Delimitation and phylogeny of Dictyochaeta, and introduction of Achrochaeta and Tubulicolla, genera nova

Dictyochaeta (Chaetosphaeriaceae) is a phialidic dematiaceous hyphomycete with teleomorphs classified in Chaetosphaeria. It is associated with significant variability of asexual morphological traits, which led to its broad delimitation. In the present study, six loci: nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode), nuc 18S rDNA (18S), nuc 28S rDNA (28S), DNA-directed RNA polymerase II second largest subunit gene (RPB2), translation elongation factor 1-alpha (TEF1-alpha), and beta-tubulin (TUB2), along with comparative morphological and cultivation studies, are used to reevaluate the concept of Dictyochaeta and establish species boundaries. Based on revised species, morphological characteristics of conidia (shape, septation, absence or presence of setulae), collarettes (shape), and setae (presence or absence) and an extension of the conidiogenous cell proved to be important at the generic level. The dual DNA barcoding using ITS and TEF1-alpha, together with TUB2, facilitated accurate identification of Dictyochaeta species. Thirteen species are accepted, of which seven are characterized in this study; an identification key is provided. It was revealed that D. fuegiana, the type species, is a complex of three distinct species including D. querna and the newly described D. stratosa. Besides, a new species, D. detriticola, and two new combinations, D. callimorpha and D. montana, are proposed. An epitype of D. montana is selected. Dictyochaeta includes saprobes on decaying wood, bark, woody fruits, and fallen leaves. Dictyochaeta is shown to be distantly related to the morphologically similar Codinaea, which is resolved as paraphyletic. Chaetosphaeria talbotii with a Dictyochaeta anamorph represents a novel lineage in the Chaetosphaeriaceae; it is segregated from Dictyochaeta, and a new genus Achrochaeta is proposed. Multigene phylogenetic analysis revealed that D. cylindrospora belongs to the Vermiculariopsiellales, and a new genus Tubulicolla is introduced.

Automated summary

This study reevaluated the concept of Dictyochaeta and established species boundaries using multiple markers and comparative morphological and cultivation studies. Thirteen species were accepted with new species and combinations proposed, indicating that Dictyochaeta is a saprobic fungus.