Emending Gymnopus sect. Gymnopus (Agaricales, Omphalotaceae) by including two new species from southern China

Based on phylogenetic analyses, some newly studied Chinese mushroom specimens were found to represent two distinct species within the genus Gymnopus. Along with G. fusipes (sect. Gymnopus) they form a distinct clade with high support, although their macromorphological characters seem to be closer to members of Gymnopus sect. Levipedes or sect. Vestipedes (Collybiopsis). When examined in detail, their micromorphological characters, especially the type of pileipellis, support them as new members of G. sect. Gymnopus. Therefore, two new species, G. omphalinoides and G. schizophyllus, and the emended circumscription of sect. Gymnopus are proposed in this paper. Detailed morphological descriptions, colour photos, illustrations of the two new species, morphological comparisons with similar taxa and the molecular-phylogenetic analyses of the combined nrITS and nrLSU data are presented. A key to the known species of G. sect. Gymnopus is also presented.