A number of wild bumblebee species are in decline, and new research points to a previously unexpected threat to their numbers - diseases spread by domestic honeybees.
According to Science Daily, several viruses that have been linked to bumblebees' dwindling populations are carried by managed bees in apiaries. By sharing flowers with wild bumblebees, they infect nearby native populations.
"Many wild pollinators are in trouble and this finding could help us protect bumblebees," the publication quoted Samantha Alger, the scientist who led the new research, saying.
Elaborating, she says this information has implications for how we manage domestic bees. Another consideration is where beekeepers should locate commercial beehives to decrease this risk.
The importance of wild pollinators has been gaining international attention as diseases and declines in honeybees threaten key crops, comments the publication.
The rusty patched bumblebee, for example, was once a major pollinator of cranberries, plums, apples and other agricultural plants. However, it was recently listed under the Endangered Species Act, after its numbers fell by nearly 90%.
Tracing how the RNA viruses spread
Some of the previously known dangers facing both managed and native bees include land degradation, certain pesticides, and diseases. The research team looked into the latter, exploring 19 sites across Vermont.
In particular, its research looks at two well-known RNA viruses found in honeybees - deformed wing virus and black queen cell virus.
The team discovered that both viruses were higher in the bumblebees they collected less than 300 meters from commercial beehives.
The scientists also found that active infections of the deformed wing virus were higher near these commercial apiaries. Significantly, they didn't find the virus in the bumblebees they collected where foraging honeybees and apiaries were absent.
Most impressive, the team detected viruses on 19% of the flowers they sampled from sites near apiaries.
"I thought this was going to be like looking for a needle in a haystack. What are the chances that you're going to pick a flower and find a bee virus on it?" Science Daily quoted Alger saying. "Finding this many was surprising."
In contrast, the scientists didn't detect any bee viruses on flowers more than one kilometer from commercial beehives.
Alison Brody, a professor in UVM's Department of Biology, and senior author on the new study, elaborated.
"Viruses in managed honeybees are spilling over to wild bumblebee populations and that flowers are an important route.
The publication also quotes Alger saying: "This research suggests that we might want to keep apiaries outside of areas where there are vulnerable pollinator species, like the rusty patched bumblebees."
"Especially because we have so much more to learn about what these viruses are actually doing to bumblebees."