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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:10137 |
| Date | 12 September 2012 |
| Creators | Van der Bank, Michelle |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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