Dissertation Research: A Molecular Investigation of Higher Level Phylogeny of the Conifers

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The doctoral student, Linda Raubeson, working under the supervision of Dr. Leo Hickey at Yale University, will undertake a study of the evolutionary history of the 7 families of conifers (pines), based on two kinds of molecular data, chloroplast DNA (cpDNA) structural rearrangements, and sequence data from the nuclear 18s rDNA (ribosomal) gene. The time since the 7 families became separate evolutionary lineages is estimated to be 300 million years; the chosen molecular characters are evolutionarily conservative and should be informative at that time depth. The proposed research timetable covers two years; although, a doctoral student at Yale, Raubeson will spend the first year doing the cpDNA work with Robert Jansen at the University of Connecticut and six months of the second year sequencing the 18s rDNA genes with Elizabeth Zimmer at LSU. The student has already isolated total DNA from 23 species including representatives of all 7 families and has done limited restriction enzyme digests and mapping. Zimmer has sequenced portions of the 18s rDNA gene for conifers. Both data types appear to be informative at the appropriate time depth. The completed research will clarify our understanding of the evolutionary history of this economically important assemblage of trees.