Bumble bee disease dynamics in agroecosystems: The roles of landscape-scale management and an introduced species

Range expansion of the Common Eastern Bumblebee (Bombus impatiens) may be altering wild bumble bee communities through various mechanisms, including disease transmission. Previous research has suggested that commercial B. impatiens colonies—used for pollination in greenhouses and elsewhere—transmit parasites to wild bumble bees. Furthermore, introduction events originating from commercial colonies continue to aid in the expansion of this already widespread and successful species. The recent release and naturalization of commercial B. impatiens in British Columbia presents an opportunity to study these dynamics in a novel environment, amongst novel congenerics. Our study assesses the prevalence of four parasite genera (Crithidia spp., Nosema spp., Apicystis spp., and Ascosphaera spp.) in bumble bees of the Lower Fraser Valley, BC. We aim to answer three questions: i) How does B. impatiens abundance impact parasite prevalence and parasite phenology in communities of native bumble bees? ii) How do landscape scale factors such as compositional/configurational diversity of farmlands affect parasite prevalence? iii) Do sites with high floral/pollinator diversity show lower parasite prevalence (dilution effects), and do low diversity, mass-flowering resources result in increased parasite prevalence (amplification effects)? This research will not only fill a gap in our understanding of the impacts of B. impatiens expansion on native pollinators, but will also tie this knowledge to our current understanding of the impacts of landscape and plant-pollinator network structure on parasite/disease dynamics.