Pollinator Species Identity, Behavioural Ecology and Life History Traits Shape Epibiont Bacterial Diversity

Pollinators interact with flowers partly through direct surface contact, yet the bacterial communities associated with their external surfaces (epibionts) remain poorly understood compared with their gut microbiomes. This study characterised the epibiont bacterial communities of four pollinator species associated with northern highbush blueberry (Vaccinium corymbosum 'Duke') in New Zealand: bumble bee (Bombus terrestris), honey bee (Apis mellifera), drone fly (Eristalis tenax), and a New Zealand native bee (Lasioglossum sordidum). Using 16 S rRNA gene sequencing, we detected distinct epibiont communities among pollinator species, with significant differences in alpha and beta diversity. Bumble bees consistently exhibited specialised and low‑diversity communities, whereas drone flies showed the highest bacterial diversity. Several pollinator gut‑associated core bacterial genera, including Gilliamella, Lactobacillus, and Snodgrassella, were detected across most species, representing the first reports of Snodgrassella on E. tenax and of Lactobacillus and Gilliamella on L. sordidum. Environmentally acquired taxa dominated the epibiont communities, consistent with pollinator exposure to floral and habitat‑specific bacterial sources. Differential abundance analysis identified species‑specific bacterial signatures and highlighted how pollinator identity, behavioural ecology, and life history traits shape epibiont composition.