Virus distributions in wild bees are associated with floral communities at local to landscape scales

Bees are focal pollinators, essential for maintaining biodiversity and crop production. Thus, reports of high annual honey bee colony losses and population declines among many wild bees in different parts of the world are of major concern. The spread of viruses is highlighted as a potential threat to bee communities. Viruses infect a wide range of bee species and can be transmitted interspecifically through shared floral resources. Therefore, the role of flowers as hubs of bee virus transmission requires a community ecology perspective. Here, we investigate local and landscape-scale characteristics of floral communities potentially associated with the spread of viruses in the solitary Andrena spp. (mining bees). We surveyed 14 sites in a Mediterranean agroecosystem with varying local densities of honey bee (Apis mellifera) foragers and diversity of flowering species and assessed the prevalence of four common Hymenoptera-associated viruses (deformed wing virus [DWV], black queen cell virus [BQCV], sacbrood virus [SBV], and Lake Sinai virus-2 [LSV-2]) in co-foraging honey bees and mining bees. We found that the probability of virus presence in mining bees was generally associated with the diversity and composition of the local (site level) floral community, and with floral resource availability at the landscape scale (up to 1000-m range). In addition, SBV and DWV prevalence in mining bees were positively related to the density of SBV-infected, and total honey bee foragers, respectively. These findings demonstrate the focal role that the floral community at multiple spatial scales, and co-foraging pollinator species, may play in virus spread and, potentially, pollinator health.