Mountain-dwelling East African honey bees have distinct genetic variations compared to their savannah relatives that likely help them to survive at high altitudes,
And the bees living in the mountain forests look and behave differently from their surrounding lowland counterparts,
Mountain bees are larger, darker and less aggressive than savannah bees, and can fly at lower temperatures and conserve honey when flowers aren’t blooming
But despite their differences, the bees are the same sub-species.
To understand the genetic basis for these high-altitude adaptations, researchers from the University of Hohenheim in Germany and Uppsala University in Sweden sequenced the genomes of 39 bees from two highland and two lowland populations in Kenya.
They report the genomes of all the populations are highly similar, but two regions located on chromosome 7 and 9 show consistent differences between bees living in high and low-altitude environments.
The segment on chromosome 7 contains e.g. receptor genes for a neurotransmitter called octopamine, which plays a role in learning and foraging. The clear divergence of these two genetic variations suggests that they have an ancient origin and likely existed in bee populations before the groups spread their mountain and savannah habitats.
The new study of the genomes of high-altitude honey bees in Kenya reveals novel insights into their evolutionary history and the genetic basis of local adaptation.
Scientists had thought that mountain and savannah populations were each distinct sub-species. The high degree of similarity in their genomes, as revealed in the current study, shows that they constantly interbreed.
The highly diverged segments likely represent structural rearrangements, such as inversions, in which the exchange of genetic material is suppressed. Previous studies have identified octopamine as an important signaling molecule in other insects living in low temperature and low oxygen conditions.
“Our findings complement several other landmark studies – for example in Heliconius butterflies and Solenopsis ants – where adaptations have been similarly tied to structural variants or supergenes,” says University of Hohenheim researcher Martin Hasselmann.
But the phenomenon has never been previously documented in honey bees, the researchers report in the journal PLOS Genetics.
“Our results should therefore spur further research into the role of supergenes in environmental adaptation,” Hasselmann says.
“We are planning now to measure the distribution of these divergent segments in other geographic locations and to elucidate the functional link of these genes with behavior.”