As pollinators like bees and butterflies decline around the world, the loss is spilling over ecosystems, a team of researchers led by Princeton University reports in the journal Nature. found that it poses a significant threat to biodiversity when they must compete for pollinators.
“Our study identifies an unexpected and insidious way in which the loss of some species in ecosystem networks can lead to the loss of yet others,” said a Princeton University professor. and senior author Jonathan Levin, Chair of Ecology and Evolutionary Biology. “It suggests that the ongoing decline of pollinators may unravel the very structures that keep plant diversity stable.”
He and his colleagues found that when pollinator numbers and diversity decreased, the playing field changed, favoring plants that excelled in competing for pollinators. This can have detrimental effects on organisms that depend on the lost plants. These knock-on effects can have devastating effects on ecosystem health.
Ecologists know that many flowering plants compete to attract pollinators that are essential to their reproduction, just as they compete for resources such as sunlight, water and soil nutrients. Competition for pollinators is expected to increase in a world of declining pollinators, but the implications of increased competition are unclear.
If plants of the same species can monopolize pollinators when together (e.g., by displaying showy flowers as a group), this can disadvantage rare plant species and reduce their coexistence in the long run. weaken the
First author Christopher Johnson, now a research scientist at the University of Basel, spearheaded the project as a Princeton postdoctoral fellow in Levine’s research group. He, Levine, and co-author, his Proneet Dutt at ETH Zurich, combined rigorously controlled field experiments with mathematical models.
“This study builds on our group’s years of work designing field experiments to inform mathematical models that predict species coexistence or exclusion,” said Levine. “Here, these methods pay off by revealing the hidden effects of plant competition for pollinators on plant diversity.”
To experimentally eliminate pollinator competition, the researchers used a paintbrush to manually pollinate some plants. Other plants were left to the whim of local pollinator communities, mostly made up of bees and bumblebees, and a few solitary bees and flies.
“Insect pollinators are much better pollinators than we are, but they don’t necessarily visit every plant,” Johnson said. We pollinated every flower, not only for abundant and showy flowers, but also for those buried by our competitors.”
At the end of the summer, the research team collected all the seeds produced by each plant and brought them back to the lab to “count and germinate” to determine how many viable seeds actually produced seedlings.
Their results suggest that an overall decline in pollinators may affect some plant species more severely than others.
“Perhaps not surprisingly, reducing pollinator diversity to a single species at very low densities dramatically increased both the number of pollinator visits and the amount of seed produced per plant. ,” says Johnson.
“It’s a bit of a wake-up call that pollinator decline can have serious effects on plants,” he said. “As someone who has gone out into the fields and tried to pose as pollinators to pollinate those plants, I can tell you that the ecosystem services they provide are tremendous. We need to get serious about maintaining pollinator diversity because it cannot be easily replaced.”
“Competition for pollinators destabilizes plant coexistence,” by Christopher A. Johnson, Proneet Dutt, and Jonathan M. Levine, published 20 July in Nature (DOI: 10.1038/s41586-022-04973). -x) was supported by Princeton University, ETH Zurich. Center for Adaptation to Environmental Change, and the National Science Foundation (DEB 2022213).