Cynanchum thesioides (Freyn) K. Schum. is one of the most widespread species in Cynanchum L., a large genus in the family Apocynaceae. It is found in temperate north-eastern Asia, from eastern Kazakhstan, Mongolia, northern China to the Korean Peninsula. Its morphological characters are much variable adapting to a variety of habitats.

During taxonomic studies on Cynanchum, researchers from Wuhan Botanical Garden found that the distinctions between C. thesioides and C. gobicum Grubov are questionable. The latter was endemic to Mongolia and was distinct from C. thesioides on the long and scandent stem, broader lanceolate leaves and puberulent (vs. glabrous in C. thesioides) outer surface of the corolla. To resolve this issue, the researchers conducted field surveys, checked numerous plant pictures and specimens, and reviewed related literature on this species.

Results show continuous variation in the morphological characteristics of the C. thesioides, including habit, leaf shape, leaf size, indumenta on the inner and outer surfaces of corollas, and relative lengths of stigmatic head to corona, which encompasses all the characteristics of C. gobicum. Thus, C. gobicum is in synonymy with C. thesioides.

Meanwhile, Vincetoxicum sibiricum f. linearifolium Debeaux is also newly synonymized, a long neglected name since Debeaux described it from specimens collected in Shandong, China in 1877.

At last, a thorough revision on this species is provided, including a new description, an updated distribution, and typification for all related names including new lectotypification of V. sibiricum var. australe Maxim. and V. sibiricum f. linearifolium.

The paper entitled "A taxonomic revision of Cynanchum thesioides (Apocynaceae) with two new synonyms" has recently been published in the journal PhytoKeys. This study was funded by the Biological Resources Program, Chinese Academy of Sciences. Dr. ZHANG Caifei is the first authors, and Prof. HU Guangwan is the corresponding author.

Cynanchum thesioides growing in different habitats (Image by WBG)

External morphological characteristics of the Cynanchum thesioides (Image by WBG)

Floral anatomy and fruit and seeds of the Cynanchum thesioides (Image by WBG)