The genus Oidiodendron: species delimitation and phylogenetic relationships based on nuclear ribosomal DNA analysis

TLDR: Parsimony analyses of 23 Oidiodendron strains showed that three highly supported monophyletic groups are resolved within the genus and a low level of sequence divergence between the species in these pairs suggests conspe- cificity for each pair.

Abstract: Nuclear ribosomal DNA sequences (ITS region) of fifteen species in the hyphomycete genus Oidiodendron and ten species from the 4 genera in the Myxotrichaceae, Byssoascus, Gymnostellatospora, Myxotrichum, and Pseudogymnoascus, were analysed to: (i) reveal the levels of intra- versus interspecific sequence variation within the genus Oidiodendron, clarify species delimitation and examine the useful- ness of some morphological characters used for iden- tification; (ii) assess the possible conspecificity of doc- umented ericoid mycorrhizal strains of Oidiodendron; and (iii) test the hypothesis based on morphological inference that the genus Oidiodendron belongs with the genus Myxotrichum in the Myxotrichaceae (Ony- genales). Comparison of molecular and morpholog- ical data for multiple strains of 0. griseum, 0. tenuis- simum and 0. maius revealed that conidiophore length and the production of a diffusing pigment are not reliable key characters for the genus. Several his- torically important ericoid mycorrhizal strains, doc- umented as 0. griseum, were reidentified as 0. maius. Parsimony analyses of 23 Oidiodendron strains showed that three highly supported monophyletic groups, each one consisting of a pair of species, are resolved within the genus. A low level of sequence divergence between the species in these pairs suggests conspe- cificity for each pair. Other interspecific relationships were not well-supported by bootstrap values. Parsi- mony analysis of a second dataset composed of mi- totic and meiotic taxa showed that Oidiodendron, My- xotrichum and Byssoascus form a well-supported monophyletic group within the Myxotrichaceae, and