Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: An important prerequisite for evolutionary change is variability in natural populations; however, when phenotypic and molecular rates of change differ, species delimitation is problematic. Such discordance has been identified in a recent radiation of dwarf chameleons (Bradypodion) from KwaZulu-Natal Province, South Africa. This radiation is comprised of several phenotypic forms, two of which have been classified taxonomically – Bradypodion melanocephalum and Bradypodion thamnobates. Early phylogenetic analysis did not support the forms primarily because geographic sampling and the set of molecular markers used were appropriate for detecting deep divergences and, therefore, less effective for understanding species boundaries within a recent radiation. In this radiation, the forms are allopatric, occupy different habitats, and vary in size and colouration, suggesting local adaptation and ecological speciation. To test this hypothesis, morphometric and habitat data were collected for each form to examine ecologically relevant morphological differences that reflect differential habitat use. Morphological differences were then associated with functional adaptations by testing locomotor performance and bite force. Next, fine-scale genetic sampling was used to examine lineage diversification using a combination of mitochondrial DNA and microsatellites. Spatial information was incorporated into these analyses to quantify the genetic effects of landscape barriers on genetic structure. Finally, ecological niche modelling was used to examine the abiotic factors involved in shaping the climatic niches of these chameleons, and to gain insight into their biogeographic history. Results show morphological distinctions between phenotypic forms, with corresponding differences in performance, indicating functional adaptations to habitats, which can be broadly classified as either open- or closed-canopy vegetation. Specifically, chameleons in open-canopy habitats have proportionally smaller forces and forefoot grip strengths. Varying degrees of sexual dimorphism were detected, with the closed-canopy forms being more dimorphic than the open-canopy forms. This suggests that sexual selection is the predominant force within the closed-canopy habitat, which are more protected from aerial predators, thereby enabling them to invest in dimorphic traits for communication; while, in open-canopy habitats, natural selection is the predominant force, ultimately enforcing their overall diminutive body size and constraining performance. Genetic structure was observed, with the mitochondrial DNA revealing three genetic clusters and the microsatellites revealing seven. This likely reflects the different mutation rates and modes of inheritance between these two markers. Three of the microsatellite clusters were supported by morphological and ecological data and should, therefore, be recognised as separate species. The remaining microsatellite clusters showed discordance with the ecomorphological data; however, given their genetic distinctiveness, they should be recognized as separate conservation units. The climatic niches of the three proposed species showed high to moderate levels of climatic stability, while the four proposed conservation units showed low climatic stability. These results indicate that this species complex is affected by both climatic niche conservatism and lability, which could explain the observed patterns of morphological and genetic diversity. In summary, these results support the hypothesis of ecological speciation within this radiation. / AFRIKAANSE OPSOMMING: 'n Belangrike voorvereiste vir evolusionêre verandering is variasie in natuurlike bevolkings, maar wanneer fenotipiese en molekulêre tempo van verandering verskil, is spesies definieering problematies. Sulke onenigheid is geïdentifiseer in ‘n onlangse radiasie van dwerg verkleurmannetjies (Bradypodion) van die KwaZulu-Natal Provinsie, Suid-Afrika. Hierdie radiasie bestaan uit verskeie fenotipiese vorms, waarvan twee taksonomies geklassifiseer is – Bradypodion melanocephalum en Bradypodion thamnobates. Vroeë filogenetiese analise het nie die vorms ondersteun nie, hoofsaaklik omdat geografiese steekproefneming en die stel van molekulêre merkers gebruik geskik was vir die opsporing van diep afwykings, en dus minder effektief is vir die begrip van spesies grense binne 'n onlangse radiasie. In hierdie radiasie is die vorms allopatries, beset verskillende habitatte, en wissel in grootte en kleur, wat dui op plaaslike aanpassing en ekologiese spesiasie. Om hierdie hipotese te toets, is morfometriese en habitat gegewens ingesamel vir elke vorm om sodoende ekologies relevante morfologiese verskille te ondersoek wat verskil in habitat gebruik reflekteer. Morfologiese verskille is geassosieer met funksionele aanpassings deur lokomotoriese prestasie en byt krag te toets. Volgende is fyn-skaal genetiese steekproefneming gebruik om afkoms diversifikasie met behulp van 'n kombinasie van mitochondriale DNS en mikrosatelliete ondersoek. Ruimtelike inligting is geinkorporeer in die ontleding om sodoende genetiese gevolge van landskap hindernisse op genetiese struktuur te kwantifiseer. Ten slotte, is ekologiese nis modelle gebruik om die abiotiese faktore wat betrokke is by die vorming van klimaat- nisse van hierdie verkleurmannetjie te ondersoek en om insig te verkry oor hul biografiese geskiedenis. Resultate toon morfologiese onderskeid tussen fenotipiese vorms, met saameenlopende verskille in prestasie, wat dui op funksionele aanpassings tot habitat, wat breedweg as oop- of geslote-kap plantegroei geklassifiseer kan word. Spesifiek verkleurmannetjies in oopkap habitatte het proporsioneel kleiner koppe en voete as hul geslote-kap eweknieë, en ooreenkomstig swakker byt krag en voorvoet greep. Wisselende vlakke van seksuele dimorfisme is vasgestel, met geslote-kap vorms wat meer dimorfies is as oop-kap vorms. Dit dui daarop dat seksuele seleksie die oorheersende krag in geslote-kap habitatte is, wat meer beskerm is teen vlieënde roofdiere, wat hulle in staat stel om te belê in dimorfiese eienskappe vir kommunikasie, terwyl in oop-kap habitatte, is natuurlike seleksie die oorheersende krag, wat uiteindelik kleiner liggaam grootte en beperkte prestasie afdwing. Genetiese struktuur is waargeneem, met die onthulling van drie genetiese groeperings gebasseer op mitochondriale DNS en sewe gebasseer op mikrosatelliete. Dit weerspieël waarskynlik die verskil in mutasie tempo en manier van erfenis tussen hierdie twee merkers. Drie van die mikrosatelliet groeperings is ondersteun deur morfologiese en ekologiese gegewens en moet dus erken word as aparte spesies. Die oorblywende mikrosatelliet groeperings dui op onenigheid met eko-morfologiese data, maar, gegewe hul genetiese eiesoortigheid, moet hulle erken word as afsonderlike bewarings eenhede. Die klimaat-nisse van die drie voorgestelde spesies het hoë tot matige vlakke van die klimaat stabiliteit, terwyl die vier voorgestelde bewarings eenhede lae klimaat stabiliteit het. Hierdie resultate dui daarop dat hierdie spesie kompleks beïnvloed word deur beide klimaat nis konserwatisme en stabiliteit, wat die waargenome patrone van morfologiese en genetiese diversiteit kan verduidelik. In opsomming, hierdie resultate ondersteun die hipotese van ekologiese spesiasie binne hierdie radiasie.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Riparian vegetation communities that occur along perennial rivers are structured in lateral zones that run parallel to river flow. This dissertation investigated the structure of South African riparian vegetation communities along perennial, single-thread headwater streams. The central assumption was that lateral zones result from differential species’ responses to changing abiotic factors along a lateral gradient up the river bank. It was first necessary to establish the pattern of zones and whether this pattern occurs repetitively and predictably on different rivers in different biomes. Since the flow regime is considered to be the master variable that controls the occurrence of lateral zones, the link between flow as the major abiotic driver and the distribution of plants in zones was determined. Predictions were made with respect to how variable flow may influence phenological traits, particularly with respect to seed dispersal, and physiological tolerances to drying out and were tested. The existence of lateral zones at reference sites in the Western Cape of South Africa was explored and their vegetation characteristics were described. Plant distribution was related to bank slope, as defined by elevation and distance from the wetted channel edge during summer (dry season) low flow, indicating a direct link to river bank hydraulics. Whether or not the same zonation patterns occur in riparian communities in other parts of South Africa was explored next. The four zones described for Fynbos Riparian Vegetation were evident at all of the other rivers tested, despite major differences in geographic location, vegetation community type, climate and patterns of seasonal flow. The four lateral zones could be separated from each other using a combination of flood recurrence and inundation duration. Functional differences were investigated between three tree species that occur in Fynbos Riparian Vegetation. Functional differences were apparent with respect to timing of seed dispersal, growth in branch length versus girth and three physiological measures of tolerance to drying out; specific leaf area (cm2.g-1), wood density (g.cm-3) and levels of carbon isotopes (δ13C). In order to determine the impact of invasive alien plants and to monitor recovery after clearing, the physical rules devised to help delineate zones were used to locate lateral zones that had been obliterated after invasion and subsequent clearing. At the sites invaded by A. mearnsii plants, the zone delineations showed that invasion started in the lower dynamic zone, where adult and sapling A. mearnsii were most abundant. In un-invaded systems, this zone was the least densely vegetated of the four zones, the most varied in terms of inundation duration and the frequency of inter- and intra-annual floods, and was an area of active recruitment comprised mainly of recruiting seedlings and saplings. An understanding of the functional differences between lateral zones was a common thread at each riparian community that was linked to the annual frequency of inundation and the period, when inundated. / AFRIKAANSE OPSOMMING: Oewer plantegroei gemeenskappe wat langs standhoudende riviere voorkom is gestruktureer in laterale sones parallel met die rivier vloei. Hierdie verhandeling ondersoek die struktuur van Suid-Afrikaanse oewer plantegroei gemeenskappe langs standhoudende, enkelloop hoof strome. Die sentrale aanname was dat laterale sones vorm as gevolg van verskillende spesies se reaksie teenoor die verandering van abiotiese faktore teen 'n laterale gradiënt met die rivierbank op. Dit was eers nodig om die patroon van die gebiede vas te stel en uit te vind of hierdie patroon herhaaldelik en voorspelbaar binne verskillende riviere in verskillende biome voorkom. Aangesien die vloeiwyse beskou word as die hoof veranderlike wat die teenwoordigheid van laterale sones beheer, is die skakel tussen die vloei, as die belangrikste abiotiese bestuurder, en die verspreiding van plante in sones bepaal. Voorspellings is gemaak met betrekking tot hoe veranderlike vloei fenologiese eienskappe kan beïnvloed, veral met betrekking tot die saad verspreiding, en fisiologiese toleransie teen uitdroog, en is getoets. Die bestaan van laterale sones binne verwysings studie terreine in die Wes-Kaap van Suid- Afrika is ondersoek en hul plantegroei eienskappe is beskryf. Plant verspreiding was verwant aan bank helling, soos gedefinieer deur hoogte en afstand vanaf die nat kanaal rand gedurende somer (droë seisoen) lae vloei, en dui dus op 'n direkte skakel met die rivier bank hidroulika. Of dieselfde sonering patrone voorkom in oewer gemeenskappe in ander dele van Suid-Afrika is volgende verken. Die vier sones beskryf vir fynbos oewer plantegroei was duidelik by al die ander riviere wat ondersoek is, ten spyte van groot verskille in geografiese ligging, plantegroei gemeenskap tipe, klimaat en patrone van seisoenale vloei. Die vier laterale sones kan onderskei word van mekaar deur middel van 'n kombinasie van vloed herhaling en oorstroomde toestand duur. Funksionele verskille is ondersoek tussen drie boom spesies wat voorkom in Fynbos Oewer Plantegroei. Funksionele verskille was duidelik met betrekking tot tydsberekening van saad verspreiding, groei in tak lengte tenoor omtrek, en drie fisiologiese maatstawwe van verdraagsaamheid teenoor uitdroging; spesifieke blaar area (cm2.g-1), hout digtheid (g.cm-3) en vlakke van koolstof isotope (δ13C). Ten einde die impak van indringerplante te bepaal en die herstel na ontbossing te monitor is die fisiese reëls voorheen vasgestel om sones te help baken gebruik om laterale sones, wat vernietig is na indringing en die daaropvolgende ontbossing, te vind. Op die terreine wat deur A. mearnsii indringerplante binnegeval is, het die indeling van sones getoon dat die indringing begin het in die laer dinamiese sone, waar volwasse en klein A. mearnsii bome die volopste was. In stelsels wat nie binnegeval is deur indringerplante was hierdie sone die minste dig begroei van die vier sones, die mees verskillend in terme van oorstroomde toestand duur en die frekwensie van inter-en intra-jaarlikse vloede, en was 'n gebied van aktiewe werwing hoofsaaklik bestaande uit rekruut saailinge en boompies. 'n Begrip van die funksionele verskille tussen laterale sones was 'n algemene verskynsel by elke oewer gemeenskap wat gekoppel was aan die jaarlikse frekwensie van oorstroming en die oorstroomde toestand duur.

Thesis (MScConsEcol (Conservation Ecology and Entomology)--Stellenbosch University, 2008. / In the Cape Floristic Region of South Africa, where wine grape production and biodiversity conservation are of major importance, innovative management of the landscape is necessary to integrate the two activities. Alternative farming, such as organic and biodynamic farming, focuses on the preservation of biological processes in agroecosystems with the aim of increasing the sustainability of these sytems. It has been demonstrated in other regions that alternative farming can enhance biodiversity. This study assessed the potential of alternative vineyard management to conserve biodiversity, in particular epigaeic arthropod diversity, relative to the more widespread integrated vineyard management in the CFR. A hierarchical design was used, consisting of three localities, with three land-uses nested within each locality. The land-uses were alternative vineyards, integrated vineyards and natural vegetation sites as reference habitats. Sampling was done in June and October 2006 using pitfall traps. Nested ANOVAs were used to test for differences in abundance and species richness of the total assemblages, functional feeding guilds and selected generalized predatory taxa. Assemblage patterns were assessed using hierarchical agglomerative clustering and non-metric multidimensional scaling. Canonical correspondence analyses were used to evaluate the effects of environmental variables, management practices and landscape variables on community composition. Alternative vineyards supported a significantly higher overall arthropod abundance and species richness, more diverse predatory, saprophagous, phytophagous and omnivorous guilds, as well as more abundant and speciose spider and rove beetle assemblages than the integrated vineyards. Integrated vineyards harboured a greater abundance of predators, whereas results for nectarivores, wood borers, parasitoids and carabid beetles were variable. The differences could be explained in part by higher non-crop vegetation complexity and reduced management intensity of the alternative vineyards. Community composition was influenced by a combination of management practices, the surrounding landscape and geographic locality, which highlighted the interdependence of the cultivated land and its surroundings.

Thesis (MSc (Conservation Ecology and Entomology)--Stellenbosch University, 2007. / A systematic conservation assessment is the first phase of a systematic conservation planning protocol; it uses spatial data and representation targets for the setting of priority areas and the assessment of risk to biodiversity. This thesis describes the findings of investigations on the use of data in systematic conservation assessments. Conservation planning can be done at different spatial scales (from global to local). Systematic Conservation planning can be done at different spatial scales (from global to local). Systematic conservation assessments rely on the use of surrogates for biodiversity and often, as well, socioeconomic criteria. Biodiversity surrogates can be classified as taxonomic, community and environmental. In Chapter 2, a literature review was performed (i) to quantify the use of biodiversity surrogates and socio-economic criteria in conservation assessments; and (ii) to test the hypothesis that surrogates are chosen in respect to the hierarchical organisation of biodiversity. In other words, fine scale conservation assessments are correlated with taxonomic surrogates, large scale conservation assessments are correlated with environmental surrogates, and assemblage surrogates are assessed at an intermediary scale. The literature review was based on a structured survey of 100 ISI journal publications. The analysis revealed that spatial scale had a weak effect on the use of biodiversity surrogates in conservation assessments. Taxonomic surrogates were the most used biodiversity surrogates at all scales. Socioeconomic criteria were used in many conservation assessments. I argue that it is crucial that assemblage and environmental data be more used at larger spatial scales. The allocation of conservation resources needs to be optimised because resources are scarce. A conservation assessment can be a lengthy and expensive process, especially when conducted at finescale. Therefore the need to undertake a fine-scale conservation assessment, as opposed to a more rapid and less expensive broader one, should be carefully considered. The study of Chapter 3 assessed the complementarity between regional- and local-scale assessments and the implications on the choice of biodiversity features at both scales. The study was undertaken in Réunion Island. A biodiversity assessment was performed at a regional scale and measured against a finer-scale assessment performed over a smaller planning domain. Two datasets composed of species distributions, habitat patterns and spatial components of ecological and evolutionary processes were compiled as biodiversity surrogates at each scale. Targets for local-scale processes were never met in regional assessments, while threatened species and fragmented habitats were also usually missed. The regional assessment targeting habitats represented a high proportion of local-scale species and habitats at target level (67%). On the contrary, the one targeting species was the least effective. The results highlighted that all three types of surrogates are necessary. They further suggested (i) that a spatial strategy based on a complementary set of coarse filters for regional-scale assessments and fine filters for local-scale ones can be an effective approach to systematic conservation assessments; and (ii) that information on habitat transformation should help identify where efforts should be focused for the fine-scale mapping of fine filters. Together with priority-area setting, the identification of threatened biodiversity features has helped to prioritise conservation resources. In recent years, this type of assessment has been applied more widely at ecosystem-level. Ecosystems can be categorised into critically endangered, endangered and vulnerable, following the terminology of the IUCN Red List of threatened species. Various criteria such as extent and rate of habitat loss, species diversity and habitat fragmentation can be used to identify threatened ecosystems. An approach based only on the criterion of the quantification of habitat loss was investigated in Chapter 4 for the Little Karoo, South Africa. Habitat loss within ecosystem type is quantified on land cover information. The study analysed the sensitivity of the categorisation process to ecosystem and land cover mapping, using different datasets of each. Three ecosystem classifications and three land cover maps, of different spatial resolutions, were used to produce nine assessments. The results of these assessments were inconsistent. The quantification of habitat loss varied across land cover databases due to differences in their mapping accuracy. It was reflected on the identification of threatened ecosystems of all three ecosystem classifications. Less than 14% of extant areas were classified threatened with the coarsest land cover maps, in comparison to 30% with the finest one; and less than 9% of ecosystem types were threatened with the coarsest land cover maps, but between 15 and 23% were threatened with the finest one. Furthermore, the results suggested that the identification of threatened ecosystems is more sensitive to the accuracy of habitat loss quantification than the resolution of the ecosystem classification. Detailed land cover mapping should be prioritised over detailed ecosystem maps for this exercise. This thesis highlighted the importance of ecosystems and processes as biodiversity surrogates in conservation assessments and suggested that results of conservation assessments based on these data, should be more widely presented in published articles. Finally, it also made apparent the important role of mapping habitat transformation for systematic conservation plans.

Thesis (MScAgric (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / Codling moth (CM), Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), is the major pest of apples and pears in the South Western Cape, South Africa. Apart from conventional insecticide sprays, area-wide biologically intensive control methods, such as Sterile Insect Technique (SIT) and pheromone mediated mating disruption (MD) are currently in use on two farms in the Elgin valley. The indigenous parasitoid Trichogrammatoidea lutea Girault (Hymentoptera: Trichogrammatidae) attacks eggs of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), as well as CM and has been found to have considerable parasitism potential on both. Elevated host egg numbers, as achieved by SIT are thought to support establishment of populations of these natural enemies in the orchards. For rapid and secure Trichogrammatoidea species identification, the ITS2 sequences of Trichogrammatoidea lutea and T. cryptophlebiae Nagaraja (an indigenous FCM parasitoid on citrus) were determined and species specific primers were developed. Lifetable studies of T. lutea indicated an optimal temperature for reproduction at around 20 °C. Food was provided by the application of honey-solution soaked cotton wool, behind fine netting. The effect of food provision by this method was found to be dependent on temperature. The acceptance of CM eggs from sterilized vs. fertile parents and of radiation-sterilized eggs vs. fertile ones was assessed in choice trials. While no difference was observed between radiated and fertile eggs, sterile eggs from irradiated parents were significantly less attractive than eggs from fertile parents. In several field studies the dispersal capacity and population sustainability of released T. lutea were investigated. Trials took place in apple and pear orchards in the Elgin valley that formed part of an area-wide sterile CM SIT program. Most of the wasp releases were carried out within blocks of up to 1 ha. A square grid of up to 36 monitoring trees per block allowed spatial distribution analysis. Following single central point releases, parasitism of sentinel eggs was recorded until the end of all experiments, the longest of which lasted 37 weeks. T. lutea females were found to disperse up to 73 m, within one week. Studies concerning toxicity of four commonly used insecticides and one fungicide to immature and adult T. lutea indicated no to low susceptibility of wasps at egg- to first-instar-stage within host eggs. Contact toxicity of the tested materials to adults differed significantly, depending on the compound. All five pesticides caused significantly higher mortality among adults relative to the control. The overall aim of above studies was to determine the potential of T. lutea for broad-scale releases against CM, within a broader integrated pest management program in apple and pear orchards in the Western Cape.

Thesis (MScAgric)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Invasion by the notorious tramp species, the Argentine ant (Linepithema humile Mayr) (Hymenoptera: Formicidae) has caused major concern around the globe, owing to its displacement of native ant species and other invertebrates where it invades. This species was first recorded in South Africa in 1901 in Stellenbosch, Western Cape Province (WCP), and has now become a significant pest in most urban and agricultural areas in the country. The Argentine ant has received relatively little attention in South Africa compared to other countries (e.g. California, North America). To date the extent of invasion by this species countrywide, as well as its impact on the local ant fauna inside protected areas, has not been quantified. In this study, the impact of the Argentine ant on native ant fauna inside three protected areas in the WCP (Helderberg Nature Reserve (HNR), Jonkershoek Nature Reserve (JNR) and Kogelberg Biosphere Reserve KBR)) was assessed. Species richness and diversity were compared between invaded and uninvaded bait stations at each protected area. Several native ant species were found to be displaced by the Argentine ant from all three protected areas, although three species: Meranoplus peringueyi, Monomorium sp. 8 and Tetramorium quadrispinosum, were found coexisting with it. Invaded bait stations had significantly lower ant species richness and species turnover than uninvaded bait stations. Uninvaded bait stations contained eight times more native ant species than invaded bait stations. Thus, the invasion of protected areas by the Argentine ant has severe negative consequences for the species richness and assemblage structure of native ants, leading to the biotic homogenization of these local ant communities. The distribution range of the Argentine ant inside the three protected areas (HNR, JNR, KBR), as well as microhabitat preferences that may facilitate the spread of this species inside these reserves, was also assessed. Helderberg Nature Reserve was the most invaded protected area, with the highest level of the Argentine ant occupancy, while JNR and KBR had lower occupancy levels. At all the three protected areas, this species was dominant at lower altitudinal areas, and also showed a clear preference for areas with high anthropogenic disturbances, i.e. around buildings and on lawns (picnic areas). In this study, there was no evidence that moisture availability facilitates the distribution and spread of the Argentine ant inside these reserves. Finally, a combination of published literature records, museum records and records collected in the current study was used to quantify the current distributional extent of the Argentine ant throughout urban South Africa. This is the first study quantifying the distribution and extent of invasion by the Argentine ant throughout the country. The Argentine ant was found in six of the nine South African Provinces, and its extent of occurrence includes approximately half of the country’s land surface area. Discontinuities in the distribution of the Argentine ant across the country revealed that range expansion of the Argentine ant in South Africa is occurring predominantly via human-mediated jump dispersal, rather than naturally via nest diffusion. This study clearly demonstrated that the Argentine ant is well established across South Africa as well as inside protected areas. The Argentine ant invasion was influenced by the presence of human modified landscapes (i.e. buildings) both at low and high altitude, and this was associated with higher rates of native ant species displacement at these areas. Therefore, limiting the development of recreational areas, such as buildings and picnic sites inside protected areas will result in the lower rate of spread of the Argentine ant. This will in turn lower the extent of displacement of native ant species. / AFRIKAANSE OPSOMMING: Indringing deur die Argentynse mier (Linepithema humile Mayr) (Hymenoptera: Formicidae) is ‘n bron van groot kommer regoor die wêreld, as gevolg van sy vermoë om inheemse mier spesies en ander ongewerweldes te verplaas. Hierdie spesie is vir die eerste keer aangeteken in Suid-Afrika in 1901, in Stellenbosch, Weskaap Provinsie (WCP), en het ‘n belangrike pes geword in die meeste stedelike en landelike gebiede in die land. Die Argentynse mier het betreklik min aandag gekry in Suid-Afrika, in vergelyking met ander lande (bv. California, Noord Amerika). Tans is die omvang van die landwye indringing van hierdie spesie, sowel as sy impak op die plaaslike mier fauna binne beskermde areas, nog nie bepaal nie. In hierdie studie word die impak van die Argentynse mier op die inheemse mier fauna binne drie beskermde areas in die WCP (Helderberg Natuurreservaat (HNR), Jonkershoek Natuurreservaat (JNR) en Kogelberg Biosfeerreservaat (KBR)) bepaal. Spesierykheid en diversiteit was vergelyk tussen ingedringde en oningedringde lokaas stasies in elke beskermde area. Verskeie inheemse mier spesies was deur die Argentynse mier verplaas in al drie beskermde areas, alhoewel drie spesies: Meranoplus peringueyi, Monomorium sp. 8 en Tetramorium quadrispinosum het saam met dit voorgekom. Ingedringde lokaas stasies het beduidend laer mier spesierykheid en spesies omset gehad as oningedringde lokaas stasies. Dus, die indringing van beskermde areas deur die Argentynse mier het ernstige negatiewe gevolge vir die spesierykheid en gemeenskap struktuur van inheemse miere, wat lei tot die biotiese verarming van hierdie plaaslike mier gemeenskappe. Die verspreidingsarea van die Argentynse mier binne die drie beskermde areas (HNR, JNR, KBR), en die mikrohabitat voorkeure wat die verspreiding van die spesie binne hierdie reservate kan vergemaklik, was ook vasgestel. Helderberg Natuurreservaat was die mees ingedringde beskermde area, met die hoogste vlak van Argentynse mier besetting, terwyl JNR en KBR laer besettingsvlakke gehad het. By al drie die beskermde areas was hierdie spesie dominant by laer hoogtes bo seevlak en het ‘n duidelike voorkeur getoon vir areas met hoë menslike versteuring d.i. rondom geboue en op grasperke (piekniek areas). In hierdie studie was daar geen bewyse dat vog beskikbaarheid die voorkoms en verspreiding van die Argentynse mier binne die reservate vergemaklik nie. Ten slotte, ‘n kombinasie van gepubliseerde literatuur verslae, museum dokumente en verslae wat in hierdie studie versamel is, was gebruik om die huidige verspreidingsomvang van die Argentynse mier te bepaal. Dit is die eerste studie wat die verspreiding en omvang van indringing in stedelike Suid Afrika van die Argentynse mier dwarsdeur die land bepaal. Die Argentynse mier is gevind in ses van die nege provinsies in Suid-Afrika, en die omvang van sy voorkoms sluit bykans die helfte van die land se landoppervlaksarea in. Onderbrekings in die verspreiding van die Argentynse mier deur die land het blootgelê dat die uitbreiding van die voorkomsgebied van die Argentynse mier in Suid-Afrika hoofsaaklik gebeur deur mens bemiddelde verspreiding eerder as natuurlike nesverspreiding. Hierdie studie het duidelik gedemonstreer dat die Argentynse mier goed gevestig is regoor Suid-Afrika sowel as in beskermde areas. Die Argentynse mier indringing was beïnvloed deur mensgewysigde landskappe (d.i. geboue) by lae en hoë hoogtes bo seevlak, en dit was verwant aan hoër vlakke van verplasing van inheemse mier species in hierdie areas. Dus, die beperking van ontwikkeling van rekreasie areas, soos geboue en piekniekareas, in beskermde gebiede sal lei tot laer vlakke van verspreiding van die Argentynse mier. Dit sal, op sy beurt, die omvang van verplasing van die inheemse mier spesies verminder.

Thesis (MScConEcol) Stellenbosch University, 2012. / ENGLISH ABSTRACT: The decline of sable antelope through much of the lowveld region of Zimbabwe and South Africa has become an issue of concern for wildlife managers. On Malilangwe Wildlife Reserve (MWR) alone, sable numbers crashed from 237 animals in 1994 to only 62 by 2005. The purpose of this study was to determine the cause of the decline and the continued lack of success in the sable population. The study had three specific aims: 1) to assess the current viability of the sable population at MWR and understand the sensitivity of the population to environmental changes, 2) to gain an understanding of the space-use and habitat selection of sable at the landscape scale, and 3) to speculate on the possible causes of the decline in sable antelope numbers at MWR. GPS collars were fitted to four sable herds at MWR and a fifth herd was monitored opportunistically over the study period. From these, life history data were collected and fed into a VORTEX population viability model to assess the current viability of the sable population at MWR. Vital rates input into the model were then manipulated, simulating the effect of natural pressures placed on the population. A sensitivity analysis was used to determine the sensitivity of the population to these natural pressures, using the long term growth rate as a relative measure of overall fitness. The results suggest the current population will remain extant but that natural pressure placed on the adult female segment of the population could have a drastic impact on the success of the sable population. The evidence indicates that the decline in sable numbers at MWR must have been driven by an increase in mortality in the adult segment of the population. The GPS collars gave regular fixes enabling the development of a spatial pattern of home-range and habitat use over time. LoCoH was used to develop seasonal home ranges and utilization distributions for the sable herds at MWR. A multiscale approach was used to investigate habitat selection by sable over time at MWR, using a Bonferonni Z-statistic, time series graphs and Maximum Entropy modeling. Sable used much larger ranges during the early wet season than during any other season at MWR and were highly selective at the broad scale spending more than 92% of their time foraging on the nutrient rich basalt derived soils. At the finer scale sable generally chose for areas characterized by a well developed grass layer on shallow calcareous soils moving onto areas of deeper clay rich soils during the dry season and consistently made use of areas further than average from water. Data from the collars were then used to conduct bi-monthly tick drags along the sable foraging paths to assess the level of tick challenge faced by each herd over time and this was related back to the survival rate of calves within each herd using linear regressions. The effects of predation were assessed again using the GPS collar data and a novel method of determining predation risk using motion sensor camera traps. The level of predation risk was then related back to the survival rate of each age class in the sable population. The long term effects of predation on the sable population was investigated using historical data on sable carcasses discovered and the annual rate of population decline. These were regressed against lion population numbers to determine whether any relationship existed between lion population numbers and the rate of population decline. Tick challenge had no effect on the survival of sable calves and the overall tick challenge at MWR was extremely low during the study period. Predators however seemed to have an impact on the sable population in a number of ways. Hyaena’s seemed to have a major impact on the survival of sable calves, particularly during the first few weeks of life and lion numbers showed a strong relationship with the overall rate of population decline. Sable antelope are highly susceptible to predators and lions seem primarily to blame for driving the decline in the species at MWR. The relationship is however not entirely clear and evidence suggests that a number of variables including vegetation cover and water distribution play a role in determining the impact that predators have on sable populations.

Thesis (MScAgric (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / The codling moth, Cydia pomonella (L.), is a key pest in pome fruit orchards in South Africa. In the past, broad spectrum insecticides were predominantly used for the local control of this moth in orchards. Concerns over human safety, environmental impact, widespread dispersal of resistant populations of codling moth and sustainability of synthetic pesticide use have necessitated the development and use of alternative pest management technologies, products and programmes, such as the use of entomopathogenic nematodes (EPNs) for the control of codling moth. Entomopathogenic nematodes belonging to either Steinernematidae or Heterorhabditidae are ideal candidates for incorporation into the integrated pest management programme currently being developed for pome fruit orchards throughout South Africa with the ultimate aim of producing residuefree fruit. However, these lethal pathogens of insects are not exempted from governmental registration requirements and have therefore not yet been commercialized in South Africa. A nontarget survey was conducted to find suitable isolates of EPNs from local soils and to test their effectiveness as control agents against the codling moth. Soil samples were collected from several habitats and regions throughout South Africa and nematodes were recovered using the insect baiting technique. All EPN isolates obtained were identified to species level using a molecular taxonomic approach. Entomopathogenic nematodes were recovered from 20 of the 200 soil samples (10 %). Of these, eight (40 %) yielded Steinernema spp., identified as three isolates of S. khoisanae and five undescribed Steinernema spp. The other 12 (60 %) of the samples were positive for Heterorhabditis spp. and included six isolates of H. bacteriophora, five H. zealandica and one H. safricana. These isolates were then evaluated in laboratory bioassays for their potential as microbial agents of codling moth under varying conditions. A morphometric study indicated that all natural openings (mouth, anus and spiracles) of final instar codling moth were large enough for the infective juveniles (IJs) of all tested EPN species to gain entry into the larvae.

Thesis (MScConsEcol(Conservation Ecology and Entomology)--Stellenbosch University, 2008. / The Succulent Karoo biodiversity hotspot is threatened by pressure caused by increasing human populations and its associated land use types. Land use is primarily focussed on agriculture, with livestock grazing as a dominant land use in the region. Cultivation is also practiced along the major perennial rivers, and in drier areas, where this largely depends on rainfall. Only about seven percent of the biome is formally protected, and this area substantially under-represents the biodiversity of the Succulent Karoo and does not incorporate key ecological processes and biodiversity drivers. Therefore, there is urgent need for outside reserve conservation initiatives, whose success depend on understanding the ecosystem function of the Succulent Karoo. This study aimed to determine the impacts of heavy grazing, light grazing and cultivation (in a 30-year old fallow field) on assemblages of ground-dwelling and flying invertebrates. Seasonal assemblage changes were also determined. Vegetation structure and composition were determined using the line-intercept method to determine if vegetation patterns explain patterns in invertebrate assemblages. Abandoned fields harbour the lowest number of plant species, and these together with the heavily grazed sizes are dominated by a high cover of Galenia africana (Aizoaceae). Lightly grazed sites have the highest structural complexity, with a high cover of succulents and non-succulent perennials. After the winter rains, annual plants occupy most of the bare ground in heavily grazed and previously cultivated sites. Seasonal changes in assemblages of ground-dwelling and flying invertebrates were determined by sampling during the four seasons at the same localities. Results of pitfall traps sampling for ground-dwelling invertebrates and coloured pan traps for flying invertebrates showed that overall species richness and diversity peaked in spring for flying invertebrates while peaks in richness for ground-dwelling invertebrates were in summer, with no difference in overall diversity. Overall abundance for ground-dwelling invertebrates was highest in summer and lowest in winter. Ground-dwelling invertebrate fauna was dominated by Formicidae and Araneae. Grazing and cultivation lead to skewed community composition of ground-dwelling invertebrates which favours disturbance tolerant and generalist species such as Anoplolepis steingroeveri (Forel).

Thesis (MSc(Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The stomachs of 286 crocodiles (17 cm to 166 cm snout to vent length) were lavaged over a two year period. Crocodylus niloticus has a similar ontogenetic shift in diet to that of other crocodilians. Yearlings predated primarily on aquatic insecta and arachnida, as crocodile size increased (juveniles) the diet became more diverse including crustacea, amphibia and fish. The largest size class (sub-adults) consumed primarily fish. Yearlings fed consistently throughout the year, however a higher proportion of empty stomachs occurred within the juvenile and sub-adult size classes during the winter months. A captive experiment with wild caught crocodiles (0.7 kg - 20 kg) indicated a decrease in satiation rate (maximum mass of food eaten as a percentage of crocodile body mass) from 11.3 % to 6.5 % with an increase in crocodile size. Wild yearlings consumed 0.48 % of their body mass in prey per day, and juveniles, 0.23 %. The wild food conversion rates of natural prey were low, 32 % and 40 % for yearlings and juveniles respectively. This was possibly due to a high percentage of indigestible (chitinous) invertebrate mass in the diet. The percentage of stomach stone mass to crocodile body mass increased with crocodile size. Seven species of nematodes were found within the stomachs, four of which represent new geographic records.