PHYLOGENY AND CHARACTER EVOLUTION IN THE ASTERACEAE BASED ON CHLOROPLAST DNA RESTRICTION SITE MAPPING

Phylogenetic relationships among species representing 57 genera from 15 currently recognized tribes of Asteraceae were assessed by chloroplast DNA restriction site mapping. Phylogenetic analyses of 328 informative restriction site mutations were performed using both Dollo and Wagner parsimony and the bootstrap method. The results provide strong support for the monophyly of the subfam. Asteroideae, which includes the nine tribes Astereae, Anthemideae, Inuleae, Senecioneae, Calenduleae, Eupatorieae, Heliantheae, Coreopsideae, and Tageteae. The monophyly of the Lactucoideae (excluding the Barnadesiinae) is less strongly supported and this subfamily consists of the six tribes Mutisieae, Cardueae, Vernonieae, Liabeae, Lactuceae, and Arctoteae. The molecular phylogeny indicates that 13 of 15 tribes are monophyletic, with the Heliantheae and Tageteae being paraphyletic. Several groups of tribes are shown to be closely related, including the Liabeae and Vernonieae, and the Tageteae, Coreopsideae, Heliantheae, and Eupatorieae, but relationships among the other tribes remain unclear. Tribal placement of five morphologically anomalous genera (Blennosperma, Cotula, Echinops, Stokesia, and Ursinia) is also clarified. The chloroplast DNA phylogeny shows almost complete congruence with the less explicit phyletic scheme proposed by Thorne but differs markedly from the cladistically-based phylogeny of Bremer. The availability of a molecular phylogeny for the Asteraceae allows for an independent assessment of the patterns of morphological, chemical, and chromosomal evolution in the family. A much higher incidence of parallelism occurs in secondary chemistry than in morphological characters. The subfam. Asteroideae has a number of evolutionarily derived floral features and it exhibits a much more diverse and biosynthetically complex secondary chemistry.