pollinator and honey producer. Yet scientists have marveled at the stark divisions of labor that separate the offspring-producing queens, sperm-yielding male drones and female worker bees assuming the defense, day care, housekeeping, construction and food gathering responsibilities.
How, researchers wondered, could the same set of genes produce such radically different behaviors among hive inhabitants – especially in insects whose tiny brains possess only one-millionth the number of neurons as human brains?
The switch from a solitary to colony-focused lifestyle required nothing less than a “revolution at the genomic level,” writes Harvard biologist Edward Wilson in today’s issue of the journal Nature. In the same publication, The Honeybee Genome Sequence Consortium reports on the social revolution “encoded subtly” within a genome possessing slightly more than 10,000 genes.
“Why care about social behavior in the bee? Is it related to humans?” asked George Weinstock, a leader of the research consortium and the co-director of the Human Genome Sequencing Center at Baylor College of Medicine in Houston. The answers have yet to emerge, but Weinstock wrote in an e-mail that the knowledge may aid in understanding the genetic underpinnings of behaviors ranging from the unusual altruism seen among worker bees to the aggressiveness that characterizes African “killer bees.”
He said the consortium also identified genes that protect the bee from toxins, a useful tool in understanding the insect’s sensitivities or resistances to the pesticides that some blame for the declining fortunes of bees and other plant pollinators in the United States.
Bees, the study suggests, have many genes for detecting odors but relatively few for taste receptors or innate immunity. Small bits of RNA – or microRNAs – even seem to show different on-off patterns depending on whether they’re in queens or workers, possibly hinting at a mechanism for maintaining social standings.
Somewhere along their evolutionary pathway, honeybees also gained a gifted memory for nectar sources and an ability to communicate the relative distance and direction of these sources with a “waggle dance,” the only symbolic language yet found beyond the primates. The new genomic data, researchers say, could help reveal the basis for both traits.
Within a swarm of accompanying studies, a separate group used genetic variations among different honeybee subspecies to suggest that the Apis mellifera lineage arose in Africa and twice migrated into Eurasia about 10,000 years ago.
And a research duo announced in the journal Science that they have discovered a 100-million-year-old amber-encased bee – by far the oldest ever found. Study co-author and Cornell University entomologist Bryan Danforth said the tiny insect may help fill in a family tree that now contains about 16,000 species. The discovery, he said, raises new insights about the possible co-evolution of early bees and the small flowering plants just beginning their expansion across a prehistoric landscape.
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