Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The geographic genetic population structure and evolutionary history of the African
four-striped mouse, Rhabdomys pumilio, was investigated using mitochondrial
(mtDNA) cytochrome b gene (1140 bp) and control region (994 bp) sequences and a
combination of cytogenetic banding techniques (G- and C-banding), and
fluorescence in situ hybridization. Two cytotypes (2n = 46 and 2n = 48) were
identified by cytogenetic analysis. No evidence of diploid number variation within
populations was found nor were there differences in gross chromosome morphology,
or subtle interchromosomal rearrangements at levels detected by ZOO-FISH. The
comparative painting data (using the complete suite, N = 20, of Mus musculus
chromosome specific painting probes) show that 10 mouse chromosomes have been
retained as chromosomal arms, or intact chromosome blocks within the R. pumilio
genome, six produced double signals, while the remaining four hybridized to three or
more R. pumilio chromosomes. In total, the 20 mouse chromosome paints detected
40 segments of conserved synteny. Their analysis revealed eight R. pumilio specific
contiguous segment associations, a further two that were shared by R. pumilio and
other rodents for which comparable data are available, the Black (Rattus rattus) and
Norwegian (Rattus nONegicus) rats, but not by the Chinese hamster, Cricetulus
grise us. The results suggest that mouse chromosomes 1, 10, and 17 have
undergone extensive rearrangements during genome evolution in the murids and
may be useful markers for enhancing our understanding of the mode and tempo of
chromosome evolution in rodents. Following initial studies using control region
sequences, the phylogeographic appraisal of R. pumilio was done using cytochrome
b gene sequences. Analyses based on a variety of analytical procedures resulted in
the detection of two major mtDNA lineages that correspond roughly to the xeric and
mesic biotic zones of southern Africa. One clade comprises specimens with 2n = 48,
and the other representatives of two cytotypes (2n = 48 and 2n = 46). The mean
sequence divergence (12.0%, range 8.3% -15.6%) separating the two mtDNA clades
is comparable to among-species variation within murid genera suggesting their
recognition as distinct species, the prior names for which would be R. dilecfus and R.
pumilio. Low sequence divergences and the diploid number dichotomy within the
mesic lineage support the recognition of two subspecies corresponding to R. d.
dilecfus (2n = 46) and R. d. chakae (2n = 48). The data do not support subspecific
division within the nominate, R. pumilio. Molecular dating places cladogenesis of the
two putative species at less than 5 million years, a period characterised by extensive
climatic oscillations which are thought to have resulted in habitat fragmentation
throughout much of the species' range. / AFRIKAANSE OPSOMMING: Die geografiesebevolkingsstruktuur en evolusionêre verwantskappe binne die Afrika
streepmuis, Rhabdoys pumilio, is ondersoek deur middel van mitochondriale ONS
volgordebepaling van die geenfragment sitochroom b (1140 basispare) en die
reguleerstreek (994 bp) in kombinasie met sitogenetiese tegnieke (G- en Cbandkleuring
en f1uoreseerende in situ hibridisasie). Twee sitotipes (2n = 46 en 2n =
48) is geidentifiseer deur sitogenetiese analasie. Geen bewys van variasie in die 2n
chromosoomgetal binne bevolkings is gevind nie. Verder is daar ook geen verskil in
die morfologies struktuur van chromosome aanwesig binne bevolkings nie.
Vergelykende data (verkry met behulp van die N = 20 Mus musculus
chromosoomspesifiekepeilers) dui daarop dat 10 muis chromosome behoud gebly
het as chromosoomarms of chromosoomblokke binne die R. pumilio genoom. Ses
peilers het dubbel seine gelewer terwyl die oorblywende vier peilers gehibridiseer het
aan drie of meer R. pumilio chromosome. In totaal het die 20
muischromosoomverwe 40 konserwatiewe segmente geidentifiseer. Die analise dui
agt R. pumilio spesifieke aaneenlopende segmentassosiasies aan, met 'n
addisionele twee wat deur R. pumilio en ander muisagtiges vir wie vergelykende data
beskikbaar is, byvoorbeeld die swart (Rattus rattus) en Noorweegse (R. norvegicus)
rot maar nie die Chinese hamster, Cricetulus grise us, gedeel word. Die resultate stel
voor dat muischromosoom 1, 10 en 17 ekstensiewe herrangskikkings ondergaan het
gedurende die genoom evolusie binne die Muridae en dat hulle waarskynlik
waardevolle merkers kan wees om beide die patroon en tempo van chromosome
evolusie in muisagtiges verder te kan verstaan. Die filogeografiese verwantskappe
binne R. pumilio is ondersoek deur middel van ONS volgordebepalings van die
reguleerstreek asook sitochroom b. Die resultate van hierdie studie het twee
divergente mitochondriale ONS eenhede ontdek wat gekorreleer kan word met
xeriese en mesiese klimaatsones binne suidelike Afrika. Een groep bestaan uit diere
met 2n = 48, terwyl die ander genetiese groep twee sitotipes (2n = 46 en 2n= 48)
insluit. 'n Gemiddelde genetiese divergensie van 12.0% (varieer tussen 8.3% -
15.5%) verdeel die twee mtDNS-groepe en is vergelykbaar met tussenspesievariasie
binne ander muisagtige genera, wat moontlik daarop dui dat twee verskillende
spesies teenwoordig is; die voorgestelde name is R. di/ectus en R. pumilio. Lae
genetiese divergensie binne die mesiese groep versterk die moontlike
teenwoordigheid van twee subspesies, R. d. di/ectus (2n = 46) en R. d. chakae (2n =
48). Die data verleen egter nie steun aan die divisie binne R. pumilio nie.
Molekulêre datering van die twee spesies dui daarop dat die divergensie ten minste 5
miljoen jaar gelede plaasgevind het. Die periode was gekarakteriseer deur ekstensiewe klimaatsossilasies, wat gely het tot habitat fragmentasie in die spesie se
verspreidingsgebied.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53504 |
| Date | 03 1900 |
| Creators | Rambau, Ramugondo Victor |
| Contributors | Robinson, T. J., 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 | 145 p. : ill. |
| Rights | Stellenbosch University |
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