Phylogenetic reassessment of Nigrospora: ubiquitous endophytes, plant and human pathogens

Species of Nigrospora commonly occur as plant pathogens, endophytes or saprobes, and have been shown to be extremely interesting for the discovery of novel metabolites. The familial placement, as well as phylogenetic relationships among Nigrospora species remain ambiguous. In this study, Nigrospora (= Khusia) is confirmed as a monophyletic genus belonging to Apiosporaceae (Xylariales), based on a phylogeny inferred from LSU sequence data. A multi-locus phylogeny based on ITS, TEF1-α and TUB2, in conjunction with morphological characters, host associations, and ecological data was employed for species delimitation in Nigrospora, as well as identification of 165 recently collected isolates from China, and three from Europe. In total 13 novelties are proposed including 12 new species and 1 new combination. Five species are re-described based on an examination of type specimens and/or fresh collections. New species described in this paper include: N. aurantiaca, N. bambusae, N. camelliae-sinensis, N. chinensis, N. guilinensis, N. hainanensis, N. lacticolonia, N. osmanthi, N. pyriformis, N. rubi, N. vesicularis and N. zimmermanii. Furthermore, N. vietnamensis is transferred to Arthrinium. Our results indicate a high level of species diversity within Nigrospora, with a general lack in host specificity. Taxa that cluster basal in Nigrospora have wide host ranges, whereas those that diverged later tend to have narrow host ranges. The currently available data suggest, therefore, that the general evolutionary direction in the genus Nigrospora is from a wide to a narrow host range.