Comparative studies of variation in nuclear DNA and chloroplast DNA have helped elucidate the pattern of evolutionary relationships in many plant groups. A phylogenetic framework is particularly important in groups of organisms used as model systems, to correctly interpret biological phenomena and apply valuable data. This research is a molecular phylogenetic investigation of a lineage of flowering plants, tribe Antirrhineae (Scrophulariaceae) that includes a model system in genetic and developmental studies, the cultivated snapdragon. To provide a broad molecular database that will insure rigorous tests of hypotheses, a broad experimental and analytical approach based on comparative DNA sequencing in nuclear and chloroplast genomes and restriction site variation of five chloroplast genes has been designed. The objectives here are to evaluate: (a) the evolution of floral morphological characters, (b) the origin and evolution of "Tam" transposable elements, and (c) how floral homeotic genes have evolved and whether their evolution has been influenced by "Tam" elements. %%% This research presents unusual opportunities for studying basic patterns and processes of molecular evolution, floral morphology, and developmental genetics using Antirrhinum majus and its relatives as model organisms. A phylogenetic context offers the chance to develop optimal application, extrapolation, and interpretation of biological results and this study, when completed, will constitute a robust demonstration of such a piece of research.
