The new species and the third Chinese member of Colubrina (C. zhaoguangii, Rhamnaceae)

ABSTRACT A novel species of Rhamnaceae, Colubrina zhaoguangii, is discovered in Sichuan, China, during the biodiversity investigations of the Second Tibetan Plateau Scientific Expedition and Research. Detailed descriptions and illustrations of the new species are presented herein. To date, the new species is only found in dry-warm river valleys of the Jinsha River basin in the Hengduan Mountains region (HDM). Compared with the other two known Chinese Colubrina species, C. zhaoguangii features by the habit of twisted shrub and tiny leaves with emarginate apex. In morphology, the new species highly resembles C. alluaudii endemic in Madagascar and C. viridis in northwestern Mexico, whereas it is distinguished from these two relatives by its minutely white scales on the leaf blades. The discovery of C. zhaoguangii reminds us again that the bottom region is also important for biodiversity conservation in HDM and should be a flora survey priority.