Ecology and description of a new species of Ophiognomonia endophytic in the leaves of Quercus emoryi

Abstract

In a study to examine plant-insect-fungal endophyte interactions, we surveyed the fungal endophyte populations in over 4600 leaves of an evergreen oak over three growing seasons. Three of the most frequently isolated endophytes were undescribed species. We describe one of these endophytes as a new taxon, Ophiognomonia cryptica, and present details of its ecology in leaves studied from 1993–1995. Ophiognomonia cryptica was not isolated from leaves during the 6 months following bud burst (May-Nov) but rapidly increases in isolation frequency from December until leaf abscission in April. The first appearance of O. cryptica coincides with a drop in temperature and increase in cumulative precipitation. Infection levels (infections/cm2) were negatively correlated with leaf area on 6 of 7 dates. However, infection frequencies (total number of infections per leaf) were negatively correlated with leaf area on only 3 of 8 sampling dates and not correlated on the other 5. We found no within-leaf pattern of infection, exterior sun leaves were more heavily infected relative to interior shaded leaves, and infection levels varied among trees. We discuss the ecology of this endophyte in relation to the theory of island biogeography. In addition, we discuss our results with respect to the prediction that each plant species may harbor 2–4 endophytes species specific to that plant species and its implications to fungal biodiversity.