Impacts of Plant-Associated Microbes on the Ecological Dominance of the Invasive Grass Eragrostis lehmanniana: A Metabolomic Approach

Abstract

The significance of plant invasion is growing at a global scale, especially in the context of climate change. In the southwestern United States, biotically rich environments such as grasslands, which provide diverse ecosystem services, face risks from shifting precipitation patterns, modified fire cycles, encroaching shrubs, and transformations in land use. Each of these factors is compounded by stress from invasive plants, where near-monodominant plant communities may be particularly susceptible to ecological collapse mediated by biotic and abiotic stressors. The non-native perennial bunchgrass, Lehmann’s lovegrass (Eragrostis lehmanniana Nees) (ERLE) is of particular concern in mid-elevation rangelands in southeastern Arizona. This grass was introduced to the southwest in the 1930s and has since displaced native grasses and increased total grass litter production of many areas, increasing the risk of fire. Like other terrestrial plants, Lehmann’s lovegrass harbors diverse microbial symbionts that may be important for its establishment and persistence. Earlier studies have revealed ERLE hosts endophytic fungi that selectively enhance the germination of ERLE seeds, as opposed to the seeds of native grasses that coexist in the same habitats. This study employs a metabolomics approach to characterize metabolites that could play a role in the success of ERLE, with a focus on one of the oldest continually maintained rangeland experimental systems in the world, the Santa Rita Experimental Range. To further assess the role of these metabolites in natural settings, I present ongoing and future work that is focused on examining the metabolome and microbial communities of soil and litter bags from the field. This work contributes to a growing area of study in the integration of metabolomics and microbial sequencing tools and techniques to elucidate mechanisms by which plants and soils are influenced through their associated microbiome. We find that endophytic fungi have acute metabolic responses to the presence of seeds, where fungal isolates express different metabolites dependent on seed type. Knowing that plants and their associated microbes are intimately linked through metabolite expression, metabolomic tools offer new pathways of insight for ecological studies of ecosystems experiencing invasion.