The so-called Caryopteris-Trichostema complex consists of these two genera and several monotypic or very small genera. Trichostema is North American where all other taxa are Asiatic. The complex has been problematic taxonomically, and Cantino in particular, has questioned the monophyly of Caryopteris. A molecular phylogenetic study of the complex was carried out using sequences from the chloroplast ndhF gene. The monophyly of Trichostema is strongly supported in the molecular phylogeny and three major clades are present in the genus. The lineages correspond closely to groupings recognized by Harlan Lewis, with the notable exception of T. brachiatum. Implications of the placement of this species in the molecular phylogeny will be discussed relative to the evolution of annuality and base chromosome number. The ndhF phylogeny suggests that Caryopteris is polyphyletic. Section Caryopteris is strongly supported as monophyletic and is sister to Trichostema. The monotypic genus Amethystea is nested within the complex and is closely related to the above group of Trichostema and Caryopteris s.s.. Section Pseudocaryopteris (C. bicolor and C. paniculata) appears to be a natural group, thus supporting its elevation from the sectional to generic level as proposed by Cantino et al. (1998). Caryopteris divaricata, characterized by its porate pollen and delimited as the monotypic genus Tripora by Cantino, is sister to Pseudocaryopteris in a moderately supported clade. Caryopteris nepetifolia and C. terniflora form a strongly supported group together with Schnabelia, providing additional evidence to support the transfer of the former two species of Caryopteris to the genus Schnabelia. Rubiteucris is well supported as sister to Schnabelia rather than to the rest of Caryopteris. These results are largely congruent with relationships inferred from ITS sequence data, but provide better resolution.

Key words: Caryopteris, Lamiaceae, ndhF, phylogeny, Trichostema