Scientists Sequence Bumblebee Genome To Explain Population Decline

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As they seek out nectar on which to feed, bees play an invaluable role in the pollination process that supports crops worldwide and encourages biodiversity. Thus, the plight of the bumblebee is the plight of our entire ecosystem.

But for the past couple of decades, their populations have been shrinking. In an effort to better understand the circumstances that have led to their decline, an international team of researchers from the SIB Swiss Institute of Bioinformatics, the University of Geneva Medical School, and ETH Zurich's Institute of Integrative Biology have collaborated on an effort to sequence the entire bumblebee genome. The results were published earlier this week in Genome Biology, in two different papers that explore the genomes of two key bumblebee species: the Common Eastern Bumblebee from North America and the European Buff-tailed Bumblebee. One paper presents the genome and provides a general analysis, while the other one takes a closer look at the bumblebees' immunity genes in order to gain a better understanding of the diseases that might be ravaging their population.

"Bumblebees are intriguing creatures to study," said Illinois State University's Dr. Ben Sadd, who helped coordinate the first of the two papers [PDF]. "But growing threats to their health are affecting bee populations around the world, making it especially critical to improve our understanding of their biology."

One of the studies focused on comparing the bumblebee genome to that of the highly-social honey bee. Because they tend to live in colonies comprised of tens to hundreds of related individuals that last for a single year, bumblebees represent a middle ground on the spectrum of social organization: They land somewhere between solitary species, like leafcutting bees, and honeybees, which live in colonies of thousands built around a queen bee who can live for several years.

Scientists were surprised to find that despite their different social structures, the genes that determine social behavior in bumblebees and honeybees were actually very similar. Where they differed was in their miRNAs, a form of RNA (ribonucleic acid) that controls the phenotypic expression of genes. In other words, the changes to the colony structure between bumblebees and honeybees didn't involve any drastic changes to any particular set of genes, but instead reflected subtle changes throughout the genome.

The study that focused on the bumblebees' immunity genes also showed a surprisingly close relationship to those of the honeybee. A previous immunity study determined that social insects exhibit relatively simple immune systems, as reflected by their genes, even though they're at a greater risk of disease (high population density and low genetic diversity can foster parasite transmission). 

“This suggests that highly social honeybees did not lose functional immune genes, but rather that an ancestor of these social and solitary bees had fewer immune genes,” researchers Sadd and Seth Barribeau write over at BioMed Central.

Although the similarities are notable, it is the tiny differences between the different species’ immune systems that could help address the dwindling bumblebees. As Dr. Barribeau explains, "These genomic resources help us to understand what it is that makes these bumblebees particularly at risk from challenges to their well-being, such as diseases and pesticides."

There is still much to be unraveled from the genome sequencing, but the hope is that whatever discoveries follow will aid in protecting bumblebees for future generations.

[h/t Science Daily]