Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In the present study, the systematic status, aspects of the evolutionary biology and phylogenetic relationships among species of the African freshwater crab genus Potamonautes in South Africa are examined. Systematic research between allopatric populations of P. brincki, using allozyme and morphometric data has revealed the existence of a new undescribed freshwater crab species occurring in mountain streams of the Cape Peninsula. This species is described in the present study. In addition, the diagnostic value of carapace dentition patterns in the taxonomy of freshwater crabs is explored among two toothed river crab species from South Africa. The latter study utilized P. warreni and P. unispinus where considerable variation in the dentition pattern of the former species has been recorded. Fixed differences in allozyme loci demonstrated that these two taxa should indeed be considered separate, yet closely related species, while the morphometric data failed to reveal this taxonomic separation. The holotype of P. warreni is re-described. The relationship of hybrid taxa between P. depressus and P. clarus populations are investigated. Evident from this study is that populations that occur equidistant from the two parental taxa have undergone extensive introgressive hybridization. Considering the pronounced sequence divergence and the occurrence of fixed allozyme loci between populations, it is postulated that the hybrid populations should be considered to be on a unique evolutionary trajectory worthy of conservation. The population genetic structure of P. calcaratus is examined as this species is unique in its occupation of water holes. Results demonstrate that the genetic population structure is the result of recent colonization and moderate gene flow among populations. Phylogenetic relationships between the southern African freshwater crab fauna is investigated with the use of sequence data from two mitochondial genes (12 S rRNA and 16 S rRNA), allozymes and morphology in an attempt to firstly, test the usefulness of freshwater crabs as biogeographic indicators, secondly to explore the relationship among hybrid taxa, and thirdly to examine Bott's (1955) subgeneric divisions. Results demonstrated that freshwater crabs can be used as biogeographic indicators, that hybrid taxa are phylogenetic ally closely related and that Bott's subgeneric divisions have no systematic basis. Among the three data sets, the sequence data provided the best resolution, while the phylogenetic inferences derived from the allozyme data and the morphology was limited. / AFRIKAANSE OPSOMMING: In hierdie studie word die sistematiek, aspekte van die evolusionêre biologie en filogenetiese verwantskappe tussen spesies van die varswater krap genus Potamonautes ondersoek in Suid Afrika. Navorsing op geografies geisoleerde populasies van P. brincki word met behulp van allosieme en morfometriese data ondersoek en dui daarop dat daar 'n nuwe onbeskryfde spesie op die berge van die Kaapse Skiereiland voorkom. Die nuwe spesies word beskryf in hierdie studie. Die diagnostiese waarde van tand patrone in varswater krappe word tussen twee spesies P. warreni en P. unispinus ondersoek. Genetiese data dui daarop dat alhoewel P. warreni morfologies baie naverwant is aan P. unispin us, is genoegsame verskille in allosiem lokusse wat daarop dui dat die twee taksa volwaardige spesies is. Die holotipe van P. warreni word herbeskryf. Die verwantkap tussen populasies van twee hibried taksa, P. depressus en P. clarus, word ondersoek. Resultate van hierdie studie dui daarop dat noemenswaardige verskille voorkom tussen die twee hibridie taxa en dat die hibriede populasies geneties verskillend is. 'n Argument word aangevoer vir die beskerming van hibriede taksa. Die populasie genetika van P. calcaratus word ondersoek en vergelyk met vorige studies. Die data dui daarop dat minimale geen vloei tusses populasies is en dat die populasie struktuur waarskynlik die resultaat is van onlangse kolonisasie. Die filogenetiese verwantskap tussen die suider Afrikaanse krappe word ondersoek met DNA, allosieme en morfologiese karakters met drie hoofdoele. Eerstens om die gebruik van varswater krappe as biografiese indikatore te toets. Tweedens om die verwantskap van hibriede taksa te ondersoek, en derdens om die status van Bott (1955) se subgenera te bepaal. Resultate dui daarop aan dat varswater krappe wel gebruik kan word as biografiese indikatore. Hibridieserende taxa naverwant is derdens en dat Bott se subgenera geen taksonomiese basis het nie. Die DNA data het die beste resolusie gebied vir die filogenetiese vrae, terwyl die allosieme en morfologiese data 'n laer resolusie bedied het, en meer beperk was.

Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2007 / Urban rivers are the most utilised and yet degraded rivers worldwide. The urban rivers of the Western Cape are no different. The Lourens River flows through the agricultural and urban areas of Somerset West in the Western Cape and as a result is subjected to a variety of pollution sources. In the upper reaches this river flows through two large farms where metal containing pesticides are used. Further downstream it passes through an urban area where a variety of pollution sources could contribute to the contamination of the river. The extent to which the Lourens River, and the ecosystem it supports, is affected by metal pollutants is not known. The aim of this study was to determine the concentrations of metals in the Lourens River as well as the contribution of agricultural and urban activities to metal contamination of the river. Sediment and crab (Potamonautes perlatus) samples were collected over a period of one year from seven sites over the length of the river. Sediment samples were also collected from a sedimentation pond on the bank of the river where orchard run-off water is remediated. Preliminary analysis of samples was done for ten metals (AI, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb and Zn). Results from these analyses determined the selection of six metals (AI, Cr, Cu, Fe, Mn and Zn) for further investigation in this study. The concentrations of metals detected in collected samples varied significantly throughout the sampling period. This can be attributed to various factors such as rainfall patterns, the fact that pesticide application varies throughout the year and other urban activities. AI, Cr, Fe and Zn were found in significantly higher concentrations in the urban areas. These higher levels of contamination, relative to the upper parts of the river, can probably be attributed to various urban activities contributing to the contamination of run-off into the river. The sedimentation pond results revealed high concentrations of AI and Fe, while Cu, Cr, Mn, and Zn were found in lower concentrations. All six metals however followed the same pattern where the first four sampling occasions showed higher concentrations than the last three occasions. It can be concluded that agricultural and urban activities do contribute significantly to the metal contamination of the Lourens River.