Molecular Phylogeny and Evolution of Compositae of the Juan Fernandez Islands

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Drs. Dan Crawford and Tod Stuessy of Ohio State University will use molecular DNA information to study the evolution of three genera of plants occurring on the Juan Fernandez Islands, located 600 km west of central Chile. Oceanic islands, and the Juan Fernandez archipelago in particular, offer ideal systems in which to study plant evolution. It is possible to place a time frame on the origin and evolution of plants on oceanic islands because the islands can be dated geologically with reasonable accuracy. In the Juan Fernandez, the older island (Masatierra) is four million years old while the age of the younger island of Masafuera is one to two million years. The flora of the Juan Fernandez is small in numbers but contains a high percentage of unique (endemic) species. This makes it feasible to study the origin and evolution of the endemic plants on the archipelago. The two largest endemic genera are Dendroseris and Robinsonia in the sunflower family, Asteraceae. These are bizarre tree-like plants whose presumptive ancestors from the South American mainland can only be guessed from morphological comparisons. The use of molecular characters such as chloroplast DNA restriction sites and sequences, ribosomal DNA, and protein iszoymes will help to compare the island taxa with mainland species and determine possible progenitor stocks. Molecular methods will also be employed to determine evolutionary relationships among the species of Dendroseris and Robinsonia on the islands, and to study the evolution of a third genus in the archipelago, Erigeron. Field trips with Chilean scientists and students will provide materials for these comprehensive studies. Once origins and phylogenetic relationships of these insular plants are determined with DNA and protein data, it will be possible to study the important changes in life-form and physiology associated with dispersal to and establishment upon isolated oceanic islands. This in turn should lead to a better understanding of processes involved in the evolution of new plant species.