Review on the taxonomy, origin, and evolution of Sanicula (Umbelliferae)

Sanicula exhibits a typical Eastern Asian-North American discontinuous distribution pattern typical of relicts from the Arcto-Tertiary flora. The genus comprises 40 species with two main centers of diversity:China (17 species, 11 endemics) and the United States (22 species, 13 endemics). Molecular phylogenetic analysis shows that the genus may not be monophyletic. The delimitation of subgenera is controversial, with different criteria emphasized in past studies, and infraspecific relationships remaining unclear (especially among species used as traditional Chinese medicine). However, previous studies have focused on the Sanicula DC. complex in North America or the Sandwicensis Shan and Constance group in Hawaii, excluding samples of endemic species from China. Therefore, explanations of the systematic position, place of origin, and migratory and dispersal patterns of the genus are not complete, nor are the evolutionary relationships among all its constituent taxa known. We present a review of recent research on the classification, origin, and evolution of Sanicula, summarize unsettled taxonomic problems, and discuss plans for future research to resolve these issues.