The distribution of the Epiphytic fungus Atkinsonella texensis and its effects on the performance of its plant host, Nassella leucotricha

by Maas, Martha Marie

The abundance of Nassella leucotricha and its rate of infection by its fungal pathogen, Atkinsonella texensis (Balansieae, Clavicipitaceae, Ascomycota), varied spatially in three savanna sites in central Texas. In two of the three sites, Nassella was much more abundant at the edge of clusters of woody plants than in the open grassy areas between them. In all three sites, the incidence of disease was highest beneath woody canopies and lowest in the open. Where Nassella was growing under or near woody plants, there was a positive relationship between the incidence of infection and Nassella density. In contrast, there was no relationship between Nassella density and the incidence of infection in the open grassy areas between clusters, possibly because infected plants there did not produce infectious fungal spores. Environmental conditions in the open might have affected the stroma adversely; the results are also compatible with an Allee effect on fungal mating. 5