Microbotryum, Kriegeria and the changing paradigm in basidiomycete classification

Until recently the sedge parasite Kriegeria eriophori has never been satisf actorily classified above the genus level. Its classification has been prob lematic in that a number of characters at the gross micromorphological and ultrastructural levels appeared to be autapomorphic. The use of nucleotide sequence data has proven to be a powerful means of addressing difficult sys tematic problems in which standard morphological approaches have failed to preside sufficient information. During this study, some of these ultrastruc tural characters were discovered to be synapomorphies for a group containin g K. eriophori and Microbotryum violaceum, a urediniomycete smut species. R ibosomal RNA gene sequences and nucleus-associated ultrastructural characte rs were analysed separately and combined. These characters serve to define the new subclass Microbotryomycetidae. Inclusion of the sequences in the an alysis provided an independent data set by which the ultrastructural charac ter states were polarized. Gross micromorphological characters proved to be homoplasious, and of less utility in determining phylogenetic groups than were ultrastructural and nucleotide characters. Cladistic analysis of ultra structural and biochemical characters provides a powerful means of identify ing monophyletic groups, the prerequisite for creating a phylogenetic class ification. A phylogenetic diagnosis is provided for the Microbotryomycetida e, which deviates from the pattern used in typical diagnoses.