Revisiting infrageneric concepts in Geastrum (Geastraceae, Geastrales) with three new species

Geastrum is a typical saprotrophic genus with nearly 130 species distributed worldwide, yet its infrageneric classification has traditionally relied on morphological characteristics whose phylogenetic significance remains uncertain. Here, we revisit infrageneric concepts in Geastrum using Chinese material, integrating detailed morphological observations with multi-locus phylogenetic analyses. Eight specimens collected from temperate forests in Northeast and East China yielded three new species: G. capillitiononramosum sp. nov., G. villopannosum sp. nov., and G. kunyuense sp. nov. These species share a sessile endoperidial body lacking a collar and apophysis, a distinctly delimited fibrillose peristome, and globose to subglobose basidiospores with columnar ornamentation but differ mainly in the structure of the mycelial layer and the branching and ornamentation of capillitial hyphae. Phylogenetic analyses based on a concatenated ITS-nrLSU-rpb1 dataset recovered 12 well-supported clades and confirmed the distinct phylogenetic positions of the three new species. The resulting topology further demonstrates that several traditional infrageneric groupings defined by key morphological traits, such as the hygroscopic behavior of the exoperidium and debris-encrusted mycelial layers, are only partially congruent with molecular relationships, reflecting repeated character evolution across distant lineages. Nevertheless, specific combinations of peristome structure, mycelial layer features, and capillitial morphology remain informative at the species level. With the descriptions of three new species and an updated key to 43 Chinese taxa, this study refines current knowledge of Geastrum diversity in China and provides new evidence for reassessing infrageneric classification within the genus.