The lettuce tribe (Cichorieae) is an economically important group within the large and biologically diverse sunflower family, Asteraceae. Previous systematic studies, relying on traditional characters of morphology, cytology, and anatomy, have not adequately resolved taxonomic and evolutionary problems in this group. Dr. Robert Jansen and his colleagues at the University of Connecticut will use recently developed molecular methods to analyze phylogenetic relationships among these plants. Variation in nuclear ribosomal and chloroplast DNA will be analyzed at the species level to assess evolutionary relationships among the 16 species of silver puffs (the genus Microseris) distributed primarily in western North America. This study will include the determination of hybrid and polyploid origins of several species in the genus. A broader focus of the study involves an analysis of chloroplast DNA variation in 70 genera in the lettuce tribe and putatively related tribes using restriction site mapping and DNA sequencing. Computer-assisted methods will be used to produce the first phylogenetic tree for the lettuce tribe, which in turn will provide the necessary framework for making predictive hypotheses about the historical biogeography of this worldwide group. The molecular analysis will also assist in resolving the evolutionary relationships of the Cichorieae to the other 16 tribes in the sunflower family. The project, combined with previous DNA analyses of this family by the P.I. and colleagues, will also generate the largest database of information concerning chloroplast DNA variation and evolution for any flowering plant family.
