Leaf chemistry and co-occurring species interactions affecting the endophytic fungal composition of Eupatorium adenophorum

The endophytic fungal composition of healthy leaves from an invasive plant (Eupatorium adenophorum) in China was investigated. Six morphologically different endophytes were found to inhabit the leaves. Based on a phylogenetic analysis of the internal transcribed spacer sequences (ITS), four morphotypes were close to Alternaria, Cladosporium, Pestalotiopsis, and Didymella, respectively, while two morphotypes were close to unidentified fungi. The frequency at which the endophytes occurred varied among leaves, branches, and individuals, with species diversity markedly increasing with increasing leaf age. Chemical conditions alone did not adequately explain the lower degree of endophytic fungal diversity in younger leaves. Competition between endophytes mediated through non-volatile and volatile metabolites were common and may be a major factor accounting for the heterogeneous distribution of endophytes in leaves of E. adenophorum.