25 January 2022
How the Western honey bee spread its wings out of Asia
Published online 9 December 2021
Extensive analysis of Western honey bee genomes suggests an Asian ancestral origin and provides insights into the species’ adaptation to diverse environments.
Scientists have long debated the origin of one of the world’s most important pollinators, the Western honey bee, Apis mellifera, with cases presented for both an African and an Asian ancestry.
Now, an international team, led by Amro Zayed at York University in Toronto, Canada and including Abdulaziz Alqarni at King Saud University in Saudi Arabia, has conducted extensive genomic analyses of 18 native subspecies of Apis mellifera. Their results suggest a Western Asia origin for the species, with at least three expansions creating the modern-day African and European lineages.
“Our study answers a mystery in bee biology: where did the Western honey bee come from?” says Zayed. “We sequenced the largest number of honey bee subspecies to date to resolve the issue.”
The team analysed genetic data from 251 individual bees collected across Apis mellifera’s geographical range, including samples from regions near the hypothesized ancestral range of Northern Africa and Asia. They then created an evolutionary tree that links all modern subspecies to their common ancestors that were alive 5 to 10 million years ago. This enabled them to track Apis mellifera’s origins to Western Asia, and explore the probable expansions of the species over time.
“Alqarni’s group provided invaluable samples from the Saudi peninsula, and our analysis shows that these bees are the closest living relatives of the ancestral Apis mellifera,” says Zayed. The researchers also discovered that the Egyptian subspecies is distinct; its genome differs greatly from honey bees found in Africa and the Saudi peninsula.
The researchers then examined how the genome evolved to enable honey bees to thrive across diverse environments.
“Honey bees are amazing organisms that have naturally colonized remarkably diverse ecosystems, from the arid mountains in Saudi Arabia, to the colder temperate regions of Northern Europe,” says Zayed. “We found that natural selection was facilitated via a small number of genes expressed largely in worker bees.” This suggests that the species adapts by modulating the behaviour of workers and colonies, rather than queen bees.
“These data, and more that we are collating, will help identify mutations that affect the behaviour and health of colonies to understand the genetic and evolutionary basis of ‘super organismal’ traits,” says Zayed. Enhanced knowledge of genetic adaptations could be used to help improve the fitness of farmed bees.
Further, the wider genetic data from this study could also help define and protect ‘pure’ native honey bee subspecies, as some subspecies are at a risk of extinction from mixed lineage managed bees.
Honey bee expert, Sarah Kocher, who was not involved in the study, comments, “The authors have compiled one of the most comprehensive datasets of its kind to help answer a longstanding question about the evolutionary origins of the world’s most prominent pollinators.” Kocher is assistant professor in behavioural and evolutionary genomics at Princeton University, USA.
Dogantzis, K.A., et al. Thrice out of Asia and the adaptive radiation of the western honey bee. Science Advances 7, eabj2151 (2021).