Abstract
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.