A genetic analysis suggests the world’s most common species of honeybee, the western honeybee, first appeared in western Asia about 7 million years ago and then spread into Africa and Europe
3 December 2021
Genomic analysis has revealed that the western honeybee – which lives across Europe, Africa and Asia – first evolved in western Asia. Understanding the evolution of honeybees can help us protect these crucial pollinators.
Ancestral honeybees are thought to have originated in south-east Asia, but whether the western honeybee species (Apis mellifera) evolved from an ancestral honeybee in Asia or after its ancestor had spread to Africa is widely debated.
Kathleen Dogantzis at York University in Canada and her colleagues have now resolved this question by analysing the genomes of 251 western honeybees, covering 18 subspecies collected from across Europe, Africa and Asia.
The team found that the western honeybee species first evolved in western Asia, before spreading into Europe and Africa, where different subspecies formed through natural selection. The key to the researchers’ approach was to include many samples from Africa and Asia.
“We focused on getting samples from Africa and Asia, because they’re generally under-represented [in studies of honeybee origins],” says Dogantzis.
By comparing how similar the bee genomes were to each other, the team estimated that the A. mellifera ancestor originated in Asia around 7 million years ago, then spread into both Africa and Europe around 6 million years ago.
Previous studies had suggested African and European subspecies evolved within the last million years, says Dogantzis. She says that time frame may be more correct, because the focus of those studies was on when the subspecies appeared, whereas the new study mainly focuses on where they spread from.
Further analysis revealed that a core set of around 145 genes had mutations in their sequences across all A. mellifera subspecies, even though these bees adapted to vastly different climates across temperate and tropical regions.
The small set of genes involved in western honeybee adaptation was a surprise, as the A. mellifera genome contains around 12,000 genes in total, says Amro Zayed, also at York University, who was involved in the study.
However, understanding the genes involved in adaptation to new environments might prove useful, says Dogantzis. It might provide targets if it is ever considered necessary to genetically engineer honeybees to cope with climate change.
In colonies, thousands of worker honeybees rear the brood, maintain the nest structure and collect food. When the researchers looked at the genes involved in bee adaptation, they found these genes were related to the morphology and behaviour of the worker bees rather than the queen bees, even though the latter produce the eggs.
“Natural selection acts on the workers to optimise the fitness of their colonies even though they are not the reproductive [members of the colony]… highlighting the altruism of these social insects,” says Pilar De la Rúa at the University of Murcia in Spain.
“This study is quite conclusive with the hypothesis of Asian origin that many of us researchers in [the honeybee field] have been proclaiming,” says De la Rúa.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abj2151
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