Bees are indispensable pollinators supporting a diverse array of flowering plants worldwide. Now a new analysis of more than 4,000 bees from 60 native species is showing that the more diversity within a bee community, the more resistant bees are to pathogens.
University of Michigan researchers examining bees at 14 winter squash farms with managed honeybee colonies found seven to 49 native bee species also pollinated the squash flowers, and that lower virus levels were linked consistently to greater species richness.
The most common native species were the eastern bumblebee, the squash bee and several species of sweat bee. Researchers tested them along with honeybees for the presence of three currently untreatable viruses that commonly infect and cause high losses among honeybee colonies. The viruses spread as bees move from flower to flower, gathering pollen and nectar and pollinating plants in the process. Consumption of virus-contaminated pollen is believed to be a primary mode of transmission.
But it seems that sharing flowers with many different bee species prevents or limits the viruses’ ability to spread. Previous studies have also suggested that native bees are less commonly infected and may be less likely to transmit the pathogens to other bees.
Given how important bees are to our food supply and how much they have also declined from habitat loss, parasites and pesticides, this study provides another strong argument for the importance of protecting biodiversity.