Studies Of Species Differentiation In Smilax And Heterosmilax (Smilacaceae)

Based on karyotypic and inflorescence features, this article represented systematic evolution of Smilax and Heterosmilax (Smilacaceae). Combined with morphologic and nrDNA ITS data, we discussed the systematics and evolution of Smilax and Heterosmilax, and suggested: (1) karyotypes of the group show bimodal karyotype, polyploidization, micro-variation and variance in basic number from 16 to 15 and 13, with the basic chromosome number of 16. (2) karyotypes of the herbaceous Smilax show the trend from symmetry in East Asia to asymmetry in North America, but no such trend between woody sections. (3) Prophyll is the persistent bract, so the young branch with single umbels borne in axil (with a prophyll at base of the branch) in Sect. China and Sect. Coilanthus is isogenous to the inflorescence with a prophyll at base or with a articulation on peduncle if only single umbel in Sect. Macranthae and Sect. Smilax. Considered the result of ITS data, it is suggested that the original type of inflorescence is spike of umbels without peduncle, then from the ancestor, two types of inflorescences are derived, one including most sections of Smilax and Hetrosmilax with solitary umbel or 2 to many umbels (panicle-liked) in axil, another including S. aspera in sect Smilax with umbels without peduncle (spike-liked). (4) Heterosmilax is not a monophyletic group, and closer to species of the herbaceous section and Sect. Coilanthus. S. corbularia is a transitional species with a 2/3 jointed perianths. It is suggested it is better to treat the Genus Hetersmilax as Subgenus. Heterosmilax; (5) The Herbaceous Smilax, origined from East Asia, then expended to North America, is a monophyletic group with co-ancestor shared by Sect. Coilanthus. We agree to recover Sect. Nemexia; (6) S. china is a widespread species with different ploidy (diploid, tetraploid and hexaploid), in which a diploid population was firstly found in Hubei. Distributive law of them has been found, which suggested that maybe before Tertiary to Middle Pleistocene when Japan and Taiwan separated from the Asian mainland, the tetraploid populations have been widely spread, and the hexaploid populations which is nowadays common in the mainland are generated after the separation. (7) Southwest China is a modern distributive and differentiation center of Smilacaceae.