New evidence for broad trophic status of leaf endophytic fungi of Quercus gambelii

Endophytic fungi inhabit the living tissues of every terrestrial plant species thus far examined. In at least some cases they significantly improve stress tolerance of their hosts. We asked whether endophytic fungi play other ecological roles, specifically whether the leaf endophytes of Quercus gambelii persist during the course of leaf decomposition, requiring a transition from a biotrophic to a saprotrophic mode of nutrition. Using automated ribosomal intergenic spacer analysis (ARISA), we found that endophyte fungal OTU diversity declined as decomposition commenced, but some endophytes persisted for months during which leaves were decomposing. In contrast, saprotroph fungi OTU diversity increased as decomposition progressed. These results are consistent with the hypothesis that some biotrophic endophytes persist in leaves during decomposition by becoming saprotrophic, and that the niche occupied by them is broader than expected.