Introduction
Saxifraga L., the largest genus of Saxifragaceae, encompasses 450–500 species that are widely distributed throughout arctic and montane regions of the Northern Hemisphere (Ebersbach et al. 2017, Tkach et al. 2015, Pan, Gornall and Ohba 2001). Recent molecular phylogenetic research is monophyletic with 13 sections and 9 subsections been recognised, providing that S. sect. Micranthes (Haw.) D. Don is excluded(Tkach et al. 2015, Deng et al. 2015). Saxifragasect. Irregulares Haw. is the earliest lineage of Saxifraga to diverge, which is characterized by asymmetric flowers with two unequally elongated and three short petals (Magota et al. 2021, Tkach et al. 2015, Zhang et al. 2020, Soltis Douglas E 2001). Section Irregularescurrently comprises 21 species, including eight recently described species from China (Wang Fa-Guo 2008, Zhang et al. 2021, Zhang et al. 2019, Zhang et al. 2018, Zhang et al. 2017, Zhao et al. 2019, Zhang et al. 2022b, Chen et al. 2022). Its distribution is concentrated in eastern Asia, and most members are confined to local areas (Magota et al. 2021, Pan et al. 2001).
The new species described here first came to our attention in 2021 when we examined the specimens in the herbarium of the Kunming Institute of Botany (KUN). We recognized it immediately as a new species ofSaxifragasect. Irregulares , as it possesses asymmetric flowers with two elongated petals, while its leaf blade abaxially with white or virescent interveinal streaks, which cannot be found in known species of S.sect. Irregulares . In May 2022, we conducted a field expedition for this undescribed specimen and confirmed its distinctiveness. Here we describe and illustrate the new species and provide morphological and molecular phylogenetic evidences to support its taxonomic status and relationships.