Data from: Pollen diet, more than geographic distance, shapes provision microbiome composition in two species of cavity-nesting bees

The microbial composition of stored food can influence its stability and
determine the microbial species consumed by the organism feeding on it.
Many bee species store nectar and pollen in provisions constructed to feed
developing offspring. Yet whether microbial composition is determined by
the pollen types within provisions, variation between bee species at the
same nesting sites, or geographic distance was unclear. Here, we sampled
two species of co-occurring cavity nesting bees in the genus Osmia at 13
sites in California and examined the composition of pollen, fungi, and
bacteria in provisions. Pollen composition explained 15% of variation in
bacterial composition and ~30% of variation in fungal composition, whereas
spatial distance among sites explained minimal additional variation.
Symbiotic microbe genera Ascosphaera, Sodalis, and Wolbachia showed
contrasting patterns of association with pollen composition, suggesting
distinct acquisition and transmission routes for each. Comparing
provisions from both bee species comprised of the same pollens points to
environmental acquisition rather than bee species as a key factor shaping
the early stages of the bee microbiome in Osmia. The patterns we observed
also contrast with the Apilactobacillus-dominated provision
microbiome in other solitary bee species, suggesting variable mechanisms
of microbial assembly in stored food among bee species.