Distribution pattern of genuine species of rhubarb as traditional Chinese medicine

The distribution pattern of Rheum palmatum, Rheum officinale and Rheum tanguticum, as three Chinese official genuine and endemic species of rhubarb and the monophyletic group in the genus Rheum, was analyzed based on the field survey and the herbarium specimens in the present paper. R. palmatum occupies the widest geographic range, that is Qinling, Daba, Wuling, Dalou, Min, Qilian, Hengduan, the south part of Taihang mountain range and the centre to the east of Qinghai-Tibet Plateau. The distribution of R. tanguticum is overlapped with that of R. palmatum in the north-west areas and occupies the higher altitude and the lower longitude areas, whereas the distribution of R. officinale is overlapped with that of R. palmatum in the south-east and occupies the lower altitude and the higher longitude areas. The overlapped between R. palmatum and R. tanguticum + R. officinale and the vicarious between R. tanguticum and R. officinale distribution pattern, combined with the minimum and ambiguous morphological differences and the diversified results on the relationship from the molecular studies of these three species, we considered that these three species might not be good species.