Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The evolutionary history of the African tribe Tragelaphini (spiral-horn antelope)
is controversial. Past phylogenetic relationships among species were based
on morphology or limited fossil evidence and are in conflict with mitochondrial
DNA sequencing studies that have been conducted more recently. Although
the group is distinguished from other African ungulates by the presence of
spirally-twisted horns, the nine recognized extant species differ considerably
in morphology, feeding habits and their habitat preference. The present study
aims to resolve the phylogenetic uncertainties of the Tragelaphini using
nuclear DNA sequence data derived from four independent DNA loci (MGF,
PRKCl, SPTBN and THY). These data were combined with all previously
published DNA sequences to produce a molecular supermatrix comprising
approximately 6000 characters. Both parsimony and model based
phylogenetic analyses of the nuclear DNA support the associations resulting
from the analysis of mitochondrial genes. These findings suggest that the
morphological characters previously used to delimit species within the group
are subject to convergent evolution. The molecular phylogeny presented
herein suggests that early members of Tragelaphini diverged from the other
bovids during the mid-Miocene approximately 15.7 million years before
present (MYBP). The common nyala (Tragelaphus enqest; and lesser kudu
(Tragelaphus imberbis) representing the most basal species, separated from
the other tragelaphids approximately 7.1 MYBP. This was subsequently
followed by the radiation of those species adapted to a more tropical
environment and they include the mountain nyala (Tragelaphus buxtom),
bongo (Tragelaphus euryceros), sitatunga (Tragelaphus spekel) and
bushbuck (Tragelaphus scriptus), and the arid adapted clade comprising the
giant eland (Taurotragus derbianus), common eland (Taurotragus oryx) and
greater kudu (Tragelaphus strepsiceros). It is thought that this split occurred
at the Miocene-Pliocene boundary approximately 5.4 MYBP. The timing of
evolutionary events within the tribe suggests climatic oscillations and
subsequent biotic shifts as the major driving forces underpinning speciation in
the tribe Tragalaphini. / AFRIKAANSE OPSOMMING; Die evolusionêre geskiedenis van die ras Tragelaphini
(spiraalhoringwildsbokke) is kontroversieël. Vorige filogenetiese
verwantskappe tussen die spesies is gebaseer op morfologie of beperkte
fossiel bewyse. Meer onlangse studies, gebaseer op mitochondriale ONS
nukleotieddata, is in teenstryding met baie van die evolusionêre hypotese
afkomstig van morfologiese studies. Alhoewel die groep van die ander
hoefdiere uitgeken kan word deur die aanwesigheid van spiraalvormige
horings, verskil die nege hedendaagse spesies grootliks ten opsigte van
morfologie, voedingswyse en habitat. Die hoof doelwit van hierdie studie was
om die filogenetise verwantskappe tussen die Tragelaphini spesies te ontleed
deur gebruik te maak van nukluêre ONS nukleotieddata afkomstig van vier
onafhanklike ONS merkers (MGF, PRKCl, SPTBN en THY). Die data verkry
is saamgevoeg by vorige gepubliseerde ONS nukleotidedata om 'n
"supermatris" van sowat 6000 karakters te produseer. Parsimonie en
modelgebaseerde filogenetise analise van die nukluêre ONS nukleotieddata
het ooreengestem met die resultate van vorige mitochondriale studies. Hierdie
bevindings dui daarop dat die morfologiese karakters wat voorheen gebruik is
om die evolusionêre verwantskappe tussen die Tragelaphini spesies te
ontleed onderhewig is aan konvergente evolusie. Die molekulêre filogenie
wat hierin beskryf word stel voor dat die ras Tragelaphini gedurende die mid-
Miocene, omtrent 15.7 miljoen jaar (MJ) gelede van die ander lede van die
subfamilie Bovinae geskei het. Tragelaphus angasi en Tragelaphus imberbis,
die mees basale spesies in die filogenie, het omtrent 7.1 MJ gelede van die
ander lede van die Tragelaphini geskei. Hierdie skeiding is gevolg deur 'n
split tussen die spesies aangepas vir 'n meer tropiese habitat (Tragelaphus
buxtoni, Tragelaphus euryceros, Tragelaphus spekei en Tragelaphus scriptus)
en die spesies aangepas vir 'n droë habitat (Taurotragus derbianus,
Taurotragus oryx en Tragelaphus strepsiceros) Hierdie finale skeiding het
gedurende die Miocene-Pliocene oorgang plaasgevind. Die tydsberekening
van die evolusionêre gebeurtenisse wat binne die Tragelaphini ras
plaasgevind het, gekoppel aan paleoklimaatdata, dui aan dat veranderinge in klimaat en die geassosieerde habitatveranderinge verantwoordelik was vir die
spesiasie patroon wat ons vandag in die Tragelaphini ras waarneem.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53659 |
| Date | 12 1900 |
| Creators | Willows-Munro, Sandi |
| Contributors | Matthee, C. A., 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 | Unknown |
| Type | Thesis |
| Format | 110 p. : ill. |
| Rights | Stellenbosch University |
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