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.

青藏高原东南部（Southeast Qinghai-Tibet Plateau）蕴藏着大量海洋冰川，横跨两处全球公认的"生物多样性热点地区"，在全球变暖背景下正面临大规模生境丧失，该独特区域内的冷适应真菌生物多样性亦正急剧下降。本研究选取了从青藏高原东南部海洋冰川的土壤或水体样本中分离得到的、最常检出的嗜冷类群（psychrophilic taxa）的23株真菌分离株，开展详尽的分类学研究。本研究结合形态学特征、多基因座系统发育分析结果，以及四种常用的分子物种界定方法——两种基于距离的方法：自动条形码间隙发现法（Automatic Barcode Gap Discovery, ABGD）和自动分区聚类物种界定法（Assemble Species by Automatic Partitioning, ASAP）；另外两种基于系统发育树的方法：贝叶斯泊松树过程法（Bayesian Poisson Tree Processes, bPTP）与广义混合尤尔合并模型（generalized mixed Yule coalescent model, GMYC）——最终描述了7个<i>Gelida</i>（原名为<i>Psychrophila</i>）物种（其中6个为新种）以及2个<i>Tetracladium</i>物种（其中1个为新种）。鉴于<i>Psychrophila</i>这一属名是某植物属的晚出同名，属于非法属名，本研究提出将<i>Gelida</i>作为<i>Psychrophila</i>的替代属名，并将4个原隶属于<i>Psychrophila</i>的非法物种以新组合的形式转移至<i>Gelida</i>属。本研究为在整合分类学框架下界定可靠且准确的物种边界提供了极具价值的研究思路，这对于面临严重生境丧失的真菌类群的高效生物多样性评估与保护工作尤为重要。