Pinpointing the origins of the most common honeybee species—the western honeybee (Apis mellifera)—ignited a long, contentious debate among scientists. Some argue that the bees originated from Asia while others claim they're from Africa, but a new study may finally settle this dispute, Alison Bosman reports for Earth.com.
Scientists analyzed the genomes of 251 western honeybees encompassing 18 different subspecies from across Europe, Asia and Africa to reveal that this species originated in western Asia, Carissa Wong reports for New Scientist.
"We focused on getting samples from Africa and Asia, because they’re generally under-represented [in studies of honeybee origins]," lead author Kathleen Dogantzis, a biologist at York University in Canada. With more representative samples in hand, the team was able to paint a better picture of the western honeybee's history.
The study, published this month in Science Advances, suggests the western honeybee originated around 7 million years ago and expanded westward a million years later. Dogantzis tells New Scientist that previous estimates proposed that the subspecies evolved more recently—within the last million or so years—but that her team's timespan is more accurate since the other studies focused on when the species appeared instead of their evolutionary history.
In fact, the species proliferated out of Asia three times. In one event, they made it into Africa; in a second exit, they moved into Europe. As they spread into new habitats and adapted to different niches, the species ultimately gave rise to seven different honeybee lineages and 27 subspecies, which are now found on every continent except Antarctica, Earth.com reports.
But their ancestor isn't the only common denominator these lineages share: each species and subspecies have the same set of only 145 genes, according to a press release.
The 145 genes were linked to the traits of worker bees—such as colony defense, immunity and the production of honey—instead of queens, who lay eggs. Since workers don't breed, natural selection is acting on them indirectly to improve the colony's health as a whole. In a video, Dogantzis says the genes were positively selected, meaning that they were helpful enough to spread throughout the population.
"We have very, very strong evidence that it's actually the ability of workers by changing their behavior and changing the calling behavior is the key trait that is really important for allowing honeybees to survive these different environments," co-author Amro Zayed, a biologist at York University, says in the video.
Dogantzis, Zayed and the team hopes that this new understanding of how the western honeybee may adapt to the effects of climate change as well as commercial honeybee colonies.