Archiascomycetes: detection of a major new lineage within the Ascomycota

For phylogenetic analysis of the higher fungi, we sequenced the nuclear small subunit rRNA (18S rRNA) gene from Taphrina populina, the type species of the genus Taphrina, and Protomyces lactucae-debilis. The molecular phylogeny inferred from these 2 sequences and 75 sequences from the DNA data bank divided the Ascomycota into three major lineages: the hemiascomycetes, the euascomycetes, and the archiascomycetes, newly described herein. The former two lineages are monophyletic, whereas the archiascomycetes, which originated first and are comprised of Taphrina, Protomyces, Saitoella, Schizosaccharomyces, and Pneumocystis, may not be monophyletic. Among the archiascomycetes, the Taphrina/Protomyces branch is monophyletic. Confirmation of the archiascomycetes as a monophyletic taxonomic class will require comparison of additional genetically defined characters.