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Pathogens Help Different Plant Species To Live Together, Study Suggests

Sometimes it’s a good year for one kind of wild plant and sometimes it’s a good year for another kind. But what causes these fluctuations in plant abundances from year to year? A new study suggests it might be linked to soil microbes underneath those plants.

“Why doesn’t one species who may be super competitive just take over the world?” asked Anny Chung, a plant ecologist and postdoctoral fellow at Utah State University. “That’s always been a puzzle for ecologists. For this study, we were interested in blue grama and black grama. Both of these species occur and do so at different levels of stability. What allows them to coexist with each other and not let one take over the other?”

In the southwestern site where she works, she saw some places where blue grama lived together happily with black grama. And she saw other places where one grama species would take over. She set up an experiment to see what role soil microbes might play in the different places.

“In static patches, we found that black grama experienced neutral to negative relationships with its own microbes, and blue grama experienced very strong negative relationships with its own microbes,” Chung said. “Because each plant is limited more by their own microbes than the microbes of their competitor plants, that keeps the system quite stable.”

And in the places where one plant started to take over?

“What we saw was that each of these plants experienced relationships with their microbes that could potentially allow them to increase without other checks and balances,” Chung said.

Chung says that even though you might expect pathogens to be bad, they actually help different plants to live together. Without pathogens that harm plant growth, there is less coexistence and more plant takeovers.