Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Forming part of a conservation programme, this study was concerned with two
species of Cichlid fish (Oreochromis mossambicus and O. ni/oticus), which were
brought into contact with each other by unnatural ways. They are now
hybridizing to some extent and there is also evidence that the foreign O. ni/oticus
may out compete the native O. mossambicus. To cast light on what the current
distribution is of both these species and the hybrids in Southern Africa, it is
important to identify specimens very accurately.
In attempting to find genetic markers to distinguish between two species of
Cichlids we tested 20 microsatellite dinucleotide (CAn) repeats during a
preliminary study and found five of these promising to exhibit little intra-specific
genetic diversity but large genetic variation between species. We amplified these
five loci in 145 individuals from 10 populations, which included the two species
and their hybrids. Exact sizes of the fragments were determined using an
automated DNA sequencer.
Between the two species, allele sizes were overlapping, but when data were
analyzed by statistical models, the differences could be seen for populations,
however on individual level there was overlap between the species. The hybrids
were found to be intermediate positioned between the two pure species. Our
attempt to assign individuals to populations provided doubtful results. Thus,
using this set of markers, populations can be ascribed to one of these species,
but not individuals by themselves. / AFRIKAANSE OPSOMMING: As deel van 'n natuurbewarings program, word daar in hierdie studie twee
spesies van vis ondersoek was in kontak met mekaar gekom het op onnatuurlike
wyse. Hierdie twee visspesies vanuit die CICHLIDAEfamilie (Oreochromis
mossambicus en 0. ni/oticus) kan hibridiseer wanneer hul saam voorkom, maar
dit is ook bekend dat die uitheemse O. ni/oticus die inheemse O. mossambicus
kan bedreig in terme van leefruimte, kos en broeispasie. Om die voorkoms van
hibriede tussen die twee spesies te ondersoek in Suider Afrika se varswater
opvangsgebiede, is dit baie belangrik om individue baie akkuraat te identifiseer.
In hierdie poging om genetiese merkers te vind wat die twee spesies van mekaar
onderskei, het ons 20 mikrosateliet di-nulkleotied (CAn) herhalende volgordes op
verskillende loci ondersoek. Vyf daarvan het belowend voorgekom om as spesie
spesifieke merkers te dien. Die fragmente op die vyf loci is ge-amplifiseer in 145
individue vanuit 10 populasies. Presiese groottes van die fragmente is bepaal
met behulp van 'n ge-outomatiseerde DNA volgorde bepaler waarna genotiepes
vir elke individu toegeken is.
Tussen die twee spesies het alleel groottes oorvleuel, maar wanneer data geanaliseer
word met behulp van statistiese metodes, was verskille tussen die
spesies duidelik op populasie vlak. Die hibriede het intemediêr tussen die twee
spesies voorgekom. Dus met behulp van hierdie stel merkers kan onderskei
word tussen die twee spesies op populasie vlak, hoewel individue nie op sig self
identifiseer kan word nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52935 |
| Date | 03 1900 |
| Creators | Esterhuyse, M. M. |
| Contributors | D'Amato, M. E., Volekaert, F. A. M., Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 141 p. : ill. |
| Rights | Stellenbosch University |
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