Integrating multi-marker phylogeny and morphology reveals hidden diversity and intraspecific morphological variation in the genus Pseudohydnum P. Karst. (Basidiomycota, Auriculariales) from China

The toothed jelly genus Pseudohydnum P. Karst. ( Basidiomycota , Auriculariales ) has historically been treated under a broad morphological concept centered on P. gelatinosum , a view that has long masked substantial cryptic diversity worldwide. However, many Chinese collections remain taxonomically unresolved and species boundaries are poorly defined. Here, we reassess the species diversity of Chinese Pseudohydnum through an integrative approach combining detailed morphology with multi-marker phylogenetics (ITS, nrLSU, and rpb1 ). We formally describe three new species, P. ellipsosporum sp. nov ., P. macroumbrosum sp. nov ., and P. roseolostipitatum sp. nov . We also refine the circumscriptions of four previously described taxa and provide new insights into their intraspecific variation, geographic distribution, and ecology. Notably, we document a previously unknown host association: P. brunneiceps was consistently found on decayed bamboo ( Phyllostachys edulis ), a substrate never before recorded for any Pseudohydnum species. Critically, our results demonstrate that morphology alone is currently insufficient for species delimitation as convergent or plastic characters obscure diagnostic differences, reinforcing the necessity of molecular validation. These findings substantially expand the known taxonomic and ecological diversity of Pseudohydnum in Asia, suggesting that China, particularly the Qinghai-Xizang Plateau, may be a global hotspot for the genus. Overall, this study underscores the essential role of phylogenetic inference in revising species boundaries and elucidating evolutionary patterns in morphologically plastic groups of fungi.