Grass-Epichloë Interactions in Current and Future Climates

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Invasive species are redefining the classical boundaries of biogeography and affecting ecosystem functioning. They are a defining feature of the Anthropocene. Several related grass species of European origin are globally significant in managed grasslands. These species have been subjected to intensive breeding programs and marketed aggressively throughout much of the temperate world. They are cultivated throughout North and South America, Australia, New Zealand, Africa and parts of Asia. They routinely escape cultivation to compete aggressively with native species, purportedly reducing biodiversity and impairing ecosystem functioning. Much of the success of these grass species, both inside and outside of cultivation, is due to their evolutionary history with beneficial, asexual, vertically transmitted endophytic fungal species in the genus Epichloë. These grass-fungal symbioses are highly desirable to farmers but endanger neighbouring unmanaged ecosystems. In the face of dramatic ongoing climatic change, an open question is whether or not these symbioses will continue to be as economically important and ecologically invasive. I have four near-term objectives. 1. Create a statistical model of the microbiome, metabolome, proteome and Epichloë concentrations across years and within the growing season, as a function of temperature and moisture. 2. Create a statistical model of the relationship between aphid herbivores population dynamics as a function of the host plant's microbiome, metabolome, proteome, Epichloë concentrations, temperature and moisture. 3. Identify the main driving variables that determine the role of Epichloë infection in promoting the grasses's invasiveness. 4. Create a biologically detailed mathematical model of the aphid-grass- Epichloë interaction. I will accomplish these objectives using a long-term multi-site experiment to investigate the effects of temperature and precipitation on this grass-fungal endophyte interaction. These sites are located along an 800 km transect beginning in Milton, Ontario, and terminating in Carbondale, Illinois. This transect spans a 12°C change in average growing season temperature and 246 mm difference in growing season precipitation. Each month during the growing season I will characterize the grasses' microbiome, proteome, metabolome, and Epichloë concentrations. I will also characterize the grasses' invasiveness and herbivore resistance with and without the Epichloë endophyte. Finally, I will further develop a mathematical model of the grass-endophyte interaction that I recently published using details from this experimental work.