Pollination From Honeybees Could Make Plants Less Fit to Survive and Reproduce - Smithsonian Magazine

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Honeybee on a flower — Honeybees, which are not native to the United States, may be outcompeting native bees for pollen. Ed Reschke via Getty Images

Honeybees are often heralded as a symbol of biodiversity and a key species for plant pollination. In recent years, calls to “save the bees” have led to a rise in backyard beekeeping—but the practice does not help declining native pollinators.

Despite the benefits of keeping bees, past studies have shown that honeybees, which are not native to the United States, can have negative effects on the environment. They compete with native bees, spread diseases and pollinate plants less efficiently. Now, new research from scientists at the University of California San Diego (UCSD) suggests honeybee pollination may also lead to lower-quality offspring from the plants they visit.

“People see honeybees as providing a valuable service, which is pollination, but there’s a decent amount of evidence to show that they’re competing with native insects for resources like pollen and nectar,” UCSD ecologist Dillon Travis says in a statement. “Many conservation efforts are focused on saving the honeybee, but they are not in any danger of going extinct. … The organisms that do need our help are the native plants and bees.”

In a new study published in late June in Proceedings of the Royal Society B, Travis and co-author UCSD biologist Joshua Kohn grew three common California plant species—white sage, black sage and distant phacelia—under different scenarios, including natural pollination, no pollination, pollination by honeybees, pollination by native bees and self- and cross-hand pollination. After four to six weeks, they collected seeds from the plants.

To measure the seeds’ fitness, they grew them in a greenhouse and analyzed how they matured. Black sage was not visited by enough native insects to demonstrate the species’ impact on its reproduction. However, the team found that white sage and distant Phacelia produced seeds that were two to five times more fit—or more likely to germinate, grow and reproduce—when pollinated by native species rather than by honeybees.

The reason for this may lie in the insects’ unusual foraging style: Honeybees tended to visit flowers on the same plant twice as often as native species did, resulting in the plant pollinating itself. This pattern leads to more inbreeding, which can create a population of native plants that is less genetically fit to survive and reproduce.

In turn, this could open up space for the invasion of introduced plants, such as annual Mediterranean grasses and mustard species, write the authors. The study is “an important demonstration” that honeybees can negatively affect native plants, Gretchen LeBuhn, an ecologist at San Francisco State University who was not involved in the study, tells New Scientist’s Jake Buehler. While honeybees are important for agriculture, we need to think carefully about their impact, she adds.

Growing native flowers and providing nesting habitat for native pollinators, such as decaying wood, can help boost their numbers, writes Science News’ Jude Coleman.

“It is time to actually shift our dependence for pollination from largely honeybees to … native species as well,” Jaya Sravanthi Mokkapati, an entomologist at Penn State University, tells the publication.

Given evidence like this, some scientists say honeybees shouldn’t be placed on a pedestal. “The honeybee has been promoted as the symbol of helping the environment and biodiversity, and really it’s not that,” Gail MacInnis, a former postdoctoral researcher at Concordia University in Montreal and lead author of a recent study examining the impact of urban beekeeping on wild bees, told the Washington Post’s Allyson Chiu in May. “You would never start keeping chickens to help save wild bird species.”