• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1972
  • 241
  • 231
  • 108
  • 96
  • 31
  • 31
  • 21
  • 18
  • 17
  • 11
  • 11
  • 11
  • 11
  • 11
  • Tagged with
  • 3577
  • 831
  • 416
  • 397
  • 351
  • 350
  • 335
  • 289
  • 278
  • 273
  • 194
  • 192
  • 188
  • 182
  • 179
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
491

New Economic Partnership for Africa's Development (NEPAD) and Africa's quest for regional economic integration: the case of Southern African Development Community (SADC)

Chigombe, Courage January 2014 (has links)
Despite according high priority to regional economic integration and being clustered by regional economic schemes, Africa’s regional economic integration record is not inspiring. With the transformation of the OAU to the African Union (AU), the New Partnership for Africa`s Development (NEPAD) was adopted as the development program of the continent to drive the impetus of economic integration through trade. At the time NEPAD was adopted, regional integration schemes in Africa were facing problems of low intra-regional trade levels despite trade being identified as the engine of activity and economic growth for regional economic integration. The study was centered on Southern Africa with precise attention on SADC. Even though trade is accepted as a vital engine of economic growth and development, this is not the case with SADC. The study was looking at the contribution of NEPAD in intra-regional trade in Africa with special focus on SADC. This was prompted by the fact that regional integration is business as usual within the sub region while problems that have been confronting regional schemes are continuing unabated after the adoption of NEPAD. The study used the historical approach because it provides the study with an advantage of accessing existing literature with regards to what is really stalling intra-regional trade in SADC. The study findings noted that NEPAD has not fully addressed the problems of intra-regional trade within SADC and the continent at large. The study lastly concludes by giving a way forward for NEPAD to respond to the specific needs of SADC for the promotion of intra-regional and equitable trade.
492

Investigating linkages between human capital, social development and corruption : evidence from a 'SADC' cross-country empirical study using panel data

Tandia, Papa Malamine 06 1900 (has links)
Corruption remains one of the most enduring phenomenon across the world and notably in Sub Saharan Africa where its scope and depth still culminate generally at distressing levels to a greater or lesser extent across countries and regions. This study presents an empirical analysis of the causes and association types of corruption across SADC countries. Through quantitative methods of analysis, it delivers an assessment of the conditional effect of the human capital and social development along with their respective and combined impact on a corruption model using panel data and multivariate regression estimates across the fifteen SADC countries for the period 2005 - 2013. The research then identifies other covariates economic or institutional - and their functional dependence to the hypothesised triad nexus - that may predict the diversity of corruption level outcomes in the region.The hypotheses considered and tested suggest that both human capital (HC) and social development (SD) are key determinants of corruption outcome levels. We report consistently strong R squared (R2) and high magnitude coefficients for the two variables under several estimation models and for various other control economic and governance variables. For robustness testing, alternate measures of corruption are also used. The results mostly but not entirely support the initial findings. The inclusion of the institutional variables does not confirm for SADC countries the largely found negative association of corruption with democracy and press freedom. Hence young and developing democracies across the region may not benefit from lower levels of corruption in the short run as institutional frameworks in formation remain weak. Meanwhile this research did not allow to derive clear arguments in relation to true causality and effects’ directions. The results remain agnostic with regards to causation between corruption and the selected explanatory variables. In the end human capital and social development in particular were found to be strong and consistent predictors of corruption control and the associations remain robust and significant under numerous specifications. While omnipresent rhetoric has largely focused on the political dimensions of corruption this study provides a substantial evidence and a nuance contribution to knowledge and literature to the concept of corruption by introducing the interaction effects of human capital and social development which indicate that both explanatory variables are consistent predictors of corruption control levels. In the footsteps of Sen’s theory, it offers a new frame which grants an understanding of the phenomenon of corruption from a capability and human development approach as a new avenue for research. All of which has crucial policy implications for concerned governments. Indeed, efforts to stamp out corruption should be designed first to eliminate or mitigate the root - conditions of its incidence focusing on policies geared towards better education and higher living standards. Relying chiefly on oversight agencies and lending disproportionate attention to enforcement actions and regulatory frameworks would indeed prove to be a misplaced priority. Fundamentally this thesis argues a new scheme of intelligibility, a renewed “episteme” of corruption which refers to the order of human developmental structures underlying the production of corrupt practices. / Business Management / D.B.L.
493

Antimicrobial activity of Melianthus villosus

Lentsoane, Robert 23 May 2005 (has links)
Many South Africans continue to use traditional medicine in their daily lives as an alternative form of health care, also as part of their cultural heritage. Medicinal plants are proving to be an important source of novel drugs, and the knowledge provided by traditional healers is a useful tool in the search for antimicrobials. The antimicrobial activity of <M. villosus was investigated against ten bacteria and six fungi. The antibacterial assay showed that the root extract had the highest inhibition against the Gram-positive bacteria at the minimum inhibition concentration of o.1 mg/ml, as well as against the Gram-negative, E. coli, at the MIC of 1.0 mg/ml. Antifungal activity was witnessed against Cladosporium cladosporoide, C. cucumerinum&C sphaerosperum all at the minimum inhibitory concentration of 1.0 mg/ml. An attempt was made to isolate and identify the active antimicrobial compounds. A flavonol, quercetin was isolated and identified by means of UV spectral graphs, and TLC comparison of the plant extract and standard. However, a second isolated antibacterial compound could not be identified fully but it can be said that it is a triterpenoid. / Dissertation (MSc (Botany))--University of Pretoria, 2006. / Plant Science / unrestricted
494

Foraging ecology of South Africa’s southern right whales (Eubalaena australis) in relation to calving success and global climate variability

Van den Berg, Gideon Leon 10 1900 (has links)
South African southern right whales (SRWs; Eubalaena australis) have been studied intensively since 1969, and annual aerial surveys between 1971 and 2006 indicate a predominant 6.9% annual population growth rate – a conservation success story after the species’ legal protection from commercial whaling in 1935. However, the prevalence of South African SRW unaccompanied adults (non-calving adults) and cow-calf pairs dropped sharply after 2009 and 2015, respectively. Additionally, the calving interval of many female South African SRWs has shifted from a three-year cycle to a four- or five-year cycle, since 2010, suggesting calving failure. This has resulted in a decrease in the population growth rate from 6.9% between 1971 and 2006, to 6.5% in 2017. SRWs are capital breeders that meet migratory and reproductive costs through seasonal energy intake, leading to strong links between their calving and foraging success. The anomalous trends in the South African SRW population have therefore raised concern about the ecological status of its broad feeding range in the Southern Ocean and ultimately about its continued population recovery. This necessitated investigation firstly into the influence of large-scale global climate drivers, Antarctic winter sea-ice extent and summer ocean productivity on the calving output of the South African SRW population. Auto-regressive integrated moving average models revealed significant model performance improvement through the inclusion of the Oceanic Niño Index (a key measure of El Niño events), the Antarctic Oscillation (the leading mode of atmospheric variability in the Southern Ocean) and chlorophyll a concentrations. The findings indicate that the South African SRW calving output appears closely influenced by not only the species’ life cycle, but also by foraging ground productivity and global climate. Secondly, the foraging strategies of South African SRWs during the 1990s (i.e. a period of high calving rates) and the late 2010s (i.e. a period of low calving rates), were assessed, through the analyses of stable carbon (δ13C) and nitrogen (δ15N) isotope values in SRW skin biopsy samples (n = 122). Results show that South African SRWs underwent a dramatic northward shift in foraging location, as well as a diversification in foraging strategy, between the 1990s and 2010s. Bayesian mixing models suggest that during the 1990s, the population foraged on prey with isotopic values similar to krill from around South Georgia. By contrast, in the 2010s, it is inferred that the population foraged on prey with isotopic values consistent with prey found in the waters of the Subtropical Convergence, Polar Front, and Marion Island. This shift could represent a new strategy to cope with changes in the availability of preferred prey or changes in habitat productivity. However, the co-occurring reproductive declines show that altering foraging strategies may not be sufficient to successfully adapt to a changing ocean. Overall, the results of this dissertation advocate that South African SRWs have recently been affected by environmental change at their foraging grounds, in turn affecting their reproductive success. Their predictive coastal presence and the existing long-term monitoring suggest that the species should be regarded as an indicator species – illustrative of climate change impacts in Southern Ocean ecosystems. / Dissertation (MSc ((Zoology))--University of Pretoria, 2020. / Zoology and Entomology / MSc (Zoology) / Restricted
495

A Lecture Recital Illustrating the Southern Influence on the Poetry of Robert Penn Warren

Calk, Judith Ann 12 1900 (has links)
This study explores the profound influence of the South on the poetry of Robert Penn Warren and creates an oral interpretation lecture-recital script illustrating this influences. The study shows Warren's poetry to be worthy of consideration. The study also defines oral interpretation, lecture recital, and poet-centered programs. Included with a biographical sketch of Warren is a chronological listing of works and events in his life. There are discussions of several poems which illustrate the influence of the Southern landscape and several which show the influence of the Southern people. The forty-five minute lecture-recital script is included as an appendix,
496

The demise of industrial paternalism: the case of southern textiles, 1880-1940

Pope, Bingham Graves 11 July 2009 (has links)
This thesis is an historical social analysis of the Southern textile industry of 1880 to 1940, the industry which brought about the industrialization of the South. The initial class relationship institutionalized between the emerging industrial elite and the proleteriat was the socio-economic system of industrial paternalism, which disappeared from the Southern Piedmont in the 40s when mills began to sell villages. This thesis attempts to explain the demise of industrial paternalism in the case of the Southern textiles. Conventional treatments of paternalism regard its disappearance as either a product of the inevitable progression toward pluralistic industrialism or as a result of one or more historical factors. In this thesis, paternalism's demise is viewed as a result of a social process--the working out of the ever-dynamic "relations of power" between textile owners and workers. Four class-analysis theories are used to highlight different social and economic features of the historical case. Specifically, I research the relative impact of the alternative labor market, the consolidation movement, scientific management, social legislation, and worker organization. My results indicate that the introduction of scientific management negated the substance of paternalistic relations, but the form of paternalism, namely the mill village, continued to function as an effective means of union prevention. Not until the New Deal did mill village paternalism really become untenable, when the state intervened to set a textile minimum wage and maximum hours and to protect union organization. It is shown that, contrary to popular opinion, worker organization and the textile union had a significant impact upon the destiny of paternalism, both sustaining its life as a means of labor control, and propelling the developments that rendered it ultimately ineffective. The findings corroborate Karl Polanyi's contention that inclusion of the non-economic is vital. / Master of Science
497

Uprooted buffelgrass thatch reduces buffelgrass seedling establishment

Jernigan, Marcus B., McClaran, Mitchel P., Biedenbender, Sharon H., Fehmi, Jeffrey S. 12 April 2016 (has links)
Buffelgrass (Pennisetum ciliare (L.) Link), a non-native perennial bunchgrass, invades ecologically intact areas of the Sonoran Desert. It competitively excludes native plants and increases fire frequency and intensity. Since the 1990s, whole buffelgrass plants have been manually uprooted and removed to control the invasion in southern Arizona. Uprooting plants results in bare, disturbed soil which promotes buffelgrass seed germination. This study examined whether leaving entire uprooted buffelgrass plants (thatch) on a field site reduces future buffelgrass establishment compared to removing uprooted plants from the site. A secondary goal was to determine whether light reduction and autoallelopathy were major factors in the negative effect of thatch on buffelgrass seedling density. Field plots with an average of 8,095 kg/ha thatch had 1.9 buffelgrass seedlings/m(2) which was significantly fewer than the 2.9 seedlings/m(2) in plots without thatch. Thatched portions of thatch plots (50% of their total area) had only 0.7 seedlings/m(2). In the greenhouse, which reduced outdoor light intensity by 35.2%, buffelgrass seeds sown in bare soil resulted in significantly higher seedling density than beneath buffelgrass thatch. Potential autoallelopathic chemicals leached from partially decomposed buffelgrass thatch and leached thatch had an intermediate but not significant (p = 0.09) effect on seedling numbers. Results suggest that leaving uprooted buffelgrass plants has the benefit of reducing seedling establishment in the area disturbed by uprooting.
498

Geomagnetic induction studies in southern Scotland

Jones, Alan George January 1977 (has links)
The Southern Uplands of Scotland is at present a region of great interest to both geologists and geophysicists. The complex tectonic history associated with the closing of the proto-Atlantic ocean has yet to be determined. Previous geophysical studies have shown that the Southern Uplands is atypical of normal continent. Geomagnetic investigations have indicated a zone of anomalously high electrical conductivity underlying the Southern Uplands region at a depth of 12-30 km. In order to determine further the exact structure and spatial variation of this conductivity zone, two geomagnetic studies have been carried out in the region. A Geomagnetic Deep Sounding Array of 19 Gough-Reitzel variometers recorded the naturally varying Earth's magnetic field during December 1973 and January 1974. This was followed by Magneto-Telluric observations on lines perpendicular and parallel to the strike of the supposed anomaly. In this thesis, reviews of various regional MT studies, the geophysical significance of conductivity measurements and the known geology and geophysics of the Southern Uplands region are given. The aims, and relevant theory, of induction studies are also presented. The observational procedures for both the GDS and MT techniques, and the type and form of the MT activity, are described. Techniques for analysing the MT data are developed in some detail. Methods are proposed, and examples given, for (a) estimating the gross structural strike direction, (b) averaging response function estimates, (c) estimating the confidence intervals of the response functions, (d) estimating new forms of coherence functions, which exhibit many desirable properties, and (e) a frequency-time analysis· for estimating the response.functions for sub-intervals of the data set. The full MT and GDS estimates from analysis of the single station data - rotated major and rotated minor impedance estimates, azimuthal angles, skew factors and real and imaginary induction vectors - are presented and qualitatively discussed. A one-dimensional interpretation of two-dimensional MT data is examined and shown to be valid for 'rotated major' impedance estimates from locations sufficiently distant from gross lateral inhomogeneity. Various methods for determining an 'optimum model' that best satisfies, in some manner, the observed MT responses are reviewed. A Monte-Carlo inversion procedure is developed and applied to the 'rotated major' data from six of the thirteen locations. It was considered, for various reasons, unjustifiable to interpret all the data. The GDS and MT results agree on the complexity of the conductivity variations in the Midland Valley, the Southern Uplands and Northern England. The simple 'Eskdalemuir anomaly' proposed by Edwards et al. (1971) cannot explain the observations. A conductive layer is required beneath the Midland Valley at a depth of no greater than 11 km. The conductive zone underlying the Southern Uplands is at a depth greater than 24 km. For the Northern England response, the top layer of highly conducting sediments 'screen' the possible effects of a 'lower crustal/ upper mantle' conductive layer. The geological and geophysical implications of the acceptable MT models are discussed. In this work, the quantitative information, offered by the MT technique, is shown to be necessary for a full interpretation of the conductivity distribution. Also, estimation of the phase response, as well as the amplitude response, of the impedance tensor elements is shown to resolve the surface structure of the acceptable models. Various suggestions are made about further investigation of the region.
499

An analysis of population structure using microsatellite DNA in twelve Southern African populations of the Mozambique tilapia, Oreochromis mossambicus (Peters)

Hall, Edward G. 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: DNA micro satellite loci express extensive allelic variation making them convenient markers for research in many fields employing population genetic tools, including aquaculture and conservation genetics. Twelve Oreochromis mossambicus populations from wild, captive and introduced sources in Southern Africa were screened for genetic variation at ten CA repeat micro satellite loci. Three of the loci - UNHI04, UNHlll, and UNH123 - were sufficiently well resolved to screen extensively and were interpreted according to a model of Mendelian inheritance. Data was analyzed in terms of genetic structure and levels of genetic variation, the effect of management regime in captivity through successive generations on genetic diversity, and the nature of phylogenetic relationships present between populations. Exact tests, carried out using Monte Carlo type multiple resampling techniques, and F-Statistics were used to detect and quantify genetic structure among the twelve populations. The Exact test X2 (P < 0.001), a FST of 0.27 (P < 0.001), eST of 0.26, RsT of 0.28, and a <l>ST of 0.17 all indicated significant structuring among the populations. The evident genetic structuring endorsed the practice of maintaining the populations as separate genetic stocks, in separate tanks, in order to preserve unique genetic material for aquaculture strain development. Populations also exhibited some significant deviations from Hardy Weinberg equilibrium characterised by an overall reduced heterozygosity across the loci. In microsatellite studies, null alleles are often suggested as major contributors to heterozygote deficits. To test for null alleles, two controlled crosses of 0. mossambicus were made. The progeny from each cross were examined for expected parental allelic ratios at the UNHI04, UNHlll and UNH123 loci. All three loci presented evidence of possible null alleles. Accelerated inbreeding and genetic drift through successive generations in captivity can reduce heterozygosity and gene diversity. To investigate loss of diversity a sample taken from the Bushmans population in 1999 (N = 25) was compared with a Bushmans 2000 sample (N = 36). The comparison highlighted altered allele frequencies, a significant increase in average observed heterozygosity and a non-significant change in average expected heterozygosity using the UNHI04 and UNH123 loci. Calculation of genetic distances and phylogenetic comparisons between the populations provided insight into the degree of management required in conserving genetic diversity in natural populations of Mozambique tilapia. UPGMA and Neighbour-Joining techniques were used to construct phylogenetic trees using Dm and ({)~)2 distance matrices. Clustering of populations appeared to reflect geographic locality of the source populations, however certain populations were not congruent with geography. Mantel tests were used to expose a possible association between genetic distance matrices generated from each individual locus. An association would support a geographic background to population genetic structure. The Mantel tests did not provide conclusive evidence. Mantel tests for association between the combined locus Dm and (81l)2 genetic distance matrices and a geographic distance matrix were similarly non-significant. Multi-dimensional scaling (MDS) plots of Euclidean distance values for Dm and (81l)2 matrices presented a two-dimensional view of the genetic distance data. The degree of similarity with the UPGMA and Neighbour-Joining tree-clustering pattern was higher for the (81l)2 than for the Dm MDS plots. Scatter plots indicated a reliable non-linear correlation between Euclidean distance and genetic distance for the two-dimensional MDS. The micro satellite markers employed in this research provided molecular information needed for complimenting a co-study on quantitative genetic evaluation of the twelve populations. The quantitative co-study provided measures of average length and weight gain indices for the populations based on progeny growth trials. No significant correlation of average heterozygosity (gene diversity) with either average weight or length gain was found. The significant genetic diversity and structure present between the twelve populations provided rationale for implementing strategies to conserve natural 0. mossambicus populations as genetic resources, and manage captive populations for long term maintenance of genetic diversity. / AFRIKAANSE OPSOMMING: Die verstaffing van groot alleliese variasie deur DNA mikrosateliete maak van hulle gerieflike merkers vir navorsing in 'n verskeidenheid van velde wat gebruik maak van populasie genetiese gereedskap, ingesluit akwakultuur en bewarings genetika. Twaalf 0. mossambicus populasies wat verkry was vanuit die natuur, in gevangeneskap en ingevoerdes, van Suidelike Afrika was getoets vir genetiese variasie by tien verskillende CA-herhalende mikrosateliet loci. Drie van die loci - UNHI04, UNHlll en UNH123 - is op grootskaal getoets en volgens In model van Mendeliese oorerwing geinterpreteer. Die data was ontleed volgens genetiese struktuur en vlakke van genetiese variasie, die effek wat bestuur strategie in gevangeneskap op genetiese diversiteit in opeenvolgende generasies uitgeoefen het, so wel as die aard van die filogenetiese verhoudings wat teenwoordig is tussen die populasies. "Exact" toetse is uitgevoer deur gebruik te maak van Monte Carlo tipe veelvuldige hermonsterinsamelings tegnieke en F-statistieke is gebruik vir die deteksie en kwantifisering van die genetiese struktuur tussen die twaalfpopulasies. Die Exact toets X2 (P < 0.001), 'n FST van 0.27 (P < 0.001), SST van 0.26, RsT van 0.28, en 'n <DST van 0.17 gee almal 'n indikasie van betekenisvolle strukturering tussen die populasies. Die genetiese struktuur bevestig die beleid dat die populasies behou moet word as aparte genetiese voorraad, in aparte tenke, om te verseker dat die unieke genetiese materiaal behoue bly om akwakultuur variante te ontwikkel. Populasies het ook betekenisvolle verskuiwings van die Hardy Weinberg ekwilibrium getoon, wat gekarakteriseer word deur 'n algemene verlaging van heterosigositeit oor die loci. Nul allele word dikwels aanbeveel om in mikrosateliet studies groot bydraes te maak tot hetersigotiese defekte. Om vir nul allele te toets was twee gekontroleerde kruisings van 0. mossambicus gemaak. Die nageslag van elke kruising was getoets vir verwagte ouer alleliese verhoudings by die UNHI04, UNHlll en UNH123 loci. Al drie loci het getoon dat dit moontlike nul allele kan wees. Versnelde inteling en genetiese drywing deur opeenvolgende generasies in gevangeneskap kan die heterosigositeit en diversiteit verminder. Om die vermindering van diversiteit te toets was 'n monster van die Busmans 1999 (N=25) populasie vergelyk met 'n monster van die Bushmans 2000 (N=36) populasie. Die vergelyking het veranderde alleel frekwensies, 'n betekenisvolle vermeerding in gemiddelde waargeneemde heterosigositeit en 'n onbetekenisvolle verandering in gemiddelde verwagte heterosigositeit getoon deur gebruik te maak van die UNHI04 en UNH123 loci. Berekening van genetiese afstande en filogenetiese vergelykings tussen die populasies het nuwe insig gegee oor die graad van bestuur wat nodig is om genetiese diversiteit in die natuurlike populasies van 0. mossambicus tilapia te behou.UPGMA en Neighbour-Joining tegnieke was gebruik om filogenetiese bome op te stel deur gebruik te maak van Dm en (OIl)2 afstand matrikse. Populasie bondeling het geblyk om geografiese lokaliteit van die bron populasies te toon, alhoewel van die populasies nie met die geografiese lokaliteit ooreengestem het nie. Mantel toetse is gebruik om 'n moontlike assosiasie tussen genetiese afstand matrikse wat verkry is van elke loci bloot te stel. 'n Assosiasie sou 'n geografiese agtergrond tot populasie genetiese struktuur steun. Oortuigende bewys is nie deur die Mantel toetse verskaf nie. Mantel toetse vir assosiasie tussen die gekombineerde loci Dm en (OJ..l)2 genetiese afstand matrikse en In geografiese afstand matriks was ook onbetekenisvol. 'n Tweedimensionele beskouing van die genetiese afstand data is voorgestel deur multidimensionele skaal (MDS) grafieke van Euclidean afstand waardes van die Dm en (OJ..l)2 matrikse te teken. Die graad van ooreenstemming met die UPGMA en Neighbour-Joining boom samevoeging patroon was hoër vir die (OJ..l)2 as vir die DmMDS grafieke. Verspreiding grafieke het 'n vertroubare nie-liniêre korrelasie tussen Euclidean afstande en genetiese afstande vir die twee-dimensionele MDS grafieke getoon. Die mikrosateliet merkers wat in die studie gebruik was het molekulêre informasie verskaf wat nodig is vir 'n komplimentêre studie oor die kwantitatiewe genetiese evalueering van dié twaalf populasies. Die kwantitatiewe studie het afmetings van gemiddelde lengte en gewig vermeerdering van die populasies verskaf gebaseer op nageslag proewe. Geen betekenisvolle korrelasie van gemiddelde hetersigositeit (geen diversiteit) was getoon met óf gemiddelde gewig óf lengte vermeerdering. Die betekenisvolle genetiese diversiteit en struktuur teenwoordig tussen die twaalf populasies het rede gegee om strategieë te implimenteer om natuurlike 0. mossambicus populasies te konserveer as genetiese bronne en om populasies in gevangeneskap te bestuur vir langtermyn instandhouding van genetiese diversiteit.
500

Molecular phylogenetics and phylogeography of sand lizards, Pedioplanis (Sauria: Lacertidae) in southern Africa

Makokha, Jane Sakwa 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The present study aims to determine the phylogenetic relationships among the sand lizards, Pedioplanis. In addition, a single mitochondrial gene is used to investigate the geographic genetic structure of the widey distributed P. burchelli. With 11 species, Pedioplanis is the most speciose genus among the southern African genera of the family Lacertidae. All the species are restricted to the subcontinent with the exception of three (P. namaquensis, P. undata and P. benguellensis), which extend their range northwards into Angola. A total of 2200 nucleotide positions derived from two mitochondrial markers (ND2 and 16S rRNA) and one nuclear gene (RAG-1) are used to determine the phylogenetic relationships among ten of the eleven Pedioplanis species. The first well resolved gene tree for the genus, drawn from 100 individuals, is presented and this is largely congruent with a phylogeny derived from morphology. Contrary to some previous suggestions, Pedioplanis forms a monophyletic assemblage with Heliobolus and Nucras. The genus Pedioplanis is monophyletic with P. burchelli/P. laticeps forming a sister clade to all the remaining congeners. Two distinct geographic lineages can be identified within the widespread P. namaquensis; one occurs in Namibia, while the other occurs in South Africa. The “P. undata” species complex is monophyletic, but one of its constituent species, P. inornata, is paraphyletic. Relationships among the subspecies of P. lineoocellata are much more complex than previously documented. An isolated population previously assigned to P. l. pulchella is paraphyletic and sister to the three named subspecies. The phylogeny identifies two biogeographical groupings that probably diverged during the mid-Miocene. The development of the Benguella Current could have initiated isolation mechanisms associated with changes in habitat that could have generated barriers and played a role in the evolution of this group. At the lower taxonomic level, the mtDNA phylogeographic structure of the wide spread P. burchelli in South Africa reveal at least six distinct clades that are geographically partitioned. The first one is restricted to the eastern mountains along the Great Escarpment (GE). The next three are found along the Cape Fold Mountains (CFM): the north-west CFM, central CFM and eastern CFM. The fifth one shares samples from central CFM and GE. The last clade is restricted to the eastern central mountains of the GE. These six geographic groupings are genetically divergent from each other and they started separating in the early Pliocene period. Phylogeographic studies on other taxa in the region have found different levels of genetic structuring among or within taxa. The fact that P. burchelli is restricted to high altitude areas could have resulted in limited dispersal and consequently contributed to its geographic structure. However, the exact cause of the pattern obtained is not readily apparent. Habitat fragmentation in the past is probably one of the most influential factors shaping the genetic distribution of the species across South Africa. The inclusion of nuclear markers will shed more light on the evolutionary history of P. burchelli in South Africa. / AFRIKAANSE OPSOMMING: Die huidige studie stel ten doel om ‘n filogenie daar te stel vir die Sand akkedisse, Pedioplanis. ‘n Enkele mitochondriale geen is ook gebruik om die geografiese genetiese struktuur van die wydverspreide P. burchelli vas te stel. Met 11 spesies is Pedioplanis die mees spesieryke genus onder die suidelike Afrika genera wat aan die Lacertidae familie behoort. Al die spesies is beperk tot die subkontinent met die uitsondering van drie (P. namaquensis, P. undata en P. benguellensis), wat ‘n uitgebreide verspreiding het noordwaarts tot in Angola. ‘n Totaal van 2200 nukleotied posisies wat afkomstig is van twee mitochondriale merkers (ND2 en 16S rRNA) en een nukluêre geen (RAG-1) is gebruik om die filogenetiese verwantskappe tussen 10 van die 11 Pedioplanis spesies vas te stel. Die eerste goed geondersteunde geen boom vir die genus, gebasseer op 100 individue, is verkry en dit is meestal ooreenstemmend met ‘n filogenie gebasseer op morfologie. In teenstelling met sekere voorstelle van die verlede vorm Pedioplanis ‘n monofiletiese groep tesame met Heliobolus en Nucras. Die genus Pedioplanis is monofileties met P. burchelli/P. laticeps wat ‘n suster groep vorm van al die oorblywende lede van die genus. Twee herkenbare geografiese lyne kan geidentifiseer word in die wydverspreide P. namaquensis; een kom in Namibia voor, terwyl die ander een in Suid Afrika voorkom. Die “P. undata” spesies kompleks is monofileties, maar een van die spesies wat deel uitmaak van die groep, P. inornata, is parafileties. Verwantskappe tussen die subspesies van P. lineoocellata is meer kompleks as wat aanvanklik aanvaar is. ‘n Geisoleerde bevolkimg wat voorheen toegesê is aan P. l. pulchella is parafileties en verteenwoordig ‘n suster groep van die benaamde subspesies. Die filogenie identifiseer twee biogeografiese groeperings wat moontlik gedivergeer het gedurende die middel-Miocene. Die ontwikkeling van die Benguella stroom het dalk versperrings geinisiëer as gevolg van die gesamentlike veranderinge in habitat wat dalk ook ‘n rol gespeel het in die evolusie van die groep. Op die laer taksonomiese vlak het die mtDNA filogeografiese struktuur van die wydverspreide P. burchelli in Suid Afrika ten minste ses groepe aangetoon wat geografies van mekaar geskei is. Die eerste een is beperk tot die oostelike berge wat aan die Groot Eskarpement (GE) behoort. Die volgende drie word gevind in die Kaapse Vouberge (KVB): die noord-westelike KVB, sentrale KVB en oostelike KVB. Die vyfde een deel eksemplare van beide die GE en die KVB. Die laaste groep is beperk tot die oostelike en sentrale berge van die GE. Hierdie ses geografiese groepe is geneties geskei van mekaar en hulle het begin om apart te ontwikkel gedurende die vroë Pliocene periode. Ander filogeografiese studies in die area het verskillende vlakke van genetiese struktuur vertoon tussen en binne taksa. Die feit dat P. burchelli beperk is tot hoogliggende dele kon moontlik bygedrae het tot die geografiese struktuur. Die presiese oorsaak van die patroon wat verkry is, is nie ooglopend nie. Habitat fragmentasie in die verlede is moontlik een van die mees invloedrykste faktore wat die genetiese verspreiding van die spesie in Suid Afrika beinvloed het. Die insluiting van nukluêre merkers sal meer lig warp op die evolusionêre geskiedenis van P. burchelli in Suid Afrika.

Page generated in 0.0297 seconds