Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The phenotype of an individual has often been used as the descriminating factor in distinguishing species. However, with the advent of more precise molecular techniques, the genotype of species is increasingly being used as the preferred method in taxonomic classifications. Many taxa have recently been demonstrated to be incongruent in terms of their genetic and morphological groupings, and this may due to the influence that the environment may have on the morphological and functional aspects of a species. Selective pressures often act upon the performance of a species within a particular habitat first, and then selection for the morphological characters that allow for optimal performance occurs. Should genetically disparate species inhabit a particular environment, convergence in morphologies and performance may evolve. Historically, lizard species descriptions were based primarily on external morphologies, and thus misclassfication of species may have occurred due to mistakenly grouping species with convergent morphologies together. In the current dissertation, the links between morphology, performance capacities, diet and behaviour is explored in comparison to the environment and genetic relationships of southern African lacertid lizards. The performance capacities and associated morphological traits were expected to be more closely linked with the environment, and not closely linked with genetic relationships. To investigate these expectations, a multidisciplinary approach was taken, and genetic, morphological and performance analyses were done and compared with dietary behavioural and environmental analyses. In the first chapter, the link between habitat openness and the lizard bauplans is investigated and the presence of convergent morphologies within this group of lizards is uncovered. These convergences are shown to have resulted in misclassification of two lacertid species, and taxonomic revisions within the family are discussed. The second chapter explores the link between performance and associated morphological traits, and the dietary composition of the members of the Nucras genus. The third chapter identifies the link between the predator escape strategies employed by the members of the Meroles genus, and their morphologies and performance capacities. The fourth chapter explores the intraspecific, inter-population differences in morphologies and investigates the link between the morphological groupings and the population genetic groupings within Pedioplanis lineoocellata. The final chapter identifies whether adaptation to a novel habitat can occur over a relatively short period of time, and the morphological traits, functional aspects, and population genetic structure is investigated in conjunction with environmental analyses of vegetation and substrate between the populations of Meroles knoxii. It was concluded that the morphological and functional aspects of the southern African lacertid lizards are more closely related to the environment, particularly the microhabitat structure, than to their genetic relationships, and that future work using this group of lizards should involve a multidisplinary approach as different selective pressures are playing a role in shaping the morphologies and performance capacities of these lizards, compared to those that are acting upon the genotypes of the lizards. / AFRIKAANSE OPSOMMING: Die fenotipe van 'n individu is dikwels gebruik as die diskriminerende faktor in kenmerkende spesies. Maar, met die ontwikkeling van meer akkurate molekulêre tegnieke, word die genotipe van spesies toenemend gebruik as die voorkeur-metode in taksonomiese klassifikasie. Die onversoenbaarheid van genetiese en morfologiese eienskappe kom voor in ‘n verskeidenheid taksa, dit kan wees as gevolg van die invloed wat die omgewing het op die morfologiese en funksionele aspekte van ‘n spesie. Selektiewe druk beїnvloed dikwels doeltreffende funktionaliteit van 'n spesie in 'n bepaalde habitat eerste, en gevolglik word morfologiese karakters wat voorsiening maak vir optimale funktionaliteit geselekteer. Indien geneties uiteenlopende spesies woon in 'n bepaalde omgewing, kan konvergensie in morfologie en soortgelyke werksverrigtinge ontwikkel. Histories, is akkedis spesiesbeskrywings hoofsaaklik gebaseer op eksterne morfologieë, en kan dus misklassifikasie tot gevolg hê wat kan lei tot foutiewe taksonomie van spesies met konvergente morfologieë. In die huidige verhandeling, is die verband tussen die morfologie, werksverrigtingsvermoë, dieët en gedrag ondersoek, in vergelyking met die omgewing en die genetiese verwantskappe van Suider-Afrikaanse sandakkedisse. Die werksverrigtingsvermoë en gepaardgaande morfologiese eienskappe word verwag om te meer verband te hou met die omgewing, en dus nie in noue verband te wees met die genetiese verwantskappe nie. Om hierdie verwagtinge te ondersoek, is 'n multi-dissiplinêre benadering geneem, en genetiese, morfologiese en werksverrigtingontledings is gedoen in vergelyking met dieët, gedrags-en omgewings-ontleding. In die eerste hoofstuk, is die skakel tussen die habitat openheid en die akkedis bauplans ondersoek en die teenwoordigheid van konvergente morfologieë binne hierdie groep akkedisse word ten toon gestel. Hierdie konvergensies het gelei tot foutiewe klassifikasie van twee sandspesies, en taksonomiese hersiening binne die gesin word bespreek. Die tweede hoofstuk ondersoek die verband tussen werksverrigting en gepaardgaande morfologiese eienskappe, en die samestelling van die dieët van die lede van die Nucras genus. Die derde hoofstuk identifiseer die verband tussen die roofdier ontsnapping strategieë, morfologieë en werksverrigtingsvermoë van die Meroles genus. Die vierde hoofstuk ondersoek die intraspesifieke, inter-bevolkingsverskille in morfologieë en ondersoek die verband tussen die morfologiese groepe en die bevolking genetiese groepe binne die Pedioplanis lineoocellata spesies kompleks. Die finale hoofstuk identifiseer hoe die aanpassings na 'n nuwe habitat kan plaasvind oor 'n relatief kort tydperk, en die morfologiese eienskappe, funksionele aspekte en die bevolking genetiese struktuur word ondersoek in vergelyking met die omgewingsanalise van plantegroei en substraat tussen die bevolkings van Meroles knoxii. Die gevolgtrekking is dat die morfologiese en funksionele aspekte van die Suider- Afrikaanse sandakkedisse nader verwant is aan die omgewing, veral die mikrohabitat struktuur, as aan hul genetiese verwantskappe. Toekomstige werk op hierdie groep akkedisse moet ‘n multidisiplinêre benadering behels siende dat verskillende selektiewe drukke 'n rol speel in die vorming van die morfologie en werksverrigtingsvermoë van hierdie akkedisse, in vergelyking met selektiewe drukke wat die genotipes van die akkedisse beinvloed.