The Influence of Flower-Microbe Interactions on Bumble Bee Behavior and Gut Microbiome Composition

This thesis examines how microbial interactions in floral nectar and environmental variation influence bumble bee (Bombus spp.) foraging behavior and gut microbiome composition. Pollen germination experiments and behavioral assays in the lab tested whether Metschnikowia reukaufii (yeast) and Acinetobacter nectaris (bacteria) induce pollen germination and bursting in nectar and affect bee behavior subsequently. Both microbes reduced intact pollen, but bees did not alter flower preference. Furthermore, the study also assessed how floral and bee community composition shaped gut microbiome composition across six Missouri prairies. Using amplicon-sequenced fungal ITS and bacterial 16S rRNA genes, I found that fungal microbiome composition varied significantly with floral and bee abundance, becoming more similar across bees when abundance declined-suggesting increased transmission via shared floral use. In contrast, bacterial composition was primarily structured by bee species identity, indicating host filtering or social transmission. By linking microbial dynamics in both floral resources and the bee gut, this work reveals how flower-microbe interactions shape pollinator behavior and microbiome composition, deepening our understanding of microbial roles in pollinator ecology.