Dysosma xishuiensis (Berberidaceae), a new species from Guizhou, China, based on morphological and molecular evidence.

Dysosma xishuiensis Y. B. Yang, M. T. An & C. H. Yang is described and illustrated as a new species from Xishui County in northern Guizhou Province, China. This species is morphologically similar to D. versipellis, but differs by its glabrous abaxial leaf surface, pedicels, and sepals; inflorescences bearing more flowers (8-20 vs. 5-8); larger obovate-oblong petals (2.8-3.4 × 1.5-2.0 cm vs. 2.5 × 0.8 cm); and an obpyriform ovary (vs. ellipsoid). The phylogenetic relationships reconstructed using ITS, matK, and rbcL sequences further confirm that it is a new species within Dysosma. This species is currently known only from the Xishui National Nature Reserve in Guizhou. According to IUCN criteria (B2, D), due to its limited distribution and low population numbers, D. xishuiensis is assessed as Endangered (EN).