Scientists Sequence Genome of Rusty Patched Bumblebee

Scientists Sequence Genome of Rusty Patched Bumblebee

The rusty patched bumblebee (Bombus affinis) is an important pollinator in North America and a federally listed endangered species. Putting together its genome is part of the Beenome 100 project, a first-of-its-kind effort to create a library of high-quality, highly detailed genome maps of 100 or more diverse bee species found in the United States.

The rusty patched bumblebee is an important pollinator of bergamot, milkweed, and other wildflowers, as well as crops such as cranberries, plums, apples and alfalfa.

The species was once abundant and widespread in Canada and the United States.

Like its close relatives in the subgenus Bombus of North America, the rusty patched bumblebee underwent significant population decline and range collapse throughout its known historic distribution over the past several decades.

Hypotheses proposed on the cause of their decline include the transmission of pathogens, specifically Vairimorpha bombi (formerly called Nosema bombi), from managed to wild bumblebee populations, habitat loss and degradation, small population biology, and climate change.

Compounding evidence for their decline at multiple spatial scales prompted the Committee on the Status of Endangered Wildlife in Canada and the United States Fish and Wildlife Service to list rusty patched bumblebee as Endangered in 2010 and 2017, respectively.

To support the genetic assessment of the species’ populations, Dr. Jonathan B. Uhaud Koch from the ARS Pollinating Insect-Biology, Management, Systematics Research Unit and his colleagues sequenced the high-quality, chromosome-scale genome of the species from a single wild caught male in Minnesota in 2020.

“With the amount of detailed information that we and other researchers now have access to in the newly sequenced genome, we have an opportunity to find a whole different approach to strengthening rusty patched bumblebee populations,” Dr. Koch said.

“Some of the factors contributing to the decline of rusty patched bumblebees are already known: loss of habitat, reduced variety of nectar sources, climate change, exposure to pesticides, and more pathogens and pests.”

“While we have known the widespread presence of Vairimorpha bombi has a detrimental impact on many rusty patched bumblebee populations, we were a bit surprised by how much Vairimorpha genetic material we found in the bumblebee sample that was used to develop the genome map.”

“We used a small piece of abdominal tissue from a single male collected from a nest in Minnesota, which, given the endangered status of the rusty patched bumblebee, seemed like a very good idea.”

“It’s only with the most cutting-edge equipment that you could resolve an entire genome of 15,252 genes and 18 chromosomes from a tiny bit of one bumblebee.”

It turns out about 4.5% of the DNA the researchers sequenced came from Microsporidia, the fungal group that includes Vairimorpha bombi.

“That’s a massive amount of genetic information from the bee tissue sample to be associated with Vairimorpha bombi. It demonstrates how pervasive the pathogen is,” Dr. Koch said.

“Having this high-quality genome will support the identification of genetic differences between rusty patched bumblebee populations that appear to be doing well versus where they are in decline.”

“This may give us a handle on identifying the genes that give the more capable population its flexibility to deal with its environment.”

“We may also gain a better understanding of the genetic basis of bumblebee behavior, physiology and adaptation to changing environmental conditions.”

“Once the more successful genes for a particular type of local condition are identified, researchers will be able to give a population a boost in the right direction when it comes to restoring the rusty patched bumblebee to an area through captive breeding programs.”

The team’s results were published in the journal G3: Genes, Genomes, Genetics.


Jonathan Berenguer Uhuad Koch et al. Chromosome-scale genome assembly of the rusty patched bumble bee, Bombus affinis (Cresson) (Hymenoptera: Apidae), an endangered North American pollinator. G3: Genes, Genomes, Genetics, published online June 20, 2023; doi: 10.1093/g3journal/jkad119

This article was first published by Sci-News  on 21 June 2023. Lead Image: The rusty patched bumblebee (Bombus affinis). Image credit: Trisha Leaf / CC BY 4.0.

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