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Going Native: Wild Bees Mingle with Honey Bees

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When honey bees interact with wild native bees, they become better pollinators.

This finding comes at a time when populations of honey bees have been decimated by parasitic mites, and it suggests that protecting wild native bees and their habitats could play a crucial role in ensuring adequate pollination for important crops.

Sarah Greenleaf, a UC Davis plant pathologist, and Claire Kremen, an assistant professor of organisms and environment at CNR, observed the behavior of managed honey bee hives and wild native bees in sunflower fields over two growing seasons.

In fields where wild bees were rare, a single visit by a honey bee produced an average of three seeds. But as wild bee numbers increased, so did the number of seeds produced per honey bee visit, up to an average of 15 seeds per visit.

When Kremen and Greenleaf followed the behavior of their tiny subjects, they discovered the reason for the boost in pollination: Like the captain of a plane switching out of autopilot when she spots a craft nearby, a honey bee alters its flight pattern after meeting up with a wild bee on a sunflower head. Anything that causes honey bees to alter their foraging behavior improves the likelihood that they will move between different kinds of flowers.

“Wild bees make the honey bees more skittish so they move more frequently between the different cultivars,” Kremen explains. “Each time they move, they have the possibility of transporting the pollen between the rows.”

The honey bee, Apis mellifera, was imported to the Americas centuries ago and now is the principal species used for crop pollination worldwide. Since the 1980s, when two species of mites that parasitize honey bees were inadvertently introduced into the United States, populations of honey bees living in the wild have all but disappeared, and the number of managed hives has plummeted from 4 million to 2.4 million. Along with honey bee declines, populations of wild bees are also dropping, Greenleaf said. Habitat loss and “unfriendly farming practices” have both taken a toll.

Conserving patches of natural habitat for native bees in agricultural areas could help maintain their populations and provide better pollination for crops, Kremen says. “Given that we don’t have enough honey bees,” Greenleaf says, “it’s really great that there’s a way to make the ones that are left better pollinators.”

-Liese Greensfelder


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