EVOLUTION OF THE GENUS DENDROSERIS (ASTERACEAE, LACTUCEAE) ON THE JUAN-FERNANDEZ ISLANDS - EVIDENCE FROM CHLOROPLAST AND RIBOSOMAL DNA

Restriction site mutations in chloroplast DNA (cpDNA) and ribosomal DNA (rDNA) were used to study variation within and phylogenetic relationships among seven of the 11 species of the genus Dendroseris, which is endemic to the juan Fernandez Islands. Variation within a species was detected in only one instance. The monophyly of the genus is supported by three shared derived restriction site mutations in cpDNA. The molecular data indicate that subgenera Dendroseris and Phoenicoseris are holophyletic but the results are inconclusive with regard to the holophyly of subg. Rea. Restriction site mutations for cpDNA and rDNA do not resolve relationships among the subgenera because all mutations in Dendroseris either occur in single species or are common to species of the same subgenus. This suggests a rapid radiation of the subgenera following colonization of the island by their ancestor. Estimated divergence times calculated from cpDNA are less than 2.6 million years for all species of Dendroseris, which suggests that the genus was not an early colonizer on Masatierra.