Vincetoxicum Wolf is a large genus in the family Apocynaceae. Formerly subsumed under Cynanchum L. or treated as a section of Cynanchum in China, Vincetoxicum has been resurrected with strong support from morphological and chemical evidence as well as molecular studies. Recent molecular studies showed that Vincetoxicum and Tylophora R. Br. are closely intermingled, and the some smaller genera are nested inside Tylophora- Vincetoxicum clade. Vincetoxicum has expanded to include Tylophora and allies (including the Chinese genera Belostemma Wall. ex Wight, Biondia Schltr., Merrillanthus Chun & Tsiang, Pentastelma Tsiang & Li). In this circumscription, nearly 90 species of Vinecetoxicum s.l. are hitherto known from China.

During field collections in the Three Gorges District in recent years, researchers photographed and collected unknown plant species of Vincetoxicum from Fengjie, Wushan, and Wuxi counties. Based on literature review, more field collections in China, and studies of specimens from different herbaria, researchers concluded that the above materials represent a species new to science.

The new species was named Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu & Q.F. Wang. The specific epithet 'pingtaoanum’ is in honor of Prof. Ping- Tao Li (李秉滔, P.T. Li; 1936– ) from South China Agriculture University, for his contributions to the taxonomy of Chinese Apocynaceae. Following a tradition of using geographic names as part of the plant vernacular names, researchers suggested ‘Three Gorges swallow- wort’ as the English common name and ‘Sanxia Baiqian (三峡白前)’ as the common Chinese name for the new species.

V. pingtaoanum is similar to V. henryi (Warb. ex Schlechter ) Meve & Liede, but it can be easily distinguished by the longer petioles (5- 16 mm vs. 2– 3 mm), longer inflorescences (2.5- 6 cm vs. 1–-  cm) with a rachis (vs. without a rachis and umbel- like) that are mostly longer (vs. shorter) than leaves, greenish- yellow (vs. purplish red) corollas with linear- lanceolate lobes ca. 5 mm (vs. triangular- ovate less than 2 mm) long. Additionally, it is similar to V. emeiense S.Y.Zeng & Q.Y.Yang based on the corolla shapes, but differs in the yellowish green (vs. yellowish brown) corollas, shorter inflorescences (2.5- 6 cm vs. 7- 11 cm), coronas attached above the upper half gynostegia (vs. inserted near base of gynostegia) with obtuse (vs. truncate) lobes, and horizontal (vs. ascending) caudicles, and a key to all known species of Vincetoxicum from the Three Gorges District are also provided.

The paper entitled "Vincetoxicum pingtaoanum (Apocynaceae: Asclepiadeae), a new species from the Three Gorges District in Central China" was published in journal of Phytotaxa.

Wuhan Botanical Garden and the Chongqing Museum of Natural History have collaborated to publish this new species. This study was supported by the Management Service Center of Chongqing Yintiaoling National Nature Reserve and was funded by the Biological Resources Program, Chinese Academy of Sciences, and a project from China National Plant Specimen Resource Center.

Dr. ZHANG Caifei of Wuhan Garden Botanical Garden, WANG Yan, a graduated master student of Wuhan Garden Botanical Garden, and Mr. CHEN Feng of Chongqing Museum of Natural History are co- first authors, and Prof. HU Guangwan is the corresponding author, while Mr. ZHOU Houlin of Forestry Bureau of Wushan County also contributed to the work.

Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu Q.F. Wang (Image by ZHOU Houlin)

Vincetoxicum pingtaoanum Cai F. Zhang, G.W. Hu Q.F. Wang (Image by WANG Yan and ZHANG Caifei)