Two strains of an unidentified perithecial ascomycete with a dactylaria-like anamorph and another morphologically similar strain of a dactylaria-like fungus were collected on decaying wood submerged in freshwater. To study their phylogenetic relationships we (i) combined sequence data from the nuclear small and large subunits ribosomal DNA (nc18S and nc28S) and the second largest subunit of RNA polymerase II (RPB2) for a multigene phylogenetic analysis and (ii) used sequences of the internal transcribed spacer region (ITS) of the rRNA operon for a species-level analysis. The new genus Pleurotheciella is described for two new species, Pla. rivularia and Pla. centenaria, with nonstromatic perithecia, unitunicate asci, persistent paraphyses and hyaline, septate ascospores and dactylaria-like anamorphs characterized by holoblastic, denticulate conidiogenesis, subhyaline conidiophores and hyaline, septate conidia. Based on morphological and molecular data, Pleurotheciella is closely related to the genera Pleurothecium and Sterigmatobotrys. A key to the three genera and the known species is provided. In the three-gene inferred phylogeny, these genera grouped as a sister clade to the Savoryellales within a robust clade of uncertain higher rank affiliation. Phylogenetic study of the 12 strains that represent Pleurothecium recurvatum revealed four that grouped apart from the core of the species. Two of these strains, which form a monophyletic well supported clade in both phylogenies and share similar morphological characteristics, are described as a new species, Pleurothecium semifecundum.

Department of Taxonomy Institute of Botany of the Academy of Sciences Průhonice Czech Republic

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