A CRITIQUE OF DNA-SEQUENCE ANALYSIS IN THE TAXONOMY OF FILAMENTOUS ASCOMYCETES AND ASCOMYCETOUS ANAMORPHS

The validity of reclassifying filamentous, ascomycetous anamorphs sole ly on the basis of ribosomal DNA sequences is examined. We suggest tha t emotional reactions to the debate are a consequence of often unackno wledged philosophical biases. From the perspective of the scientific m ethod, neither morphological nor sequence-based taxonomic studies are inherently superior. A review of published information on the internal transcribed spacer of filamentous Ascomycetes and ascomycetous anamor phs demonstrates that uniform species concepts based on DNA sequences alone are presently infeasible. Because a phylogenetic scheme should c lassify species, the concept that fungi can be typified or classified solely by DNA sequences is challenged. Similarly, because no adequate nonmorphological species concept exists for anamorphic fungi that lack a sexual state, integration of the Deuteromycetes into the holomorphi c classification on the basis of DNA sequences alone is also presently impractical.