科研之友
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摘要
Phylogenetic relationships among the species of Smilax sect. Nemexia (Smilacaceae) were investigated by separate and combined cladistic analyses of plastid trnL-F, rpl16, and nuclear internal transcribed spacer sequences. Results strongly support a clade of two well-defined East Asian species, Smilax riparia and S. nipponica. Likewise, all North American species form a clade in which S. jamesii, the only species from western North America, is sister to the morphologically variable "S. herbacea complex';'; from eastern North America. Our data are inconclusive regarding whether this complex should be treated as one or more species. Smilax sect. Nemexia exhibits an East Asian-North American phytogeographic disjunction. The common ancestor of the group is hypothesized to have originated in Asia and to have spread northeastward to North America through the Bering Strait land bridge. Pleistocene glaciation likely fragmented the continuous distribution of the group into the three refugial areas where the species grow today: East Asia, northern California, and the eastern United States. On both continents, nonclimbing erect herbs evolved independently from climbing ancestors within the section.
- 出版日期2005-3
- 单位浙江大学
