Phylogenetic relationships of Memnoniella and Stachybotrys species and evaluation of morphological features for Memnoniella species identification

Members of the anamorphic fungal genus Memnoniella demonstrate morphological and biological similarities to species within the genus Stachybotrys, and the taxonomic distinctions between the genera have been the subject of controversy in the past. Sixteen strains representing described species of Memnoniella were examined for morphology using light and scanning electron microscopy and for phylogenetic relationships using comparative sequence analysis of a segment of the nuclear ribosomal RNA gene operon (rDNA) including the internal transcribed spacer 1 and 2 regions (ITS1 and ITS2) and 5.8S gene. These analyses resolved the Memnoniella strains into two highly divergent phylogenetic clades with morphologies generally consistent with the current descriptions of M. echinata and M. subsimplex. One strain, showing morphological features more similar to M. subsimplex was placed in the M. echinata clade in the phylogenetic analysis and probably represents a new species. A second strain, showing a typical M. echinata DNA sequence, showed morphological features that were similar to Stachybotrys species when grown on certain culture media. The evolutionary relationships between the genera were evaluated by phylogenetic analyses of sequence data from the 18S, 28S, 5.8S rDNA genes and ITS1 and ITS2 regions. Results of several differ ent analyses were in agreement in indicating that Memnoniella is paraphyletic to Stachybotrys.