New and notable taxa of Basidiomycota on the Qinghai-Xizang Plateau and its surrounding areas

The Qinghai-Xizang Plateau (abbreviated as Q-X Plateau) is the world’s highest plateau, characterized by a Holarctic flora. The plateau and its surrounding mountainous areas cover two of the 34 world’s biodiversity hotspots. Former studies have shown that the diversity of fungal species on the plateau, especially that in the east-southeastern part, is remarkably high. In 2017, the Chinese government initiated the second scientific expedition to the Q-X Plateau. Supported by this comprehensive project, we conducted intensive fungal sampling on the Q-X Plateau and its surrounding areas, including the middle and southern parts of the Gaoligong Mountains, the Ailao Mountains, and the Yunnan-Guizhou Plateau. Ninety-two new and notable species of Basidiomycota are reported in this paper, based on 501 specimens and 1706 newly generated DNA sequences. These taxa involve 37 genera of seven orders, i.e., Agaricales, Auriculariales, Boletales, Cantharellales, Phallales, Polyporales, and Russulales, covering both Heterobasidiomycetes and Homobasidiomycetes. One new section, 64 new species, one new subspecies, two new varieties, one new combination, five new synonyms, and 11 new records to China, were documented. Ectomycorrhizal fungi account for two-thirds of the species, while the remaining ones are saprotrophic. Most specimens studied are from altitudes 2000–3700 m, in broad-leaved fagaceous forests, mixed forests with pines and fagaceous trees, and subalpine coniferous forests. Among the 92 species documented, 30 species are exclusive to the subalpine region, and 12 species cover both the subalpine and subtropical zones. Most of these subalpine species are either formerly described temperate species or close relatives of north temperate taxa, which suggests a strong temperate affinity of the funga on the Q-X Plateau. In obvious contrast to the subalpine elements, species from the adjacent subtropical zone often sit on long branches with an isolated position or have a close relationship with species from other subtropical and tropical parts of the world. In the surrounding areas with lower altitude of the Q-X Plateau, the endemic species apparently have evolved for a longer time, some relict species found their refuge, and the funga received more immigrants from the tropics. By comparing the species reported from the western Himalayas, through the Hengduan Mountains and central China to Taiwan Island, we found that altitude matters more than geographical distance in the development of the funga. The sharp altitude gradient on the Q-X Plateau and its surrounding mountains acts as a biodiversity hotspot to further test such speculation. In future studies, more efforts should be focused on other representative groups (Gomphalales, Hymenochaetales, Thelephorales, and Tremellales) and on the southern slope of the western Himalayas and the Pamir-Kunlun regions.