Phylogenetic relationships among species of Hypochaeris (Asteraceae, Cichorieae) based on ITS, plastid trnL intron, trnL-F spacer, and matK sequences.

Nuclear internal transcribed spacer (ITS) regions and chloroplast trnL intron and trnL/trnF spacer and matK sequences were used from 86 accessions to assess relationships among 31 European and South American species of Hypochaeris plus 18 representatives of related genera of tribe Cichorieae. The ITS tree shows high resolution compared to that of the maternally inherited trnL intron, trnL/F spacer, and matK sequences. The ITS and the combined tree reveal clades that agree well with sections of the genus established previously on morphological and cytological grounds, except for H. robertia, which groups with Leontodon helveticus and L. autumnalis. Monophyly of species of Hypochaeris from South America is strongly supported by both ITS and the joint matrix of ITS, trnL, and matK data. European species lie basal to South American taxa, which suggests that species in South America evolved from a single introduction from European progenitors and not from H. robertia as suggested previously. Low levels of sequence divergence among South American taxa suggest a pattern of rapid speciation, in contrast to much greater divergence among European representatives. Different species of Leontodon form two different clades that are also supported by chromosome numbers and morphology. Both nuclear and chloroplast markers suggest that Helminthotheca, Leontodon, and Picris are closely related to each other as well as to Hypochaeris.