Thesis (MSc (Conservation Ecology and Entomology))--University of Stellenbosc, 2005. / Biodiversity is under enormous pressure from an increasing human population. Urbanisation, agriculture, and mining are just some of the factors responsible for the continuous degradation of the natural environment. Of these, urbanisation is one of the leading factors of diversity loss. To address this problem, it is necessary to understand the relationship between biodiversity and urban areas, as well as the relationship between society and biodiversity. This study focuses on these relationships and suggest ways in which urban biodiversity can be maximised without compromising on development. In order to create an urban environment that successfully supports maximised biodiversity, new methods and ideas must be developed to promote the protection of urban ecosystems. The Cape Floristic Region in South Africa is a good example of an area that requires immediate action in order to prevent enormous losses in biodiversity. Data have shown drastic decreases in natural vegetation cover in this area, and with its close to 9000 species, of which approximately 60% occurs nowhere else in the world. This state of affairs should be regarded as a serious crisis. This study consists of three main parts, the first being a literature review on the current relationships between the urban environment, society, and biodiversity. The second and third parts report on two empirical investigations on the campus of the Faculty of Health Sciences at the University of Stellenbosch in the City of Cape Town. The first of these investigates the possibility of using spirituality connected to nature as a promotional tool for conservation through rehabilitation or restoration of damaged urban vegetation habitats. For this purpose students’ and staff members’ opinions of the urban nature at the campus were tested. In the second investigation the options of restoring biodiversity to the campus was considered by exploring the best options available for rehabilitation while taking the current biodiversity status on and around the premises into account. This was carried out through three smaller projects that included the physical reintroduction of plant species, vegetation analysis, and bird identification and attraction. The response of employees and students at the Faculty of Health Sciences was found to be in favour of restoring vegetation and animal life to the campus. This is supported by a belief that their attitude towards their work would improve with improved natural surroundings. Initial rehabilitation attempts highlighted the complexity of rehabilitation practices by bringing forward challenges and problems experienced with the reintroduction of plant species. Despite these problems, increased plant diversity in experimental areas showed the possibility of successfully completing the project. Biodiversity analysis showed that methods of controlling vegetation used by the university are doing more harm than good, as it results in indigenous vegetation being displaced by exotic vegetation. This study introduces a number of questions regarding the relationship between urbanisation and biodiversity and to what extent the two should be linked. Hopefully it is a step in the direction towards marrying the urban and natural environment, and to create a sustainable urban environment where society no longer sees nature as something outside the city boundaries.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosc, 2007. / Freshwater insect species and their host ecosystems are widely threatened, particularly within agricultural and urban landscapes of Mediterranean areas, including that of the Western Cape Province, South Africa. The study here determined the biodiversity value of nineteen artificial ponds (temporary and permanent) and two river margin sites in the Cape Floristic Region (CFR). The aim was to determine aquatic beetle and bug abundance and species richness in these ponds, a topic which has been hardly explored in South Africa. Sites were sampled from September 2005 to September 2006. A total of 18 677 aquatic beetle and bug individuals were sampled, representing 43 genera (28 beetle and 15 bug genera), 64 species (44 aquatic beetle and 20 bug species). Different pond types had distinct species assemblages. The associated physico-chemical characteristics of these sites were also investigated. The key environmental variable affecting aquatic beetle and bug distribution was naturalness (no human and environmental impact on waterbody). The results showed that the most important determinant of aquatic beetle and bug species richness across all sites was emergent macrophytes, such as Typha capensis and Persicaria decipiens. Artificial ponds in the CFR clearly increase the area of occupancy for insects, and therefore play a major role in conserving them. This is especially so when the ponds are at moderate temperatures (i.e. 19º C). Although all ponds contributed to the aquatic beetle and bug diversity in the region, they differed in relative value, depending on the combination of environmental variables affecting each pond.

Thesis (PhD)--University of Stellenbosch, 2010. / The aim of the study was to assess the importance of spatial and temporal variation in diet quality and abundance for determining sustainable stocking rates on commercial, communal and game ranches in a semi-arid savanna, with the ultimate goal of avoiding land degradation in the long term, to provide sustainable livelihoods in rangelands and to make policy that will help in managing the available natural resources in the rangelands. Thus, firstly the effects of grazing, fire, nitrogen and water availability on nutritional quality of grass in semi-arid savanna was assessed. Secondly, spatial and temporal variation in plant quantity and quality among management (commercial, communal and game) types and habitat types (open savanna, rocky, shrubby and pans) and stocking rates in different management types were determined. Thirdly, the quality and quantity of variation inside and outside herbivore exclosures among commercial, communal and game management and habitat types in the semi arid savanna were estimated. Fourthly, faecal profiling was used to assess the effects of different management types on diet quality in semi-arid savanna. Lastly, policy based on the results of the present study was formulated.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Both taxonomic diversity and diversity of species interaction networks are experiencing declines as a result of agricultural intensification at habitat and landscape scales. Reversing this trend is a key conservation issue, particularly for important functional groups such as flower-visiting insects and the networks within which they interact. This is of great concern in regions of high conservation priority such as the Cape Floristic Region (CFR), known for its high level of floral and faunal endemism and exceptional species turnover. Holistic approach to conservation in agricultural landscapes involves both preservation of natural land and wildlife friendly management of the farm land to achieve conservation targets. The value of these extensive management approaches is yet to be fully assessed, especially in perennial systems such as vineyards. I examined here the effects of vineyard management and landscape context on species richness and abundance of flower-visiting insects and their species interaction networks. Possible taxon specific effects were verified. I also investigated whether vineyards under organic and conventional management homogenized insect-flower interaction networks and whether vineyards with different management practices vary in patterns of species turnover. I sampled flower-visiting insects and their interactions in organic and conventional vineyards, and in natural reference sites. Inclusion of natural reference sites enabled me to make management recommendations for patches of natural vegetation in CFR agricultural landscape. Statistical models showed taxon-specific benefit of organic farm management, and of landscape (distance to natural habitat). There was benefit to monkey beetles (Scarabaeidae) but not to bees (Apidae). Organic vineyards had a higher number of insect-flower interactions than conventional ones, but vineyards under the two types of management were similar in terms of other important network indices. However, networks of the vineyards were more nested than the natural sites, indicating that they may be potentially more stable to perturbation and random extinctions. Multivariate dispersion tests revealed insect-flower interaction networks were not homogenized by both organic and conventional vineyards across the landscapes. I also found, through additive partitioning, that organic and conventional vineyards were similar in terms of species turnover of bees and flowering plants. The findings of this study provide heuristic value to current debates on the value of vineyard habitats for insect conservation. Both organic and conventional vineyards that promote sustainable management of the non-crop floral vegetation between vineyard rows are potential solutions for conservation of flower-visiting insects and their interactions. Also, attention has to be paid to the quality and connectivity of the natural habitat patches that are within CFR agricultural landscape. Site specific management and assessment of the value of these landscape elements is important. Management approaches such as carefully controlled burning may be beneficial, as the CFR natural vegetation is a fire-driven community. / AFRIKAANSE OPSOMMING: Taksonomiese diversiteit en diversiteit van spesies-interaksie netwerke ondervind beide afnames as gevolg van landboukundige intensifikasie op habitat en landskap skaal. Om die neiging terug te swaai, is ’n sleutel bewaringsaangeleentheid, veral vir belangrike funksionele groepe soos blom-besoekende insekte en die netwerke waarbinne hulle op mekaar inwerk. Dit is van groot kommer in streke met hoë bewaringsprioriteite soos in die Kaapse Floristiese Streek (KFS), bekend vir sy hoë vlak van plant- en dierendemisme en buitengewone spesies kentering. ’n Holistiese benadering tot bewaring van landboukundige landskappe behels beide die bewaring van natuurlike land en natuurlewe-vriendelike bestuur van die plaasgrond om bewaringsdoelwitte te bereik. Die waarde van hierdie ekstensiewe bestuursbenaderings moet nog volledig bepaal word, veral in meerjarige sisteme soos wingerde. Ek het die uitwerkings van wingerdbestuur en landskapsamehang op spesiesrykheid en volopheid van blombesoekende insekte en hulle spesies interaksie netwerke ondersoek. Moontlike takson-spesifieke uitwerkings is nagegaan. Ek het ook ondersoek ingestel of wingerde onder organiese en gebruiklike bestuur ooreenstemmende insek-blom interaksie netwerke met wingerde met verskillende bestuurspraktyke in patroon van spesies kentering gewissel het. Ek het blom-besoekende insekte en hulle interaksies in organiese en konvensionele wingerde, asook in natuurlike verwysingsgebiede gemonster. Insluiting van natuurlike verwysingsgebiede het my in staat gestel om bestuursvoorstelle vir gebiede van natuurlike plantegroei in KFS landboulandskappe voor te stel. Statistiese modelle toon takson-spesifieke voordeel van organiese plaasbestuur en van die landskap (afstand van natuurlike habitat) self. Daar was voordeel vir bobbejaankewers (Scarabaeidae), maar nie vir bye (Apidae) nie. Organiese wingerde het ’n groter getal insek-blom interaksies as konvensionele wingerde gehad, maar wingerde onder beide tipes van bestuur was soortgelyk in terme van ander belangrike netwerk aanduiders. Netwerke van wingerde was egter meer geklomp dan natuurlike gebiede wat aandui dat hulle potensieel meer stabiel betreffende versteuring en lukrake uitsterwings is. Multivariate verspreidingstoetse het aangetoon dat insek-blom interaksie netwerke by beide organiese en konvensionele wingerde oor landskappe nie eenvormig was nie. Ek het ook bevind deur aanvullende verdeling dat organiese en konvensionele wingerde gelykwaardig was in terme van spesies kentering van bye en blomplante. Die bevindings van hierdie studie verskaf heuristise waarde tot huidige debatte oor die waarde van wingerdhabitatte vir insekbewaring. Beide organies en konvensionele wingerde wat volhoubare bestuur van die nie-gewas plantegroei binne wingerdrye bevorder, is moontlike oplossings vir die bewaring van blom-besoekende insekte en hulle wisselwerkings. Bykomend moet aandag gegee word aan die kwaliteit en verbindings van en tussen natuurlike habitat gebiede binne die KFS landboulandskap. Plekspesifieke (plaaslike) bestuur en bepaling van die waarde van hierdie landskapelemente is belangrik. Bestuursbenaderings, soos noukeurig beheerde brand, mag voordelig wees aangesien die KFS natuurlike plantegroei ’n vuurgedrewe gemeenskap is.

Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Land use change is leading to rapid biodiversity loss in terrestrial ecosystems worldwide. Ecological networks (ENs) are systems of remnant natural habitat which remain intact in a transformed matrix, and have been suggested as a means to mitigate the effects of habitat loss and transformation and the resulting loss of biodiversity. Conceptually, ENs are similar to habitat corridors but are larger in scale and more heterogeneous in their design and management. Like corridors, the efficacy of ENs for biodiversity conservation has been called into question and requires empirical investigation. South Africa boasts a unique system of extensive ENs associated with exotic timber plantations, mostly within the highly endangered grassland biome and Indian Ocean Coastal Belt in KwaZulu-Natal Province, South Africa. In these regions, grasshoppers respond sensitively to management practices such as grazing, mowing and burning, justifying their a priori selection as an ecological indicator. In this study, I utilize grasshopper assemblages to determine the efficacy of ENs for biodiversity conservation and suggest guidelines for EN optimization. Specifically, I assess grasshopper assemblage sensitivity and robustness to habitat quality within ENs, congruence of grasshoppers with butterflies, and I identify indicator species which can be utilized by managers for EN assessment in future. I also perform a case study of isolated fragment utilization by a highly mobile generalist species, the bird locust, Ornithacris cyanea (Stoll, 1813) (Acrididae: Cyrtacanthacridinae). Grasshopper assemblages were sampled within ENs in two geographic regions (Zululand and the KwaZulu-Natal Midlands) and in two years (2007 and 2008) during the peak season of grasshopper abundance, late summer (February-April). Local-scale environmental variables relating to management practices and landscape-scale environmental variables relating to design of the ENs were quantified. Management practices explained, on average, two-thirds of the variability in grasshopper assemblages that could be explained, while design variables explained one-third. Grass height and the time since the last fire event were most consistently influential, while area, context, isolation, proportion of bare ground and proportion of forbs at a site, proved influential in some analyses but not others. This response was robust over time and among geographic regions. Grasshopper species richness and abundance were highly congruent with that of butterflies and did not differ among isolated fragments, connected corridors and reference sites, although they did differ among geographic regions. Not all grasshopper species responded similarly to ENs. There was a strong phylogenetic signal in species response to environmental variables, with the distribution of highly mobile families varying more among years. Linear, heavily disturbed power line servitudes had higher grasshopper abundance, and generalist species consistent with early successional assemblages. Reference sites had more graminivorous species and those with intermediate mobility. Three species of grasshopper were identified with IndVal and validated on an independently collected dataset as indicators of high habitat quality. A case study of the bird locust showed that populations of this highly mobile species were effectively isolated and undergoing anthrovicariance even at short distances. These results indicated that heterogeneous ENs supported diverse grasshopper assemblages, although movement among isolated fragments may have been limited. A grasshopper bioindication method for South Africa’s ENs is suggested and has great potential for assessment of a crucial and sensitive trophic layer within the ENs. This method should be field-tested and revised over time as grasshopper relative abundances and species compositions may change. Increased heterogeneity, simulation of multiple successional stages, and increased connectivity are expected to positively impact biodiversity, particularly of insect primary herbivores. Globally, ENs, if managed and designed appropriately, have potential to enhance biodiversity, particularly of smaller resident organisms which can utilize the ENs for movement and live within them. / AFRIKAANSE OPSOMMING: Veranderinge in grondgebruik lei tot ‘n vinnige verlies van biodiversiteit in terrestriële ekosysteme wêreldwyd. Ekologiese netwerke (ENs) is sisteme van oorblywende natuurlike habitat wat ongeskonde bly in getransformeerde matrikse, en is voorgestel as ‘n manier om die verlies aan biodiversiteit as gevolg van habitatverlies en transformasie te verminder. Konseptueel, is ENs soortgelyk aan habitat korridors, maar is groter in omvang en meer heterogeen in hulle ontwerp en bestuur. Soos korridors, is die effektiwiteit van ENs om biodiversiteit te bewaar bevraagteken, en vereis dit empiriese ondersoek. Suid-Afrika spog met ‘n unieke stelsel van uitgebreide ENs wat geassossieer is met uitheemse plantasies, meestal in die hoogs bedreigde grasveld bioom en Indiese Oseaan kusstrook in KwaZulu- Natal Provinsie, Suid Afrika. In hierdie streek reageer sprinkane sensitief op bestuurspraktyke soos beweiding, sny en brand. In hierdie studie het ek sprinkaan gemeenskappe gebruik om die effektiwiteit van ENs vir bewaring van biodiversiteit te bepaal en om riglyne te stel vir EN optimering. Spesifiek het ek sprinkaan gemeenskap sensitiwiteit en robustness tot habitat kwaliteit bepaal, oreenstemming tussen sprinkane en skoenlappers getoets, en het ek indikator species geïdentifiseer wat in die toekoms deur bestuurders gebruik kan word vir EN assessering. Ek het ook ‘n gevallestudie gedoen van geïsoleerde fragment benutting deur ‘n hoogs mobiele, algemene spesie, Ornithacris cyanea (Stoll, 1813) (Acrididae: Cyrtacanthacridinae). Sprinkaan gemeenskappe was versamel in twee geografiese gebiede (Zululand en die KwaZulu-Natal Midlands) en in twee jare (2007 en 2008) gedurende die seisoen van hoogste sprinkaan aktiwiteit, laat somer (Februarie – April). Plaaslike-skaal omgewingsveranderlikes met betrekking tot bestuurspraktyke en landskap-skaal omgewingsveranderlikes met betrekking tot die ontwerp van ENs is gekwantifiseer. Bestuurspraktyke verduidelik, gemiddeld, twee derdes van die variasie in die sprinkaan gemeenskappe, terwyl ontwerpveranderlikes een derde verduidelik. Grashoogte en tyd sedert die laaste brand was konsekwent invloedryk, terwyl area, konteks, isolasie, hoeveelheid kaal grond en hoeveelheid kruidagtige plantegroei invloedryk was in sekere analyses, maar in ander nie. Hierdie reaksie was konstant oor tyd en tussen geografiese gebiede. Sprinkaan spesies rykheid en hoeveelheid was hoogs kongruent met die van skoenlappers, en het nie verskil tussen geïsoleerde fragmente, verbinde korridors en verwysingsareas nie, maar hulle het verskil tussen geografiese streke. Nie alle sprinkaan spesies het soortgelyk gereageer tot ENs nie. Daar was ‘n sterk filogenetiese sein in spesies reaksies op die omgewingsveranderlikes, met meer variasie tussen jare in die verspeiding van hoogs mobiele families. Liniêre, hoogs versteurde kraglyn dienspaaie het hoer sprinkaan hoeveelhede gehad en algemene spesies wat geassosieer is met gemeenskappe in vroeë stadiums van suksessie. Verwysingsareas het meer graminivorous spesies gehad en spesies met intermediêre mobiliteit. Drie sprinkaan spesies is geïdentifiseer met IndVal en bevestig met ‘n onafhanklik versamelde dataset as indikators van hoë kwaliteit habitat. ‘n Gevallestudie op O. cyanea het aangedui dat populasies van hierdie hoogs mobiele spesie geïsoleerd is en dat hulle anthrovicariance ondergaan, selfs op kort afstande. Hierdie resultate dui aan dat heterogene ENs diverse sprinkaan gemeenskappe ondersteun, hoewel beweging tussen geïsoleerde fragmente dalk beperk is. Verhoogde heterogeneïteit, simulasie van verskeie suksessiewe fases en meer konnektiwiteit sal moontlik ‘n positiewe invloed op biodiversiteit hê, aangesien sprinkane verteenwoordigend was van insek primêre herbivore. Wêreldwyd, as ENs op ‘n gepaste manier bestuur en ontwerp word, het dit die potensiaal om biodiversiteit te bevorder. Dit is veral belangrik vir kleiner, plaaslike organisms wat ENs kan benut vir beweging en as leefhabitat. ‘n Sprinkaan bioindikasie metode vir Suid-Afrika se ENs is voorgestel en het groot potensiaal vir die assessering van ‘n belangrike en sensitiewe trofiese laag binne die ENs. Hierdie metode moet in die praktyk getoets word en hersien word oor tyd om veranderinge in sprinkaan relatiewe hoeveelhede en spesies komposisies in ag te neem.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Invasive species are among the most important global conservation threats. Their management is one of the key conservation challenges that will have to be addressed in the next few decades. The study of real invasions and their management in natural ecosystems provides an opportunity to gain important information on theoretical and applied aspects of biological invasions. This project focuses on the broader ecological context of invasive ant management in an ecologically sensitive island habitat. The thesis has three main components: 1) assessing the role of the invasive ant Pheidole megacephala in the ecosystem and evaluating its threat to the system, 2) evaluating a low-impact management program for the ant, and 3) using a community-level approach to assess ecosystem response to ant removal. The ant occupied almost 30% of the island‘s total land area and reached extremely high densities in some areas. The ant was associated with exotic hemipteran scale insects through trophobiotic mutualisms that facilitated high ant and hemipteran abundances. The highly destructive scale insect Pulvinaria urbicola was among the hemipterans that benefited from ant attendance. High levels of hemipteran feeding resulted in dieback of functionally important and threatened native Pisonia trees, which represented a significant threat to the forest ecosystem. A management program was initiated in response to this threat, consisting of baiting with selective hydramethylnon-based bait delivered in bait stations, accompanied by detailed pre-and post-baiting monitoring. The method was highly effective at suppressing the ants, whilst preventing bait uptake by non-target organisms. It was also cost-effective and adaptable to ant density in the field, but was only effective over short distances. The method may be applicable to other sensitive environments with similar challenges. After ant control, the ant-scale mutualism was decoupled and the Pu. urbicola population collapsed. There were variable responses in different taxa to the removal of these highly abundant exotic species, the most important of which was the recovery in Pisonia trees. Shoot condition and foliage density improved and there was a decrease in sooty mold. Herbivory on Pisonia increased due to recovery of native canopy herbivores, but the overall impact was far less than that of the exotic hemipterans. Soil surface arthropods, a group that may have been vulnerable to the treatment method, were unaffected by baiting. Instead, they increased significantly after ant removal, confirming the ant‘s impact on other arthropods. Other ant diversity and non-ant arthropod abundance increased post-baiting, including the endemic ant Pheidole flavens farquharensis and some functionally important insects such as the Indian cockroach. Natural enemies that interacted predictably with the mutualists were influenced by management. Predators of hemipterans increased significantly after ant removal and were instrumental in the scale population collapse, whereas parasitoids of hemipterans that benefited from the mutualism declined. Additionally, groups that were unrelated to the mutualism were indirectly influenced by management. The natural enemy assemblage as a whole showed recovery to pre-invasion conditions. The study shows how widely interconnected and influential the ant was in the ecosystem. It highlights the threat of the species in natural systems as well as the complex responses following invasive ant removal. Yet, it also demonstrates the potential to safely and effectively manage the species, thereby raising the opportunity for ecosystem recovery. / AFRIKAANSE OPSOMMING: Indringerspesies is van die belangrikste globale bedreigings vir natuurbewaring. Hulle bestuur is van die grootste bewaringsuitdagings wat in die volgende paar dekades aangespreek moet word. Die studie van werklike invalle en hul bestuur in natuurlike ekosisteme bied 'n geleentheid om belangrike inligting te verkry oor teoretiese en toegepaste aspekte van biologiese indringing. Hierdie projek fokus op die breër ekologiese konteks van uitheemse mier bestuur in 'n ekologies sensitiewe eiland habitat. Die tesis het drie hoofkomponente: 1) die beoordeling van die rol van die indringer mier Pheidole megacephala in die ekosisteem en evaluering van sy bedreiging vir die sisteem, 2) die evaluering van 'n lae-impak bestuursprogram vir die mier, en 3) die gebruik van 'n gemeenskaps-vlak benadering om ekosisteem reaksie op mierverwydering te assesseer. Die mier het byna 30% van die totale landoppervlak van die eiland beslaan en het in party areas baie hoë digthede bereik. Die mier was geassosieer met uitheemse dopluis spesies in mutualismes wat hoë mier en dopluis getalle gefasiliteer het. Die hoogs beskadigende dopluis Pulvinaria urbicola was een van die spesies wat bevoordeel is deur die mutualisme. Hoë vlakke van dopluis voeding het die terugsterwe van funksioneel belangrike, bedreidge inheemse Pisonia bome veroorsaak, wat ʼn groot bedreiging vir die ekosisteem verteenwoordig het. ‗n Bestuursprogram is geïmplimenteer as gevolg van hierdie bedreiging, wat bestaan het uit selektiewe hidrametielnoon-gebaseerde lokaas wat in die veld geplaas is in lokaashouers, vergesel deur intensiewe monitering voor en na lokaasplasing. Die metode was hoogs effektief in die onderdrukking van die miere en het lokaasinname deur nie-teiken organismes verhoed. Dit was ook koste-effektief en aanpasbaar volgens mierdigtheid in die veld, maar was slegs effektief oor kort afstande. Die metode mag van toepassing wees in ander sensitiewe omgewings met soortgelyke uitdagings. Na mierbeheer is die mier-dopluis mutualisme ontkoppel en die Pu. urbicola bevolking het drasties verminder. Daar was verskillende reaksies in verskillende taxa tot die verwydering van die oorvloedryke eksotiese spesies, maar die belangrikste reaksie was die herstel van Pisonia bome. Spruittoestand en blaardigtheid het verbeter en daar was ʼn afname in roetskimmel. Herbivorie op Pisonia het toegeneem as gevolg van ʼn herstel in inheemse herbivore, maar die algehele impak was veel minder as dié van die eksotiese dopluis. Grondoppervlak gelidpotiges, 'n groep wat kwesbaar kon wees vir die behandelingsmetode, was onaangeraak deur die lokaas, maar het beduidend na mierverwydering vermeerder. Mierdiversiteit het vermeerder en die Seychelles endemiese mier Pheidole flavens farquharensis is hervestig. Ander gelidpotiges het ook vermeerder, insluitend funksioneel belangrike spesies soos die Indiese kakkerlak. Natuurlike vyande wat geassosieer was met die mutualiste is beïnvloed deur die mierbestuur. Predatore van dopluis het beduidend toegeneem na mierverwydering en was hoogs betrokke by die vermindering van dopluis, terwyl parasiete van dopluis, wat voordeel getrek het uit die mutualisme, gedaal het. Daarbenewens is groepe wat onverwant was aan die mutualisme indirek beïnvloed deur mierbestuur. Die algehele natuurlike vyand gemeenskap het herstel na pre-indringing toestand. Die studie toon hoe wydverbind en invloedryk die mier was in die ekosisteem. Dit beklemtoon die bedreiging van die spesies in natuurlike stelsels asook die komplekse reaksies wat uitheemse mierverwydering volg. Tog demonstreer dit die potensiaal om die spesies veilig en doeltreffend te bestuur, en sodoende die geleentheid vir ekosisteemherstel te skep.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Conservation planners use many traditional biodiversity conservation tools to help alleviate the global biodiversity crisis. However, ongoing biodiversity loss has stimulated the development of new and improved methods for conserving biodiversity. One such new conservation tool is the mesofilter approach. Mesofilters are biotic or abiotic ecosystem elements which are critical to the well-being of many species, and therefore could help to explain spatial heterogeneity in species across a landscape. It is also complementary to more traditionally used concepts such as coarse- and fine-filter conservation concepts. Applying the mesofilter approach in protected area, conservancy, or land-sparing design and management, could optimise biodiversity conservation in a rapidly developing world. For example, the timber industry has been pro-active in its approach to lessen biodiversity loss, by optimising design and management of the plantation matrix through ecological networks. Here, I explore the use of mesofilters within highly threatened remnant Afro-montane grasslands in KwaZulu-Natal, South Africa, to optimise biodiversity conservation planning for such landscapes. As per anecdotal evidence, I used rockiness in the landscape as a possible driver of species richness and species assemblage variability at the meso-scale, using a multi-taxon and multi-trophic approach. In this montane landscape, I also examined the effect of elevation on spatial heterogeneity of taxa. I further examined the functional responses of taxa to rockiness in the landscape. Rockiness in the landscape significantly influenced the species richness and assemblage structure of three key grassland taxa: flora, butterflies, and grasshoppers. I showed that for plants, this response was due to growth forms such as geophytes and perennial grasses that were more closely associated with rockiness, and therefore the main contributors to observed differences in the dispersion patterns of flora. Grasshoppers were not necessarily responding to higher rock exposure per se, but rather towards the environmental conditions created by rockiness within the landscape, such as lower vegetation density. For butterflies, certain behavioural traits, such as resting, territorial behaviour and/or mate-locating behaviour, were more typical in areas of higher rock exposure. This suggested that rocks are a definite habitat resource to certain butterflies. Overall, this finding where an abiotic surrogate is representative of key taxa in an ecosystem is interesting, as cross-taxon surrogacy has been shown to be stronger than surrogates based on environmental data. Furthermore, taxa responded functionally to rockiness in the landscape. This thesis therefore supports the idea that environmental surrogates are indeed useful for biodiversity conservation planning. Furthermore, ecosystems can potentially have many attributes or features that would be of conservation interest, and delineating a set of mesofilters is a useful way of expressing particular attributes to be used in wildlife conservation evaluation. The concept of the mesofilter as a practical biodiversity conservation tool is therefore validated here. I also argue the importance of habitat heterogeneity for biodiversity conservation planning in this montane grassland landscape. The potential for optimising the design of landscape configurations such as ecological networks, through information obtained from the mesofilter, is emphasised. We can safely add another tool in the biodiversity conservation toolbox of this Afro-montane grassland ecosystem. / AFRIKAANSE OPSOMMING: Bewaringbeplanners gebruik tans baie tradisionele biodiversiteit-bewarings metodes om die huidige biodiversiteits krisis te help verlig. Tog, die huidige voortdurende verliese in biodiversiteit wêreldwyd, vra na nuwer en verbeterde metodes van biodiversiteit-bewaring. Een so ‘n nuwe bewaring metode, is die mesofilter. Mesofilters is biotiese of abiotiese ekosisteem elemente wat kritiek is tot die welstand van spesies, en daarom veral waardevol is om variasie in spesies verspreiding in ‘n landskap te help verduidelik. Daarby is die mesofilter konsep ook komplementêr tot meer tradisioneel gebruike bewaringskonsepte, soos fyn-filter en breë-filter konsepte. Deur die mesofilter benadering toe te pas in die ontwerp en bestuur van beskermde areas, bewaareas, of land-spaar initiatiewe, kan ons biodiversiteitbewaring in ‘n vining ontwikkelende wêreld optimaliseer. Byvoorbeeld, die bosbou industrie is pro-aktief in hul benadering om biodiversiteit verliese te verminder, deur optimalisering van die ontwerp en bestuur van ekologiese netwerke in die plantasiematriks. In hierdie tesis, ondersoek ek die gebruik van mesofilters in hoogs bedreigde oorblyfels Afrikaberg grasvelde in KwaZulu-Natal, Suid-Afrika, om die bewaringsbeplanning van dié gebiede te optimaliseer. Vanaf anekdotiese bewyse, het ek spesifiek gebruik gemaak van klipperigheid in die landskap as ‘n moontlike drywer van spesies-rykheid en spesies-samestelling variasie by ‘n meso-skaal, deur ‘n multi-takson en multi-trofiese benadering. In hierdie berglandskap, het ek ook die effek van hoogte bo seevlak op ruimtelike verspreiding van taksa bestudeer. Verder het ek ook gekyk na die funksionele reaksie van taksa tot klipperigheid in die landskap. Klipperigheid in die landskap het ‘n beduidende invloed gehad op spesies-rykheid en spesiessamestelling van drie sleutel grasveld taksa: plante, skoenlappers, en springkane. Ek wys dat vir plante, hierdie reaksie as gevolg was van spesifieke plantgroeivorme, soos bolplante en meerjarige grasse, se noue verband met klipperigheid, en daarom, dat hierdie groepe die hoof bydraers is tot gesiene variasie in plantspesies verspreiding in die landskap. Vir springkane, was hierdie reaksie nie noodwendig omdat hulle die klippe self gebruik het nie, maar meer as gevolg van die omgewingskondisies geskep deur verhoogde klipperigheid in die landskap, soos laer plantegroei digtheid. Vir skoenlappers, was hierdie reaksie tot klippe as gevolg van sekere gedragskaraktereienskappe, soos rus op klippe, gebied beskerming en/of paarmaat soektog, wat tipies meer gesien was in klipperige omgewings. Dit dui daarop dat klippe ‘n definitiewe habitat hulpbron is vir sekere skoenlappers. Oor die algemeen is hierdie bevinding, waar abiotiese surrogate verteenwoordig is van drie sleutel taksa in ‘n ekosisteem, baie interessant, siende dat tussen-takson surrogate soms gesien word as sterker as surrogate gebaseer op omgewingsdata. Verder, taksa het funksioneel gereageer teenoor die klippe in die landskap. Hierdie tesis ondersteun dus die idee dat omgewingssurrogate wel nuttig is vir biodiversiteit-bewaring beplanning. Ekosisteme mag vele potensiele elemente van bewarings belang bevat, maar om sulke elemente as ‘n stel mesofilters te klassifiseer, is ‘n nuttige manier om spesifieke elemente te gebruik in natuurbewarings evaluasie initiatiewe. Gevolglik word die konsep van die mesofilter as ‘n praktiese biodiversiteit-bewaring gereedskapstuk hier bevestig. Ek beredeneer ook die belangrikheid van habitat heterogeniteit vir biodiversiteit-bewaring van hierdie berggrasveld landskap. Die potensiaal vir optimalisering van ontwerp en bestuur van landskap konfigurasies, soos ekologiese netwerke, word beklemtoon. Ons kan met veiligheid nog ‘n gereedskapstuk plaas in die biodiversiteitbewarings gereedskapkis van hierdie Afrikaberg grasveld ekosisteem.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: West Coast Renosterveld is one of the most threatened vegetation types in South Africa. Less than 5% of the original extent of this vegetation type remains, of which 80% is on private land. In addition to fragmentation, much of the vegetation has been ploughed for crop production and then abandoned and invaded by alien plants. Restoration of transformed areas may improve the conservation status of this vegetation type. Indigenous species do not return to abandoned agricultural fields for decades even if these are adjacent to natural areas since their return is limited either by seed dispersal or seedling establishment. The aim of this study was to examine the recovery of indigenous vegetation on abandoned fields. Renosterveld, as we know it today, is an asteraceous shrubland, dominated mainly by renosterbos (Eytropappus rhinocerotis), but might have been a grassland or a grassland-shrubland mosaic. Historical records indicate that species of large game were common in the Western Cape when the early settlers arrived, but most of these have since disappeared. It is thus impossible to reconstruct exactly the ecological processes and functioning of Renosterveld. The first part of the study was designed to examine the effects of grass competition, grazing by indigenous large herbivores, and interaction of these two factors on the establishment, growth and survival of transplanted Renosterveld seedlings on an abandoned agricultural field. Experimental transplanting of indigenous shrubs into an old field showed that most of the plants investigated competed for resources with lawn grasses on the field, and competition affected the seedlings throughout the experiment. Mortality was higher, and growth was reduced for seedlings exposed to grass competition. With the exception of wild olive (Olea europaea spp.africana), herbivory alone had no significant impact on the target species. Herbivory was at a low intensity (20 ha/large animal unit); higher grazing pressures might have given different results. No interaction between competition and herbivory was found for the species investigated; competition and grazing therefore seem to influence the seedlings independently. The second part of this study was conducted to examine the effects of different management strategies, viz: brush cutting, burning and herbicide application on plant species recruitment and community composition and to ascertain their applicability by farmers for large scale restoration of Renosterveld. My comparison of the different strategies for controlling annual alien grasses indicated that these did not differ significantly in their effects on species richness. Burning reduced shrub cover and increased overall species richness and diversity. Burning also reduced grass biomass, and increased recruitment of indigenous seedlings. The use of herbicide resolved the problem of grass biomass invasion and increased shrub species richness. The herbicide application did not appear to have long-term negative effects on the soil quality. Brush cutting did not remove grass biomass on the old field. Experimental re-seeding with an indigenous grass and shrub species into treated plots resulted in low recruitment. My conclusion is that grass can reduce recruitment and growth of many indigenous shrub species. My recommendation for the restoration of old fields in West Coast Renosterveld is to apply herbicide to remove grass competition, and then, after the herbicide has degraded, to oversow the field with seeds of indigenous shrub and grass species of early successional stages to increase overall species diversity. / AFRIKAANSE OPSOMMING: Weskus Renosterveld is een van die mees bedreigde plantegroei soorte in Suid Afrika. Minder as 5% van die oorspronklike omvang van hierdie plantegroei tipe is oor, en dit hoofsaaklik (80%) op privaatlande. Saam met fragmentasie, is baie Renosterveld areas ook omgeploeg vir boerdery en dan net so gelos, met die gevolg dat uitheemse plante hierdie areas ingedring het. Restorasie of herstelling van sulke bewerkte lande kan dalk die bewaringsstatus van hierdie plantegroei tipe verbeter. Natuurlike vestiging van Renosterveld spesies op sulke ou bewerkte lande gebeur nie, selfs al is daar Renosterveld direk langs so ‘n ou veld. Die hervestiging van inheemse spesies is dus tot saadverspreiding or saailingbevestiging beperk. Die doel van hierdie studie is om die stadige terugkoms van inheemse plantegroei na verlate bewerkte velde te verduidelik. Renosterveld is ‘n struikveld waarin die renosterbos (Eytropappus rhinocerotis) domineer, maar kan ook ‘n grasveld of ‘n grasveld-struikland mengsel wees. Groot herbivore was algemeen in die Wes Kaap toe die eerste settelaars gearriveer het, maar intussen het omtrent al die groot wild spesies verdwyn. Dit is dus ontmoontlik om die ekologiese prosesse en funksionering van Renosterveld presies so te herstel. Die eerste deel van hierdie studie bestudeer die effek van graskompetisie, weiding deur inheemse groot herbivore, en die interaksie tussen hierdie twee faktore op die vestiging, groei en oorlewing van oorgeplante Renosterveld saailinge in ‘n verlate ou veld. Die eksperimentele oorplanting van inheemse struike in ‘n ou land het gewys dat die meeste van hierdie plante kompeteer vir hulpbronne met kweekgras wat op die ou veld groei. Kompetisie het die saailinge deur die hele eksperiment geaffekteer. ‘n Hoër mortaliteit en verminderede groei in saailinge wat aan gras kompetisie blootgestel was, is waargeneem. Met die uitsondering van Olea europaea spp. africana, het herbivorie alleen geen betekenisvolle impak op plant spesies gehad nie. Weidingsdruk was laag (20 ha/groot vee eenheid); ‘n groter weidingsdruk sou miskien ‘n ander uitkoms gehad het. Geen interaksie tussen kompetisie en herbivorie is waargeneem in die bestudeerde plantspesies nie. Dit wil dus voorkom of kompetisie en weiding die saailinge onafhanklik van mekaar beïnvloed. Die tweede deel van hierdie studie was onderneem om die effek van verskillende behandelings (kontrole, sny, brand en herbisied toediening) op plantspesie vestiging en samestelling te bestudeer asook om bestuurmetodes te toets was deur boere op groot skaal gebruik kan word om Renosterveld te herstel. In ‘n vergelyking van verskillende bestuur metodes (kontrole, besnoeiing, brand en herbisied) om eenjarige uitheemse gras te beheer, is gewys dat die behandlings nie betekenisvol van mekaar verskil in hulle effek op spesierykheid nie. Vuur het struikbedekking verminder en totale spesies rykheid en diversitiet verhoog. Die gebruik van ‘n herbisied het die probleem van grasindringing opgelos en het ook struikspesiesrykheid verhoog. Die herbisied het nie lang termyn negatiewe effekte op grond kwaliteit gehad nie. Sny het nie gras biomassa verlaag op die ou land nie. Eksperimentele plant van inheemse grasse en struike in die behandelde areas, het lae vestiging tot gevolg gehad. My algemene afleiding is dus dat gras die hervestinging en groei van baie inheemse struikspesies verminder. Ek stel voor dat herbisied gebruik moet word om gras kompetisie te verminder. Nadat herbisied residue in die grond afgebreek is, moet die ou land met inheemse struik en grasspesies, wat in vroeë suksessie stadiums is, beplant word om sodoende totale spesiediversiteit te verhoog en uiteindelik ou bewerkte lande in Weskus Renosterveld te herstel.

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Climate has shown some remarkable changes over the past century, especially at the polar and sub-polar regions. Southern Ocean Islands provide good models for studies related to climate change effects, since effects may be evident in the short term and may also be clearer. Marion Island is an example of such a system with a harsh abiotic environment, and low species richness often vulnerable to change. Climate change is predicted, and also reported, to have biological consequences on plant communities, affecting the phenology, morphology, and the interaction between individuals and species. This study examines the association between the keystone plant species, Azorella selago Hook. (Apiaceace), and its dominant epiphyte Agrostis magellanica Lam. (Poaceae). Two complimentary approaches were used, one observational and the other experimental. The main objective for the observational study was to quantify bioticallyrelevant microclimate temperature, as well as the morphology, epiphyte load and phenology of A. selago at three different altitude sites on Marion Island. This provided information on baseline variation for understanding specific variability in plant response to the experimental part of this study, against which future patterns arising from biological monitoring can be compared. Studying plants at different altitudes provides a possible analogue for temperature-related climate change consequences for the ecology of A. selago, and its interaction with A. magellanica. The microclimate temperature associated with A. selago differed between the three sites examined. This difference was related to local topographic conditions and altitude differences. Cushion size differed distinctively between the three altitude sites, with this difference related to environmental heterogeneity such as differences in age and substrate structure. Azorella selago annual growth rate was estimated through stem length and the number of leaves on both exposed and shaded stems. Within-site variability, as well as epiphyte cover were found to be the contributing factors on A. selago annual growth rate. This highlights the importance of site-specificity when estimating growth rate within and between different altitude sites. Leaf characteristics differed between the sites, with this attributed to local habitat conditions, such as topography, as well as epiphyte cover. As expected, the difference in leaf size between exposed and shaded leaves demonstrated a larger specific leaf area on leaves shaded by A. magellanica. Agrostis magellanica abundance and density were altitudinally related, with A. selago demonstrating facilitation effects on A. magellanica. The trend shown in this study suggests that in spite of general facilitative effect of A. selago on A. magellanica towards higher altitudes, the abiotic environmental threshold for A. magellanica occurs at lower altitudes than it does for A. selago. Phenological differences were also apparent between the three sites. The objectives of the experimental part of this study were to quantify the effect of the dominant epiphyte, A. magellanica on biotically-relevant microclimatic temperatures, as well as on the phenology and physical condition of A. selago. Different treatments were applied to cushions at the three altitude sites to examine the shading effect of epiphytic A. magellanica on cushion plants, as well as the effect of treatment-related disturbance. Azorella selago microclimate temperature showed no significant difference between treatments, suggesting that on average epiphytic A. magellanica cover has no effect on cushion microclimate temperature. The percentage of flower budding and flowering of A. selago was negatively related to epiphyte cover. Cushion vitality was also responsive to epiphyte cover, with higher vitality scores on low grass covered cushions than on high grass cushions. This shows that A. magellanica competes with A. selago, while A. selago facilitates A. magellanica. Heavy epiphyte numbers impose negative effects on A. selago vegetative and reproductive performance, as well as cushion vitality. Therefore, the results of this research show that the vegetative and reproductive performance of A. selago and cushion vitality are likely to be negatively affected under ongoing climate change on Marion Island if this brings about heavier epiphyte loads on this keystone cushion plant species. / AFRIKAANSE OPSOMMING: In die afgelope eeu het die klimaat in die Antarktiese en sub-Antarktiese gebiede merkwaardige verandering getoon. Die Suidelike See Eilande dien as goeie modelle vir studies verwant aan die gevolge van klimaatsverandering, aangesien die kort termyn effekte in die gebiede duideliker mag wees in die toekoms. Marion Eiland is ‘n voorbeeld van so ‘n sisteem, met ‘n ruwe abiotiese omgewing en lae spesies rykheid, wat vatbaar is vir verandering. Daar word voorspel, en is reeds bevind dat klimaatsverandering biologiese gevolge op plant gemeenskappe het, in terme van morfologie, fenologie en die interaksie tussen individue en spesies. Hierdie studie ondersoek die assosiasie tussen die hoeksteen plant spesie, Azorella selago (Apiaceace), en sy dominante epifietiese gras, Agrostis magellanica Lam. (Poaceae). Die studie is op twee komplimentêre maniere benader, naamlik deur waarneming en eksperiment. Die hoof doel van die studie was om die biotiese belang van mikroklimaat temperatuur te kwantifiseer, en die hoeveelheid epifiete, die morfologie en die fenologie van A. selago te bepaal by drie verskillende hoogtes op Marion Eiland. Laasgenoemde het inligting verskaf oor die variasie in die reaksie van plante tot die eksperimentele aspek van die studie, waarteen patrone vanaf toekomstige biologiese beheer vergelyk kon word. Deur plante te bestudeer by verskillende hoogtes bo seespieël word ‘n moontlike analoog vir die gevolge van temperatuur-verwante klimaatverandering in terme van die ekologie van A. selago, en laasgenoemde se interaksie met A. magellanica verskaf. Die mikroklimaat temperatuur geassosieer met A. selago verskil tussen dié drie liggings. Die versil was verwant aan die plaaslike topografiese toestande en die verskillende hoogtes bo seespieël. Die grootte van die kussingplante het duidelik versil tussen die drie liggings, met die verskille verwant aan die omgewing se heterogeneïteit, byvoorbeeld die verskille in ouderdom en substraat struktuur. Azorella selago se jaarlikse groeitempo was bepaal deur die stingel lengte en die aantal blare, op beide die wat oorskadu is deur die gras, en die was nie oorskadu is nie. Daar is gevind dat die faktore wat bygedra het tot die jaarlikse groeitempo van A. selago, varieër binne die verskillende liggings, en bedekking deur epifiete. Dit beklemtoon die belang van spesifisiteit van ligging wanneer groeitempo in en tussen die liggings van verskillende hoogtes bepaal word. Die blaar eienskappe het verskil tussen verskillende liggings, as gevolg van plaaslike habitat toestande, soos topografie en bedekking deur epifiete. Soos verwag, het die blare wat oorskadu was deur A. magellanica ‘n groter spesifieke blaar area getoon as blare wat blootgestel was. Die hoeveelheid en digtheid van Agrosits magellanica was verwant aan hoogte bo seespieël, met A. selago wat fasiliterende effekte toon op A. magellanica. Die tendens waargeneem in hierdie studie is dat ten spyte van die algemene fasiliterende effek van A. selago op A. magellanica, die abiotiese omgewingsdrempel op ‘n laer hoogte is vir A. magellanica as vir A. selago. Fenologiese verskille was ook duidelik tussen die drie liggings. Die doel van die eksperimentele deel van die studie was om die effek van die dominante epifiet, A. magellanica, te bepaal op bioties relevante mikroklimaat temperature, asook op die fenologie en fiesiese toestand van A. selago. Verskeie behandelings is aangewend op die kussingplante by die drie liggings om die effek van skaduwee van die epifietiese A. magellanica op die plante te bepaal, asook die effek van versteurings versoorsaak deur die behandelings. Azorella selago se mikroklimaat temperatuur het geen betekenisvolle verskille tussen behandelings getoon nie, wat voorstel dat epifitiese A. magellanica oor die algemeen geen effek op die kussingplante se mikroklimaat temperatuur het nie. Daar was ‘n negatiewe verwantskap tussen die hoeveelheid epifiete op A. selago en die persentasie blomme en blomknoppe op die kussingplante. Die plante se vitaliteit was ook afhanklik van epifiet bedekking, met ‘n hoër vitaliteit telling vir kussingplante bedek met lae gras as die bedek met hoë gras. Dit toon dat A. magellanica met A. selago wedywer, terwyl A. selago vir A. magellanica fasiliteer. Hoë epifiet getalle het negatiewe effekte op A. selago se vegetatiewe en reproproduktiewe nakoming, asook die kussingplante se vitaliteit. Die resultate van hierdie studie toon dus dat die vegetatiewe en reproduktiewe nakoming van A. selago en kussingplant vitaliteit heel moontlik negatief geaffekteer sal word indien klimaatsverandering op Marion Eiland hoër epifiet getalle op die sleutel kussingplant spesie tot gevolg sal hê.

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / Benthic macroinvertebrates (sampled using South African Scoring System, SASS5) and adult male Odonata (sampled with close-focus binoculars) were recorded on two streams and a river of Soutpansberg, with the aim of determining the effect of invasion and removal of alien riparian vegetation on their assemblages. A secondary aim was to establish the importance of dragonflies as indicators of degree of disturbance in rivers. Forty two aquatic macroinvertebrate families and 33 adult Odonata species were recorded at a total of 71 sampling units. Three distinct riparian vegetation types were selected (natural, alien and cleared). Cleared vegetation refers to clearing of invasive alien trees, allowing regrowth of natural vegetation. Natural and cleared vegetation supported more benthic macroinvertebrate families compared to alien vegetation. Certain families that were lost to alien vegetation were recorded from natural vegetation. The highest SASS5 score was recorded from natural vegetation, followed by cleared vegetation, and the lowest was from alien vegetation. The highest number of adult Odonata was recorded at cleared vegetation, with alien and natural vegetation supporting the least number of Odonata species. Vegetation type, stream flow and microhabitats were statistically identified as the most influential variables for benthic macroinvertebrate assemblages. For adult Odonata assemblages, vegetation type, shade and temperature were the most important environmental variables. Species assemblages of adult Odonata can be used as indicators of environmental condition of rivers. The clearing of alien riparian vegetation clearly benefits the indigenous benthic macroinvertebrates as conditions are restored to their natural state. It also benefits dragonfly species richness, but if natural succession proceeds to a shaded tree canopy, the effect becomes similar to that of habitat shaded by alien vegetation. The impact of alien vegetation is to reduce sun-loving invertebrate species, especially dragonflies, with lesser impact on shade-loving species.