A phylogenetic analysis of Doronicum (Asteraceae, Senecioneae) based on morphological, nuclear ribosomal (ITS), and chloroplast (trnL-F) evidence

A phylogenetic analysis of the Old World genus Doronicum (26 species, 4 subspecies) based on sequence data of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA, the chloroplast spacer trnL-F, and morphology is presented. Congruence among the three data sets was explored by the computing of several indices, all of which suggest homogeneity between only the two molecular matrices. We argue that the morphological data set contains poor phylogenetic signal and advocate simultaneous analysis of the three data sets (total evidence approach) so that morphological characters are tested for homology by congruence with molecular data. The resulting phylogenetic hypothesis allows several well-supported conclusions including the placement of a Corsican endemic (D. corsicum), sister to the remainder of the genus, and the inference that an early southern European or Mediterranean diversification took place in the genus. Shifts in morphological characters (e,g,, homocarpy to heterocarpy) are confirmed to have evolved several times. Results from comparative studies of sequence data of the chloroplast gene ndhF support inclusion of Doronicum in tribe Senecioneae. (C) 2001 Academic Press.