Phylogeny of Actaea including Cimicifuqa (Ranunculaceae) inferred from nrDNA ITS sequence variation

Phylogenetic analysis of the rapidly changing nuclear ribosomal DNA ITS region in all 23 taxa of Cimicifuga and in all five taxa of Actaea was performed. The phylogenetic affinities of Souliea were investigated. Eranthis and Anemonopsis were shown to be separated from the ingroup by a similar number of steps. A monophyletic clade including all studied species of Actaea, Cimicifuga and Souliea is strongly supported and within it a group consisting of all Actaea species and Cimicifuqa racemosa is identified. A large but weakly supported clade consisting of only Eurasian species is divided into two subclades; one with taxa possessing yellow staminodia, the other with taxa possessing white staminodia. Three other well supported groups are indicated: one clade consisting of two North American species with long carpel stipes: C. americana and C. laciniata, another with three North American species with short carpel stipes: C. arizonica, C. elata and C. rubifolia, and a third with three eastern Asian species with caducous bracts: C. biternata, C. japonica and C. purpurea. Cimicifuga is paraphyletic at least with respect to Actaea and possibly also with respect to Souliea.