Reclassification of Actaea to include Cimicifuga and Souliea (Ranunculaceae): phylogeny inferred from morphology, nrDNA ITS, and cpDNA trnL-F sequence variation

Phylogenetic analyses using parsimony were performed on three independent data sets to test generic relationships between Actaea, Cimicifuga, and Souliea. Analyses of morphology and nuclear ribosomal DNA ITS were performed on 23 species of Cimicifuga, 4 species of Actaea, and the single species of Souliea. Analysis of chloroplast DNA tmL-F was applied to the same species, less two of Cimicifuga. The outgroup taxa Eranthis and Anemonopsis both resolved outside the ingroup in all parsimony analyses, whereas Souliea resolved within it. Jukes-Cantor pairwise sequence distances confirm Eranthis and Anemonopsis to be most distant. Souliea distances are comparable with those of taxa within the Actaea-Cimicifuga assemblage. A strongly supported monophyletic clade including all studied species of Actaea, Cimicifuga, and Souliea was found in all analyses. Evidence presented here allows a broader concept of Actaea to be adopted, reverting to the circumscription of Linnaeus in 1753. Seven sections, based on clades found in the total analysis, could be defined by morphological characters: A, sect. Actaea, sect. Podocarpae, sect. Cimicifuga, sect. Dichanthera, sect. Oligocarpae, sect. Pilyrosperma, and sect. Souliea. One species, A. taiwanensis, is newly described and 23 new combinations are made in the ranks of section, species, and variety. Keys are provided to identify taxa at all ranks within the revised circumscription of Actaea. Maps showing the distributions of all seven sections and their constituent species are presented. Phytogeographic patterns suggest a Tertiary origin for the newly redefined genus, with species surviving in refugia during the glacial periods of the Pleistocene.