Most studies concerning endophytic fungi emphasize their impacts on the performance of host plants. In order for endophytic fungi to influence plant performance, they have to be able to tolerate the conditions experienced by their hosts, yet we know little about the environmental requirements of the fungi themselves. Utah has an average elevation of nearly 1900 m above sea level. Thus, the ability to thrive at low temperatures is important even during the growing season. High elevations also expose plants to relatively high levels of UV radiation, some of which passes through leaves, subjecting foliar endophytic fungi to significant levels of UV radiation. After the growing season ends, many endophytic fungi persist in the environment as saprotrophs in litter. In order to do so they need to be able to shift from a biotrophic to a saprotrophic mode of nutrition for which cellulose may be an important source of energy. Therefore, we initiated a series of investigations to determine the variation among endophytic fungi in three key traits: ability to grow at low temperature, ability to tolerate UV radiation, and ability to utilize cellulose as a reduced carbon source.
Results/Conclusions
We found that significant variation exists among endophytic fungal isolates in their ability to grow at a low temperature (5 C), in their ability to tolerate relevant levels of UV radiation, and in their capacity to exist as saprotrophs by utilizing cellulose as a reduced carbon source. Such variation is likely to produce predictable temporal and spatial patterns of occurrence of endophytic fungi across seasons, altitudes, levels of shade and within plant litter. Because endophytic fungal species composition influences host plant stress tolerance and the rate of litter decomposition and nutrient cycling, these patterns may indirectly influence host plant performance and important ecosystem-level properties, including primary productivity. We will continue to investigate these topics and others in our ongoing characterization of variation among the niches of endophytic fungi.