Ribosomal and RPB2 DNA sequence analyses suggest that Sporidesmium and morphologically similar genera are polyphyletic

Abstract

Sporidesmium and morphologically similar dematiaceous, hyphomycetous genera are characterised by holoblastic phragmoconidia produced on proliferating or non-proliferating conidiophores. They include a number of asexual (anamorphic) genera taxonomically segregated from Sporidesmium sensu lato and are similar in having schizolytic conidial secession. The taxonomy of these ubiquitous asexual fungi and their affinities with known Ascomycetes are, however, still obscure. This study incorporates a phylogenetic investigation, based on the LSU nu-rDNA and RNA polymerase II second largest subunit (RPB2) gene sequence, to assess the possible familial placement of Ellisembia, Linkosia, Repetophragma, Sporidesmiella, Sporidesmium and Stanjehughesia, and justify whether anamorphic characters are proper phylogenetic indicators. Phylogenies provide conclusive evidence to suggest that Sporidesmium is not monopyletic and species are phylogenetically distributed in two major ascomycete classes, Dothideomycetes and Sordariomycetes. Morphologies currently used in their classification have undergone convergent evolution and are not phylogenetically reliable. The possible teleomorphic affinities of these anamorphic genera are discussed in light of morphology and molecular data. As these anamorphs, in most cases, are the sole known morph of the holomorph, it is proposed that in the absence of or failure to detect their teleomorphic phase, the anamorph names should be used for the holomorph.