What we know about pesticide-induced disturbance of social bee gut microbiota

Social corbiculate bee gut microbiota play important roles in host performance, contributing to nutrient processing, immune response, and pathogen defense, among other processes. Recently, research has begun to investigate how pesticide exposure impacts these gut microbial communities; however, no attempt has been made to formally synthesize data across studies. We searched literature databases for studies examining the effects of pesticides on social corbiculate bee gut microbiota and synthesized their findings to: 1) Describe the current state of research on pesticide-bee gut microbiota interactions; and 2) Identify key gaps that require further investigation. We identified 25 studies that fit our criteria, the majority of which were published from 2016 onwards. Most of these studies examine the effects of insecticides and use European honey bees, Apis mellifera, as the host organism, though some use Bombus or meliponines. We found that pesticide-induced disturbances in core bee gut microbes are subtle (i.e., taxa shift in abundance but are never eliminated) and that changes are consistent with common signs of social bee gut microbiota dysbiosis. Finally, while many studies attempt to link pesticide-induced disruption of bee gut microbiota to declines in host performance, we identified only one study which provides sufficient evidence to support this link. We recommend that future studies focus on determining whether subtle shifts in bee gut microbiota caused by pesticide exposure are sufficient to affect host performance, and that efforts be made to examine non-Apis bees as their ecology may make them more vulnerable to pesticide-induced gut microbiota disturbance.