Dissertation Research: Systematics of Stylocline (Asteraceae)

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Gradute student Morefield under the guidance of Dr. Loren Rieseberg of the Rancho Santa Ana Botanic Garden is studying the several species of an American Southwest sunflower relative, Stylocline, and its relatives, in order to assess levels of genetic and genomic variability within and among populations of these annual and highly inbreeding plants. Primary methods of analysis include protein electrophoresis to sample variation in soluble enzymes extracted from the plants, along with methods of DNA analysis to measure mutational differences in nuclear ribosomal genes and in chloroplast genes. Several related groups of plants also will be studied, in order to construct a phylogenetic framework indicating evolutionary relationships among the species. Much of the theoretical discussion about speciation processes relies upon knowledge acquired from organisms that cross-breed, but many groups of plants include high proportions of self-fertilizing individuals. It is unclear whether these inbreeding groups follow the same evolutionary rules, and whether they harbor similar amounts of genetic variability within local populations. With additional data from studies of morphological features, the student will also be able to determine reliable features for species identification, map geographic distributions for all the taxa, and evaluate the correct scientific names for all those groups with distinguishable characteristics. The student will thus gain valuable training in a broad range of modern systematic methods in the analysis of plant diversity.