Psychrophilic fungi from the world’s roof, II: Species delimitation within an integrative taxonomic framework

Southeast Qinghai-Tibet Plateau, which harbors large numbers of marine glaciers and spans across two worldwide “biodiversity hotspots,” is facing massive habitat loss in the context of global warming, and the biodiversity of coldadapted fungi in this unique area is also suffering drastic reduction. In this study, we selected 23 fungal isolates that represented the most commonly encountered psychrophilic taxa isolated from soil or water samples of marine glaciers in the southeast Qinghai-Tibet Plateau for detailed taxonomic studies. Incorporating morphological characteristics, multilocus phylogenetic analyses, and the results of four widely used molecular species delimitation methods, including two distance-based: Automatic Barcode Gap Discovery (ABGD) and Assemble Species by Automatic Partitioning (ASAP), and two tree-based: Bayesian Poisson Tree Processes (bPTP) and generalized mixed Yule coalescent model (GMYC), seven <i>Gelida</i> (formerly <i>Psychrophila</i>) species, including six new species, and two <i>Tetracladium</i> species, including one new species, were described. As the genus name <i>Psychrophila</i> is an illegitimate later homonym of a plant genus, we proposed the new name <i>Gelida</i> as a replacement for <i>Psychrophila</i> and transferred four illegitimate <i>Psychrophila</i> species to <i>Gelida</i> as new combinations. Our study provides a valuable perspective on how to delimit robust and accurate species boundaries within an integrative taxonomic framework, which is especially important for efficient biodiversity assessment and conservation of the fungal groups that are facing serious habitat loss.