The prevalence of parasites within pollinator communities is reduced when there are more bee species and a greater abundance of flowers, reports a study published this week in Nature Ecology & Evolution.
Declines in insect groups such as bees are a major concern because of the pollination services they provide. Increasing the number of flowers may improve bee health, but flowers can also act as transmission hubs for bee diseases. However, little is known about how infection risk changes over time, particularly across entire bee-flower communities.
Peter Graystock and colleagues characterized the diversity and abundance of 110 bee species and 89 flower species over the course of one growing season in three old-field sites in upstate New York, and measured the presence of five common bee parasites using molecular screening. After screening more than 5,000 flowers and bees, the authors found that 42% of bee species and 70% of flower species harboured at least one parasite species. However, the prevalence of parasites in bees was lowest early in the season, when bee diversity was highest and there were fewer common social species like honeybees and bumblebees. In contrast, the prevalence of parasites on flowers was lowest late in the season when there greater numbers of flowers.
These findings suggest that increasing the diversity of bee species and the number of flowers in natural communities may improve pollinator health by diluting the transmission of disease.
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