Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to determine how P nutrition affects biological nitrogen fixation (BNF) via effects on the N2-fixing bacteria in the nodules of Virgilia species native to the Cape Floristic Region (CFR), South Africa. This was evaluated in 3 separate studies: The first study aimed to determine how phosphorus deficiency affects N nutrition of two legume tree species from the Mediterranean Fynbos ecosystem. This study showed that during prolonged P deficiency, V. divaricata maintained a constant biomass, while V. oroboides showed a decreased biomass. V. oroboides showed a decrease in nutritional concentrations, which resulted in the decrease of symbiotic nitrogen fixation (SNF). Both plants utilized atmospheric N more efficiently per nodule under P deficiency. Maximum photosynthesis decreased in V. oroboides, while V. divaricata maintained its photosynthesis. Both species also had greater carbon construction costs during P deficiency. V. divaricata showed clear adaptive features during P-deficiency, as it maintained its growth respiration. The two legume species appear to have different adaptations to P deficiency, which may influence their performance and distribution in their naturally low P environment. The second study aimed to evaluate if soil environmental conditions and mineral nutrient concentration play a major role in microbial communities in plant rhizosphere and nodulation during N2 fixation in legumes. Therefore this study firstly aimed to determine the composition of the N2 fixing bacterial population in the rhizosphere and nodules of V. divaricata. Secondly, it aimed to determine the contribution of these bacteria to N2 fixation during conditions of P deficiency in the Fynbos environment. In the study, the effects of phosphate (P) nutrition on N2 fixing bacterial community structures in Virgilia divaricata rhizosphere and nodules were examined in a pot experiment. V. divaricata were germinated in Fynbos soil as natural inoculum, transferred to clean sand cultures and supplied with 500 μM P and 5 μM P. The N2 fixing bacterial communities in the rhizosphere and nodules were examined based on the PCR-DGGE banding patterns of 16S rDNA and sequencing methods. The GenBank blast results revealed that V divaricata was efficiently nodulated by a wide range of root-nodule bacterial strains, including Burkholderia phytofirmans, Burkholderia sp. and Bradyrhizobium sp. during low P supply. The 15N natural abundance data also confirmed that 40-50% of the N nutrition was acquired through symbiotic N2 fixation. This is not only evidence of nodulation, but also an indication of the adaptation of a range of N2 fixing bacterial strains / species to the nutrient poor, sandy, acidic soil of the Mediterranean-type ecosystems of the Fynbos. The third study examined the physiological effects, such as N2 fixation parameters, plant dependence on N2 fixation, N preference, legume plant growth, carbon costs and amino acid biosynthesis during P deficiency and mineral N supply as NH4NO3 in a slow-growing, Fynbos legume tree, Virgilia divaricata. Continued application of NH4NO3 to the legume plant showed a greater increase in plant dry matter compared to plants with two nitrogen sources (mineral N and atmospheric N2) or plants that relied on atmospheric N2 fixation. Carbon construction costs were more pronounced in plants supplied with two N sources and during P deficiency. Maximum photosynthetic rates per leaf area increased during prolonged P deficiency, irrespective of the N sources. Though plants nodulated, plant dependence on N2 fixation decreased with the addition of NH4NO3. Roots and nodules of the P deficient plants showed an increase in asparagine content, most strikingly so in plants treated with a single source of N. These studies reveal that different legume species of the same genus, may employ contrasting adaptations in order to maintain N nutrition under P deficiency. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die bepaling van die wyse waarop fosfaat (P) voeding die biologiese stikstof binding (BNF) deur middel van die effek op N2-bindingsbakterië in die wortelknoppies van Virgilia spesies wat inheems tot die Kaap floraryke area (CFR), Suid Afrika is, affekteer. Drie aparte eksperimente is uitgevoer om die doel te evalueer: Die eerste studie het gepoog om te bepaal hoe 'n fosfaat tekort N voeding van twee peulplant spesies van die Mediterreense Fynbos ekosisteem affekteer. Hierdie studie het getoon dat V. divaricata 'n konstante biomassa tydens verlengde P tekort behou, terwyl V. oroboides ‟n verlaagde biomassa getoon het. V. oroboides het 'n verlaging in voedingskonsentrasies getoon, wat tot 'n verlaging in simbiotiese stikstof binding (SNF) gelei het. Beide plante benut atmosferiese N meer doeltreffend per nodule tydens P tekort. Die maksimum fotosintese in V. oroboides het afgeneem, terwyl V. divaricata sy fotosintese gehandhaaf het. Beide spesies het ook 'n groter koolstof konstruksie koste tydens P tekort gehad. V. divaricata toon duidelike aanpassingsmeganismes tydens P-tekort, aangesien hierdie species sy groei respirasie konhandhaaf. Dit wil voorkom asof die twee peulplant spesies verskillend aangepas is vir P tekort, wat hulle producksie en verspreiding in hulle natuurlike lae P omgewing mag beïnvloed. Die doel van die tweede studie was om te bepaal of grond omgewingskondisies en minerale voedingskonsentrasie 'n belangrike rol speel in die mikrobiese gemeenskappe in die plant risofeer en wortelknoppie vorming tydens N2 binding in peulgewasse. Eerstens het die studie dus gepoog om die samestelling van die N2 bindende bakteriële populasie in die risosfeer en die wortelknoppies van V. divaricata te bepaal. Ten tweede, is die bydrae van die bakterië tot N2-binding tydens P tekort kondisies in die Fynbos omgewing bepaal. In die studie is die effek van fosfaat (P) voeding op die N2-bindende bakteriële gemeenskapstrukture in die Virgilia divaricata risofeer en wortelknoppies in 'n pot eksperiment ondersoek. V. divaricata sade is in fynbos grond as 'n natuurlike inokulum ontkiem, waarna dit na skoon sand kulture oorgedra is en van 500 μM P en 5 μM P voorsien is. Die N2-bindende bakteriële gemeenskappe in die risofeer en wortelknoppies is op grond van die PCR-DGGE band patrone van die 16S rDNA en volgorde bepalingsmetodes ondersoek. Die GenBank Blast resultate het getoon dat V. divaricata doeltreffend deur 'n wye reeks wortel-wortelknoppie bakteriële stamme genoduleer is, insluitende insluitende Burkholderia phytofirmans, Burkholderia sp. en Bradyrhizobium sp. tydens lae P toediening. Die natuurlike 15N voorkoms data het ook bevestig dat 40-50% van die N voeding deur simbiotiese N2 binding bekom is. Dit dien nie net as bewys vir wortelknoppie vorming nie, maar ook 'n aanduiding van die aanpassing van 'n reeks N2 bindende bakteriële stamme/ spesies tot die voedingsarme, sanderige, suur grond van die Mediterreanse ekosisteem van die Fynbos. Die derde studie het die fisiologiese effekte soos bv. N2 fikserings faktore, die afhanklikheid van plante op N2 fiksering, N voorkeur, peulgewas groei, koolstof kostes en aminosuur biosintese tydens P tekort en minerale N toediening soos NH4NO3 in 'n stadig-groeiende, Fynbos peulgewasboom, Virgilia divaricata ondersoek. Volgehoue toediening van NH4NO3 aan die peulplant toon 'n groter toename in plant droë weefsel. Tydens P tekort is die koolstof bou koste meer verhoog in plante wat met twee N bronne voorsien is. Tydens verlengde P tekort het die maksimum fotosintese tempo per blaaroppervlakte toegeneem, ongeag die N bron. Alhoewel die plante wortelknoppies gevorm het, het die plant se afhanklikheid van N2 binding tydens die toediening van NH4NO3 afgeneem. Wortels en wortelknoppies van die P tekort plante het 'n toename in asparagien inhoud getoon, veral in die plante wat met 'n enkele bron van N behandel is. / The DST/NRF-Center of Excellence for Tree Health and Biotechnology, based at the University of Pretoria, for their financial support

Thesis (MScConsEcol (Conservation Ecology and Entomology)--University of Stellenbosch, 2009. / Apiculture in the Western Cape is a well-developed industry based on honey production and pollination services to agriculture. Apart from Eucalyptus trees, fynbos vegetation serves well as bee forage to managed honeybee colonies outside the agricultural pollination season. Eucalyptus trees are cleared as invasive plant species while fynbos are rigorously protected as one of the 34 Biodiversity Hotspots identified worldwide. Thus, bee forage is in short supply and is most probably the only limitation to the number of honeybee colonies that beekeepers can feasibly maintain. The impact of a collection of commercially managed honeybee colonies on other floral resource-dependent species in the Cape Floristic Region is unknown. This is one of the first studies on the topic in South Africa and specifically in the Western Cape. Managed hives were introduced to near pristine fynbos habitat in De Hoop Nature Reserve and Marine Protected Area during July. The aim was to induce stronger competition for floral resources through greater resource exploitation by managed honeybee colonies and record the change in foraging behaviour for several insect guilds on specific plant species. The results suggest that eight hives per site proved insufficient to increase honeybee density above the natural density of honeybees. Honeybee abundance did not increase during the presence of the managed hives, while honeybee visitation frequency was significantly greater during the presence of the managed hives. Neither the abundance nor the visitation frequency of non-Apis bees and wasps differed significantly between treatments. Honeybees were the most abundant foragers on the three focal plant species during all three treatments and also made the most visits to flowers. Honeybee abundance and visitation frequency increased with distance from the managed hives. The significant increase in honeybee visitation frequency during hive presence, coupled with a significant decrease in the time honeybees spent per flower extracting nectar, were an indication of a lower standing crop of nectar during that treatment. Nevertheless, no competition for floral resources was obvious, as the number of honeybees did not increase the abundance and visitation frequency of all other insect guilds (except for a significant decrease in Muscidae, which could be ascribed to changes in weather conditions).

Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The Restionaceae is a dominant family in the Fynbos Biome, an area in which fire plays a role as an important disturbance, yet little is known about their population dynamics. Two species of the Restionaceae (Thamnochortus insignis and T. erectus) are economically important as thatching reed and differ in their life-histories. This study aims to determine the effects of variation in life history (sprouter vs. non-sprouter) on the population structure and dynamics of T. erectus (“wyfies riet”, sprouter) and T. insignis (“mannetjies riet”), a non-sprouting species. A matrix-modelling approach based on field data collected by Ball (1995) is used to determine population growth rates, stable stage distributions and stage sensitivity and elasticity for the two species with no disturbance present. The sprouter (T. erectus) shows a positive population growth rate (λ >1) and greater persistence within all stages. The non-sprouting species (T. insignis) shows a negative population growth rate (λ <1) between disturbances as well as greater seed production, germination and growth between stages. Based on the population dynamics of these two species, further research was done to understand the effect of disturbance (harvesting and fire) on these species. A matrix modelling approach was used to determine which disturbance frequency maximises population output and success. Harvesting as well as fire results in a decline in T. insignis populations. A five year frequency for harvesting results in the greatest output of adult plants with the lowest effect on the population, and a fire frequency of 50 to 65 years is recommended. Testing indicates that the model underestimates the number of adults in the population and thus the model is conservative. T. erectus populations grow despite fire or harvesting; thus any reasonable harvesting (3-5 year frequency) and fire (10+ years between fire) regime would ensure population persistence. As data were limited it was not possible to test the results although T. erectus appears resilient to disturbance and therefore a predetermined regime is not as important as in T. insignis. Recommendations to farmers are made based on these results.

Thesis (MScConEcol)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The fire-prone mediterranean-type climate regions of the world are immensely biodiverse. Changes in fire frequency due to anthropogenic ignitions and climate change are one of the factors threatening the plant diversity of these regions. Many postfire regeneration studies have focused on seedling recruitment, whereas much can still be learned about regeneration through resprouting. This project focused on resprouters after a fire and assessed if there are differences between the obligate (OS) and facultative (FS) resprouting life history types. OS species have to resprout after fire, as their seeds are not fire resistant and seedling recruitment takes place in fire-free periods, whereas FS species have the ability to resprout and recruit seedlings after a fire. My analyses found a significant difference in postfire resprout success between OS species and FS species, supporting the division of woody resprouting shrubs into these two life history types. OS species had minimal fire-related mortality and this was related to their ability to resprout early and vigorously after fire. OS species had no postfire mortality, which points to traits that enable them to endure the hot and dry summer months. The FS species varied in their response to fire and had greater fire induced mortality than the OS species. Postfire mortality (post-sprouting) was also greater compared to OS species, especially towards the end of the long dry summer suggesting a link to water stress. A postfire seedling survey of target FS, OS and non-sprouters (NS), revealed that NS species had seedling/adult ratios that were orders of magnitude higher ranging between 40-200 seedlings per adult against less than 1-10 seedlings per adults for FS, with OS species recruiting no seedlings directly postfire, as is consistent with their life history type. Although the NS species do not sprout and the FS species had some mortality, the population was at or above replacement two-year postfire on account of seedling recruitment. OS species maintained their pre-fire population by successfully resprouting and by experiencing almost no postfire mortality. These results provide strong justification for grouping woody resprouters into OS and FS species in future studies seeking to understand the underlying differences in postfire recovery. Postfire flowering phenology was also observed during the two year study period. Geophytes, mostly belonging to the Iridaceae and Orchidaceae were overrepresented within the first year postfire, many displaying fire-stimulated flowering. This suggests that some geophytes limit their reproductive cycle to the immediate postfire environment, when nutrients and light are abundant. Smaller resprouting shrubs generally flowered earlier than larger resprouting shrubs. Many non-sprouting shrubs did not reach maturity within the study period and those that did mostly belonged to the Fabaceae and Asteraceae families. This study added 71 species to the existing Paarl Mountain species list, including eight new red listed species, highlighting the importance of early postfire field surveys. / AFRIKAANSE OPSOMMING: Veldbrande is ‘n natuurlike verskynsel in die meditereense klimaatstreke van die wereld. Hierdie areas is ook bekend vir hulle ryk biodiversiteit. Veranderinge in die vuur frekwensie as gevolg van klimaatsverandering en veldbrande wat deur mense veroorsaak word, bedreig die plantdiversiteit van hierdie streke. Vorige veldbrandstudies het meestal gefokus op saailinge en daar bestaan ‘n groot leemte om regenerasie deur herspruiting beter te verstaan. Hierdie navorsingsprojek fokus op herspruiting van fynbos plante as ‘n oorlewingstrategie na ‘n veldbrand. Spesifiek word daar gekyk na verskille tussen verpligte (VH) en nie-verpligte (fakultatiewe) herspruiters (FH). VH spesies moet herspruit na vuur om hulle populasie stabiel te hou, aangesien hulle saad nie vuurbestand is nie. FH spesies het die vermoë om te herspruit sowel as saailinge te werf na ‘n brand. Die studie bevindinge dui op betekenisvolle verskille tussen hierdie twee lewensgeskiedenistipes en regverdig die groepering van houtagtige herspruiter spesies as VH of FH. VH het minimale mortaliteit getoon na die veldbrand. Bykans alle plante het vinnig en kragtig herspruit. VH besit ook eienskappe wat hulle in staat stel om die warm, droeë somers te oorleef. Die oorlewing van FH was wisselvallig, met mortaliteit as gevolg van direkte vuurskade en verdere mortaliteit gedurende die lang somermaande, moonlik as gevolg van water stress. ‘n Saailingstudie van VH, FH en ook nie-spruiters (NS) het getoon dat die saailing/volwasse verhoudings van NS ordes hoër is as die van FH. VH het geen saailinge direk na die vuur geproduseer nie. Twee jaar na die vuur was FH en NS saailing getalle steeds heelwat meer as die aantal volwasse plante wat dood is in die veldbrand. VH het hul populasie stabiliteit gehandhaaf deurdat alle volwasse plante suksesvol herspruit het. Hierdie bevindinge regverdig die verdeling van herspruitende fynbos spesies as VH of FH. Verdere studies is belangrik om die onderliggende ekofisiologiese verskille tussen die twee lewensgeskiedenistipes beter te verstaan. Die blompatrone van verskillende spesies is ook aangeteken tydens die tweejaar studieperiode. Bolplante, veral in die iris- (Iridaceae) en orgidee (Orchidaceae) families het oorheers gedurende die eerste jaar na die brand, aanduidend van ‘n vuur-gestimuleerde blompatroon. Sommige bolplante mag hul voorplantingssiklus beperk tot die periode direk na veldbrand, terwyl daar genoeg lig is en die grond verryk is met voedingsstowwe. Kleiner herspruitende struike het in die algemeen vroeër geblom as groter struike. Nieherspruitende struike het meestal nie seksuele volwassenheid bereik binne twee jaar na die veldbrand nie, buiten sommige in die ertjie- (Fabaceae) en asterfamilies (Asteraceae). Die studie het 71 nuwe spesies tot die bestaande Paarlberg spesielys gevoeg, waarvan agt rooidataspesies was, wat die waarde van plantopnames direk na ‘n veldbrand beklemtoon.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Antimicrobial resistance is one of the major problems faced by the medical industry today. The ability of bacteria to rapidly acquire resistance against antibiotics and the over prescription and inappropriate use of antibiotics further exacerbate this crisis. Few new antimicrobials are, however, making it through the drug discovery pipeline. The search and development of novel and effective antimicrobials is therefore of the utmost importance. Lantibiotics are ribosomally synthesized cationic antimicrobial peptides with extensive post-translational modifications. They are active against a wide range of Gram-positive bacteria, including antibiotic-resistant strains. They are characterized by the presence of lanthionine and methyllanthionine rings and have been suggested as alternatives or for use in conjunction with antibiotics against resistant pathogens. Staphylococcus aureus is the most common bacteria isolated from skin and soft tissue infections (SSTIs). Strains of S. aureus have emerged with resistance against antibiotics with the most common being methicillin-resistant S. aureus (MRSA). Several lantibiotics are active against MRSA in vivo and have even shown superior activity to traditional antibiotics. Lantibiotics therefore show much promise for the treatment of SSTIs caused by resistant- and non-resistant S. aureus. In this study the bacterially diverse soil of the Fynbos in the Western Cape was screened for novel antimicrobials. Two antimicrobial producing Bacillus strains were isolated, Bacillus clausii AD1 and Bacillus amyloliquefaciens AD2. Both of these strains produce lantibiotics with B. clausii AD1 producing a known lantibiotic, clausin. B. amyloliquefaciens AD2 produces a novel two-component lantibiotic which was designated amyloliquecidin. The lantibiotic operon of amyloliquecidin was sequenced and annotated. All the genes required for successful production of amyloliquecidin are present in the operon. Amyloliquecidin was characterized in vitro and along with clausin is active against clinical strains of S. aureus (including MRSA), Enterococcus spp., Listeria spp. and beta-haemolytic streptococci. Amyloliquecidin has remarkable stability at physiological pH compared to nisin and clausin. A comparative in vivo murine infection model was used to evaluate the effectiveness of amyloliquecidin, nisin, clausin and Bactroban (commercial S. aureus topical treatment) in treating wound infections caused by S. aureus. All the lantibiotics proved to be just as effective as the Bactroban treatment. Furthermore, the tested lantibiotics did not have a negative influence on the wound closure rates of infected and non-infected wounds. Bactroban had a negative effect on wound healing compared to the lantibiotics. To our knowledge amyloliquecidin is the third two-component lantibiotic isolated from Bacillus. This study represents the first to test the effectiveness of amyloliquecidin in vivo and is one of a handful to test lantibiotics as topical treatments. / AFRIKAANSE OPSOMMING: Antimikrobiese weerstandbiedende bakterieë is op die oomblik een van die grootste probleme in die mediese veld. Die antibiotika krisis word vererg deur die vermoë van bakterieë om vinnig weerstand op te bou teen antibiotika, asook die alledaagse misbruik van antibiotika. Daar is ook ʼn tekort in die hoeveelheid antibiotika wat na die finale fases van ontwikkeling gaan. Om die oorhand teen antibiotika-weerstandige bakterieë te kry is dit van uiterste belang dat meer effektiewe antibiotika ontdek word. Lantibiotika is kationiese antimikrobiese peptiede wat deur die ribosoom gesintetiseer word en bevat ʼn verskeidenheid van modifikasies wat na translasie ingebou word. Hulle word gekarakteriseer deur lanthionien en metiellanthionien ringe. Lantibiotika is aktief teen ʼn verskeidenheid Gram-positiewe bakterieë en kan in kombinasie met antibiotika, of as alternatief gebruik word. Staphylococcus aureus is die mees algemene bakterium wat geassosieer word met vel en sagte weefsel infeksies (VSWIs). Staphylococcus aureus met weerstand teen antibiotika is ook al geïsoleer, die mees algemene weerstandige ras is methisillien-weerstandige S. aureus (MWSA). Lantibiotika is wel aktief teen MWSA in vitro en in vivo, met van hulle wat tot beter aktiwiteit as die voorgeskrewe antibiotika het. Lantibiotika kan dus gebruik word as behandeling vir VSWIs wat veroorsaak word deur weerstandige S. aureus, asook teen nie-weerstandige rasse. In hierdie studie was die bakteriese diverse grond van die Fynbos in die Wes-kaap ondersoek vir bakterieë wat antimikrobiese middels produseer. Twee Bacillus rasse, Bacillus clausii AD1 en Bacillus amyloliquefaciens AD2, wat antimikrobiese middels produseer, is geïsoleer. Bacillus clausii AD1 produseer ʼn bekende lantibiotikum, naamlik clausin. Bacillus amyloliquefaciens AD2 produseer ʼn nuwe twee-komponent lantibiotikum, amyloliquecidin. Die lantibiotikum operon wat verantwoordelik is vir die produksie van amyloliquecidin is geïdentifiseer en geannoteer. Die operon bevat al die gene benodig vir die biosintese van amyloliquecidin. Amyloliquecidin is in vitro gekarakteriseer en het aktiwiteit teen ʼn verskeidenheid Gram-positiewe bakterieë. Amyloliquecidin en clausin is aktief teen S. aureus (insluitend MWSA), Enterococcus spp., Listeria spp. en beta-hemolitiese streptococci wat vanaf infeksies geïsoleer is. Amyloliquecidin is baie stabiel by filologiese pH en aansienlik meer stabiel as nisin en clausin. Die effektiwiteit van nisin, clausin en amyloliquecidin in die behandeling van muis vel infeksies veroorsaak deur S. aureus was vergelyk met die kommersiële behandeling Bactroban. Al drie lantibiotika het die verspreiding van S. aureus met die selfde effektiwiteit as Bactroban belemmer. Geen van die lantibiotika het ʼn negatiewe effek op wond genesing nie. Bactroban, inteendeel, belemmer wond genesing. So ver ons weet is amyloliquecidin die derde twee-komponent lantibiotikum wat uit Bacillus geïsoleer is. Die studie is ook die eerste om die effektiwiteit van amyloliquecidin in vivo te rapporteer, asook ook een van die min studies wat kyk na lantibiotika as behandeling vir topikale infeksies.

Thesis (DSc (Botany and Zoology))—-Stellenbosch University, 2008. / The south-western Cape is a unique region of southern Africa with regards to generally low soil nutrient status, winter rainfall and unusually species-rich temperate vegetation. This region supported a diverse large herbivore (> 20 kg) assemblage at the time of permanent European settlement (1652). The lowlands to the west and east of the Kogelberg supported populations of African elephant, black rhino, hippopotamus, eland, Cape mountain and plain zebra, ostrich, red hartebeest, and grey rhebuck. The eastern lowlands also supported three additional ruminant grazer species - the African buffalo, bontebok, and blue antelope. The fate of these herbivores changed rapidly after European settlement. Today the few remaining species are restricted to a few reserves scattered across the lowlands. This is, however, changing with a rapid growth in the wildlife industry that is accompanied by the reintroduction of wild animals into endangered and fragmented lowland areas. These reintroductions, together with the realisation that we have limited knowledge of the functional role of native large herbivores in the fynbos ecosystem, provided the rationale for this study. Questions on large herbivore ecology were addressed at three different spatial scales. At the biome level, the reason for the absence of three ruminant grazers from the western lowlands was investigated. It was hypothesised that the absence of adequate high quality fodder in the form of C4-grass during the hot and dry summers made it impossible for buffalo, blue antelope, and bontebok to survive on the western lowlands. The results from carbon isotope analysis of late prehistoric, historic and contemporary large herbivore remains were consistent to this Summer Nutritional Stress Hypothesis. I found that eland, elephant, grey rhebuck, ostrich, and red hartebeest (all species that historically occurred in both coastal lowlands) can survive with very little (< 15%) C4 grass in their diet. In contrast, bontebok utilized at least 43% C4 grass biomass in what was considered their natural habitats. At a regional level, I tested the hypothesis that the large herbivores avoid nutrient-poor sandstone, sand, and limestone fynbos shrublands in favour of the more nutrient-rich shale renosterveld habitats. Support for this Renosterveld Preference Hypothesis was found by means of dung count surveys, which showed that both eland and bontebok readily utilize renosterveld, but avoid sandstone and limestone fynbos. In the latter they only utilize grassy microhabitats such as karstic sinkhole depressions. The same hypothesis was addressed in a novel way by using strontium isotope analysis and concluded that the technique needs more refinement for it to produce reliable results. At a landscape level, interactions between fire and grazing by native large herbivores in relation to renosterveld vegetation dynamics were addressed. I conclude that the disappearance of the native herbivores probably had little bearing on the putative structural changes in renosterveld (grassland-shrubland dynamics). Support was found for the notion that a high fire frequency followed by intense grazing by livestock could have converted original renosterveld grasslands to unpalatable shrublands. Herbivory by native grazers/browsers, or the release from it, cannot by itself bring about the vegetation-state (structural) changes in renosterveld patches which had already been altered to herbivoretolerant plant communities. However, in combination with fire, the presence or absence of large herbivores can change the trajectory of the system among the alternative structural states.

Dissertation (PhD)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: South Africa, Lesotho and Swaziland are home to an endemic group of dwarf chameleons (Bradypodion). They are small, viviparous, insectivorous, arboreal lizards, found in a variety of vegetation types and climatic conditions. Previous work on Bradypodion pumilum suggests prolonged breeding and high fecundity which is very unusual for a viviparous lizard inhabiting a Mediterranean environment. It has been suggested that the alleged prolonged reproduction observed in B. pumilum may be a reproductive adaptation to life in a fire-prone habitat. In addition, Chamaesaura anguina a viviparous, arboreal grass lizard also occurs in the fire-frequent fynbos and exhibits an aseasonal female reproductive cycle with high clutch sizes; highly unusual for the Cordylidae. With the observation of two species both inhabiting a fire-driven environment and exhibiting aseasonal reproductive cycles with high fecundity, it was thought that this unpredictable environment may shape the reproductive strategies of animals inhabiting it. However, detailed reproductive data for B. pumilum were unavailable. The first aim was provide baseline reproductive data for B. pumilum and to discuss the reproductive strategy in relation to a fire-prone environment. To establish the significance of fire in the reproductive strategy of B. pumilum, reproductive data of other Bradypodion species, not inhabiting the fire-prone area was required. The second aim was to provide baseline reproductive data for Bradypodion with discussion on possible scenarios facilitating the evolution of dwarf chameleon reproduction. Bradypodion pumilum specimens were collected in monthly samples from Stellenbosch and Somerset West in the Western Cape, South Africa. Specimens of other Bradypodion species were obtained from South African museums. Data were collected for both sexes of Bradypodion, and sperm storage ability was investigated in B. pumilum. Bradypodion females all showed an aseasonal reproductive cycle with relatively high clutch sizes for their body size and the possibility of individual females producing multiple clutches per year. Male Bradypodion have sperm available the entire year round however, there appears to be an increase in sperm production in autumn and again in spring in B. pumilum. Elements of this bimodal pattern are seen in other Bradypodion species. Dwarf chameleons regardless of habitat and associated climatic conditions are thus able to reproduce through out the year. It has also been demonstrated in B. pumilum that both sexes are able to store sperm and it is expected that other Bradypodion species would posses this character. This type of reproductive strategy is highly unusual for viviparous, temperate-zone lizards. It is likely that the cooling of the climate due to the development of the Benguela current facilitated the transition to viviparity in Bradypodion. Bradypodion may be aseasonal reproducers for a number of reasons. They are of tropical ancestry, they relatively recently inhabited tropical forests, or fluctuations in climate may have caused this. Bradypodion most likely have a high reproductive output due to their intense vulnerability to predation as in other chameleon species. The proposed hypothesis that the unusual reproductive characteristics of B. pumilum (and possibly the ancestral Bradypodion) were due to inhabiting a fire-prone environment now appears an unlikely explanation. However, even if this extraordinary reproduction was not in direct response to fire, the strategy appears beneficial in this type of unpredictable environment. / AFRIKAANSE OPSOMMING: Suid-Afrika, Lesotho en Swaziland huisves ‘n endemiese groep van dwergverkleurmannetjies (Bradypodion). Hulle is klein, lewendbarende, insekvretende, arboreale akkedisse en word gevind in ‘n verskeidenheid van plantegroeitipes en klimaatsomstandighede. Vorige studies op Bradypodion pumilum dui op ‘n verlengde broeiseisoen en hoë fekunditeit, wat ongewoon is vir ‘n lewendbarende akkedis wat in ‘n Mediterreense omgewing voorkom. Daar is voorheen voorgestel dat die skynbare verlengde voortplanting in B. pumilum ‘n aanpassing tot oorlewing in hoogs brandvatbare habitat kan wees. Chamaesaura anguina is ook ‘n lewenbarende, arboreale akkedis wat in fynbos voorkom wat hoogs vatbaar is vir brande en groot werpsels produseer en ‘n aseisoenale voortplantingsiklus in wyfies toon; hierdie patroon is ongewoon vir lede van die Cordylidae. Met die waarneming dat twee species wat in ‘n brandvatbare omgewing voorkom albei aseisoenale voortplantingsiklusse en hoë fekunditeit toon, het die gedagte ontstaan dat hierdie onvoorspelbare omgewing die voortplantingstrategieë van diere wat daarin voorkom, bepaal. Gedetailleerde voortplantingsdata ontbreek egter vir B. pumilum. Die eerste doelstelling van die studie was dus om basisinligting te voorsien oor voortplanting by B. pumilum en om die voortplantingstrategie aan die hand van die brandvatbare omgewing te bespreek. Om die moontlike rol van brand in die vorming van die voortplantingstrategie van B. pumilum te ondersoek, is voortplantingsdata vir ander Bradypodion species wat nie in brandvatbare habitat voorkom nie, nodig. Die tweede doelstelling was dus om basisinligting oor voortplanting by Bradypodion in die breë in te samel, gevolg deur bespreking van moontlike scenarios in die evolusie van voortplanting by dwergverkleurmannetjies. Bradypodion pumilum eksemplare is maandeliks versamel te Stellenbosch en Somerset-wes in die Weskaap, Suid-Afrika. Eksemplare van ander Bradypodion species is vanaf Suid-Afrikaanse museums verky. Data is vir beide geslagte van Bradypodion versamel, en die vermoë tot spermstoring in B. pumilum bepaal. Bradypodion wyfies het almal ‘n aseisonale voortplantingsiklus getoon met relatief hoë werpselgroottes vir hul liggaamsgrootte en daar bestaan die moontlikheid dat individuele wyfies verskeie werpsels per jaar kan lewer. Bradypodion mannetjies produseer sperms dwarsdeur die hele jaar, maar daar blyk tog ‘n toename in spermstoring te wees in die herfs en weer in die lente in B. pumilum. Spore van hierdie bimodale patroon word in ander Bradypodion species gesien. Dwergverkleurmannetjies is dus instaat om dwardeur die jaar voort te plant, ongeag die habitat en geassosieerde klimaatsomstandighede. Daar is getoon dat beide geslagte van B. pumilum sperms kan stoor en daar word verwag dat ander Bradypodion species ook hierdie vermoë het. Hierdie tipe van voortplantingstrategie is ongewoon vir lewendbarende akkedisse van die gematigde sone. Dit is moontlik dat die ontwikkeling van ‘n koue klimaat weens die onstaan van die Benguela-stroom aanleiding gegee het tot die oorskakeling na lewendbarendheid in Bradypodion. Bradypodion mag aseisonale voortplanting toon vir ‘n aantal moontlike redes. Hulle is van tropiese oorsprong, het redelik onlangs tropiese woude betrek, of fluktuasies in klimaat kon ook die oorsaak wees. Bradypodion het waarskynlik hoë voortplantingsuitset omdat hulle besonder kwesbaar is vir predasie, soos dit die geval is by ander verkleurmannetjies. Die aanvanklike hipotese dat die ongewone voortplantingseienskappe van B. pumilum (en moontlik die voorvaderlike Bradypodion) ‘n gevolg is van lewe in ‘n hoogs brandvatbare omgewing, blyk nou ‘n onwaarskynlik te wees. Selfs as hierdie buitengewone voortplantingstrategie nie ‘n direkte gevolg van brandvatbaarheid is nie, blyk die strategie voordelig te wees vir oorlewing in hierdie onvoorspelbare omgewing.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: see item for full text / AFRIKAANSE OPSOMMING: sien item vir volteks

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: My master’s research combines aspects of pollination biology and invasion biology to explore the invasive predictors and impacts of a globally invasive group of plants – Australian acacias. Specifically, I investigate the role of reproductive biology in their invasion success (Chapter 2), the impacts of a specific species, Acacia saligna, on native plant-pollinator communities in South Africa (Chapter 3), and if the impact of A. saligna on native plant species can be predicted, based on floral trait similarity (Chapter 4). Australian acacias possess many floral traits implicated in plant invasion success, including extensive, dense floral displays, prolific seed production, long-lived seed banks, and propensity for vegetative reproduction. In Chapter 2 of my thesis, co-authors and I investigate if such reproductive traits influence whether or not a species becomes invasive once it is introduced by qualitatively and quantitatively analyzing literature and data collected from published and unpublished data. We found that invasive species reach reproductive maturity earlier and are more commonly able to resprout. Our findings have important implications for management of existing Acacia invasions as well as the assessment and prevention of further introductions of Acacia species leading to invasion. Impacts of invasive plant species on native plant visitation and consequent reproduction are often negative and have important implications for future ecosystem health. Acacia saligna is a problematic woody invasive shrub in many Mediterranean regions, and in South Africa, it invades fynbos vegetation, which boasts one of the highest plant diversities per area in the world as well as many specialized pollination mutualisms. It blooms during the flowering peak of most native species and forms dense, showy floral displays, thus the possibility of pollinator-mediated interactions with co-flowering native species is high. In Chapter 3, I assess the impact of flowering A. saligna on insect visitation to co-flowering native species by conducting flower observations at both an invaded and uninvaded (control) site. One of the native species most-visited by native honeybees, Roepera fulva, had high flower visitor overlap with A. saligna and suffered significantly lower visitation from all insects and from bees when A. saligna was present than at the control site. The native honeybee appears to be the most important visitor to A. saligna as it was the most frequent and mobile. Due to its foraging efficiency and dominance in pollinator communities, Apis mellifera subsp. capensis could be an important mediator of the negative effect of A. saligna on co-flowering natives, especially those frequently visited by honeybees. The use of floral traits as predictors of a species’ effect on co-flowering plants via pollination is commonly used in pollination biology. In the fourth chapter of my thesis, I apply the predictive principle of floral traits on flower visitation to see if floral traits can predict the impact of an invasive plant species on co-flowering native species, and if so, which floral traits are the most important. Following the same flower observation protocol as Chapter 3, I assess two measures of invasion impact on native flowers – change in visitation rate to native plant species between invaded and uninvaded sites and flower visitor overlap between A. saligna and native species – and test for a correlation with floral trait similarity of native species to and A. saligna. Similarity of categorical traits and all traits combined (categorical and continuous) were significantly positively correlated with flower visitor overlap, indicating that native species with categorical traits similar to A. saligna were more likely to share flower visitors with A. saligna. Floral symmetry and shape similarity were the most important categorical traits in driving flower visitor overlap. Findings suggest an important link between categorical floral traits and ability to predict invasive plant impact on native flower-insect interactions; however, more comprehensive studies are required for conclusive results. / AFRIKAANSE OPSOMMING: My Meestersgraad se navorsing kombineer aspekte van bestuiwingsbiologie en indringerbiologie om ondersoek in te stel na die indringing-voorspelbaarheid en die impak van Australiese Akasias, 'n wêreldwye indringende groep van plante. Ek het spesifiek gekyk na die rol van voortplantingsbiologie in hul indringing sukses (Hoofstuk 2), die impak van 'n spesifieke spesie, Acacia saligna, op die inheemse plant-bestuiwer gemeenskappe in Suid-Afrika (Hoofstuk 3), en of die impak van Acacia saligna op inheemse plantspesies voorspel kan word, gebaseer is op die ooreenkomste in blomeienskappe (Hoofstuk 4). Australiese Akasias het baie voortplantingseienskappe wat geassisioeer word met plantindringing sukses, insluitend ‘n uitgebreide, digte blommedrag, uitermatige hoë saadproduksie, langlewende saadbank, en die geneigdheid vir vegetatiewe voortplanting. In hoofstuk 2 van my tesis, ondersoek ek en my medeskrywers of sulke voortplantingseienskappe beïnvloed of 'n spesie ‘n indringer raak, deur 'n ontleding van die literatuur en data wat versamel is uit gepubliseerde en ongepubliseerde data. Ons het gevind dat indringerspesies geslagsrypheid vroeër bereik en meer algemeen in staat is om weer uit te loop. Ons bevindinge het belangrike implikasies vir die bestuur van die bestaande Akasiastande sowel as die evaluering en die voorkoming van verdere vestiging van Akasia spesies wat lei tot indringers. Impakte van uitheemse plantspesies op inheemse plant-besoeke deur bestuiwers, en gevolglike voortplanting is dikwels negatief en het belangrike implikasies vir die toekomstige ekosisteem gesondheid. Acacia saligna is 'n problematiese houtagtige indringende struik in baie Mediterreense streke, en in Suid-Afrika. Dit dring in die Fynbos in, wat spog met een van die wêreld se hoogste plant diversiteit per oppervlak, sowel as baie gespesialiseerde bestuiwing-mutualismes. Dit blom gedurende die bloeiseisoen van die meeste inheemse spesies en vorm digte, pronkerige blomuitstallings, dus is die moontlikheid hoog vir bestuiwer-gemedieerde interaksies met inheemse spesies wat saam blom. In Hoofstuk 3, het ek die impak van Acacia saligna, op insek besoeke aan saamblommende inheemse spesies bepaal, deur waarnemings op beide ingedringde en natuurlike studie gebiede. Een van die inheemse spesies, Roepera fulva, wat die meeste besoek is deur inheemse heuningbye, het 'n hoë blom besoeker oorvleueling met Acacia saligna en het aansienlik minder besoeke van alle insekte en van bye gekry toe Acacia saligna teenwoordig was as by die natuurlike studie gebied. Die inheemse heuningby, Apis mellifera subsp. capensis, blyk die mees belangrikste besoeker aan Acacia saligna te wees aangesien dit die mees gereeldste en beweeglikste was. As gevolg van sy oorheersing in bestuiwer gemeenskappe, is die by 'n belangrike faktor van die negatiewe uitwerking van Acacia saligna op die inheemse plante wat dieselfde tyd blom, veral dié wat gereeld besoek word deur heuningbye. Die gebruik van blomeienskappe as voorspellers van 'n spesie se effek op saamblommende plante deur middel van bestuiwing, word algemeen gebruik in bestuiwingsbiologie. In die vierde hoofstuk van my tesis, het ek die voorspellende beginsel van die blomeienskappe op blombesoeking toegepas, om te sien of blomeienskappe die impak van 'n uitheemse plantspesie kan voorspel op saamblommende inheemse spesies, en indien wel, watter blomeienskappe die belangrikste is. Deur dieselfde blom waarneming protokol as in Hoofstuk 3 te gebruik, het ek twee maatstawwe van indringings impakte op inheemse blomme vergelyk - verandering in besoek gereeldheid aan inheemse plante tussen ingedringde en natuurlike studie gebiede en blom besoeker oorvleueling tussen die Acacia saligna en inheemse spesies – en die toets vir 'n korrelasie van blomeienskap ooreenkomste in inheemse spesies en Acacia saligna. Soortgelykheid van kategoriese eienskappe en al die eienskappe gekombineer (kategoriese en deurlopende) is beduidend positief gekorreleerd met blombesoeker oorvleueling, wat aandui dat inheemse spesies met kategoriese eienskappe soortgelyk aan Acacia saligna meer geneig was om blom besoekers te deel met Acacia saligna. Blom simmetrie en vorm ooreenkoms was die belangrikste kategoriese eienskappe wat ly tot blombesoeker oorvleueling. Bevindinge dui op 'n belangrike skakel tussen die die kategoriese blomeienskappe en die vermoë om indringerplant impakte op inheemse blom-insek interaksies te voorspel, alhoewel, meer omvattende studies nog nodig is. / DST-NRF Centre of Excellence for Invasion Biology and the Department of Botany and Zoology at Stellenbosch University for research funding

The objective of this study was to investigate endophagous insect species richness in Fynbos. The influences of plants as determinants of insect occurrence were given special attention. The endophagous insects associated with Proteaceae in Fynbos were compared to endophage assemblages from northern, non-Capensis Proteaceae. The Cape Fynbos genus Protea is utilized by many more insect taxa than the non-Fynbos species. The high diversity of host plants in Fynbos appears to have contributed to generating high, local endophagous insect diversity. Influences of regional climate, biotope and host-plant characteristics on the frequency of occurrence of insect borers exploiting Protea species was investigated in Fynbos. Distinct differences in frequency of encounter of the various insect taxa were recorded for the various host-plants studied. This variability was primarily accounted for by physical host-plant characteristics (infructescence and seed-set variables). These findings have important implications for evolution of insects associated with these plants, as well as for the conservation of insects and in pest control programmes on indigenous cut flowers. The relative species richness of endophagous and ectophagous insects in Fynbos was compared. Gall-forming insects (Diptera: Cecidomyiidae), were found to be considerably more speciose than other feeding guilds, showing that the ratio of endophages to ectophages in sclerophyllous vegetation types is high. The intimate relationship that endophagous insects have with their host plants tends to habitat specialization. These insects are therefore likely to undergo radiation together with their host-plants. Species richness of gall-insects in Fynbos was investigated to establish whether insect richness was proportional to plant species richness. The relationship between gall-insect species richness and plant-species richness was investigated. Fynbos harboured more gall-insect species than other Cape Floristic Region vegetation types. Gall-insect species richness was positively correlated with plant-species richness. Plant species richness appears to have contributed to the evolution of a rich gall-insect fauna in the region. Fynbos gall-insect species richness is comparable to other sclerophyllous vegetation types globally, underscoring the importance of this vegetation type as a centre of galler diversification. Finally, the importance of plant species richness as a determinant of gall-insect species richness was investigated by comparing different sclerophyllous vegetation types under the same climatic conditions. Gall were sampled from Fynbos and Karoo vegetation. Fynbos had higher gall-insect species richness, correlated with plant-species richness. Plant-species richness, or the distal factors that generated it, appear to have contributed significantly to the radiation of gall-insects in this region. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1995.