The prevalence of bumblebee pathogens in their hosts and the wider environment
Joanne D. Carnell, Joanne D. Carnell , Rosaline A. Hulse , Sam Page , Dave Goulson , William O. H. Hughes
University of Sussex, UK; University of Sussex, UK ; University of Sussex, UK ; Bumblebee Conservation Trust ; University of Sussex, UK ; University of Sussex, UK
Many species of bumblebee (Bombus spp.) are experiencing population declines globally. The availability of floral resources and the presence of pathogens are critical factors in their health and survival. Wild bumblebees are naturally exploited by three known, longstanding microbial pathogens (Crithidia bombi, Nosema bombi and Apicystis bombi) and more recently by Nosema ceranae, which has jumped host from honey bees. These pathogens are transmitted horizontally via shared flowers, however very little is known about the prevalence – or indeed survival – of these pathogens on flower vector sites. Once deposited, they may be exposed to UV light, floral phytochemicals (some producing harsher environments than others), or removed by wind or rain. These factors are likely to affect the transmission efficiency and virulence of pathogens. We screened common bumblebee species and the flowers they forage on for the known microbial pathogens. We investigated the effect of flower structure and phylogeny on pathogen presence, measured the proportion of live cells present, and identified where on flowers (the pollen, nectar or petal) pathogens were most common.