New insights into Gymnopus s.l.: its systematic rearrangements and novel taxa

Gymnopus (sensu lato) is significant both economically and ecologically. However, the boundaries that demarcate these genera are indistinct, partly because of limited taxa sampling, and, also due to the insufficient use of gene fragments employed for phylogenetic analyses. Furthermore, species diversity in Gymnopus s.l. is likely to have been vastly underestimated, due to the lack of its detailed investigation outside of America and Europe, including in China and other countries. In this study, we examined 527 gymnopoid collections from China and performed a comprehensive phylogenetic analysis of both these collections and related genera within Omphalotaceae combined with ITS and nLSU sequences data. In this dataset, 159 sequences from 93 species were provided. Furthermore, sect. Levipedes and sect. Impudicae were newly recognized as independent genera by combined morphological and phylogenetic evidences and the relationships within Omphalotaceae, thus we propose accepting them as separate genera, namely: Impudipilus and Levipedipilus. Section Vestipedes was also found to share close affinity with Collybiopsis, which nests with it, while divided into three independent clades, for the reasons we propose accepting them as separate genera, namely: Neomarasmius, Ligymopus, and Vestipedipilus. The infrageneric analyses within Impudipilus, Levipedipilus, and Gymnopus were also performed. Impudipilus was divided into three sections - sect. Impudicae, sect. Dysodes, and sect. Similis. Levipedipilus was divided into three sections, namely sect. Levipedes, sect. Erythropus, and sect. Alkalivirens. Gymnopus was divided into six sections, based on the reactions with Melinda's reagent, namely sect. Gymnopus, sect. Androsacei, sect. Efibulatus, sect. Omphalinoides, sect. Irresolutus, and sect. Brunneiniger. Fifty-seven species of Gymnopus s.l. and allied from China were recorded, including 11 novel species and seven new records from China. In addition, we performed the first comprehensive divergence-times estimation between the genera within Omphalotaceae. Data from our molecular clock analyses suggest that the divergence of Omphalotaceae probably occurred during the Jurassic period, while the divergence of Gymnopus s.l. likely occurred during the early Cretaceous period. This study also provides keys for the identification of the Gymnopus s.l. species.