Yeasts from exudates ofQuercus, Ulmus, Populus, andPseudotsuga: New isolations and elucidation of some factors affecting ecological specificity.

The yeast flora associated with exudates ofQuercus, Ulmus, Populus, andPseudotsuga was examined in the light of new isolations in geographic areas different from those in previous reports. Application of multivariate analytic methods indicated that geographic distance, although a meaningful ecological factor, is largely overshadowed by host tree specificity, provided that yeast community physiological profiles and not yeast taxa, are used as ecological descriptors. Some physiological attributes used in classifying yeasts were identified as particularly important in shaping the yeast communities of those trees. The possible divergence between these attributes and those generally considered taxonomically useful is discussed.