It is broadly accepted that species delimitation is the most primary aspect in evolutionary biology and often provides the focus for biological conservation efforts (Goldstein et al. 2000, Gaines et al. 2005). This issue is critical for taxonomically difficult plant genera like Clematis. Clematis Linnaeus (1753: 543) is one of the few cosmopolitan genera in Ranunculaceae (Ziman & Keener 1989). The taxonomy of this genus has been relatively complicated since its description. In addition to infrageneric classification, species estimates of Clematis have differed strikingly in recent classifications. Tamura (1995) estimated that Clematis includes approximately 240 species (with the exclusion of seven species of Naravelia (De Candolle 1817: 167) and one species of Archiclematis (Tamura 1967: 31). Johnson (1997) estimated that Clematis comprises about 320 species, including Archiclematis and Naravelia. Grey-Wilson (2000) recorded 297 species of Clematis with Archiclematis included and Naravelia excluded. Wang & Li (2005) recorded 354 species of Clematis (including Archiclematis and excluding Naravelia) in their systematic classification of the genus. These differences in the number of species included in Clematis may be at least partly due to varying emphasis on particular morphological characteristics by the authors.