RICE U. / INDIANA U. (US)—A fungus living inside a popular turf grass called tall fescue, used widely for golf courses and home lawns, is having far-reaching effects on plant, animal, and insect communities.
“Competition and environment have traditionally been seen as the driving forces for community dynamics, so it’s significant to see that the composition and diversity of a plant community can be affected by changing a few genes in an invisible fungus inside one species of grass,” says Jennifer Rudgers, the Godwin assistant professor of ecology and evolutionary biology at Rice University.
“This suggests that cooperative microorganisms should not be overlooked as significant contributors to ecological diversity.”
Tall fescue is native to Europe and North America, but can be highly invasive in North America. In the U.S., it covers an area that’s estimated to be larger than Virginia and Maryland combined.
It can also sicken livestock, thanks to a symbiotic fungus called Neotyphodium coenophialum. The fungus and fescue have a mutually beneficial relationship: the fungus lives inside the plant, where it gets shelter and food, and in return it laces the plant’s leaves with toxic alkaloids that are a turnoff to some plant-eating animals.
Results of a six-year study by ecologists at Rice and Indiana University are available online in the Journal of Applied Ecology.
In 2002, Rudgers and study coauthor Keith Clay, professor of biology at Indiana University, selected 42 grassland plots, each about 1,000 square feet. The researchers selected two varieties of fescue called Georgia-5 and Jesup, and two varieties of the fungus, called KY-31 and AR-542. KY-31 is a common variety that produces alkaloids that are toxic to mammals, and AR-542 naturally lacks these alkaloids. Additionally, some plots were planted with grass and no fungus.
Over the next six years, the team returned to the plots several times and counted individual flowers, cataloged the number and species of every plant, and even counted the number of stems of grass that had been gnawed by plant-eating voles.
The investigation offered specific results for conservation managers: Jesup with either fungus works best for maintaining a fescue monoculture; and if a symbiotic fungus is desirable, the combination of Georgia-5 and AR-542 supports maximum plant diversity and minimal invasiveness.
The study also suggests that the ecological effects of plant-microbe symbiosis aren’t easy to predict. For example, the researchers found that voles were less likely to eat fescue that contained either fungus, including the AR-542 variety, which lacks mammal-toxic alkaloids.
“That indicates that plant-microbe symbioses have complex ecological effects,” explains Clay,. “It signals the need for more investigations of the long-term effects of cooperative symbiosis.”
The research was sponsored by the National Science Foundation and the Indiana University Research and Teaching Preserve.