A phylogenetic study was conducted on current members (Chelone, Chionophila, Keckiella, Nothochelone, Pennellianthus, Penstemon, and Tetranema) and former members (Collinsia, Freylinia, Halleria, Russelia, Scrophularia, Tonella) of tribe Cheloneae to test for monophyly, examine biogeographic patterns, and assess relationships of Cheloneae to genera previously excluded from the tribe. Nucleotide sequence data from ITS and matK used in separate and combined analyses yielded congruent trees. Our results provide evidence that Collinsia and Tonella should be transferred from Collinsieae to Cheloneae and that Russelieae should be expanded to include Tetranema. Our results also indicate a New World origin for Cheloneae with dispersal of the Asian component over Beringia. North American Cheloneae may have originated in the Klamath Region of the western United States with expansion to the Rocky Mountain/Columbia Plateau region followed by diversification of several genera. We propose a post-Tertiary evolutionary radiation of the large North American genus Penstemon.

Communicating Editor: James F. Smith