Cytological evidence supports the taxonomic status of the Sino-Himalayan species Cimicifuga frigida (Ranunculaceae)

Although Cimicifuga foetida L. (Ranunculaceae) has been shown to be a distinct species distributed only in northern Asia (Siberia, Mongolia), the Sino-Himalayan species C. frigida Royle remains to be much confused with the Chinese endemic C. mairei H. Lev. The independent species status of C. frigida is recognized by some authors, but refuted by others. A cytogeographical study has shown that the ploidy level is well correlated with the geographical distribution of C. frigida and C. mairei. Cimicifuga frigida is a tetraploid (2n = 32) occurring in the Sino-Himalayan region, whereas C. mairei is a diploid (2n = 16) occurring in central and southwestern China. There is only minor overlap in their geographical distributions in northwestern Yunnan, China. The ploidy level is also well correlated with the morphological characters, in particular the shape of the staminodes, which has previously been used as the only reliable morphological character to distinguish between C. frigida and C. mairei. The cytogeographical pattern, therefore, lends strong support for the recognition of the independent species status of C. frigida. This species is the only polyploid species currently known in the genus.