M.Sc. / Five plastid regions as source for phylogenetic information were used to investigate the relationships among ten genera of Vitaceae. These comprised the tmL intron, trnL-F intergenic spacer, rpL16 intron, rbcL gene and accDpsa/ spacer. Congruent results were obtained between separate, combined and Bayesian analysis with all four major clades being shared among trees. All bootstrap consensus trees obtained from single sequences or combined analysis suggest that Vitaceae is a monophyletic group with Leea weakly supported as sister to Vitaceae. The results presented provide novel insights into the relationships within ten Vitaceae genera and suggest direction for further studies.

M.Sc. / The tribe Podalyrieae is a group of Papilionoid legumes that are largely endemic to the Cape Floristic Region of southern Africa. A phylogenetic study of the tribe was undertaken using gene sequences obtained from the internal transcribed spacer (ITS) as well as the plastid gene rbcL. Although the resolution was poor in the resulting trees, several groupings were noted within the tribe. The subtribe Xiphothecinae remains relatively unchanged and consists of the genera Amphithalea and Xiphotheca. The subtribe Podalyriinae was found to be paraphyletic. A close relationship was observed between the genera Liparia and Podalyria with Stirtonanthus as sister. Additional chloroplast genes (trnL-F and trnS-trnG) were sequenced to obtain better resolution within this group. While Podalyria and Stirtonanthus are monophyletic, the monophyly of Liparia is still uncertain. Virgilia and Calpurnia are closely related and Cyclopia retains its isolated, monophyletic position sister to the tribe. The species of Cadia included in the phylogenetic analysis formed a sister grouping to the tribe Podalyrieae and the inclusion of this genus in Podalyrieae is discussed. A date for the root node of the tribe was estimated at 28.55 MYA, using non-parametric rate smoothing (NPRS), indicating a major radiation to have taken place during the Pliocene. By means of independent contrasts it was determined that the rate of molecular evolution is higher in reseeders than resprouters, perhaps due to more reproductive cycles in these individuals, that would in turn affect the rate of DNA substitution.

Ph.D. / Genetic variation estimates and phylogenetic studies (based on genetic differentiation) of the Podalyrieae and related tribes (family Fabaceae) are presented. The tribe is endemic to the Cape fynbos region of South Africa, except for Calpurnia. Although Podalyrieae have been the focus of many taxonomic studies no genetic variation studies have been done on this group of plants. Genetic variation in selected populations, species and genera was studied to evaluate the use of enzyme electrophoresis in systematic studies on these three levels. Eight case studies are presented. Allelic data proved to be extremely useful at the population and congeneric species level. However, at a higher level, it showed some potential when treated with caution. It is not possible to predict beforehand if meaningful results can be obtained at this higher (i.e. confamilial genus) level of divergence. A large number of plant genetic data sets from the literature was analysed to determine typical levels and ranges of genetic differentiation within families, genera and species. A graph of probability against taxonomic rank was constructed and compared with results published by Thorpe (1982, 1983). The results indicate that plant taxa have a reduced biochemical evolution (less diverse than animals at comparable taxonomic ranks) in contrast to Thorpe's (1982, 1983) reports (which were based on less data for plant taxa). Genetic identity values between 3041 pairs of taxa were used in the present study. The phylogenetic relationships among genera of the tribe Podalyrieae were estimated from sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA as well as morphological and chemical data. Morphological and. ITS sequence data produced cladograms with similar topologies, both supporting the exclusion of Hypocalyptus from Podalyrieae. A broadening of Podalyrieae, which includes Xiphothecinae, Podalyriinae and Cyclopia, is suggested. The multidisciplinary approach followed in this study provided a better understanding of taxonomic and evolutionary relationships in the Podalyrieae and some other Cape legumes.