A review of wild bee microbiomes and immunity

Urban sprawl negatively impacts bee communities by reducing forage and habitat, ultimately selecting for smaller bodied, cavity nesting, generalist species. It is therefore important to characterize and study the differential impact of urban area on bee health across a wide variety of taxa. As urban sprawl has been shown to alter bee microbiomes, and microbial dysbiosis can negatively impact bee health, we sought to study the impact of bee phylogeny, plant choice, impermeable surface area, and environmental variables on bee fungal and bacterial communities across the Greater Toronto Area. Fungal and bacterial community composition were most impacted by bee phylogeny, with 20.55% and 10.73% of variation explained respectively. Other variables that impacted fungal community composition were mean annual precipitation (9.21%), impermeable surface (3.83%), and plant species choice (3.43%). Variables important for bacterial community composition were plant species choice (3.04%), mean annual precipitation (1.50%), and impermeable surface area (1.46%). Bee phylogeny was not a significant predictor of alpha diversity for fungi or bacteria, but bee family alpha diversity responded differently to increases in impermeable surface area, with Megachilidae fungal diversity increasing and Apidae bacterial diversity decreasing with increased impermeable surface area.