Hypericum chishuiense (Hypericaceae, sect. Ascyreia), a new St. John's wort species from Guizhou, China

Hypericum chishuiense (Hypericaceae), a new species from Chishui County, Guizhou Province, China, is described and illustrated. Molecular phylogenetic analyses, based on five plastid DNA markers (psbA-trnH, psbC-trnS, rbcL, trnL-trnF, and trnS-trnG), place the new species within H. sect. Ascyreia. Morphologically, the new species is closely related to H. stellatum and H. rotundifolium, but it can be distinguished by several features, including broadly ovate, ovate-elliptic to subcircular leaves (vs. oblong-lanceolate or lanceolate to narrowly ovate leaves of H. stellatum) and broadly elliptic, ovate to triangular-ovate sepals (vs. narrowly lanceolate and rare markedly leaf-like sepals H. stellatum), and it can be distinguished from H. rotundifolium by its longer style (1.2–1.5 cm vs. 0.5–0.9 cm) and shorter ovary (0.4–0.6 cm vs. 0.7–0.9 cm). The distribution, habitat, and conservation status of the new species are also provided.