The effects of microbes on the nutrition of an important pollinator Megachile rotundata

Gut microbiota play an important role in pollinator health. As with mammals, microbes that inhabit the gut aid in digestion and immunity in bees. In the solitary bee, Megachile rotundata, females build brood cells with cut leaves, provision them pollen and nectar, then lay a single egg in each cell. This maternal brood cell preparation will be the only dietary provision to sustain the bee throughout larvae development, and their only encounter with environmental microbes, until they emerge as adults. We hypothesize that altering the microbiome of these provisions will affect the health of the larval bee. In order to test this hypothesis, we gamma-irradiated pollen provisions from managed M. rotundata, which we then inoculated with different microbial treatments. Megachile larvae were reared on four different microbial treatments: sterile, Lactobacillus only, treated with entire community of wild microbes, and un-manipulated. Larvae were weighed and protein assimilation was assessed in their final larval instar. Larvae with sterile pollen or Lactobacillus only inoculated pollen assimilated significantly more protein compared to larvae treated with the entire microbiome. Lactobacillus does not appear to affect nutrition, but some wild microbes apparently compete with the larvae for protein. Further studies on the function of these microbes could yield insight into how gut microbiome composition plays a role in the health of pollinators that are often less studied, like the solitary M. rotundata.