Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Food demands for the ever-increasing human population is increasing the pressure on the agricultural sector to produce more food. In order to satisfy these demands, farmers are turning to chemical biocides for the control of pest species to produce greater crop yields. All pesticides must be toxic or poisonous to the target species they intend to control. Unfortunately, most pesticides are toxic or poisonous to non-target organisms as well, with detrimental effects on their health. Organic farming was developed to enhance the overall health of the farm's natural soilmicrobe- plant-animal biodiversity. No synthetic fertilisers and/or pesticides are used when farming organically. Life in the soil consists of intricate food webs and interactions between the soil dwelling invertebrates. The soil-organisms are divided into three main groups, viz., Micro-organisms (e.g. protozoa, bacteria and fungi) mesofauna (nematodes, Collembola and Acari) and macro-fauna (e.g. millipedes, isopods, insects, molluscs and earthworms). The invertebrates are very susceptible to chemical contamination by chemical biocides in natural and agro-ecosystems. The soil invertebrate communities are responsible for the decomposition of organic material in soil, thereby remineralising the soil. The decomposition processes start with comminution of the large pieces of organic material by meso- and macro-fauna and ends with the micro-fauna and microbial organisms that complete these processes by returning the nutrients in an inorganic form to the soil. The aim of this study was to investigate whether, and to what extent the soil organisms are influenced by different management practices viz., organic management practices versus conventional management practices. A vineyard on the farm Plaisir de Merle, in Simondium, Western Cape was used for the present study. One half of a one hectare vineyard was managed organically and the other half conventionally. Within each vineyard block six different treatments were performed. Three of the treatments were strictly organic and the other three were strictly conventional. Four replicates of each management treatment were performed. The bait-lamina technique was used to assess the feeding activity of the soil organisms exposed to the different management treatments. In addition to the bait-lamina trials in the vineyard itself, bait-lamina tests were performed in microcosm studies with soil from the organically and conventionally managed vineyard blocks under controlled conditions. In order to assess the impact of the various pesticides that are used in the vineyards in the conventional way, on the soil fauna, standard acute toxicity tests and behavioural tests were performed on Eisenia fetida, the compost worm. The bait-lamina tests in the vineyard revealed that the moisture content of the soil plays an important role in the biological activity of soil fauna. The different management treatments did affect the biological activity of the soil fauna, but seasonal changes also proved to be one of the important factors governing biological processes in the soil. The acute toxicity tests showed that the active ingredients (mancozeb, penconazole and trifloxystrobin) of three of the pesticides that were tested in this study, had negatively affected E. fetida at their recommended application concentrations. The remaining two pesticides' active ingredients (glyphosate and N-acetyl salicylic acid) did not affect the earthworms negatively at the recommended application concentrations. The preference behavioural trials showed that E. fetida could detect and avoid contaminated substrates at the LCso-concentrations of the different pesticides. All the earthworms were influenced positively in the preference behaviour experiments. Because of certain limitations of the bait-lamina technique, it was difficult to formulate conclusions on what happens in the soil. A possible explanation for the differences in feeding activity of soil fauna could be attributed to the migration of the soil fauna to more habitable soil horizons during the dry summer conditions, when most of the pesticides are applied. The ecological relevance of the acute toxicity tests conducted need to be investigated further. It is clear that the acute toxicity tests provided important information that should be considered, but care should be taken and the necessary safety factors be determined and considered when doing risk assessment studies. The results of the preference behaviour studies showed that for certain pesticides E. fetida can be a sensitive bioindicator of acute and/or sub-acute lethal toxicity testing but this might not necessarily be the case for other pesticides. The goal of doing laboratory studies is to gain as much information to make reliable extrapolations to field situations from laboratory data. Laboratory-to-field extrapolations are very complicated because of the physico-chemical composition of soil, the unpredictable way pesticides behave within soil and the reaction of soil organisms to the soil and to the chemical biocides that are used. Further studies need to be done in order to fully understand to what extent the soil fauna were affected by the different management practices applied to the vineyard at Plaisir de Merle. / AFRIKAANSE OPSOMMING: Voedsel aanvraag vir die toenemende menslike bevolking plaas groot druk op die landbou sektor om meer kos te produseer. Om aan die voedsel eise te voldoen, gebruik boere al meer chemiese biosiede om pesspesies te bestry. Alle pestisiede moet toksies of giftig wees vir die teiken organisme waarvoor dit bestem is. Ongelukkig is die meeste pestisiede ook toksies of giftig vir nie-teiken organismes, wat tot nadelige effekte op hul gesonheid kan lei. Organiese boerdery is ontwikkel om die algehele gesondheid van die plaas se natuurlike grond-mikrobe-plant-dier biodiversiteit te bevorder. Geen sintetiese bemestingstowwe en/of pestisiede mag gebruik word wanneer daar organies geboer word nie. Die lewe in die grond bestaan uit ingewikkelde voedselwebbe en interaksies tussen die grondlewende invertebrate. Die grond invertebrate word verdeel in drie hoof groepe, nl. mikro-organismes (bv. Protozoa, bakterieë en fungi) meso fauna (Nematoda, Collembole en Acari) en makrofauna (bv. Millipoda, Isopoda, Insecta, Mollusca en erdwurms). Die Invertebrata is die mees vatbaarste vir chemiese kontaminasie deur chemiese biosiedes in natuurlike en landbou ekosisteme. Die grond invertebraat gemeenskappe is verantwoordelik vir die afbreek van alle organiese materiaal in die grond en dus vir remineralisering van die grond. Die afbreekproses begin by die komminusie van groter stukke organiese materiaal deur die meso- en makrofauna en eindig met die mikrofauna en mikrobes wat die prosesse voltooi deur die nutriente terug te plaas in die vorm van anorganiese produkte in die grond. Die doel van hierdie studie was om te ondersoek of, en tot watter mate, grond organismes geraak word deur verskillende grondbestuurspraktyke, nl. Organiese grondbestuurspraktyke teenoor die konvensionele grondbestuurspraktyke. 'n Wingerd op die plaas Plaisir de Merle, in Simondium, Wes-Kaap, was gebruik vir die huidige studie. Een helfte van 'n een hektaar wingerd is organies bestuur en die ander helfte is op die konvensionele manier bestuur. Op elk van die twee wingerd blokke is ses verskillende behandelings toegepas. Drie van die behandelings was streng organies en die ander drie was streng konvensioneel van aard. Vier replikate van elke behandeling is toegepas op elk van die twee wingerdblokke. Die bait-lamina metode is gebruik om die voedingsaktiwiteit van die grond organismes te asses seer. As toevoeging tot die bait-lamina proewe in die wingerd self, is bait-lamina toetse ook in mikro-kosmosse in die laboratorium gedoen met grond afkomstig vanaf die twee wingerdblokke. Om die impak van die verskillende pestisiede op die grondorganismes te ondersoek, is standaard akute toksisteitstoestse en gedragstoetse uitgevoer met die komposerdwurm, Eisenia fetida. Die bait-lamina resultate in die wingerd het getoon dat die voginhoud van die grond die belangrikste rol speel wat die biologiese aktiwiteit van die grondorganismes beïnvloed. Die verskillende behandelings het die biologiese aktiwiteit van die grond fauna geaffekteer, maar seisoenale veranderings is ook uitgesonder as een van die bepalende faktore wat die biologiese prosesse in die grond stuur. Die akute toksisiteitstoetse het getoon dat die aktiewe bestandeie van drie van die pestisiede (mancozeb, penconazole en trifloxystrobin), E. fetida negatief beïnvloed het teen die aanbeveelde konsentrasies wat toegedien is. Die aktiewe bestandeie van die ander twee pestiede (glyphosate en N-asetiel sallisiel suur) het nie die erdwurms nadelig beïnvloed teen die aanbeveelde konsentrasies wat toegedien is nie. Die gedragsproewe het getoon dat E. fetida die LCso-konsentrasies van al die verskillende pestisiede kan waarneem en vermy. Al die erdwurms is positief beïnvloed in die gedragseksperimente met die verskillende pestisiede. Omdat die bait-laminametode sekere beperkings het, was dit moeilik om tot gevolgtrekkings te kom oor wat presies in die grond gebeur. 'n Moontlike verklaring vir die verskillende voedingsaktiwiteite van die grond fauna kan toegereken word aan die migrasie van die grondorganismes na meer leefbare grondhorisonne gedurende die droë somer toestande, wat toevallig met die spuit van die meeste pestisiede ooreenstem. Die ekologiese relevansie van die akute toksisiteitstoetse wat uitgevoer is, moet meer deeglik ondersoek word. Die belangrikheid van die akute toksisteitstoetse is duidelik en het waardevolle informasie gelewer, maar sorg moet geneem word, en die nodige veiligheids faktore moet bepaal word en in ag geneem word, wanneer riskobepalingstudies gedoen word. Die gedragsproewe het getoon dat vir sekere pestisiede E. fetida 'n sensitiewe bioindikator van akute en/of sub-akute letale toksisiteits toetse kan wees, maar nie noodwendig vir ander pestisiede nie. Die doel van laboratoriumstudies is om so veel as moontlik inligting te versamelom vertroubare ekstrapolasie te kan maak na situasies in die veld vanaf laboratorium data. Laboratorium-na-veld ekstrapolasies is dikwels baie gekompliseerd as gevolg van die fisies-chemiese samestelling van die grond, die onvoorspelbare manier waarop chemiese pestisiede met die grond reageer en die reaksie van die grondorganismes op chemiese biosiede in die grond. Verdere studies moet gedoen word om so deeglik maanlik die mate van die impak wat die verskillende bestuurspraktyke op die grond fauna het, te verstaan op Plaisir de Merle.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The geometric tortoise, Psammobates geometricus, found in the Western Cape, South Africa, is one of the world's rarest tortoises. At present, it is only known from five isolated geographical areas, one being the Worcester-Tulbagh Valley. The primary aims of my study were to determine the status of geometric tortoise subpopulations along the Nl highway in the Worcester Valley, to determine the population structure of these subpopulations and, if necessary, to provide recommendations for the mitigation ofNI highway-induced impacts on geometric tortoise subpopulations along the road. All Renosterveld remnants along the Nl between Du Toitskloof and Worcester were surveyed for the presence of geometric tortoises, and tortoise density and population structure were determined for each remnant that supports tortoises. Two geometric tortoise subpopulations on opposite sides of the Nl were identified. In the larger remnant of the two, females dominated both the subadult and adult classes, whereas in the other remnant male frequency was slightly higher than female frequency for the adult class only. In both remnants, adult females were significantly larger than adult males in mean carapace length. Mean body mass for adult females and males also differed significantly in both remnants. Analysis of habitat quality showed that both remnants supporting the geometric tortoise are seriously infested by encroaching indigenous and alien plants. The barrier effect of the Nl highway can be mitigated by constructing underpasses, linking the two remnants on opposite sides of the road. Furthermore, road mortality of tortoises can be avoided by erecting tortoise proof fencing along appropriate sections of the highway in the Worcester Valley. By linking the remnants, the largest single area available to the geometric tortoise in the Worcester Valley will also be formed. An additional aim of my study was to investigate the correspondence of geometric tortoise density in individual habitat remnants to the West-to-East change in vegetation composition/characteristics occurring along the Nl in the Worcester Valley. Vegetation composition/characteristics were thus determined in all remnants also surveyed for tortoises. The West-to-East change in vegetation composition/characteristics of the study area indicates that there is a transition from Renosterveld in the West to karroid veld in the East. / AFRIKAANSE OPSOMMING: Die geometriese skilpad, Psammobates geometrieus, wat in die Wes-Kaap, Suid- Afrika, voorkom, is een van die wêreld se skaarste skilpaaie. Vandag word hierdie skilpad net nog in vyf geïsoleerde geografiese streke gekry, een van hulle die Worcester-Tulbagh Vallei. Die primêre doel van my studie was om die status van geometriese skilpad subpopulasies langs die Nl snelweg in die Worcester Vallei te ondersoek en om die populasiestruktuur van hierdie subpopulasies te bepaal. Verder was die doelook, om aanbevelings te maak oor hoe die impakte van die pad op die geometriese skilpad subpopulasies langs die Nl verminder kan word. Al die Renosterveld oorblyfsels langs die Nl tussen Du Toitskloof en Worcester, en binne die bekende gebied van die geometriese skilpad, is deursoek vir geometriese skilpaaie. Populasiedigtheid en populasiestruktuur van die skilpaaie is bepaal vir elke oorblyfsel wat skilpaaie bevat. Twee geometriese skilpad subpopulasies is gekryaan teenoorgestelde kante van die Nl. In die groter oorblyfsel, het wyfies albei die onvolwasse en volwasse klasse gedomineer. In die ander oorblyfsel is gevind dat die frekwensie van mannetjies ietwat hoër was as die frekwensie van wyfies, maar vir slegs die volwasse kategorie. Binne albei oorblyfsels is gevind dat volwassse wyfies betekenisvol groter in gemiddelde doplengte is as volwasse mannetjies. Gemiddelde liggaamsgewig het ook betekenisvol verskil tussen volwasse wyfies en mannetjies in albei oorblyfsels. 'n Analise van habitatkwaliteit het gewys dat beide oorblyfsels wat die geometriese skilpad ondersteun grootliks ingeneem is deur inheemse indringers, sowel as uitheemse plante. Die versperrings effek van die Nl snelweg kan verminder word deur duikwege te skep wat die twee ooblyfsels, op teenoorgestelde kante van die pad, verbind. Bowendien, deur 'n ondeurdringbare heining langs passende dele van die snelweg in die Worcester Vallei op te rig, sal skilpadmortaliteit vermy word. Deur oorblyfsels te verbind, salook die grootste enkele area, beskibaar aan die geometriese skilpad in die Worcester Vallei, gevorm word. 'n Addisionele doel van hierdie studie was om veranderinge in vegetasie langs 'n wes-na-oos gradient binne die studie area te korreleer met die teenwoordigheid van skilpaaie langs hierdie gradient. Vegetasie samestelling/eienskappe is dus bepaal vir elke oorblyfsel wat deursoek is vir skilpaaie. Die wes-na-oos verandering in vegetasie samestelling/eienskappe binne die studie area wys dat daar 'n oorgang van Renosterveld in die weste na 'n karooagtige veld in die ooste is.

Thesis (MSc)--Stellenbosch University, 2013. / This study examined the biogeography and taxonomic status of the Cape legless skink, Acontias meleagris species complex using phylogenetic analyses, population genetics, demographic history aspects, time of lineage diversification estimation, environmental statistic analyses and a morphological evaluation. A total of 231 specimens from 55 localities were collected from the entire known distribution range of the A. meleagris complex throughout the Eastern, Northern and Western Cape, South Africa. Partial sequence data were collected from two mitochondrial DNA loci, 16S rRNA and cytochrome oxidase subunit one (COI), and one protein-coding nuclear DNA locus, exophilin 5 (EXPH 5). DNA sequences were analyzed for phylogenetic methods and biogeographical dating, while population genetic analyses were conducted on the COI sequences. Geographical boundaries amongst cryptic lineages were determined and evolutionary drivers of cladogenesis within the species complex were inferred. Marked genetic structure was observed within the A. meleagris complex, and five clades were retrieved, most of which were statistically well supported. These five clades were also evident within the haplotypic analyses and were characterized by demographic stability. Lineage diversification and the current biogeographical patterning observed for lineages within the A. meleagris species complex reflect the impact of sea level oscillations on historical coastal habitat availability. Additional historical evolutionary drivers within this subterranean species complex were inferred and discussed. The five clades within this species complex were considered discrete species, characterised by phylogenetic and biogeographic distinctiveness. While, morphological characters that could be used to identify the five species demonstrated widespread overlap for morphometric and meristic characters as well as colour pattering. Consequently, the phylogenetic species concept was employed for a taxonomical revision of A. meleagris sensu lato. Here, three of the previously recognised subspecies A. m. meleagris, A. m. orientalis and A. m. orientalis–'lineicauda' were elevated to full species, and two new species A. caurinus sp. nov. and A. parilis sp. nov. were described. / National Research Foundation (NRF)

Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In the present study, the systematic status, aspects of the evolutionary biology and phylogenetic relationships among species of the African freshwater crab genus Potamonautes in South Africa are examined. Systematic research between allopatric populations of P. brincki, using allozyme and morphometric data has revealed the existence of a new undescribed freshwater crab species occurring in mountain streams of the Cape Peninsula. This species is described in the present study. In addition, the diagnostic value of carapace dentition patterns in the taxonomy of freshwater crabs is explored among two toothed river crab species from South Africa. The latter study utilized P. warreni and P. unispinus where considerable variation in the dentition pattern of the former species has been recorded. Fixed differences in allozyme loci demonstrated that these two taxa should indeed be considered separate, yet closely related species, while the morphometric data failed to reveal this taxonomic separation. The holotype of P. warreni is re-described. The relationship of hybrid taxa between P. depressus and P. clarus populations are investigated. Evident from this study is that populations that occur equidistant from the two parental taxa have undergone extensive introgressive hybridization. Considering the pronounced sequence divergence and the occurrence of fixed allozyme loci between populations, it is postulated that the hybrid populations should be considered to be on a unique evolutionary trajectory worthy of conservation. The population genetic structure of P. calcaratus is examined as this species is unique in its occupation of water holes. Results demonstrate that the genetic population structure is the result of recent colonization and moderate gene flow among populations. Phylogenetic relationships between the southern African freshwater crab fauna is investigated with the use of sequence data from two mitochondial genes (12 S rRNA and 16 S rRNA), allozymes and morphology in an attempt to firstly, test the usefulness of freshwater crabs as biogeographic indicators, secondly to explore the relationship among hybrid taxa, and thirdly to examine Bott's (1955) subgeneric divisions. Results demonstrated that freshwater crabs can be used as biogeographic indicators, that hybrid taxa are phylogenetic ally closely related and that Bott's subgeneric divisions have no systematic basis. Among the three data sets, the sequence data provided the best resolution, while the phylogenetic inferences derived from the allozyme data and the morphology was limited. / AFRIKAANSE OPSOMMING: In hierdie studie word die sistematiek, aspekte van die evolusionêre biologie en filogenetiese verwantskappe tussen spesies van die varswater krap genus Potamonautes ondersoek in Suid Afrika. Navorsing op geografies geisoleerde populasies van P. brincki word met behulp van allosieme en morfometriese data ondersoek en dui daarop dat daar 'n nuwe onbeskryfde spesie op die berge van die Kaapse Skiereiland voorkom. Die nuwe spesies word beskryf in hierdie studie. Die diagnostiese waarde van tand patrone in varswater krappe word tussen twee spesies P. warreni en P. unispinus ondersoek. Genetiese data dui daarop dat alhoewel P. warreni morfologies baie naverwant is aan P. unispin us, is genoegsame verskille in allosiem lokusse wat daarop dui dat die twee taksa volwaardige spesies is. Die holotipe van P. warreni word herbeskryf. Die verwantkap tussen populasies van twee hibried taksa, P. depressus en P. clarus, word ondersoek. Resultate van hierdie studie dui daarop dat noemenswaardige verskille voorkom tussen die twee hibridie taxa en dat die hibriede populasies geneties verskillend is. 'n Argument word aangevoer vir die beskerming van hibriede taksa. Die populasie genetika van P. calcaratus word ondersoek en vergelyk met vorige studies. Die data dui daarop dat minimale geen vloei tusses populasies is en dat die populasie struktuur waarskynlik die resultaat is van onlangse kolonisasie. Die filogenetiese verwantskap tussen die suider Afrikaanse krappe word ondersoek met DNA, allosieme en morfologiese karakters met drie hoofdoele. Eerstens om die gebruik van varswater krappe as biografiese indikatore te toets. Tweedens om die verwantskap van hibriede taksa te ondersoek, en derdens om die status van Bott (1955) se subgenera te bepaal. Resultate dui daarop aan dat varswater krappe wel gebruik kan word as biografiese indikatore. Hibridieserende taxa naverwant is derdens en dat Bott se subgenera geen taksonomiese basis het nie. Die DNA data het die beste resolusie gebied vir die filogenetiese vrae, terwyl die allosieme en morfologiese data 'n laer resolusie bedied het, en meer beperk was.

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The use of organophosphate pesticides is still an integral part of commercial farming activities and these substances have been implicated as a major source of environmental contamination in South Africa. Evidence exists that many non target animals in and around agricultural areas are at risk of being affected due to the mobile nature of pesticides and the intermittent nature of pesticide application. The extent to which non-target animals are affected by exposure to two organophosphates (azinphos-methyl and chlorpyrifos) was investigated through monitoring selected biomarker responses and life cycle effects under laboratory conditions in two selected test species. A representative species from both the aquatic and terrestrial environment was used as these two compartments of the environment are inevitably linked due to the mobility of pesticides from the area of application to surrounding areas. The earthworm Eisenia fetida was used as test organism in the terrestrial environment while the fish Oreochromis mossambicus served as representative of the aquatic environment. Juvenile life stages of both species were subjected to standard acute toxicity tests which showed that for both species, juvenile life stages were more sensitive to both pesticides than adults. It was also illustrated that azinphos-methyl is more toxic than chlorpyrifos to both species. Both test species were also subjected to an intermittent exposure regime in order to assess the effects of repeated pesticide application on biomarker, life-cycle and behaviour responses. The results indicated that for similar exposure regimes, azinphos-methyl was more toxic to E. fetida than chlorpyrifos and detrimentally affected all endpoints investigated. The present study suggests that exposure concentration may have a more pronounced effect in inducing a toxic response than exposure interval, irrespective of the pesticide used. In addition to this, E. fetida was unable to avoid the presence of these pesticides in soil, even at concentrations as high as 50% of the LC50 value, indicating that the presence of pesticides in the soil pose a realistic threat to earthworms and other soil dwelling organisms. Biomarker responses, morphological effects and feeding behaviour was assessed for O. mossambicus and similar to the terrestrial toxicity experiments, there was evidence to suggest that in the case of an intermittent exposure scenario, azinphos-methyl was more hazardous than chlorpyrifos to this species. For the majority of endpoints that were investigated, it appeared that exposure interval played a more important role in inducing an effect than exposure concentration. At a shorter exposure interval, the majority of endpoints showed no difference between higher and lower exposure concentrations, while at a longer exposure interval the effects of exposure concentration became evident. In addition, feeding behaviour was affected by pesticide exposure in a dose-dependent manner. The present study yielded important results that improve the understanding of biological impacts of pesticide pollution on the environment. This can aid in optimising farming practices such as pesticide application not only in terms of eradicating the pest organisms, but also in terms of mitigating the environmental effects associated with large-scale pesticide use, thereby ensuring sustained biodiversity in these areas. / AFRIKAANSE OPSOMMING: Die gebruik van organofosfaat plaagdoders is ‘n integrale deel van kommersiële landbou aktiwiteite maar hierdie middels is ook ‘n prominente bron van omgewingsbesoedeling in Suid-Afrika. Daar is bewys dat verskeie nie-teiken diere in en om landbouareas geaffekteer word weens die nie-statiese aard van plaagdoders in die omgewing, sowel as die herhalende aard van plaagdodertoediening. Die graad waartoe nie-teiken diere geaffekteer word deur die plaagdoders azinphos-metiel en chlorpyrifos is ondersoek deur die monitering van verskeie biomerkerresponse en lewenssiklus-effekte in geselekteerde toetsspesies binne ‘n beheerde laboratoriumomgewing. ‘n Verteenwoordigende spesie van beide die akwatiese en die terrestriële omgewing is gebruik aangesien hierdie twee dele van die omgewing onlosmaaklik verbind is weens die beweging van plaagdoders vanaf die area van toediening na omringende areas. Die erdwurm Eisenia fetida is gekies as toetsorganisme vir die terrestriële omgewing en die varswatervis Oreochromis mossambicus het gedien as verteenwoordigende spesie vir die akwatiese omgewing. Onvolwasse diere van beide spesies is onderwerp aan standaard akute toksisiteitstoetse en daar is gevind dat, vir beide spesies, onvolwasse diere meer sensitief vir die betrokke plaagdoders is as volwasse diere. Dit is ook gevind dat azinphosmetiel giftiger is as chlorpyrifos vir beide spesies. Beide toetsspesies is ook onderwerp aan ‘n chroniese blootstellingsregime om die effek van herhaalde plaagdodertoediening op biomerker-, lewenssiklus- en gedragsresponse te ondersoek. Die resultate van die herhaalde blootstelling het aangedui dat vir soortgelyke blootstellingsregimes, azinphos-metiel giftiger is as chlorpyrifos vir E. fetida en dat beide middels alle eindpunte wat ondersoek is, nadelig affekteer. Die huidige studie toon ook bewyse dat blootstellingskonsentrasie ‘n meer prominente effek as blootstellingsinterval kan hê in die teweegbringing van ‘n toksiese respons. Verder was E. fetida nie in staat om die teenwoordigheid van die plaagdoders in grond te vermy nie, self nie by konsentrasies so hoog as 50% van die LC50 waarde nie. Laasgenoemde resultaat dui dus aan dat die aanwesigheid van plaagdoders in die grondomgewing ‘n realisitese bedreiging inhou vir erdwurms en ander grondorganismes. Soortgelyk aan die terrestriële toksisiteitseksperimente, was daar getuienis vir die verhoogde toksisiteit van azinphos-metiel relatief tot chlorpyrifos vir O. mossambicus. Dit blyk dat blootstellingsinterval ‘n meer prominente rol as blootstellingskonsentrasie speel in die teweegbringing van effekte vir die meerderheid van die eindpunte wat ondersoek is. In die geval van ‘n korter blootstellingsinterval het die meerderheid van eindpunte wat ondersoek is geen verskille getoon tussen ‘n hoër en ‘n laer konsentrasie nie, terwyl met ‘n langer blootstellingsinterval daar ‘n aanduiding was dat blootstellingskonsentrasie ‘n meer prominente rol gespeel het. Verder is gevind dat voedingsgedrag in O. mossambicus geaffekteer is op ‘n konsentrasie verwante manier. Die huidige studie toon resultate wat ‘n belangrike bydrae kan lewer tot die begrip van die biologiese impakte van organofosfaat plaagdoders op die omgewing. Die resultate kan gebruik word vir die optimisering van boerderypraktyke soos plaagdodertoediening, sodat laasgenoemde effektief is vir die beheer van pes-organismes, maar ook die impakte van grootskaalse plaagdodertoediening kan minimaliseer en sodoende die biodiversiteit binne hierdie areas sal beskerm.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The terrestrial Oligochaete species Eisenia andrei and Enchytraeus doerjesi were exposed to different concentration series of Cd and Zn, both separately and in mixtures for 28 days in artificial OECD soil at 15, 20 and 25°C. At the end of the four week exposure period, survival and reproduction were assessed in E. doerjesi and survival, reproduction, biomass change, metal uptake and biomarker responses (MTT and comet assays) in E. andrei. Survival results for both E. andrei and E. doerjesi indicated that the lethality of Cd increased at higher temperatures, whereas the opposite was observed for Zn.Cadmium LC50 values were the highest at 15°C and the lowest at 25°C. In the Zn exposures LC50 increased with increasing temperature. Mixture results in both test organisms indicated that mixtures were less lethal than the metals separately. Effects of mixtures on survival, nonetheless, increased with increasing temperature. In the Cd experiment, reproduction in E. andrei was only recorded in the control treatments at the three temperatures investigated. However, the deleterious effect of Zn on the reproduction of both E. andrei and E. doerjesi decreased with increasing temperature and Zn EC50 for reproduction increased with increasing temperature. Results for exposures to mixtures indicated in both test organisms that the interaction between Cd and Zn were antagonistic. In both E. andrei and E. doerjesi, the effect of mixture exposures on reproduction decreased with increasing temperatures. The highest mixture EC50 values for reproduction were found at higher temperature. In E. doerjesi (using reproduction results in MixToxModules) Cd and Zn interactions were dose level dependent at the three temperatures investigated. Antagonism was the predominant interaction at lower mixture concentrations whereas synergism occurred at mixture concentrations equal to or higher than the mixtures’ EC50 values. Biomass loss increased with increasing temperature in the Cd exposures (p 9 0.05) but not in the Zn exposures in E. andrei. In this species mixture results indicated antagonistic interactions between Cd and Zn at all temperatures investigated. The deleterious effect of mixtures on the biomass of E. andrei increased with increasing temperature. When Cd and Zn interactions were further investigated in E. andrei (using biomass results in MixToxModules) it was found that they were dose level dependent at the three temperatures investigated. Antagonism was the predominant interaction at lower mixture concentrations whereas synergism occurred at mixture concentrations higher than the mixtures EC50 values. The assessment of metal uptake in E. andrei revealed a temperature dependent Cd uptake with higher Cd body burdens occurring at higher exposure concentrations and temperatures (p ≤ 0.05). In the case of Zn, although uptake was lower at higher temperature, there was no statistical difference in uptake between exposure concentrations and between temperatures. Mixture results however indicated that in mixture exposures less Cd was accumulated by E. andrei than in single Cd exposures (p ≤ 0.05). Inversely, in mixture exposures more Zn was accumulated by E. andrei than in single Zn exposures (p ≤ 0.05). Biomarker studies revealed that Cd and Zn were both cytotoxic and genotoxic whether in single or mixture exposures. Factorial ANOVA analyses of the effects of temperature and metals on the reduction of MTT by E. andrei indicated that temperature rather than the metals was the most important factor controlling mitochondrial activity (p < 0.001). In both Cd and Zn exposures significant deleterious metal effects on mitochondrial processes were found to increase with temperature (p ≤ 0.01). Mixture exposures indicated decreasing cytotoxicity with increasing temperature (p ≤ 0.05) and possible antagonism between Cd and Zn at cellular level. Results of the comet assay showed that the genotoxic profile of Cd was the opposite of the genotoxic profile of Zn. Cd was less genotoxic at lower temperature and increasingly deleterious at higher temperature while Zn was more genotoxic at lower than higher temperature (p ≤ 0.05). The results of mixture exposures indicated decreasing mixture genotoxicity with increasing temperature and suggested that the interactions between Cd and Zn at molecular level were probably antagonistic. / AFRIKAANSE OPSOMMING: Eisenia andrei en Enchytraeus doerjesi is aan verskillende konsentrasiereekse van Cd en Zn, afsonderlik en in mengsels, vir 28 dae in OECD kunsmatige grond onderskeidelik by 15, 20 en 25°C blootgestel Die volgende eindpunte is aan die einde van die vier weke blootstellingsperiode gemeet: oorlewing en voortplanting (by E. doerjesi) en oorlewing, voortplanting, biomassaverandering, metaalopname, MTT en komeettoetse (by E. andrei). Oorlewingsresultate by beide E. andrei en E. doerjesi het getoon dat toenemende temperatuur die letale toksisiteit van Cd laat toeneem terwyl die teenoorgestelde waar was vir Zn. By die Cd blootstellings was die LK50 waardes die hoogste by 15°C en die laagste by 25°C. By die blootstellings aan Zn het die LK50 waardes toegeneem by hoër temperatuur. Resultate by die mengsels by beide toestspesies het aangetoon dat die mengsels minder letaal was as die afsonderlike metale. Effekte van mengsels op oorlewing het nietemin toegeneem met toenemende temperatuur. By die Cd blootstellings is voortplanting slegs by die kontroles en in die geval van E. andrei by die drie onderskeie temperature ondersoek. Die nadelige uitwerking van Zn op voortplanting by beide E. andrei en E. doerjesi het afgeneem met stygende temperatuur en die Zn LK50 vir voortplanting het toegeneem met toenemende temperatuur. Resultate van die blootstellings aan mengsels het getoon dat die wisselwerking tussen Cd en Zn by beide spesies antagonisties was. By beide spesies het die invloed van die mengsels op voortplanting afgeneem met stygende temperatuur. Die hoogste mengsel LK50 waardes vir voortplanting is by hoër temperature gevind. By E. doerjesi was Cd en Zn wisselwerkings by blootstelling aan mengsels (voortplantingsresultate ondersoek deur van MixToxModules gebruik te maak) dosisvlak verwant by die drie temperature wat ondersoek is. Antagonisme was die oorwegende wisselwerking by laer mengsel konsentrasies terwyl sinergisme voorgekom het by mengsel konsentrasies gelyk aan of hoër as die LK50 waardes van die mengsels. In die geval van die Cd blootstellings by E. andrei het biomassaverlies toegeneem met toenemende temperatuur (p ≤ 0.05) maar nie by die Zn blootstellings nie. Resultate van blootstellings aan mengsels het getoon dat die uitwerking van mengsels op die biomassa van E. fetida toegeneem het met toenemende temperatuur. By die verdere ondersoek van Cd en Zn wisselwerkings, waar gekyk is na dosis verhouding of dosisvlak antagonisme (deur van biomassa resultate in MixToxModules gebruik te maak), is gevind dat Cd en Zn wisselwerkings dosisvlak afhanklik was by die drie temperature wat ondersoek is. Antagonisme was die oorwegende wisselwerking by laer mengselkonsentrasies terwyl sinergisme voorgekom het by mengselkonsentrasies hoër as die mengsel EK50 konsentrasies. Die bepaling van metaalopname deur E. andrei het ’n temperatuurafhanklike opname van Cd getoon met hoër Cd liggaamskonsentrasies by hoër blootstellingskonsentrasies en temperature (p ≤ 0.05). Alhoewel Zn opname laer was by hoër temperatuur was daar geen statisties betekenisvolle verskille in opname tussen blootstellingskonsentrasies of temperature nie. Die bepaling van metaalopname by wurms wat aan mengsels blootgestel is, het getoon dat minder Cd deur E. andrei opgeneem is as waneer die wurms aan Cd as enkelmetaal blootgestel is (p ≤ 0.05), Daarteenoor het die teenoorgestelde gebeur in die geval van Zn, Meer van die metaal is opgeneem wanneer E. andrei aan mengsels blootgestel is as aan die enkelmetaal. Biomerkerstudie het getoon dat Cd en Zn beide sito- en genotoksies kan wees ongeag of dit as enkelmetale of in mengsels toegedien is. Faktoriale ANOVA analises van die effekte van temperatuur en metale op die verlaging van MTT by E. andrei het getoon dat temperatuur ’n belangriker faktor was as metaalbesoedeling by die kontrole van mitochondriale aktiwiteit. (p ≤ 0.001). By beide Cd en Zn blootstellings was daar in elk geval statisties betekenisvolle metaaleffekte op mitochondriale prosesse met toename in temperatuur (P ≤ 0.01). By blootstellings aan mengsels is gevind dat sitotoksisiteit afgeneem het met toenemende temperatuur (p ≤ 0.05) asook ’n moontlike antagonisme tussen Cd en Zn op sellulêre vlak. Resultate van die komeettoets het getoon dat die genotoksiese profiel van Cd die teenoorgestelde was as die van Zn. Cd was minder genotoksies by laer temperature en meer en meer skadelik by hoër temperature terwyl Zn meer genotoksies was by laer as by hoër temperature (p ≤ 0.05). Die resultate van blootstlling aan mengsels het laer genotoksisiteit getoon met toename in temperatuur. Dit dui daarop dat wisselwerkings tussen Cd en Zn op molekulêre vlak moontlik antagonisties was.

Thesis (PhD)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: Climate change and biological invasions are major threats to biodiversity. In particular, these threats are predicted to influence terrestrial systems in the sub-Antarctic, where significant ecosystem responses to both have already been seen. In this thesis, the sub-Antarctic Prince Edward Island group is used as a model system in which to investigate key questions relating to climate change and invasive species impacts. The island group comprises two islands, Marion (MI) and Prince Edward (PEI), both of which are experiencing rapid warming, yet have different invasive assemblages and in consequence are experiencing different impacts. Variation in the patterns of invasive species richness and abundance and their underlying causes are matters of considerable ecological and conservation significance. While an increase in thermal energy availability typically results in an increase in species richness, the mechanisms underlying these patterns are poorly understood. In Chapter 2 of this thesis, these relationships are explored for springtails, an important component of the soil fauna on Marion Island. Energy explains a large amount of the spatial variation in indigenous and invasive springtail species richness. Disturbance thresholds and stressful temperatures are more important than increased population sizes in determining this variation in species richness. As both indigenous and invasive springtail species richness and abundance are strongly related to temperature, a warming climate could have far-reaching consequences for these organisms. In particular, invasive species are predicted to be at an advantage relative to indigenous species under warming conditions. One species where this seems especially likely, given its physiological responses to experimental warming and drying, is the large invasive tomocerid, Pogonognathellus flavescens. Determining whether this will be the case depends on understanding the factors underlying its range limits and abundance structure. Moreover, few studies have sought to distinguish the causal basis of abundance structure and range limits, particularly for invasive species. Thus, in Chapter 3, local microclimate variables and physiological tolerances of the invasive springtail, P. flavescens (a habitat generalist), are examined. The results suggest that the species should be widely distributed across a range of habitats on MI. However, the springtail is restricted to indigenous Poa cookii tussock grassland habitats in the southeast. The current range limits are set by dispersal limitation (i.e. contingent absences) whilst abundance structure is a function of variation in soil substrate quality. However, over time, the widening distribution of P. cookii, as a consequence of a major management intervention (the eradication of feral cats), may enable P. flavescens to colonise all suitable areas. In Chapter 4, the focus changes to what has been considered the third major response to climate change, along with range and phenological responses - changing animal body sizes. Body size is one of the most significant and obvious features of animals and is of considerable ecological and physiological importance. A prediction of the temperature-size rule (TSR) is that with warming, body size of the weevil species on both MI and PEI should decline. However, predation by mice of the weevils on MI should fundamentally affect the pattern of such change, causing it to differ from neighbouring PEI, indicating synergistic impacts between climate change and invasions. Analysis of a 24-year data set indicates a decline in the body size of all weevil species on PEI with increasing temperature. However, on MI, a negative relationship between mean annual temperature and body size is found only for Palirhoeus eatoni, a species not eaten by mice. A possible explanation for the positive relationships found for the other species could be due to higher metabolic demands imposed on mice in colder years than in warmer ones. Any increase in predation coupled with a preference for larger sizes, which the mice clearly show, would lead to a decline in the mean size of the weevil species. Due to the relationship between body size and metabolic rate and the importance of the weevils in the islands’ food webs, changes to the body size of these organisms could have significant consequences for the island ecosystems’ functioning. The thermal environment experienced by organisms also has a direct effect on survival, growth and reproduction. The physiological response of organisms to rapidly changing climates is therefore a primary concern. Organisms may respond to variable environmental conditions through phenotypic plasticity as well as behaviour. Chapter 5 of this thesis shows that of the weevil species and populations investigated on MI, most display phenotypic plasticity, the form of which is in keeping with the ‘Hotter is Better’ hypothesis. This could be due to rare extreme temperature events and the advantage for the performance curves to incorporate high temperatures experienced in the environment. Mismatches between thermal optima and preferred temperatures displayed by all species could mean that these weevils are well equipped to cope with warming conditions on MI unless the prediction of an increase of rare extreme events such as extreme temperatures is realised. Rapidly changing climates and an increase in the introduction of non-indigenous species are issues of major conservation concern. This has increased the significance of studies on the impacts of these threats. However, this thesis shows that to understand such processes, it is essential that an integration of disciplines be undertaken. This thesis thus adopts a multidisciplinary approach and highlights key issues associated with both climate change and biological invasions. The patterns and predictions of species and community responses to these environmental changes are complex. Moreover, predicting such responses is likely to be problematic, especially as multiple factors will change concurrently and how these factors might change is unclear. This highlights the importance of long-term records for understanding organism responses to such changes. Furthermore, impacts on indigenous species are likely to be exacerbated by the predicted increase in the rate of introductions with climate change. This makes the case for preventing the dispersal of invasive species to new areas all the more important. / AFRIKAANSE OPSOMMING: Klimaatsverandering en indringer spesies is belangrike bedreigings vir biodiversiteit. In besonder word voorspel dat hierdie bedreigings terrestriële sisteme in die sub-Antarktiese sal beïnvloed, waar beduidende ekosisteem reaksie aan beide reeds gesien is. In hierdie tesis word die sub-Antarktiese Prince Edward eiland groep as a model sisteem gebruik om belangrike vrae met betrekking tot klimaatsverandering en die impak van indringer spesies te ondersoek. Die eiland groep bestaan uit twee eilande, Marion (ME) en Prince Edward (PEE), wat beide versnellende verwarming ervaar, maar tog verskillende indringer samestellings het en vervolgens verskillende impakte ervaar. Variasie in die patrone van indringerspesierykheid en vollopheid en hulle onderliggende oorsake is van aansienlike omgewings en bewarings betekenis. Terwyl 'n toename in die beskikbaarheid van energie tipies lei tot 'n toename in spesierykheid, word die onderliggend meganismes van hierdie patrone swak verstaan. In Hoofstuk 2 van hierdie tesis, word hierdie verhoudings vir springsterte ondersoek, 'n belangrike komponent van die grond fauna op ME. Energie verduidelik 'n groot hoeveelheid van die ruimtelike variasie in inheemse en indringende springstert spesierykheid. Versteuringsdrempels en stressvolle temperature is meer belangrik as die toename in bevolking groottes in die bepaling van hierdie variasie in spesierykheid. Aangesien beide inheemse en indringende springstert spesierykheid en vollopheid sterk verwant is aan temperatuur, kan 'n verwarmende klimaat verreikende gevolge vir hierdie organismes hê. In die besonder word voorspel dat indringerspesies bevoordeeld sal wees relatief tot inheemse spesies onder verwarmende toestande. Een spesie waar dit veral blyk om geneig te wees, gegewe sy fisiologiese reaksie tot eksperimentele verhitting en uitdroging, is die groot indringer tomocerid, Pogonognathellus flavescens. Om te bepaal of dit die geval sal wees, hang af van die begrip van die onderliggende faktore van sy voorkomsgrense en vollopheidstruktuur. Daarbenewens is daar min studies wat gepoog het om te onderskei tussen die veroorsakende basis van vollopheidstruktuur en voorkomsgrense, veral vir indringerspesies. Dus, in Hoofstuk 3, word plaaslike mikroklimaat veranderlikes en fisiologiese toleransies van die indringer springstert, P. flavescens ('n habitat generalis), ondersoek. Die resultate stel voor dat die spesie wyd verspreid moet wees oor 'n verskeidenheid van habitatte op ME. Maar, die springstert is beperk tot inheemse Poa cookii polle grasveldhabitatte in die suidooste. Die huidige voorkomsgrense word daar gestel deur verspreidingsbeperking (dws voorwaardelike afwesighede), terwyl vollopheidstruktuur 'n funksie is van die variasie in die grond substraat kwaliteit. Maar, die uitbreidende verspreiding van P. cookii as gevolg van 'n groot bestuursingryping (die uitwissing van wilde huiskatte), kan P. flavescens in staat stel om alle geskikte gebiede te koloniseer met verloop van tyd. In Hoofstuk 4 verander die fokus na wat as die derde groot reaksie op klimaatsverandering beskou word, saam met voorkoms en fenologiese reaksies - veranderende diere liggaamsgroottes. Liggaamsgrootte is een van die beduidendste en mees voor die hand liggende eienskappe van diere en is van aansienlike ekologiese en fisiologiese belang. 'n Voorspelling van die temperatuur-grootte-reël (TGR) is dat met verwarming, liggaamsgrootte van die snuitkewerspesies op beide ME en PEE sal afneem. Hoe ookal, predasie deur muise van die snuitkewers op ME moet fundamenteel die patroon van sodanige verandering op PEE beïnvloed, wat sinergistiese impakte tussen klimaatsverandering en indringings aandui. Die ontleding van 'n 24-jarige datastel dui aan op 'n afname in die liggaamsgrootte van alle snuitkewer spesies op PEI met ‘n toename in temperatuur. Maar, op ME is 'n negatiewe verhouding tussen die gemiddelde jaarlikse temperatuur en liggaamsgrootte net gevind vir Palirhoeus eatoni, 'n spesie wat nie deur die muise geëet word nie. 'n Moontlike verduideliking vir hierdie positiewe verhoudings wat gevind is vir die ander spesies kan wees as gevolg van hoër metaboliese eise op die muise in kouer jare as in warmer jare. Enige toename in predasie, tesame met 'n voorkeur vir groter mates, wat die muise duidelik wys, sou lei tot 'n afname in die gemiddelde grootte van die snuitkewer spesies. As gevolg van die verhouding tussen liggaamsgrootte en metaboliese tempo, sowel as die belangrikheid van die snuitkewers in die eilande se voedselwebbe, kan veranderinge in die liggaamsgrootte van hierdie organismes beduidende gevolge op die eiland ekosisteme se funksionering hê. Die termiese omgewing wat deur organismes ervaar word het ook 'n direkte invloed op oorlewing, groei en voortplanting. Die fisiologiese reaksie van organismes op vinnig veranderende klimate is dus 'n primêre bron van kommer. Organismes kan reageer op veranderlike omgewingstoestande deur fenotipiese plastisiteit sowel as gedrag. Hoofstuk 5 van hierdie tesis toon dat van die snuitkewerspesies en bevolkings wat ondersoek is op ME, die meeste fenotipiese plastisiteit vertoon, die vorm wat in ooreenstemming is met die ‘Warmer is Beter’ hipotese. Dit kan wees as gevolg van seldsame uiterste temperatuur gebeure en die voordeel vir die prestasie kurwes om hoë temperature wat ervaar word in die omgewing in te sluit. Mismatches tussen termiese optima en voorkeur temperature vertoon deur alle spesies kan beteken dat hierdie snuitkewers goed toegerus is om die verhitting op ME te hanteer, tensy die voorspelling van 'n toename van seldsame uiterste gebeure soos uiterste temperature gerealiseer word. Vinnig veranderende klimate en 'n toename in die bekendstelling van nie-inheemse spesies is kwessies van groot bewarings kommer. Dit het die betekenis van studies oor die impak van hierdie bedreigings verhoog. Hierdie tesis toon egter dat om sulke prosesse te verstaan, dit noodsaaklik is dat 'n integrasie van die dissiplines onderneem word. Hierdie tesis aanvaar dus 'n multi-dissiplinêre benadering en beklemtoon die belangrike kwessies wat verband hou met beide klimaatverandering en biologiese indringing. Die patrone en voorspellings van spesies en die gemeenskapsreaksies op hierdie omgewingsveranderinge is kompleks. Verder, die voorspelling van sodanige reaksies sal waarskynlik problematies wees, veral omdat verskeie faktore gelyktydig sal verander en hoe hierdie faktore kan verander is onduidelik. Dit beklemtoon die belangrikheid van lang termyn rekords vir die begrip van organisme reaksies op sulke veranderinge. Verder, die impak van inheemse spesies is geneig om te vererger deur die voorspelde toename in die tempo van bekendstellings met klimaatsverandering. Dit maak die taak vir die bestuur van die voorkoming dat indringerspesies nuwe gebiede bereik al hoe meer belangrik.

Dissertation (PhD)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The taxonomic status of southern Africa’s rupicolous crag lizards (genus Pseudocordylus) was investigated. As considerable confusion exists in the literature regarding the type specimens and type localities of the various taxa, resolution of these problems were considered the starting point of the study. Examination of museum specimens allowed for the designation of lectotypes, alloparalectotypes and/or paralectotypes. Of particular relevance to this study was the rediscovery of Andrew Smith’s type specimens of P. m. melanotus and P. m. subviridis. Restriction of the type locality of P. m. subviridis, based on entries in Smith’s diary and journal, allowed for the confirmation of previous interpretations and definitions of the two taxa. The geographical distribution of the various taxa and populations was determined using an extensive locality database. Two kinds of molecular markers, namely allozymes and mitochondrial DNA, were used in an attempt to resolve taxon boundaries within the P. melanotus species complex. The allozyme analysis indicated that P. m. melanotus might be polyphyletic and comprised of two unrelated lineages. Furthermore, fixed allelic differences between parapatric populations of P. m. melanotus and P. m. subviridis, and between sympatric populations of P. m. subviridis and P. langi, suggested that all three forms might be considered full species, with the possibility of more cryptic species present in the complex. Pseudocordylus transvaalensis differed from most other populations by 1-3 fixed allelic differences, but was indistinguishable from the Nkandhla district (central KwaZulu-Natal) population of P. m. melanotus. There were no heterozygous individuals in a sample from Monontsha Pass (Qwa-Qwa), a population reportedly comprising P. m. melanotus and P. m. subviridis, as well as intermediates, and all specimens were assignable to P. m. subviridis. The allozyme study was, however, based on phenetic principles and for further taxonomic resolution a cladistic approach was required. An mtDNA analysis (16S rRNA gene) using Maximum Parsimony, Maximum Likelihood and Bayesian analyses was therefore conducted to determine phylogenetic relationships among species and subspecies and to re-assess the taxonomic status of forms in the P. melanotus species complex. The mtDNA analysis corroborated most of the results obtained in the allozyme analysis. Firstly, P. langi was again found to be basal. With the addition of P. microlepidotus and P. spinosus to the ingroup, it is now apparent that P. langi is the basal species in the genus. (Recent studies have indicated that P. capensis and P. nebulosus are not congeneric with Pseudocordylus.) Secondly, the 16S rRNA results confirm that P. m. melanotus, as presently construed, is comprised of two clades that are not sister groups. The northern populations of P. m. melanotus (Sabie and Lochiel) form a fairly deeply divergent clade that may represent a separate species. The Nkandla population was, however, found to cluster with the other southern P. m. melanotus populations and not with P. transvaalensis as was the case in the allozyme electrophoretic analysis. However, the most surprising result of the 16S rRNA analysis was the finding that both P. microlepidotus and P. spinosus are embedded within P. m. subviridis. This suggests that these two species evolved from within P. m. subviridis and may have been separated only recently, with rapid morphological divergence occurring, but with limited genetic differentiation. It is suggested that all of the above three taxa be provisionally treated as full species. There was also morphological support for the uniqueness of all groupings indicated by the mtDNA analysis. Pseudocordylus transvaalensis is characterized by its large size, unique dorsal and gular (black) colour patterns, as many as three horizontal rows of lateral temporal scales, a series of small scales posterior to the interparietal scale, and usually two subocular scales behind the median subocular on either side of the head. The various populations currently classified under the name P. melanotus are more difficult to separate, but P. m. melanotus and P. m. subviridis usually differ as follows: frontonasal divided in P. m. melanotus, undivided in P. m. subviridis (and most Northern melanotus); lateral temporals in two rows, upper more elongate versus single row of much elongated scales; longitudinal rows of dorsolaterals closely-set versus widely separated; femoral pores of females pit-like versus deep with secretory plug. Northern melanotus differs from Southern melanotus in usually having an undivided frontonasal scale and seldom having a small scale present behind the frontonasal. Pseudocordylus langi has unique dorsal and gular colour patterns (including a series of blue spots on the flanks), granular dorsals with 6-9 paravertebral rows of enlarged flat scales, high total numbers of femoral pores (25-34) and usually only five (smooth not keeled or ridged) infralabial scales on either side of the head. Pseudocordylus spinosus also has unique dorsal and gular colour patterns, spinose lateral scales, frontonasal longer than wide and excluded from the loreal scales, low total femoral pore counts (6-9), and females (not only males) have differentiated femoral scales. Both Principal Components Analysis (PCA) and Canonical Discriminant Analysis (CDA) distinguished four groups, namely P. transvaalensis, P. langi, P. spinosus and a P. melanotus/subviridis/microlepidotus cluster. A separate CDA of all P. melanotus populations partly distinguished between Southern melanotus and P. m. subviridis, and largely separated Northern melanotus; whereas a CDA of P. transvaalensis showed that all three allopatric populations are 100% distinguishable in morphological space. A Nested Clade Analysis indicated that fragmentation as well as range expansion played a role in the distribution of the P. melanotus species complex. This may be explained by climatic oscillations (high-low temperatures and wet-dry cycles) during the Cenozoic that caused habitat expansion and contraction. Based on the topology of the mtDNA phylogram it is apparent that the genus Pseudocordylus originated along the eastern escarpment. A P. langi-like ancestor may have had an extensive range along the eastern escarpment, with the Maloti-Drakensberg forming the southern limit of its range. During a subsequent rise in global temperatures, range contraction and fragmentation took place, leaving an isolated population in the south and one in the north. The southern population survived unchanged in the Maloti-Drakensberg refugium, but the northern population was forced to adapt to the warmer conditions. Thereafter, the northern form expanded its range again, but during a subsequent cooler period, range contraction occurred, resulting in an isolated north-eastern population in the Sabie-Lochiel area in Mpumulanga (Northern melanotus) and a western population. Relationships in the latter clade are not sufficiently resolved to allow further reconstruction of biogeographic history, but it is clear that a P. m. subviridis-like form became isolated in the south where it eventually came into contact with P. langi at high elevations. Pseudocordylus m. subviridis eventually extended its range southwestwards into the inland mountains of the Eastern Cape and Cape Fold Mountains to give rise to the P. microlepidotus complex. This cycle of range expansion and contraction may also account for the isolated populations at Suikerbosrand, Nkandhla district, and in the Amatole-Great Winterberg mountain region. Furthermore, it is suggested that P. spinosus originated from a P. m. subviridis-like ancestral population that became isolated on the lower slopes of the Drakensberg where terrestrial predation pressure resulted in a quick shift in morphology from fairly smooth body scales to a more spiny morphology. / AFRIKAANSE OPSOMMING: Die taksonomiese status van suidelike Afrika se rotsbewonende krans-akkedisse (genus Pseudocordylus) is ondersoek. Omdat daar aansienlike verwarring in die literatuur bestaan met betrekking tot die tipe monsters en die tipe lokaliteite van die verskillende taksa, is die oplossing van hierdie probleme as die beginpunt van hierdie studie geneem. Die bestudering van akkedismonsters in museums het dit moontlik gemaak om lektotipes, alloparalektotipes en/of paralektotipes aan te wys. Van besondere belang vir hierdie studie is die herontdekking van Andrew Smith se tipe monsters van P. m. melanotus en P. m. subviridis. Die beperking van die tipe lokaliteit van P. m. subviridis, gebaseer op inskrywings in Smith se dagboek en joernaal, het dit moontlik gemaak om vorige interpretasies en definisies van die twee taksa te bevestig. Die geografiese verspreiding van die verskillende taksa en bevolkings is bepaal deur middel van ’n omvattende lokaliteit databasis. Twee soorte molekulêre merkers, naamlik allosieme en mitokondriale DNS, is gebruik in ʼn poging om uitsluitsel te verkry oor die takson-grense binne die P. melanotus-spesiekompleks. Die allosiem-analise het daarop gedui dat P. m. melanotus moontlik polifileties mag wees en uit twee onverwante stamboom-vertakkings kan bestaan. Verder het vaste alleliese verskille tussen parapatriese bevolkings van P. m. melanotus en P. m. subviridis, en tussen simpatriese bevolkings van P. m. subviridis en P. langi, daarop gedui dat al drie vorme as volledige spesies beskou kan word, met die moontlikheid dat meer kriptiese spesies in die kompleks teenwoordig kan wees. Pseudocordylus transvaalensis het van die meeste ander bevolkings verskil met 1-3 vaste alleliese verskille, maar was ononderskeibaar van die bevolking van P. m. melanotus van die Nkandhla distrik (sentraal KwaZulu-Natal). Daar was slegs homosigote individue in ʼn steekproef van Monontsha Pas (Qwa-Qwa), ʼn bevolking wat volgens die literatuur P. m. melanotus en P. m. subviridis, sowel as intermediêre omvat, en alle monsters was toekenbaar aan P. m. subviridis. Die allosiemstudie is egter gebaseer op fenetiese beginsels en vir verdere taksonomiese oplossing is ʼn kladistiese benadering vereis. ʼn Mitokondriale DNS-analise (16S rRNS geen) wat gebruik maak van Maksimum Parsimonie-, Maksimum Waarskynlikheids- en Bayes-analises is daarom uitgevoer om die filogenetiese verwantskappe tussen spesies en subspesies te bepaal en om die taksonomiese status van vorme in die P. melanotus-spesiekompleks te herondersoek. Die mtDNS-analise het die meeste van die resultate van die allosiem-analise bevestig. Eerstens, P. langi is weer bevind om basaal te wees. Met die byvoeging van P. microlepidotus en P. spinosus tot die binne-groep het dit nou duidelik geword dat P. langi die basale spesie in die genus is. (Onlangse studies het aangedui dat P. capensis en P. nebulosus nie kongeneries met Pseudocordylus is nie.) Tweedens, die 16S rRNS resultate bevestig dat P. m. melanotus, soos tans vasgestel, saamgestel is uit twee klade wat nie sustergroepe is nie. Die noordelike bevolkings van P. m. melanotus (Sabie en Lochiel) vorm ʼn redelik diep divergente klaad wat ʼn afsonderlike spesie mag verteenwoordig. Dit is egter bevind dat die Nkandla bevolking saamgegroepeer het met die ander suidelike P. m. melanotus-bevolkings en nie met P. transvaalensis soos wat die geval was in die allosiem-elektroforetiese analise nie. Die mees verbasende resultaat van die 16S rRNS-analise was egter die bevinding dat beide P. microlepidotus en P. spinosus genestel was binne P. m. subviridis. Dit dui daarop dat hierdie twee spesies kon ontwikkel het vanuit P. m. subviridis en slegs onlangs van mekaar geskei het, toe vinnige morfologiese splitsing voorgekom het, maar met beperkte genetiese differensiasie. Dit word voorgestel dat al drie die bogenoemde taksa voorlopig as volledige spesies beskou word. Daar was ook morfologiese steun vir die uniekheid van al die groeperings wat die mtDNS-analise uitgewys het. Pseudocordylus transvaalensis kan uitgeken word aan sy bogemiddelde grootte, unieke dorsale en (swart) kleurpatrone op die keel, so veel as drie horisontale rye lateraaltemporale skubbe, ʼn reeks klein skubbe agter die interpariëtale skub, en gewoonlik twee subokulêre skubbe agter die middelste subokulêre skub op beide kante van die kop. Die verskillende bevolkings wat tans geklassifiseer word as P. melanotus is moeiliker om van mekaar te skei, maar P. m. melanotus en P. m. subviridis verskil gewoonlik soos volg: frontonasale skub in twee gedeel in P. m. melanotus, heel in P. m. subviridis (en in die meeste Noordelike melanotus); lateraal-temporale skubbe in twee rye, die boonste ry met verlengde skubbe teenoor ʼn enkele ry verlengde skubbe; longitudinale rye van dorsolaterale skubbe naby aan mekaar teenoor ver uit mekaar; femorale porieë van wyfies klein en vlak teenoor diep met sekreterende proppe. Noordelike melanotus verskil van Suidelike melanotus deurdat hulle gewoonlik ʼn heel frontonasale skub het en daar selde ʼn klein skub teenwoordig is agter die frontonasale skub. Pseudocordylus langi het unieke dorsale en keel-kleurpatrone (wat ʼn reeks blou kolle op die sye insluit), granulêre dorsale skubbe met 6-9 rye vergrote plat skubbe langs die rugsteen, ʼn groot totale aantal femorale porieë (25-34), en gewoonlik net vyf (glad, ongerif) infralabiale skubbe op elke kant van die kop. Pseudocordylus spinosus het ook unieke dorsale en keel-kleurpatrone, skerp laterale skubbe, frontonasale skub langer as wyd en nie in kontak met die loreale skubbe nie, klein totale aantal femorale porieë (6-9), en wyfies (nie net mannetjies nie) het gedifferensieerde femorale skubbe. Die Hoof-komponent Analise (HKA) en die Kanonieke Diskriminant Analise (KDA) het albei vier groepe geïdentifiseer, naamlik P. transvaalensis, P. langi, P. spinosus en ʼn P. melanotus/subviridis/microlepidotus groepering. ʼn Aparte KDA van alle P. melanotus bevolkings het gedeeltelik onderskei tussen Suidelike melanotus en P. m. subviridis, en die Noordelike melanotus is grootliks van die ander onderskei; terwyl ʼn KDA van P. transvaalensis daarop gedui het dat al drie allopatriese bevolkings 100% onderskeibaar in morfologiese ruimte is. ʼn Genestelde Klaad-Analise het aangedui dat fragmentasie, sowel as gebiedsuitbreiding, ʼn rol gespeel het in die verspreiding van die P. melanotus-spesiekompleks. Dit kan moontlik verklaar word deur die klimaatswisselinge (hoë-lae temperature en nat-droë siklusse) gedurende die Senosoikum wat habitat-uitbreiding en –verkleining veroorsaak het. Gebaseer op die topologie van die mtDNS filogram is dit duidelik dat die genus Pseudocordylus al langs die oostelike platorand ontstaan het. ʼn Voorouer soortgelyk aan P. langi kon ʼn uitgebreide gebied al langs die oostelike platorand gehad het, met die Maloti-Drakensberg wat die suidelike limiet van hierdie gebied gevorm het. Gedurende ʼn daaropvolgende toename in globale temperature het gebiedsverkleining en fragmentasie plaasgevind, wat ʼn geïsoleerde bevolking in die suide en een in die noorde tot gevolg gehad het. Die suidelike bevolking het onveranderd oorleef in die Maloti-Drakensberg skuilplek (“refugium”), maar die noordelike bevolking is geforseer om aan te pas in die warmer toestande. Daarna het die noordelike vorm se gebied weer uitgebrei, maar gedurende ʼn daaropvolgende koeler periode het gebiedsverkleining weer plaasgevind, met die gevolg dat daar ʼn geïsoleerde noord-oostelike bevolking in die Sabie-Lochiel-area in Mpumalanga (Noordelike melanotus) en ʼn bevolking in die weste was. Verwantskappe in die laasgenoemde klaad is nie voldoende opgelos om verdere rekonstruksie van die biogeografiese geskiedenis moontlik te maak nie, maar dit is duidelik dat ʼn vorm soortgelyk aan P. m. subviridis geïsoleer geraak het in die suide waar dit eindelik op hoë liggings in kontak gekom het met P. langi. Die gebied van P. m. subviridis is ook later suidweswaarts uitgebrei tot in die binnelandse berge van die Oos-Kaap en Kaapse Plooiberge om tot die ontstaan van die P. microlepidotuskompleks aanleiding te gee. Hierdie siklus van gebiedsuitbreiding en verkleining kan ook ʼn verklaring bied vir die geïsoleerde bevolkings by Suikerbosrand, Nkandhla distrik, en in die Amatole-Groot Winterberg-streek. Verder word voorgestel dat P. spinosus ontstaan het uit ʼn voorouerlike bevolking soortgelyk aan P. m. subviridis wat geïsoleerd geraak het op die laer hange van die Drakensberg waar die druk van aardsbewonende roofdiere tot ʼn vinnige verandering in morfologie vanaf redelik gladde liggaamskubbe tot ʼn meer skerppuntige morfologie gelei het.

Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The central goal in macroecology is to determine species diversity patterns across ecological gradients. Altitudinal and latitudinal patterns in species richness are often assumed to be analogous. Furthermore, the primary mechanisms underlying richness patterns along these two gradients might be similar. To date, few studies have tested whether the hypotheses proposed to explain latitudinal richness variation apply to patterns across altitude. This study therefore tests several hypotheses proposed to explain patterns in species diversity (i.e. ambient energy, productivity, area and geometric constraints) and their underlying mechanisms using altitudinal gradients in epigaeic ant and beetle species richness in the Greater Cederberg Biodiversity Corridor (GCBC) (Western Cape, South Africa). The study was conducted across an altitudinal gradient that was laid out from sea level to the top of a mountain (approximately 2000 m above sea level) and down the other side thereof. First, it was determined how the ant and beetle assemblages differ between the main vegetation types included in the transect and which environmental variables might underlie these differences. Thereafter, the variation in species richness and range size patterns of the two groups was investigated across the full altitudinal gradient. This is the first study that tests the applicability of two mid-domain models across such an altitudinal gradient using both complete and partial assessments. The models explained large proportions of the variance in range sizes across three domains but the ranges could have been constrained to show peaks in the middle of the domains due to the way in which the boundaries of the domains were selected. By contrast, the mid-domain models were not important in explaining species richness patterns, which suggests that they cannot explain diversity across the gradient. The species richness patterns of the two groups did not show the predicted mid-altitudinal peak. Moreover, it was demonstrated that different processes structure ant and tenebrionid assemblages across the same altitudinal transect. Ant species diversity was highly correlated to contemporary climatic variables, while historical factors appear to play a more important role in structuring tenebrionid beetle assemblages. Furthermore, support was found for the species energy theory in the ant assemblages, as well as for two of its underlying mechanisms, namely the more individuals hypothesis and the niche position mechanism. These results suggest that there are likely to be substantial and complex changes to ant assemblages under the predicted climate change scenarios for the region. Given the crucial role played by this group in ecosystem functioning (e.g. myrmecochory) it is suggested that these responses are not likely to be a response solely to vegetation changes, but might also precipitate vegetation changes. This study also forms the basis of a long-term monitoring programme to establish baseline data for the epigaeic ants and tenebrionids and to monitor changes in these communities due to climate change. / AFRIKAANSE OPSOMMING: Een van die sentrale idees in makro-ekologie is om die patrone in spesies diversiteit oor ekologiese gradiënte te ondersoek. Verder word daar aangeneem dat spesie rykheidspatrone oor hoogte- en breedtegradiënte analoog is aan mekaar en dat die primêre onderliggende meganismes van die patrone dieselfde kan wees oor hierdie twee gradiënte. Tot dusver het min studies getoets of die voorgestelde hipoteses wat breedtegradiënte in spesie rykheid verduidelik van toepassing is op hoogtegradiënte. Hierdie studie toets dus verskeie van hierdie hipoteses (aanvoelbare temperatuur, produktiwiteit, area en geometriese beperkinge) en hulle onderliggende meganismes in mier en kewer spesie rykheid in die Groter Cederberg Biodiversiteits Korridor (GCBK) (Wes Kaap, Suid Afrika). Die studie is uitgevoer oor ‘n hoogtegradiënt wat vanaf see vlak tot ongeveer 2000 meter bo seevlak en weer aan die ander kant van die berg af uitgelê is. Eerstens is daar bepaal hoe die mier en kewer diversiteit verskil tussen die hoof planttipes wat oor die hoogtegradiënt voorgekom het en watter omgewingsveranderlikes daarvoor verantwoordelik is. Daarna is die variasie in spesie rykheid en area van verspreiding van die twee groepe ondersoek oor die hele hoogtegradiënt. Hierdie is die eerste studie wat die toepaslikheid van twee mid-domein modelle oor so ‘n hoogtegradiënt toets met behulp van volledige en gedeeltelike ondersoeke. Die modelle het baie van die variasie in area van verspreiding verduidelik oor drie domeine maar die areas van verspreiding kon beperk gewees het om pieke in die middel van die domeine te vorm as gevolg van die manier waarop die grense van die domeine gekies is. In teenstelling, het die modelle nie spesie rykheid verduidelik nie en dus kan hulle nie spesie diversiteit oor hierdie gradiënt verduidelik nie. Die spesie rykheidspatrone van die twee groepe het nie die verwagte piek by midhoogte gewys nie. Verder het verskillende prosesse mier en kewer groeperings oor die hoogtegradiënt gestruktureer. Mier diversiteit was hoogs gekorroleer met kontemporêre klimaatsveranderlikes, terwyl historiese faktore belangriker was vir die kewers. Die spesie-energie teorie was ondersteun deur die data, asook die meer individue hipotese en die nis posisie meganisme. Hierdie resultaat dui daarop dat daar moontlik komplekse veranderinge in mier groeperings gaan plaasvind soos die klimaat verander. Miere vervul belangrike ekologiese prosesse in ekosisteme, wat beteken dat die laasgenoemde verandering nie bloot net gaan plaasvind as gevolg van veranderinge in die plantegroei nie, maar dat hulle self ook veranderinge kan veroorsaak. Hierdie studie vorm ook die basis van ‘n langtermyn moniteringsprogram om basislyn data vir hierdie twee ekologies belangrike groepe vas te stel en om veranderinge wat in hierdie gemeenskappe plaasvind, as gevolg van klimaatsverandering, te monitor.

Thesis (PhD (Zoology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The Cape Floristic Region (CFR) is a biodiversity hotspot in South Africa, threatened by climate change and various other processes. The Greater Cederberg Biodiversity Corridor (GCBC) is a conservation area incorporating both public and private land, providing a practical and effective solution to conserve biodiversity in the CFR. This area is also home to two of the eight melanistic cordylid lizard species found in south-western South Africa. One of the herpetological conservation targets identified for the GCBC was an understanding of the ecology of melanistic cordylid populations with particular reference to global environmental change. Most melanistic cordylids occur in cool coastal and montane localities, and it was suggested that melanism has a thermoregulatory function in these species. The first aim of this study was to determine the climatic conditions with which melanistic cordylids are currently associated. Several melanistic cordylid populations showed a distinct association with a high incidence of fog and cloud cover, underscoring the thermal melanism hypothesis, which predicts that melanistic lizards should occur in cool environments. Several other populations, however, did not show such an association. The next aim was thus to compare habitat use and morphology among 10 melanistic cordylid populations. Individuals of the northern population of Pseudocordylus capensis and the Cordylus peersi population occurred in the warmest environments, used significantly higher rock formations, and had relatively longer limbs than those of other melanistic populations. Having a morphology that allows for flexibility in habitat use, may enable species such as P. capensis to overcome the constraints of melanism in warm environments. Being melanistic may result in decreased activity times in warm environments. The variation in habitat thermal quality and daily activity patterns of two melanistic cordylid species with different morphologies and habitat preferences, occurring sympatrically, was investigated. During summer, high rocks provided a better thermal quality habitat to P. capensis than small rocks, and P. capensis had a longer activity period than C. oelofseni. This suggests that the thermal opportunities provided by high rock enables P. capensis to increase its activity time. The impact of terrestrial and aerial predators can help shape body armour in lizards, with those species more exposed to aerial predators being faster and less armoured, and those more exposed to terrestrial predators being more heavily armoured. The degree of body armour in melanistic cordylids and their non-melanistic relatives was investigated. Melanistic members of the cordylus-niger-oelofseni and C. polyzonus clades had less armour than their non-melanistic relatives, supporting the prediction that melanistic cordylids basked more and were more exposed to aerial predators than non-melanistic lizards. An increase in body armour in C. peersi indicated exposure to terrestrial predators, whereas P. capensis had a reduction in body armour, indicating exposure to aerial predators. Little body armour, together with a slender morphology and long limbs, may thus enable this species to move with ease on large boulders and scale vertical surfaces to successfully avoid predators. Pseudocordylus capensis displayed much greater movement rates during activity than other cordylids. A less sedentary foraging strategy may be a prerequisite for life on large, barren rock surfaces where food availability may be low or not uniformly distributed. Both males and females of this species also had large home ranges, a unique phenomenon for cordylids. Space use of males only overlapped marginally, but extensive overlap among males and females and among females, respectively, was observed. Due to the constraining effect of climate on the distribution of most melanistic populations, melanistic cordylids should be considered as priority species for conservation. While P. capensis is pre-adapted for survival in warm climates, it is dependent on the availability of suitable habitats. The GCBC would thus play an important role in the conservation of this species’ habitat. / AFRIKAANSE OPSOMMING: Die Kaapse Blommeryk (KBR) is ‘n “biodiversity hotspot” in Suid-Afrika wat deur klimaatsverandering en verskeie ander prosesse bedreig word. Die Groter Cederberg Biodiversiteitskorridor (GCBK) is ’n bewaringsarea wat beide openbare en privaatgrond inkorporeer, en ’n praktiese en effektiewe oplossing tot die bewaring van biodiversiteit in die KBR bied. Twee van die ag melanistiese gordelakkedisse wat in suidwestelike Suid-Afrika aangetref word, kom ook hier voor. Een van die herpetologiese bewaringsdoelwitte vir die GCBK was om insig oor die ekologie van melanistiese gordelakkedis populasies met verwysing na globale omgewingsveranderinge in te win. Die meeste melanistiese gordelakkedisse kom in koel kus- en berggebiede voor, en daar is voorgestel dat melanisme ‘n termoregulerende funksie by hierdie spesies het. Die eerste doel van die studie was om die huidige klimaatstoestande waarmee melanistiese gordelakkedisse geassosieer word, te bepaal. Verskeie melanistiese gordelakkedis-populasies het ‘n duidelike assosiasie met mis en wolkdekking getoon, wat die termiese melanisme hipotese se voorspelling dat melanistiese akkedisse in koue omgewings moet voorkom, ondersteun. Verskeie ander populasies, het egter nie so ‘n assosiasie getoon nie. Die volgende doel was om habitatgebruik en morfologie tussen 10 melanistiese gordelakkedispopulasies vergelyk. Individue van die noordelike populasie van Pseudocordylus capensis en Cordylus peersi het in die warmste omgewings voorgekom, het relatief langer ledemate gehad en beduidend hoër rotsformasies as ander melanistiese populasies benut. ’n Morfologie wat buigsame gebruik van die habitat toelaat, kan sommige spesies soos P. capensis in staat stel om die beperkinge van melanisme in ‘n warm omgewing te oorkom. In warm omgewings mag melanisme tot ’n afname in aktiwiteitstye lei. Variasie in termiese kwaliteit van die habitat en daaglikse aktiwiteitspatrone van twee melanistiese spesies, met verskillende morfologieë en habitatvoorkeure, wat simpatries voorkom is bestudeer. Gedurende somer het hoë rotse ‘n beter termiese kwaliteit habitat aan P. capensis verskaf as die klein rotse, en P. capensis het ‘n langer aktiwiteitsperiode as C. oelofseni gehad. Dit stel voor dat die termiese geleenthede wat deur hoë rotse verskaf word, P. capensis in staat stel om sy aktiwiteitsperiode te verleng. Die invloed van terrestriële en lugpredatore kan help om liggaamspantser in akkedisse te vorm. Spesies wat hoofsaaklik aan lugpredatore blootgestel is, is vinniger en het minder pantser, terwyl spesies wat hoofsaaklik aan terrestriële predatore blootgestel is, meer pantser het. Die graad van pantser in melanistiese gordelakkedisse en hulle nie-melanistiese naasverwantes is ondersoek. Melanistiese lede van die cordylus-niger-oelofseni en C. polyzonus klades het minder pantser as hulle nie-melanisties naasverwantes gehad, en ondersteun die voorspelling dat melanistiese gordelakkedisse meer in die son gebak het en meer aan lupredatore blootgestel was. ’n Toename in pantser by C. peersi dui op blootstelling aan terrestriële predatore, terwyl P. capensis die minste pantser van alle melanistiese gordelakkedisse het, wat dui op blootstelling aan lugpredatore. Min beskerming, tesame met ‘n lenige morfologie en lang ledemate, mag dus hierdie spesie toelaat om gemaklik oor groot rotse en vertikale oppervlaktes te beweeg en roofdiere suksesvol te vermy. Pseudocordylus capensis het groter bewegingstempo’s tydens aktiwiteit as ander gordelakkedisse getoon. ‘n Meer beweeglike voedingstrategie mag ook ‘n voorvereiste wees vir ‘n lewe op groot, leë klipoppervlaktes waar voedselbeskikbaarheid dalk laag kan wees en nie eweredig versprei is nie. Beide mannetjies en wyfies het ook groot tuisgebiede gehad, ’n unieke verskynsel by gordelakkedisse. Mannetjies se ruimtes het slegs marginaal oorvleuel, terwyl daar heelwat oorvleueling tussen mannetjies en wyfies se ruimtes was. As gevolg van die beperkende invloed van klimaat op die verspreiding van die meeste melanistiese populasies, moet melanistiese gordelakkedisse as prioriteitspesies vir bewaring beskou word. Terwyl P. capensis pre-aangepas is vir oorlewing in warm klimate, is hierdie spesie afhanklik van die beskikbaarheid van gepaste habitatte. Die GCBK sal dus ’n belangrike rol vervul in die bewaring van die habitat van hierdie spesie.