Comparison of fungal endophyte communities in the invasive panicoid grass 'Hyparrhenia hirta' and the native grass 'Bothriochloa macra'

Abstract

Communities of fungal endophytes from roots, stems and leaves of the introduced grass 'Hyparrhenia hirta' (Coolatai grass) and the native species 'Bothriochloa macra' (redgrass) were compared at two sites to identify characteristics that may be associated with invasiveness of 'H. hirta'. The most frequently isolated fungi from both hosts were species of 'Nigrospora', 'Alternaria', 'Cladosporium', 'Phoma', 'Epicoccum', 'Fusarium' and 'Periconia'. Most of these occurred at a similar frequency in the two hosts, although Nigrospora sphaerica was much more frequently isolated from 'H. hirta' at both sites. There was little support for the hypothesis that the introduced species ('H. hirta') would have a less diverse endophyte community than the native species. There was a greater degree of dominance by the most frequent species in communities from 'H. hirta' than from 'B. macra', leading to lower diversity indices, but no significant difference in species richness. Cluster analysis of the endophyte communities suggested that host had a greater influence than site on community structure, and that this was expressed mostly in the relative frequency of fungi isolated from stems and leaves, with very similar fungal communities present in the roots of both species at both sites. Analysis of co-occurrence showed no evidence that competition among fungi affected community structure within individual plants. The dominance of 'N. sphaerica' in 'H. hirta' was therefore due to fungus–plant interactions rather than fungus–fungus interactions. Interactions with 'N. sphaerica' could potentially affect the population ecology of 'H. hirta'.