The evolutionary history and taxonomy of the Kobus leche species complex of South-Central Africa in the context of palaeo-drainage dynamics

Cotterill, Fenton P. D. (2006-12)

Dissertation (PhD)--University of Stellenbosch, 2006.

Thesis

ENGLISH ABSTRACT: This multi-disciplinary study compiled taxonomic and biogeographical data to elucidate the extant diversity of lechwe antelopes (Kobus leche complex), and reconstruct their evolutionary history. Their diversification has been confined to wetlands across the south-central Africa plateaux. Lechwes are specialist grazers in water meadow floodplains; these stenotopic habitat requirements are invoked to explain why their evolution is atypical of terrestrial large mammals. Combined analyses of morphological (171 adult males), genetic (208 genotyped individuals) and palaeo-environmental datasets, revealed a recent (Middle Pleistocene) pulse of speciation in the K. leche complex. Multivariate morphometric analyses revealed the presence of five distinct groups that could be tied to the geography of the region. Furthermore, the genetic analyses supported the existence of at least four of these lineages, which show significant population separation at the level of the mtDNA control region. Most of the differences among populations were confined to frequency differences among populations and Bayesian analyses strongly suggest that the pattern obtained is the result of the retention of ancestral haplotypes with limited female geneflow among the extant populations. Evolution of the five lineages identified by the morphological and population genetic analyses were further investigated by making use of additional genetic data (mtDNA cyt b, SPTNB, SRY, Protamine 1, and b-Fibrinogen) and a subset of the samples. Topologies were largely unresolved due to the recent common ancestry of the lineages. Following the Evolutionary Species Concept, which was motivated by a philosophical review, five allopatric species could be recognized (anselli, kafuensis, leche, robertsi and smithemani). A model of drainage evolution compiled disparate facets of biological and geological evidence to detail interlinked histories of wetlands and their biota across the south-central Africa plateaux. This wetland archipelago is recognized as a distinct biogeographical unit in its own right - the Katanga-Chambeshi region. Evolutionary diversification of lechwes represents a dominant biogeographical signal reflecting how the aquatic biota have evolved in tandem with palaeo-drainage dynamics across this evolutionary theatre. Delimitation of key events in lechwe and drainage evolution was refined by archaeological dating of the Victoria Falls Formation, to decipher when the Zambezi river eroded the Batoka gorge. Demographic expansion in K. leche s.s (early Middle Pleistocene) corresponds to dessication of Palaeo-Lake Makakgadikgadi while more recent phylogeographic signals correspond to the tenure of Palaeo-Lake Bulozi. These speciation events in the Middle Pleistocene preceded peripatric speciation of K. kafuensis that accompanied the morphosis of the Kafue Flats (from palaeo-lake to floodplain), when the Kafue River attained its modern topology. The present study highlights that Lechwes represent a biota of evolutionary vibrant clades, rich in endemic species. As ecologically-dominant species in wetlands, lechwes deserve priority conservation attention, which is challenged to perpetuate evolutionary and ecological processes across an archipelago straddling five countries.

AFRIKAANSE OPSOMMING: Die multidisiplinêre studie bring saam taksonomiese en biogeografiese data om die evolusionêre geskiedenis en huidige diversitiet van basterwaterbokke (Kobus leche kompleks) te verklaar. Hulle diversifikasie is beperk to vleilande regoor die suid-sentraal Afrika plato. Basterwaterbokke is gespesialiseerde grasvreters in grasvloedvlaktes; hierdie stenotipiese habitatsvereiste word voorgehou om te verduidelik hoekom die evolusie van hierdie diere atipies is vir terrestriële groot soogdiere. Gekombineerde analise van morfologie (171 volwasse manlike diere), geneties (208 genotipes) en plaeo-omgewings datstelle toon aan dat daar ‘n onlangse (middel Pleistoseen) pols van spesiasie plaasgevind het in die K. lechwe kompleks. Multivariate morfometriese analyses het aangetoon dat vyf verskillende groepe diere bestaan wat ook sin gemaak het op grond van geografiese ligging. Verdermeer, die genetiese analise het die bestaan van ten minste vier van hierdie lyne geondersteun wat betekenisvolle bevolkings isolasie vertoon het op die vlak van die mtDNA kontrole gebied. Meeste van die verskille tussen bevolkings was beperk to frekwensieverkille tussen die bevolkings en Bayesian analise het sterk aanduidings getoon dat die patroon wat gekry is die gevolg was van die behoud van voorvaderlike haplotiepes met beperkte vroulike geenvloei tussen die huidige bevolkings. Evolusie van die vyf lyne wat deur die morfologie en bevolkingsgenetika studies geidentifiseer is was verder ondersoek deur gebruik te maak van addisionele genetiese data (mtDNA cytb, SPTBN, SRY, Protamien 1, en b-Fibrinogeen) en ‘n subset van die monsters. Topologieë was hoofsaaklik onopgelos as gevolg van die kort tyd tot die onlangse gemeenskaplike voorouer van lyne. Deur die Evolusionêre Spesies Konsep aan te hang, wat gemotiveer is deur ‘n filosofiese oorsig, is vyf allopatriese spesies herken (anselli, kafuensis, leche, robertsi and smithemani). ‘n Model wat dreinerings evolusie voorstel het verskeie fasette van biologiese en geologiese bewyse saamgvat om die verbindingsgeskiedenis van vleilande en hulle biota oor die suidsentraal Afrika plato te beskryf. Die vleiland argipelago word herken as ‘n onafhanklike biogeografiese eenheid in sy eie reg – die Katanga-Chambeshi streek. Evolusionêre diversifikasie van basterwaterbokke verteenwoordig ‘n dominante biogeografiese sein wat voortsel hoe die akwatiese biota ontwikkel het in tandem met die palaeo-dreinerings dinamika in hierdie evolusionêre konsert. Die afbakening van sleutelgebeure in basterwaterbok en dreinerigsevolusie is beter toegelig deur argeologiese datering wat gebasseer was op die vorming van die Victoria Valle om te bepaal waneer die Zambezi rivier die Batoka skeurgroef gevorm het. Demografiese uitbreiding binne K. leche s.s (gedurende die vroë Middel Pleistoseen) stem ooreen met die uitdroging van Palaeo-Meer Makakgadikgadi terwyl meer onlangse filogeografiese syne ooreenstem met die ontstaan van Palaeo-Meer Bulozi. Hierdie spesiasie gebeure in die Middel Pleistoseen het die peripatriese spesiasie van K. kafuensis voorafgegaan wat die morfose van die Kafue Vlaktes vergesel het (van palaeo-meer na vloedvlakte), toe die Kafue Rivier sy huidige vorm aangeneem het. Die huidige studie het uitgelig dat basterwaterbokke verteenwoordig ‘n biota van evolusionêre energieke eenhede, ryk aan endemiese spesies. As ‘n ekologiese dominante spesie in vleilande, moet basterwaterbokke as ‘n prioriteit gesien word in bewaring, waar dit dan die geleentheid sal hê om voort te bou op die evolusionêre en ekologiese prossese van die archipelago wat oor vyf lande strek.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/21773
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