Experimental manipulation of the provision microbiome in Osmia lignaria

Many insects benefit from the metabolic activity of bacteria and fungi that reside within the insect or on its food substrate. Most bee species, including the blue orchard bee Osmia lignaria, provision their offspring with nectar and pollen which contains fungi and bacteria hypothesized to preserve or transform this stored food. Previous work suggests that microbial communities within the provisions of Osmia lignaria are sourced primarily from flowers and affect larval nutrition and development. However, whether microbial composition in flowers can affect provision microbial composition and larval success is poorly understood. Here, we allowed free-flying Osmia lignaria to forage on Phacelia plants that were either uninoculated (contained a limited microbial community) or inoculated with a full community of floral microbes (contained a diverse microbial community). Flowers, adult bees and provisions from completed nests were sampled, DNA extracted and sequenced using 16S and ITS metabarcoding to compare microbial composition between treatments. Preliminary data from microbial culturing suggest that microbial inoculation increased microbial abundance in flowers, but data on microbial community composition across environments and larval success are forthcoming. Our experiment will reveal if the composition of floral microbial communities can shape the provision microbiome structure and function and have cascading effects on larval bee survival and development.