Identification and phylogeny of ascomycetous yeasts from analysis of nuclear large subunit (26S) ribosomal DNA partial sequences

Approximately 500 species of ascomycetous yeasts, including members of Cand ida and other anamorphic genera, were analyzed for extent of divergence in the variable D1/D2 domain of large subunit (26S) ribosomal DNA. Divergence in this domain is generally sufficient to resolve individual species, resul ting in the prediction that 55 currently recognized taxa are synonyms of ea rlier described species. Phylogenetic relationships among the ascomycetous yeasts were analyzed from D1/D2 sequence divergence. For comparison, the ph ylogeny of selected members of the Saccharomyces clade was determined from 18S rDNA sequences. Species relationships were highly concordant between th e D1/D2 and 18S trees when branches were statistically well supported.