With spring in the air across most of North America, it wouldn’t be difficult to notice the vibrantly colored flora that has begun to bloom all around. It’s hard to imagine a pastoral setting without catching a glimpse of plump furry bumblebees lumbering from one flower to the next, but with declining population numbers across several species that scenario could become a reality—with devastating consequences to many ecosystems.
In order to understand the underlying genetic makeup of bees and the role individual genes play in bee society, an international collaboration of scientists published the genome sequences and analyses of two key bumble species: the European buff-tailed bumblebee, Bombus terrestris, and the North American common eastern bumblebee, Bombus impatiens.
The findings from this endeavor were released recently in Genome Biology through two articles entitled “The genomes of two key bumblebee species with primitive eusocial organization” and “A depauperate immune repertoire precedes evolution of sociality in bees.”
Despite their often slow and plodding flight, bumblebees are anything but lazy. With over 250 bumblebee species globally, they have the laborious, but critical task of pollinating wild and agriculturally important plants.
“Bumblebees are intriguing creatures to study,” explained Ben. Sadd, Ph.D., assistant professor of infectious disease ecology at Illinois State University and lead author on one of two recent publications “but growing threats to their health are affecting bee populations around the world, making it especially critical to improve our understanding of their biology.”
Interestingly, the researchers found that when they compared the genome sequences of the bumblebees to those from the highly social honeybee they identified many conserved similarities, as well as some key differences. For example, some honeybee genome features originally thought to contribute to advanced eusociality are also present in bumblebees—indicative of an earlier evolution in the bee lineage. The scientists classified bumblebees as exhibiting a level of social organization that is intermediate between solitary insects, such as houseflies, and the highly social honeybee.
Additionally, the investigators took note of some interesting genomic data surrounding the immunological capacity of the two bumblebee species.
“The catalogue of genes involved in immune defense responses is well conserved among different bee species regardless of their level of social organization,” stated Robert Waterhouse, Ph.D., research fellow from the University of Geneva and the SIB Swiss Institute of Bioinformatics and co-author on one of the two recent publications. “But it is much smaller than in solitary insects such as flies and mosquitoes that often live in more pathogen-rich environments.” Nevertheless, variations in evolutionary signatures of selection amongst immune genes from bumblebees and honeybees may point to different pressures exerted by the distinct pathogens that threaten these bees.
The scientists also noted at least one key difference between male and female bumbles, which was also tied to the insects immune systems. When young Swiss bumblebees from mature colonies were exposed to various bacteria, the researchers noticed a greater elevated response from immune genes in females than from males.
“This suggests a greater investment in protective immunity by the females, which will one day start their own colonies, than by the males, whose role is essentially just for reproduction,” said Seth Barribeau, Ph.D., assistant professor of ecology and evolution of infectious disease at East Carolina University and lead author on one of the two recent publications.
The collaborative teams were energized by the publication of these preliminary findings and hope that it will usher in a new and vested interest into these agriculturally vital insects.
“These genomic resources,” said Dr. Barribeau, “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.”
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