The Origin of the Honeybee – A Worldwide Survey of Honeybee Genomes Reveals their Evolutionary History

by Thomaz Pinotti and Fay Morland

A large group of international researchers have united to try to answer one of the most lasting questions in the biology regarding one of the most economically important animals mankind has domesticated: where does the honeybee come from?

The honeybee, scientifically named Apis mellifera, is humanity’s most important pollinator, currently valued at more than $200 billion for agriculture worldwide. The fact that populations of bees are mysteriously decreasing is, therefore, quite the cause for alarm. In search for a better understanding, a team of scientists, led by the Sweden-based Dr. Andreas Wallberg, performed a large-scale genome sequencing of honeybees. They sampled from 14 different populations from across the world, including extremely important domesticated strains. The research hoped to reveal the evolutionary history of the honeybee, including the species’ adaptions to different climates and resistance to disease. What did they find? • The honeybee was previously believed to originate in Africa, however this study contradicted this, finding evidence that the honeybee may originate in East Asia, where all other bee species are believed to originate. • Genes related to immunity are unexpectedly very different between European and African strains, explaining the difference in disease resistance. Further studies of these genes may be very important in protecting the honeybee from disease and further population decline. • Genes related to sperm motility and maturation have undergone especially strong selection, suggesting that they may be a major driver of honeybee evolution. The study also revealed facts about the evolutionary history of honeybees. The results show that honeybees split into 4 groups (fig 1) 1 million years ago: A. Africa M. West and North Europe C. East and South Europe O. Middle East and Asia So what? Parasites, such as mites, that are restricted to Africa have resulted in the difference in immunity genes between African and European honeybees. The exportation of bees from Africa spreads the parasites to populations of bees without immunity, causing colonies to decline. Additionally, they found that African populations peaked at glacial maximums, whereas all other populations peaked during interglacial periods. Since the last glacial maximum, 20,000 years ago, African populations have been declining, whereas other populations have been slowly increasing. These results suggest that honeybee populations are affected by climate, and in particular that the African subspecies thrives in cold climates. Is this paper perfect? Although these results are interesting, there may be some problems with how they were obtained. Samples from each population were only 10 bees in size. Additionally, Africa and West and North Europe groups contained more samples than East and South Europe and Asia . A skew in sampling and small sample sizes can lead to an erroneous representation of populations and a lack of statistical significance. This and issues with methodology means that these results are not universally accepted by the scientific community, but they are a large step forward in understanding the genomics of the honeybees and the reasons behind colony decline. What’s all the buzz about? This study has provided innovative insights into the evolution and genetic adaption of the honeybee. This key pollinator is of critical importance to human society and the natural world and an understanding of genes relating to immunity may open doors to future studies into disease prevention. Additionally, understanding how subspecies respond to changes in climate sheds light on how populations may respond to current climate change.     References: Walberg et al., Nature 2014

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