Polyphyletic genera in Xylariaceae (Xylariales): Neoxylaria gen. nov. and Stilbohypoxylon

Several genera in Xylariaceae are polyphyletic in phylogenetic trees and represent more than one distinct genus. However, it is challenging to resolve these genera that are often phylogenetically distantly related, because many taxa have never been recollected and sequenced. Those that have been named and sequenced often lack documented characters or herbarium material. In this paper, we use descriptive morphology of fresh collections, and molecular data to resolve some taxonomic problems in Xylariaceae. During the of microfungi on palms in Thailand, we collected several novel xylariaceous taxa. Herein, we introduce a new genus Neoxylaria which is distantly related to Xylaria sensu stricto and a new species Stilbohypoxylon elaeidis. Neoxylaria is characterized by relatively small stromata with conspicuously exposed perithecial contours under a narrowly striped outer layer. Neoxylaria accommodates a species morphologically similar to Xylaria juruensis, which was also collected from palm material in Brazil and X queenslandica collected from Archontophoenix alexandrae in Australia. As no molecular data exists for these old collections, we have linked them with morphology to our fresh collection and use both molecular data and morphology to introduce the new genus. Neoxylaria juruensis (Henn.) Konta & K.D. Hyde, comb. nov. and N. queenslandica (Joanne E. Taylor, K.D. Hyde & E.B.G. Jones) Konta & K.D. Hyde, comb. nov. are therefore established. Multigene phylogenetic analysis shows that our new species (S. elaeidis) clusters with Stilbohypoxylon sensu stricto (Stilbohypoxylon Glade II) and clarifies the nature of the genus. The new species differs from other species in having solitary, smooth stromata and forms synnemata-like structures on the host, but not on the stroma. The novel taxa introduced here are supported by multigene phylogeny and morphology. Comprehensive morphological descriptions, illustrations and a phylogenetic tree to show the placement of new taxa are provided.