Morphology and phylogeny reveal Gymnopus pseudoandrosaceus sp. nov. (Agaricales, Basidiomycota) from Southwest China

Gymnopus pseudoandrosaceus sp. nov. is described from Southwest China. It is characterized by a brown marasmioid pileus, a shining black stipe, and abundant rhizomorphs, a pileipellis in the form of a cutis with encrusted pigments and without broom cells, and cheilocystidia with apical projections. The phylogenetic analysis placed the new species within the Gymnopus sect. Androsacei clade with well-supported lineages across Impudicae, Levipedes, Gymnopus, Androsacei, and Paragymnopus. Strong bootstrap values affirm these relationships, with notable diversity in Gymnopus indicating potential adaptive radiation. The pileipellis lacking broom cells is a rather unique feature in this section. Detailed morphological descriptions, basidiomata photographs, microscopic structure images, and phylogenetic analysis results are provided.