Impatiens namchabarwensis is distinct from I. arguta

Impatiens namchabarwensis was described as a new species in 2005 by Morgan et al. As already mentioned in the species description, I. namchabarwensis is morphologically similar to I. arguta and the small range of I. namchabarwensis in the eastern Himalaya is nested within the large, Himalayan range of I. arguta. Therefore, I. namchabarwensis has frequently been treated as synonym of I. arguta (e.g. in the Flora of China). We compared plant longevity, flower morphology and other functional floral traits and analyzed the differences between the two taxa. We found that I. namchabarwensis is a short-lived perennial reaching maximally three years whereas I. arguta is a long-lived perennial. Further, the floral traits of the two species differ significantly. These differences are also reflected in the main pollinator groups of the two species, which are hawk moths for I. namchabarwensis and bumblebees for I. arguta. Hence, we follow the argumentation of Morgan et al. and conclude that I. namchabarwensis and I. arguta are two distinct species.