Characterizing difference in pollen carriage by bumblebee species in unimproved pastures

Resolving the role of food availability in the decline of bumblebees (Bombus sp.) is especially challenging for bumblebee species. We combined Cytochrome Oxidase I (COI) barcoding to aid bee identification and rbcL metabarcoding to characterize pollen carriage to study 269 bumblebees captured in three UK species-rich pastures. Representation of individual bee species and variance in their pollen carriage was both site- and date-dependent. Pollen profiles of bees from the cryptic Bombus lucorum complex (B. terrestris, B. cryptarum and B. magnus) were initially indistinguishable but later diverged across all sites. Throughout the season, individuals of most species carried pollen from mature residential gardens >800 m from the capture site. Our findings support landscape-level foraging for all species and suggest differences in the foraging behaviour of cryptic species are patchy and restricted to limited scenarios