The critters that pollinate much of the world's crops and provide sought-after honey aren't just under attack from colony collapse disorder (CCD), the disease that has been destroying beehives since 2006. Bees are also vulnerable to intestinal parasites that threaten their health and that of their colonies. Now a new study out of Dartmouth University suggests that bees are finding a way to self-medicate against those parasites by choosing plants with certain naturally occurring compounds.
The researchers focused on a group of secondary metabolites in plants known as iridoid glycosides. They discovered that bees infected with a common intestinal parasite preferentially visited certain flowers of turtlehead plants, a type of wetland plant--in fact, they were drawn to the flowers with the highest concentrations of iridoid glycosides.
What's more, they found that flowers with nectar containing the highest concentrations of the beneficial metabolites donated more pollen to neighboring flowers, thereby perpetuating the production of antiparasitic medicine that can protect the bees. The study appears in the journal Ecology.
"Secondary metabolites are commonly present in floral nectar and pollen, yet their functions are not well understood," says lead author Leif Richardson, a former Dartmouth graduate student who is now at the University of Vermont. "In this study, we show that these compounds could influence plant reproduction via complex suites of interactions involving not only pollinators but also their natural enemies."
International concerns about bee health have prompted a variety of studies linking plant chemistry with the well being of hives. In July, a team of researchers from Harvard, for example, provided evidence that a class of pesticide called neonicotinoid could be to blame for CCD. They demonstrated that 70% of pollen and honey samples collected from more than 60 beekeepers in Massachusetts contained at least one neonicotinoid. The growing body of knowledge from these studies and others could guide horticulturists towards better practices in growing and maintaining plants.