THE ORIGIN OF DENDROSENECIO WITHIN THE SENECIONEAE (ASTERACEAE) BASEDON CHLOROPLAST DNA EVIDENCE

Chloroplast DNA restriction-site variation was surveyed using 15 enzym es for 37 accessions from the tribe Senecioneae (Asteraceae), plus two outgroup species, in order to determine the placement within the trib e of the giant senecios (Dendrosenecio). The survey revealed 176 phylo genetically informative mutations and 121 autapomorphic mutations. Den drosenecio is diagnosed by a minimum of 15 mutations, which suggests t hat the giant senecios evolved from a relatively isolated lineage with in the Senecioneae, and this conclusion is supported by earlier eviden ce from chromosome counts and phytochemistry. Among the taxa sampled, the closest relatives of Dendrosenecio are Cineraria deltoidea and two species of Euryops. Support was not found for suggestions in the lite rature that the closest relatives of Dendrosenecio are species in Sola necio or Senecio subgen. 'Crociseris.' The position of the Dendrosenec ia/Cineraria/Euryops clade is weakly supported as basal to the majorit y of other senecionoid genera. The tussilaginoid genera sampled (Ligul aria, Petasites, Roldana, and Tussilago) are monophyletic in our analy sis, with the surprising inclusion of Pericallis hybrida as the sister -taxon to Roldana suffulta. The sister-group to the Dendrosenecio/Cine raria/Euryops clade includes all species of Delairea, Gynura, Kleinia, Packera, Senecio, and Solanecio sampled. Within Senecio, subgenera Se necio and 'Crociseris' form a monophyletic core, with subgenus 'Kleini oidei' being broadly paraphyletic or possibly polyphyletic.