WANG, XIAO-QUAN* AND DE-YUAN HONG. Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P. R. China. - Molecular phylogenetic, morphological, and biogeographic evidence for the origin of the genus Actaea within the genus Cimicifuga (Ranunculaceae).
The phylogeny of two closely related genera, Cimicifuga and
Actaea, was studied using sequences of the internal transcribed
spacers of nuclear ribosomal DNA. Trollius and Beesia
were chosen as the outgroups for the parsimony analysis. In the
strongly supported monophyletic group containing the species of
Cimicifuga and Actaea, Actaea species are nested
within Cimicifuga and are most closely related to C.
racemosa. Morphologically, C. racemosa has nearly sessile
stigma and firm-walled follicle which are similar to the fruit
morphology of Actaea. Therefore, the genus Actaea is
most likely to have originated within the genus Cimicifuga with
an ancestor that was closely related to C. racemosa.
Biogeographically, the genus Actaea has a disjunct distribution
in North America and Eurasia while C. racemosa, the single
species in sect. Macrotrys of Cimicifuga, occurs in
North America. The distribution pattern appears to suggest that
Actaea was originated from North America. This study also
indicates that the genus Beesia is a close relative of
Cimicifuga and Actaea.
Key words: Actaea, Cimicifuga, ITS, phylogeny, Ranunculaceae