Global diversity and phylogeny of Onnia (Hymenochaetaceae) species on gymnosperms.

Onnia includes white rotting polypores with annual basidiocarps, a duplex context, monomitic hyphal structure, hymenial setae, and hyaline, thin-walled, smooth basidiospores. Specimens of Onnia, originating mainly from East Asia, Europe, and North America, were studied using both morphology and phylogenetic analyses. Our concatenated data set was derived from 25 collections and included (i) 25 nuc rDNA internal transcribed spacer region sequences (ITS1-5.8S-ITS2 = ITS), 17 generated in this study; and (ii) 14 nuc rDNA 28S rDNA sequences, including the D1-D2 domains, 11 of them generated in this study. The resulting maximum likelihood and Bayesian phylogenies recovered all sampled collections of Onnia as a well-supported clade. In this clade, three previously accepted species, viz., Onnia leporina, O. tomentosa, and O. triquetra, received strong support, whereas three additional lineages with strong support represent the new species described in this paper, O. subtriquetra, O. microspora, and O. tibetica. Of the six Onnia species occurring on gymnosperms, O. tomentosa and O. leporina grow mainly on Picea and have circumboreal distribution in the Northern Hemisphere. In contrast, other species that mostly grow on Pinus are geographically restricted to limited regions, viz., O. triquetra in Europe, O. subtriquetra in North America, and O. microspora and O. tibetica in Asia.