THE ISSUE
Native Bees:
For our native bees, one of the most compelling hypotheses for rapid population decline is the transfer of pathogens from managed bees(bees housed in hives) to wild bumblebees. The pathogens in question are small organisms called protozoans whose names go by Crithidia bombi and Nosema bombi. However, other pathogens may be effecting populations as well.
Field documentation of pathogen transfer shows the spread emanating from infested commercial hives. Also, the timing of decline onset in native bee species corresponds with the acceleration of transportation of managed colonies during the 1990s. Declines in Bombus occidentalis, Bombus affinis, Bombus terricola and Bombus pensylvanicus have all been attributed to this disease.
CASE STUDY
Honey bees may be spreading viruses to wild bumble bees
Introduced European honey bee (Apis mellifera)
Native eastern bumble bees (Bombus impatiens)
The Issue:
Bumblebee declines have been linked to diseases that spillover from domesticated honey bees. It has been hypothesized that with some bee diseases caused by viruses, honey bees leave viral particles on flowers that they visit, which can then spread to bumble bees that later visit the same blooms. Scientists in Vermont, USA examined evidence for this in the fatal deformed wing virus (DWV), and found that the disease was more common in bumblebees collected near honey bee apiaries, especially when the nearby honey bees had high infection levels. Furthermore, they did not find the disease in bumblebees that were not near honey bee apiaries. Another disease, the black queen cell virus (BQCV), was also higher in bumblebees collected near honey bees apiaries. These viruses were also detected on the surfaces of flowers within apiaries. This suggests that high intensity honey bee domestication may have detrimental effects on wild bees.
Alger SA, Burnham PA, Boncristiani HF, Brody AK (2019) RNA virus spillover from managed honeybees (Apis mellifera) to wild bumblebees (Bombus spp.). PLoS ONE 14(6): e0217822. https://doi.org/10.1371/journal.pone.0217822