Dissertation Research: Molecular Data and the Evolution of Sonchus (Asteraceae: Lactuceae) in the Canary Islands

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9521017 Crawford The diversity of plants and animals on oceanic islands has long fascinated naturalists, and continues to pose challenging questions about evolution and biogeography. Graduate student Seung-Chul Kim under the guidance of faculty adviser Prof. Daniel Crawford at Ohio State University is studying the numerous speaies of woody sunflowers of the group Dendrosonchus on the several islands of the Canaries in the mid-Atlantic Ocean. Morphological features of these plants have been analyzed by other taxonomists, who have concluded that some 17 species of Dendrosonchus inhabit various parts of the Canary Islands chain. Worries about the reliability of various morphological characters and the possibility of parallel evolution of particular growth forms provide a rationale for searching for additional, new characters to test current taxonomic and phylogenetic notions about these plants. The study will emphasize the collecting and analyzing of DNA sequence data from fresh and herbarium material of all Dendrosonchus species and of several potential mainland African relatives, in order to use mutational differences as a gauge of evolutionary relationships among the species. The study of Macaronesian Dendrosonchus will integrate morphological comparisons, DNA sequence differences in nuclear and chloroplast genes, and protein electrophoretic assessments of genetic variability within and among populations. The goal is to construct a robust phylogenetic tree for the many species of Dendrosonchus and to examine their geographical distributions and morphology in order to understand the island-based evolution of these plants.