Study unlocks how wild bees can survive habitat pressures

A research team led by University of Oregon biologist Lauren Ponisio has uncovered how native bee species may be best equipped to survive intensive agricultural practices and climate change in California’s Central Valley.

Wild bees that are persisting amid shrinking habitats are those that are flexible in their pollination behavior when around other wild bee populations, Ponisio’s team reported in a study published April 1 in Nature Ecology & Evolution.

The research examined 1,150 network interactions involving 157 wild bee species and 152 plant species at 63 sites spread across three counties. The final analysis focused on adult bees from 31 species whose pollination activities with at least five plants overlapped during crop-growing seasons.

“We looked at the ability of these bees to change their roles in these plant-pollinator interaction networks,” Ponisio said. “This ability proved to be important for which species persisted in the landscape as well as for the higher number of habitat patches being occupied.”

A key to that vitality was the ability of bee species to choose plants being less targeted for pollination by competing species, said co-author Marilia Gaiarsa, a postdoctoral researcher in Ponisio’s former lab at the University of California, Riverside.

Ponisio joined the UO’s Data Science Initiative in July 2020 as an assistant professor in the Department of Biology. She’s also a member of the Institute of Ecology and Evolution. Gaiarsa is now a Marie Sklodowska-Curie Fellow at the University of Zurich, where she is studying the response of species interactions to climate change.

“In the Central Valley, there are areas of intensive industrial agriculture, monocultural farming, that are experiencing a 90 percent habitat loss for native bees,” Ponisio said.

Understanding what factors promote ecosystem health and ecosystem services, including pollination, Gaiarsa said, is vital for helping species facing extinction from such drivers as intensive agriculture, deforestation and climate change.

“One way to turn around these negative effects is through the process of ecosystem restoration,” she said. “By going into a degraded area and planting native plants known to be important resources for bees, we can restore some of the lost interactions and potentially restore the populations of these species.”

The valley is a product of large land grants obtained for farming years ago. Large, single-crop enterprises dominate the region. Over time, hedgerows were added between some farms to restore patches of native plants that support native species, especially bees crucial to pollination. Bees, in turn, need the plants’ nectar for nutrition.

Hedgerows observed in the study were created by planting flowers along the margins of fields more than a decade ago in a project led by study co-author Claire Kremen, Ponisio’s doctoral adviser at the University of California, Berkeley.

“At these hedgerows there are tiny patches of bee populations in these seas of monoculture agriculture,” Ponisio said. “Some colonize these patches; others go live in them for a while but eventually go extinct.”

By looking at the population dynamics of various species, the researchers sought to understand if some visited different habitat patches and, in turn, how well they persisted. Occupying different patches, Gaiarsa said, should increase interactions at each site and potentially increase plant diversity and overall ecosystem health.

“If a particular bumblebee species pollinates several plants that are only pollinated by a couple of other bee species, maybe that bumblebee species will be able to colonize more habitat patches because there may be very little competition with other bees for its plant resources,” she said.

The Army Research Office, National Science Foundation and U.S. Department of Agriculture supported the project.

—By Jim Barlow, University Communications