A team of researchers has uncovered alarming trends in the first range-wide genetic study of an endangered bee species. Bumblebee -- a species that was once common in the United States but has declined from about 90% of its historic range. The rusty-patched bumblebee was the first bee species to be federally listed as endangered in 2017 through the U.S. Endangered Species Act. Its numbers dropped rapidly starting in the late 1990s, likely due to a combination of pesticides, pathogens, habitat loss and degradation, and climate change.

Scientists observed fewer colonies than a stable species would have and a high rate of inbreeding, which can threaten the long-term viability of a species. Of the bees sampled, 15% showed evidence of inbreeding, through the presence of what are called diploid males. In bees, males are typically haploid and have only one set of chromosomes, but when they're inbred, they can have two sets of the same chromosomes and lack genetic diversity. Analysis revealed three genetically distinct populations among rusty-patched bumblebees -- in the upper Midwest, central Midwest and Appalachians -- that will need to be handled differently for potential recovery efforts.

This research is invaluable -- it helps us refine healthy colony targets and shows us the importance of optimizing conservation efforts in genetically distinct areas, like the Appalachians, restoration projects that benefit bumblebees benefit other wildlife and landscape health in general. Surveying the rusty-patched bumblebee across its entire U.S. range required a vast network of collaborators with proper permits to collect genetic samples from the endangered species. Sampling involved catching the bees in nets, briefly putting them on ice and clipping off a tiny bit of leg -- enough to conduct the study but not so much that it would interfere with their ability to function.