Abstract
The fungal family Mortierellaceae represents ubiquitous and ecologically significant components of soil ecosystems across terrestrial habitats. Through an integrative taxonomic approach combining multi-locus phylogenetic analyses (ITS, LSU, SSU rDNA, RPB1, and Act) with detailed morphological examinations of rhizosphere soil isolates, four novel species within this family were proposed. This study elucidates the morphological distinctions of novel species from allied species and the phylogenetic relationships among the novel and existing species within the family. Linnemannia rotunda sp. nov. (closely related to L. longigemmata) is distinguished by its globose sporangia and sporangiospores. Mortierella acuta sp. nov. (clustering with M. yunnanensis) is characterized by spiky collarettes. Mortierella oedema sp. nov. (a sister to M. macrocystis) exhibits distinctive ampulliform swellings. Mortierella tibetensis sp. nov. (clustering with M. parvispora) is named for its geographic origin in Tibet. As the eighth installment in a systematic investigation of early diverging fungal groups in China, this work expands the global taxonomic inventory of Mortierellaceae to 148 species, underscoring the ongoing discovery of cryptic biodiversity within this ecologically pivotal group.