Do honey phytochemicals modulate forager aggression and the gut microbiome in the honey bee (Apis mellifera L.)?

Plant phytochemicals found in nectar impact bee learning and memory and plant pollination success. Especially for generalist pollinators, dietary changes that alter phytochemical consumption could be common sources of behavioral variation. For honey bee (Apis mellifera L.) foragers, a major potential change in phytochemical consumption occurs when individuals switch from collecting nectar from flowers to collecting honey from neighboring colonies, a phenomenon known as honey robbing. In this study we investigated whether phytochemicals dominant in honey compared to nectar act as a short-term trigger of robbing behaviors in honey bee, which include increased aggression. We fed forager honey bees sucrose diets containing different phytochemicals found in nectar and honey and tested aggression using a lab-based assay. We found no evidence that phytochemicals altered forager behavior. We also compared the microbiome composition for foragers fed different phytochemicals and again found no effects. Our results suggest that neither direct effects of neuroactive phytochemicals, nor indirect effects through the structure or function of the gut microbiome, trigger honey robbing behaviors.