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 constructed using Wagner and weighted parsimony, and evaluated by bootstrap and decay analyses. Relationships of Old and New World taxa indicate complex geographical relationships; there was no clear geographic separation by hemisphere. The relationships between Old and New World Vernonias found here support prior morphological analyses. The sister group to all New and most Old World taxa was composed of a small group of Old World species including yellow-flowered, trinervate-leaved species 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 separation of Vernonia or the tribe Vernonieae into geographically distinct lineages. The pattern of relationships within the Vernonieae for taxa from North America, Asia, Africa, Central and South America is most similar to that of several other groups of both plants and animals with a boreotropical origin, rather than an origin in Gondwanaland. Such a pattern of distribution suggests more ancient vicariant events than are routinely postulated for the Asteraceae.