Researchers in Canada playing detective with the yellow-banded bumblebee’s genome have found evidence that inbreeding and disease are the likely reasons for the decline of the species, York University associate professor Amro Zayed says.
The team led by Zayed, Sheila Colla and biology researcher Clement Kent believes it is the first time the genome of an at-risk bumblebee has been sequenced.
“We took one queen and used new sequencing technology that gave us very long stretches of DNA to sequence and assemble the reference genome for Bombus terricola,” the yellow-banded bumblebee, Zayed said.
The research, published in the journal Frontiers in Genetics on Monday, found evidence of large-scale inbreeding and signs of disease among the yellow-banded bumblebee population.
“Inbreeding is especially bad for bees because it increases the chances of producing sterile males which then drives the decline further,” said Zayed. “Inbreeding is both a consequence of the decline but could also generate lower fitness that leads to further declines.”
Kent says this means queen bees may be left with as little as half the workers needed to build a colony.
The yellow-banded bumblebee was once common in southern Ontario and Quebec. It is now listed as vulnerable to extinction globally on the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species.
Researchers believe disease may be spreading to wild bumblebees from commercial bumblebees used in greenhouses that forage outside for nectar and could be transmitting pathogens through the flowers they visit.
“If that hypothesis was correct we might expect bumblebees to show fast rates of evolution in their immune genes to cope with some of these pressures,” Zayed said. “That is indeed the pattern that we found.”
The team says further field research is needed to test the hypothesis, and believe that sequencing the genome makes this easier.
Zayed said it is too early to say whether the research has implications for other bumblebee populations.
“There are limits on how much we can extrapolate to other bumblebees,” he said. “Some of the threats could be common to many different lineages of bees … but specific pathogens might be specific to one or two species.”
Bumblebees are key pollinators of crops such as blueberries and cranberries, and are almost the only insect pollinator of tomatoes in the United States, according to the U.S. Fish and Wildlife Service.