Gut microbes contribute to variation in foraging intensity in the honey bee,Apis mellifera

Gut microbiomes are increasingly recognized for mediating diverse biological aspects of their hosts, including complex behavioral phenotypes. While many studies have reported that experimental disruptions to the gut microbiome result in atypical host behavior, studies that address how gut microbes contribute to adaptive behavioral trait variation are rare. Eusocial insects represent a powerful model to test this, due to their simple microbiomes and complex division of labor characterized by colony-level variation in behavioral phenotypes. While previous studies report correlational differences in gut microbiome associated with division of labor, here, we provide evidence that gut microbes play a causal role in defining differences in foraging behavior between honey bees. Gut microbial community structure consistently differed between hive-based nurse bees and bees that leave the hive to forage for floral resources. These differences were associated with variation in the abundance of individual microbes, including Bifidobacterium asteroides, Bombilactobacillus mellis, and Lactobacillus melliventris . Manipulations of colony demography and individual foraging experience suggested that differences in microbiome composition were associated with task experience. Moreover, single microbe inoculations with B. asteroides , B. mellis, and L. melliventris caused changes in foraging intensity. These results demonstrate that gut microbes contribute to division of labor in a social insect, and support a role of gut microbes in modulating host behavioral phenotypic variation.