Insights into the genus Xeromphalina, X. tenuipes (Schwein.) A.H. Sm. complex and discovery of a novel species, X. pseudotenuipes from Thailand

Xeromphalina belonging to the family Xeromphalinaceae and characterized as a saprobe thriving on fallen, decayed logs, has undergone taxonomic revisionary study predominantly in the Northern Hemisphere. Despite approximately 36 documented species, studies on complex groups with similar-looking species within this genus are quite fragmentary and have led to misnaming and misidentification. Recent observations have revealed one interesting species from Thailand belonging to the X. tenuipes species complex. Morphological features along phylogenetic analysis (nrITS, nrLSU, and rpb2) inferred that this species is new to science. This novel species, namely X. pseudotenuipes can be distinguished from X. tenuipes by its pileocystidia appearing brownish in 5% KOH, and hyphae of pileipellis and stipitipellis turning orangish brown in 5% KOH. Moreover, this study is the first attempt to undertake a comprehensive phylogenetic analysis encompassing all potential species of Xeromphalina for which sequences are available, aiming to identify which sequence accurately represents each species.