Nuclear internal transcribed spacer regions (ITS) and the chloroplast trnL intron and trnL/trnF intergenic spacer and matK sequences were used to assess relationships among European and South American species of Hypochaeris. The ITS tree shows high resolution compared to that of the maternally inherited trnL and matK. Monophyly of south American Hypochaeris is strongly supported by both ITS and the joint matrix of ITS, trnL and matK data. The European species lie basal to the South American taxa. This, plus small molecular divergence among South American species, suggests that they evolved from a single introduction from a European progenitor similar to H. maculata (or possibly H. cretensis or H. oligocephala), and not from H. radicata or H. robertia as suggested previously. Hypochaeris is also revealed to be paraphyletic in relation to generic relatives. ITS data indicate that H. robertia is closer to Leontodon helveticus and L. autumnalis, which brings its placement within Hypochaeris into serious question. Species of Leontodon form two clades based on molecular data, each also supported by chromosome numbers and morphology. Both nuclear and chloroplast markers suggest that Leontodon, Picris and Helminthotheca are very closely related genera and all need taxonomic re-evaluation.

Key words: Asteraceae, DNA, evolution, Hypochaeris, phylogeny, South America