*Clay, Keith. Ecological  consequences of endophyte symbiosis with grasses. In: International Meeting on "Population and Evolutionary Biology of Fungal Symbionts", Ascona, Switzerland, 2007. AB-38.

We are investigating the ecological consequences of endophyte symbiosis with grasses. Most research has focused on tall fescue (Lolium arundinaceum) and has utilized a series of large-scale and long-term field experiments. Tall fescue is the most common plant in the eastern United States and is one of the most widely-distributed plant species in the world. In the US most tall fescue is infected by a single wild-type (WT) endophyte genotype described originally in variety KY-31. Tall fescue is extremely persistent and resistant to invasion and succession, and endophyte infection may be an important mechanism for its ecological success.  Two large experimental grasslands were established in 1994 and 2000 respectively where E+ or E- seed (var KY-31) were sown at a constant rate in a checkerboard pattern in either 20m x 20m (N=8, 1994) or 30m x 30m (N=16, 2000) plots. A variety of other plant species established from the seed bank, dispersal or vegetative fragments. Using these experimental plots, a series of past and continuing experiments have examined the effect of endophyte symbiosis on soil interactions (feedback and decomposition rate), plant-plant interactions (competition, invasibility and succession), plant-herbivore interactions (arthropod and vertebrate herbivores), higher trophic level interactions (generalist predators and parasitoids) and ecosystem processes (diversity, productivity). Endophyte symbiosis has a highly significant and dramatic effect on all of these properties, indicating that the effect of individual species on ecological systems is unrelated to their absolute abundance or biomass. In general, endophyte-infected fescue is more dominant and provides less energy flow to other trophic levels compared to endophyte-free fescue. While tall fescue is just one example of a great diversity of endophyte interactions, it illustrates the mechanisms by which fungal symbiosis can be a primary determinant of critical ecological processes. It further illustrates how natural selection can act on symbiotic units rather than on separate populations. Data from other endophyte systems will also be compared and contrasted with tall fescue for insights into grass-endophyte diversity, ecology and evolution.

Keywords: Lolium, Neotyphodium, grasses, herbivory, competition, ecology

*Institution: Indiana University

Email: clay@indiana.edu