Pseudomitrulaceace, fam. nov., and three new species of Pseudomitrula expand the known diversity of South American earth tongues.

Abstract

Pseudomitrula (Leotiomycetes, Helotiales) is a genus of minute earth tongues. Pseudomitrula horakii, the only described species in the genus, is recognized by cylindrical to spathulate apothecia. It was originally placed within Geoglossaceae but is currently classified within Helotiales, as genus incertae sedis, or within either Cenangiaceae or Helotiaceae. Through recent expeditions to southern South America, dozens of collections of Pseudomitrula were made. Based on the phylogenetic reconstruction of an internal transcribed spacer (ITS) data set, we identified eight distinct groups among our collections, representing P. horakii and seven putative species, three of which are formally described here: P. gamundiae, P. mapuche, and P. variabilis. We present morphological descriptions and illustrations for all four named species. To resolve the placement of Pseudomitrula within Helotiales, we included newly generated Pseudomitrula sequences in a 15-locus class-wide data set. The resulting phylogeny showed that Pseudomitrula species form an independent clade sister to five families in Helotiales: Helotiaceae, Lachnaceae, Pleuroascaceae, Solenopeziaceae, and Tricladiaceae. Morphologically, Pseudomitrula has little in common with taxa in these families that either form sessile or stalked cup- or cushion-shaped apothecia or cleistothecia or produce aquatic hyphomycetous or microscopically small asexual morphotypes. For these reasons, we propose the new family Pseudomitrulaceae within Helotiales. This study expands the knowledge of southern South American diversity of Leotiomycetes.