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

摘要

In a study of plant-insect-fungal endophyte interactions, the fungal endophyte populations in over 4600 leaves of an evergreen oak (Q. emoryi) over 3 growing seasons were surveyed in central Arizona, USA. Three of the most frequently isolated endophytes were undescribed species. One of these endophytes is described as a new taxon, O. cryptica, and details of its ecology in leaves studied during 1993-95 are presented. O. cryptica was not isolated from leaves during the 6 months following bud burst (May-November) but rapidly increased in isolation frequency from December until leaf abscission in April. The first appearance of O. cryptica coincided 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. There was no within-leaf pattern of infection, exterior sun leaves were more heavily infected relative to interior shaded leaves, and infection levels varied among trees. The ecology of this endophyte in relation to the theory of island biogeography and the prediction thateach plant species may harbour 2-4 endophyte species specific to that plant species is discussed.