Valerianaceae is a relatively small (ca. 300+ species), but morphologically diverse, lineage of angiosperms. Although the species of Valerianaceae and its sister group Dipsacaceae + Triplostegia are primarily distributed in the Northern Hemisphere, and our data imply than Valerianaceae diversified initially within Asia (the Himalayan Patrinia and Nardostachys falling at the base of the clade), the center of species diversity for the group is in the Andes of South America with as many as 200 species restricted to that area. Previous hypotheses concerning the origination of the South American Valerianaceae have suggested that as many as three colonization events may have occurred and subsequently led to the diversity we see there today. However DNA sequence data from both the chloroplast and nuclear genomes suggest that the South American Valerianaceae form a clade, with its closest relatives in North and Central America. In order to estimate divergence times, fossil data from Valerianaceae and related taxa (other Dipsacales) were used to calibrate a molecular clock using a variety of methodologies and previously published datasets. Estimated dates for the common ancestor of the South American taxa indicate a rapid diversification of this clade. Diversification rates within the South American clade will be presented and compared to rates in other angiosperm lineages.

Key words: Dipsacales, diversification, molecular clock, Valerianaceae