The 275 species of Penstemonare distributed in North America from Alaska to Guatemala and coast-to-coast, exclusive of the Canadian shield. The area of richest species diversity is the Intermountain Region and the area of lowest diversity lies east of the Rocky Mountains. Penstemonhas been divided into six subgenera. The primary morphological characters defining subgenera are anther dehiscence and pubescence patterns. We used nrITS sequence data to reconstruct the phylogeny of Penstemon. The strict consensus tree was used to assess biogeographic and taxonomic relationships, the evolution of anther dehiscence and pubescence, the shift from bee- to bird-pollination syndromes, and evolution of polyploidy. Our results suggest an origin of Penstemonin the Rocky Mountains, a subsequent migration to the west early in the history of the genus followed by migration throughout the Intermountain region, the southwest and finally east of the Rocky Mountains. Our results also suggest that anther characters are insufficient to define subgenera and that bird-pollination and polyploidy have originated independently numerous times in Penstemon.

Key words: biogeography, character evolution, Cheloneae, Penstemon, Scrophulariaceae