Wild bees across the west face a growing threat from microscopic parasites. Last week Lauren Ponisio, from the University of Oregon, visited Utah State University’s Ecology Center to talk about about how parasites move through bee communities.
“There are these high-elevation meadows that are basically islands within islands in the southwest. We have these gorgeous, kind of like Rocky Mountain style, high-elevation meadows that are absolutely full of bees and flowers," Ponisio said as she described one of her field sites.
Ponisio and her team study bumble bees, feral honeybees, and the many solitary bees that nest on their own. They look at the community ecology of bee–parasite interactions — how different bee species, flowers, and parasites all fit together.
“A lot of these parasites will give them basically like bee dysentery. And so, when they’re out there foraging, you’re kind of a sick bee, and you’ll defecate on a flower, and then another bee will come and they’ll pick up that infected material, and then they’ll become infected," she said.
Between species, flowers are the main route of transmission.
“Flowers are kind of, you know, the bee bathroom doorknobs,” said Ponisio.
Over the past decade, her group has sampled bees from harvested forests in the Cascades to those high-elevation meadows in New Mexico and Arizona, looking for patterns in parasite prevalence.
They tested classic ideas: looking for patterns of either dilution, where diverse bee communities dampen disease spread, or amplification, where high numbers of good hosts — like honeybees — boost infections. Instead, she says, it depends.
“It seems like it was very host-specific, very parasite-specific, and very landscape-specific, which, you know, is ecology,” Ponisio said.
This means that, like most things in ecology, it’s complicated. But what’s at stake? Ponisio said healthy bee communities are essential — not just for wild ecosystems, but for our food supply.
“Bee pollination is very important for our food system,” she said.
With ongoing declines in native bees and annual winter losses of honeybees, understanding how diseases spread may help protect both.
