XVI International Botanical Congess

ITS data were used to analyze relationships in north temperate Eupatorieae. Parsimony analysis supported the contention that Eupatorium be defined narrowly, and suggested that Eupatoriadelphus is distinct. The ITS data suggested that Eupatorium and Eupatoriadelphus share a common North American ancestor with Liatris relative to other Eupatorieae. The ITS data show that the presumed sister taxa in Eupatoriinae from South America belong to a different clade. These results suggest that following initial divergence in North America, Eupatorium reached Europe via dispersal during the late Pliocene with subsequent radiation in Asia.