Pollinators such as bumble bees rely upon chemosensory cues to effectively localize and evaluate essential resources in both natural and agricultural landscapes. Increasingly, it is recognized that microbes can alter resource quality, as well as produce chemosensory cues such as volatile and non-volatile metabolites that may alter the quality of sensory information received by pollinators in a species-specific manner. Here, we test the hypothesis that species of nectar-inhabiting microbes differentially influence pollinator attraction and feeding via microbial metabolites in nectar. We examined electrophysiological potential of bumble bee antennae to respond to volatile microbial metabolites, followed by behavioral responses using choice assays. Moreover, gustatory responses to nectar-inhabiting microbes were assessed through both no-choice and choice feeding assays. Bombus impatiens antennae responded to a subset of volatile metabolites produced, with 2-ethyl-1-hexanol eliciting the strongest response. Naïve workers also displayed a clear preference for Asaia bacteria compared to Metschnikowia yeast based on volatiles alone. However, B. impatiens consumed significantly more Metschnikowia-inoculated nectar, suggesting distinct roles for non-volatile and volatile microbial metabolites in mediating feeding decisions, with potential to affect associative learning and future foraging. The distinct roles of microbial olfaction and gustatory responses suggest bumble bees may use multiple microbial chemical cues to assess floral attractiveness and reward quality, with potential consequences for forager economics and crop yield.

Microbial metabolites mediate bumble bee attraction and feeding

2019 Fall National Meeting

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