Distribution, abundances, and associations of the endophytic fungal community of Arizona fescue (Festuca arizonica)
We documented patterns of species diver- sity, relative abundances, and associations of the fun- gal endophyte community inhabiting Arizona fescue (Festuca arizonica), a dominant perennial bunchgrass in ponderosa pine-grassland communities of the Southwestern USA. We also determined spatial vari- ation in frequency of a vertically-transmitted and asexual fungus, Neotyphodium starrii, a dominant en- dophyte in Arizona fescue. To determine if Neoty- phodium frequency is affected by grazing, we com- pared frequency of infected grasses inside and out- side long-term grazing exclosures in four Arizona fes- cue populations. Likewise, we correlated soil nitrogen levels within and among these four, and an additional, population to determine if the frequency of Neotyphodium-infected plants is related to available soil nutrients. More than 400 different fungi were isolated from Arizona fescue. However, most of these were extremely rare and isolated only once. Neoty- phodium starrii and 13 other morphospecies com- prised the majority of fungal taxa. These results sug- gest that the fungal endophyte communities of pe- rennial grasses may be as diverse as fungal endophyte communities of woody shrubs and trees, despite high infection levels of the asexual and vertically-transmit- ted Neotyphodium. The diversity and dominance of non-Neotyphodium endophytes were highly variable among Arizona fescue populations and varied season- ally and yearly within and among populations. Most of these fungal species are probably opportunistic colonizers that increase in abundance in late summer with seasonal rains that promote spore transmission and germination and hyphal growth. Neotyphodium starrii also varied spatially within and among Arizona fescue populations, although always occurring at higher levels than other endophytic fungi. However, Neotyphodium frequencies were not greater outside grazing exclosures as expected if the endophyte con- fers increased resistance to vertebrate herbivores.