Phylogenetic evaluation and taxonomic revision of Schizothecium based on ribosomal DNA and protein coding genes

Abstract

The taxonomy of Schizothecium and Podospora has been a subject of debate. Both of these genera have previously been treated as congeneric due to the lack of distinguishing morphological characters. This study focuses mainly on the phylogenetic relationships of Schizothecium and Podospora, and also a re-evaluation of the taxonomic significance of morphological characters. Multiple gene sequences (partial 28S rDNA, ITS/5.8S rDNA and partial β-tubulin) were analysed using maximum parsimony and Bayesian analyses. In all analyses, Schizothecium species characterised by perithecia adorned with swollen agglutinated hairs or prominent protruding peridial cells, grouped in a strongly supported monophyletic clade. Schizothecium should therefore, be given appropriate generic status and not treated as congeneric to Podospora. Phylogenetic analyses provide good support indicating that ascomatal morphologies are more phylogenetically informative than ascospore characters and host or habitat association. A synopsis of and key to Schizothecium species now recognised in the genus are given. Podospora was found to be a polyphyletic genus, consisting of a group of morphologically heterogeneous and phylogenetically distant species. Preliminary data indicate that a complete revision of Podospora and related genera is necessary.