CHLOROPLAST DNA RESTRICTION SITE VARIATION IN THE VERNONIEAE (ASTERACEAE), AN INITIAL APPRAISAL OF THE RELATIONSHIP OF NEW AND OLD-WORLD TAXA AND THE MONOPHYLY OF VERNONIA

Chloroplast DNA restriction site variation was examined for 35 taxa in the Vernonieae and four outgroup tribes, using 17 restriction enzymes mapped for ca. 900 restriction sites per species; 139 mutations were found to be phylogenetically informative. Phylogenetic trees were cons tructed using Wagner and weighted parsimony, and evaluated by bootstra p and decay analyses. Relationships of Old and New World taxa indicate complex geographical relationships; there was no clear geographic sep aration by hemisphere. The relationships between Old and New World Ver nonias found here support prior morphological analyses. The sister gro up to all New and most Old World taxa was composed of a small group of Old World species including yellow-flowered, trinervate-leaved specie s previously postulated to be basal in the tribe. The majority of both New and Old World taxa are derived from a lineage beginning with the monotypic genus Stokesia, an endemic of the southeastern United States . The genus Vernonia was also found to be paraphyletic within both the New and Old World. Available data do not support either the separatio n of Vernonia or the tribe Vernonieae into geographically distinct lin eages. The pattern of relationships within the Vernonieae for taxa fro m North America, Asia, Africa, Central and South America is most simil ar to that of several other groups of both plants and animals with a b oreotropical origin, rather than an origin in Gondwanaland. Such a pat tern of distribution suggests more ancient vicariant events than are r outinely postulated for the Asteraceae.