Endosymbionts that threaten commercially raised and wild bumble bees (Bombus spp.)

by Figueroa et al.

A worker Bombus bifarius approaches an inflorescence of
Lupinus bakeri to collect pollen in the Colorado Rocky Mountains.
Photo by David W. Inouye.

Parasites have been linked to bumble bee (Bombus spp.) population declines around the world. Here we review the diversity, detection methods, and pathology for potentially deleterious (parasitic) bumble bee endosymbionts. We find that bumble bees have known associations with a broad diversity of endosymbionts, including viruses, bacteria, protozoans, fungi, and nematodes, which are frequently detected using a combination of microscopy and/or existing and emerging molecular techniques. For many of these endosymbionts, pathologies are understudied, and the impacts of detected pathogens are often unknown, particularly so in bumble bee species beyond the relatively well-studied B. impatiens and B. terrestris, both of which are abundant and commercially available. Prevalence of many endosymbionts has been found to vary across geographic and temporal scales. We have strong evidence that the national and international commercial trade of bumble bees for crop pollination has facilitated the dispersal (spillover) of many of these endosymbionts to wild bees in non-native ranges. It is likely that many endosymbiont species and strains remain to be described. We conclude that additional monitoring efforts to understand the impacts of endosymbionts in diverse and wild bumble bee communities are clearly warranted.

Read the scientific publication in JPE