The ecological importance of invasive Epichloë-Poöideae symbioses

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The long-term objective of this research program is to predict how climate change will impact the invasiveness of a group of common grasses and their associated symbiotic fungi. Many Poöideae grasses used in pastures and for turf (e.g. parks, roadsides, etc.) in Canada originated in Europe. Because of their superior performance, they are preferred over native species. For some of these species, their global success is partly due to a mutualism that they form with fungal endophytes in the genus Epichloë. Fungus-infected grass: produce alkaloids that kill or deter herbivores, produce greater vegetative growth, have higher seed production, and are more tolerant of stressful conditions, particularly drought, than uninfected conspecifics. These traits are extremely useful for turf and pasture grass applications, and there is a significant industry built around exploiting this naturally occurring symbiosis. Unfortunately, the same traits that make these grasses desirable for human uses, also make them very successful when they escape cultivation, where they alter biodiversity, and change ecosystem functioning. Here I propose to advance my research program by accomplishing three near-term research objectives. Objective 1: To study how the interaction between elevated CO2 and fungal strain affects the suite of metabolic compounds that the grasses produce and how these changes affect a generalist herbivore. This will lead to a predictive model. Objective 2: To characterize the full fungal biodiversity of microbial fungal species that inhabit these grasses, and to investigate the impacts of the presence of these Epichloë fungi on the broader fungal community. The functional consequences of the resultant biodiversity will be assessed by examining its impact on a generalist herbivore. Objective 3: To continue to follow the invasive success of these grasses and their fungal symbionts, and to test the role soil nutrients play in the success of these invaders. Using a large long-term experiment established in 2007, I continue to chart the time course of 340 artificial invasions (and associate controls) in S. Ontario. Impact: As serious invasive species throughout much of North America, understanding the factors that contribute to their success, and how these factors may change under climate change are important for our management and conservation of our natural and semi-natural grasslands. This work provides significant advancement toward our ability to predict the outcomes and future changes of these biological invasions.