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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53078 |
| Date | 12 1900 |
| Creators | Daniels, Savel R. (Savel Regan) |
| Contributors | Cook, B. A., Matthee, C. A., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 309 p. : ill. |
| Rights | Stellenbosch University |
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