Cladistic Analyses of Viburnum Based on Molecular Characters

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Dr. Michael Donoghue of the University of Arizona, working initially with colleague Dr. Kenneth Sytsma at University of Wisconsin, plans to study evolutionary relationships within the flowering plant genus Viburnum and relationships to other groups, emphasizing characters obtained from chloroplast DNA. The chloroplast genome will be digested with a battery of restriction enzymes, each of which cleaves the molecule at specific sites, and the exact position of these sites on the molecule will be determined. Comparison of nucleotide site similarities and differences among the species will allow determination of the evolutionary pattern of mutations separating taxa. In assessing more distant relationships, between genera and families, complete nucleotide sequences of chloroplast genes will be obtained and compared, using computer-aided methods. Phylogenies derived from molecular data will be compared to trees obtained previously based on morphological characteristics, and the nature and extent of congruence will be evaluated. Molecular data are likely to resolve relationships that remain equivocal based on morphology alone. Further, resolved phylogenetic trees will provide a framework for study of the evolution of particular morphological traits of interest. This will be especially vaulable in the case of fruit characters, because these have recently been studied in detail by Dr. Donoghue and developmental data are available for these. The use of phylogenetic information to analyze developmental changes will contribute to emerging analyses of the evolution of form and function in organisms.