The systematics of reduced, soil-inhabiting ascomycetes

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Lack of information concerning the phylogenetic relationships and diversity of fungi is acute, particularly within the Ascomycota, a group that includes the majority of economically important fungi. Ascomycetes have been enumerated and identified in many habitats, but studies documenting their diversity are limited by the selective nature of isolation methods and the difficulty of identifying these fungi. Many ascomycetes do not form sexual states and are defined on the basis of their asexual spore forms (anamorphs). Anamorphic ascomycetes are typically simple anatomically and thus challenging to identify. Ascomycetes that form no spore stages in pure culture cannot be identified using microscopy-based methods. Fortunately, the problem of accurately identifying anamorphic and non-sporulating ascomycetes has been solved largely through the PCR (polymerase chain reaction)-amplification of target gene regions and the comparison of DNA sequences of the resulting amplicons. Sequence data are also valuable for inferring phylogenies that permit the recognition of monophyletic groups and the assessment of hypotheses based on ecological and morphological characters.