Unveiling Species Diversity Within Early-Diverging Fungi from China VI: Four <em>Absidia</em> sp. nov. (<em>Mucorales</em>) in Guizhou and Hainan

Absidia represents the most species-rich genus within the family Cunninghamellaceae, with its members commonly isolated from diverse substrates, particularly rhizosphere soil. In this study, four novel Absidia species (A. irregularis sp. nov., A. multiformis sp. nov., A. ovoidospora sp. nov., and A. verticilliformis sp. nov.) were discovered from south and southwestern Chinese soil samples through integrated morphological and molecular phylogenetic analyses. Phylogenetic analyses based on concatenated ITS, SSU, LSU, Act, and TEF1α sequence data reconstructed trees that strongly supported the monophyly of these four new taxa each. Key diagnostic features include A. irregularis (closely related to A. oblongispora) exhibiting irregular colony morphology, A. multiformis (sister to A. heterospora) demonstrating polymorphic sporangiospores, A. ovoidospora (forming a clade with A. panacisoli and A. abundans) producing distinctive ovoid sporangiospores, and A. verticilliformis (next to A. edaphica) displaying verticillately branched sporangiophores. Each novel species is formally described with comprehensive documentation, including morphological descriptions, illustrations, Fungal Names registration identifiers, designated type specimens, etymological explanations, maximum growth temperatures, and taxonomic comparisons. This work constitutes the sixth installment in a series investigating early-diverging fungal diversity in China, expanding the recognized Absidia species to 71. The findings enhance our understanding of mucoralean biodiversity in Asian tropical and subtropical ecosystems.