Studies on the incidence of coniferous needle endophytes in the Pacific Northwest

Abstract

The incidence of internal fungal infections has been scored in coniferous needles from 19 hosts sampled in over 200 sites dispersed throughout western Oregon and southern Washington. Abies grandis, A. magnifica, Picea sitchensis, Pseudotsuga menziesii, and Sequoia sempervirens have proved congenial hosts for needle blade endophytes; petiole fungi are common in all species of Picea and Tsuga sampled. An undescribed taxon in the Hemiphacidiaceae, Chloroscypha spp., Cryptocline spp., Leptostroma spp., Naemacyclus spp., Phomopsis spp., Phyllosticta sp., and several unidentified Coelomycetes with Phoma-like spores were the dominant fungal taxa in the coniferous hosts sampled. The observed patterns of species dominance and diversity suggest that the true population of endophytes has been inadequately sampled in the present study and that an order of magnitude more intensive sampling might be required for real patterns of dominance and diversity to emerge. Many endophytes are restricted to a single coniferous host or to a restricted group of hosts. When similarity coefficients between coniferous species are computed on the basis of their internal needle microfloras, the resultant taxonomic groupings appear similar to those derived from consideration of conventional morphological criteria. Comparison of endophyte incidence with host distribution patterns for Pseudotsuga menziesii reveals that infection rates decrease at high elevations and dry sites.