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- ItemAbiotic and biotic drivers of African aquatic insect distribution(Stellenbosch : Stellenbosch University, 2020-03) Deacon, Charl; Samways, Michael J.; Pryke, James S.; Stellenbosch University. Faculty of AgriSciences. Department of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Freshwater habitats are disproportionately rich in biodiversity, and are among the most threatened, yet poorly protected ecosystems. Aquatic insects make up much of the total freshwater fauna and contribute greatly to ecosystem functioning. At the broad-scale, aquatic insect distribution is driven by combinations of traits, as well as regional climate gradients and historical landscape context. Locally, both aquatic insect species richness and diversity are driven by various aspects related to vegetation and to physiochemical environments. Effective conservation requires thorough understanding of species distribution patterns at various spatial scales. My overall aim here is to combine broad-scale, theoretical biogeography, and local-scale empirical ecology to investigate drivers of aquatic insect distribution across Africa. Species are often binarily classified as ‘widespread generalists’ or ‘narrow-range specialists’ based on their ecological traits. Results in Chapter 2 show that ecological and biological traits are highly interactive among dragonflies, and inferring geographical range size based on ecological preference and/or biotope specialization alone should be approached with caution. Biological traits related to phenology and mobility were also strong drivers of dragonfly range size, indicating that conservation efforts should include multiple species across all habitat types. Regional climates show considerable variation across latitudinal and longitudinal gradients, and determine areas of high species richness and diversity. In Chapter 3, I show strong latitudinal and longitudinal gradients for South-African dragonfly species richness and endemism. Dragonfly assemblage-turnover boundaries coincided with significant geographical features and/or areas where contemporary climate changed from one condition to another. However, these dragonfly assemblage turnover-boundaries were gradual rather than discrete throughout South Africa. At the local scale, natural and artificial ponds contribute greatly to overall biodiversity, especially when they are of high quality and occur in networks across the landscape. I show that ponds characterized by high heterogeneity support diverse aquatic insect assemblages (Chapters 4 and 5). Chapter 4 showed artificial reservoirs, occurring alongside natural ponds in ecological networks, to expand the area of occupancy for most widespread dragonflies, aquatic beetles and true bugs. Some species with specific habitat requirements were confined to natural ponds, suggesting the significance of natural ponds for conserving the full range of insects. Dragonflies, aquatic beetles and true bugs occupy low-quality artificial reservoirs at low abundance to survive the adverse effects of drought (Chapter 5). However, many insects exclusively occupied natural ponds, emphasizing the overall importance of naturalness, and suggests that there is merit in improving artificial reservoirs. This would most likely be by having macrophytes and vegetated banks similar to those of natural ponds.Investigating aquatic insect distribution patterns is important for conservation, and here, I demonstrate the value of dragonflies as model organisms for investigating the drivers of broad-scale distribution patterns. Studying other taxa is also appropriate, as I have demonstrated at the local scale, but not always possible due to limited distribution knowledge. I recommend broad-scale investigations of other complementary taxa to determine their added value for elucidating the drivers of overall insect distribution patterns, and so address our current shortfalls to improve insect conservation.
- ItemAccelerated microbial degradation of nematicides in vineyard and orchard soils(South African Society for Enology and Viticulture, 2014-03) Hugo, H. J.; Mouton, C.; Malan, Antoinette P.Accelerated microbial degradation (AMD) of organophosphate and carbamate nematicides is a phenomenon whereby biodegradation in the soil is increased, leading to a dramatically shortened persistence of nematicides. More intensified agriculture practices in South Africa in response to the future demand for food may lead to increased pest and disease pressure, which in turn will lead to more frequent pesticide application. The same principle applies to plant-parasitic nematode control practices, and the overuse and misuse will have a pronounced effect on the enhancement of AMD. With limited management options available, the responsible use of nematicides becomes more pertinent. Producers should be aware of the problems associated with multiple soil applications of organophosphates and carbamates against plant-parasitic nematodes. This article reviews factors contributing to the AMD of carbamate and organophosphate nematicides in soil and makes practical recommendations to avoid the occurrence of AMD in vineyard and orchards.
- ItemAcoustic monitoring and response of katydids (Orthoptera: Tettigoniidae) to the landscape mosaic in a Biosphere Reserve(Stellenbosch : Stellenbosch University, 2017-03) Thompson, Aileen Celeste; Samways, Michael J.; Bazelet, Corinna S.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH SUMMARY: A charismatic group within the Orthoptera, katydids can be found in a variety of habitat types world-wide due to their excellent bark and leaf mimicry skills. Most male katydids produce species-specific calls to attract female mates. If katydids, like their close relatives the grasshoppers, can function as effective biological indicators, then acoustic monitoring of katydid songs may result in a novel and non-invasive method to rapidly assess local biodiversity. Furthermore, information regarding threat statuses, distributions and life history traits can be inferred for all South African katydid species, leading to the development of a Katydid Biotic Index (KBI) based on the highly effective Dragonfly Biotic Index. If proven effective, the KBI would allow for biodiversity assessments to account for detailed aspects of katydid species composition in addition to the diversity measures normally utilized for biodiversity assessment (e.g. species richness and abundance). In this thesis, I provide the first steps towards determining whether the KBI could be an effective assessment technique. First I assess the utility of the KBI at a coarse-scale by determining its ability to identify regions of high conservation priority. Secondly, I conduct a fine scale study to determine the response of the katydid assemblage to habitat quality. And lastly, the first two aims are combined to determine whether the KBI is an appropriate method to assess habitat quality at a fine-scale. In Chapter 2, by using a subset of museum records, I investigate the distribution of the katydids within the Cape Floristic Region (CFR), a global biodiversity hotspot. The katydids found within the CFR follow the same trends with regards to threat status, endemism and life history traits to the overall South African katydid assemblage. The KBI assessment method was able to select, at this coarse-scale, the ecosystems of conservation priority. For Chapters 3 and 4, the Kogelberg Biosphere Reserve (KBR) was selected as a study area as it allowed for the acoustic monitoring and direct comparison of katydid assemblages and responses across the core, buffer and transition zones through the use of passive recordings. In Chapter 3 I found that the katydids of the KBR are not complementary across the zones. However, they respond positively in terms of abundance to measured habitat quality when the entire assemblage is considered. In Chapter 4 I found that katydids responded towards coarse-scale habitat quality and they were not as sensitive towards habitat change as was expected. By including abundances of the katydid species in to the KBI calculations, the sensitivity of the KBI as an assessment method was improved. For this reason, katydids in the fynbos biome are likely to not be effective indicators of habitat change on a small scale, likely due to the surprisingly low diversity of katydid species in the KBR. However, if the KBI were to be tested out in forest patches or areas with higher diversity, the KBI may prove more promising. For these reasons, a rapid assessment technique based on the KBI is likely to be more appropriate for some habitat types over others.
- ItemAcoustic profiling of the landscape(Stellenbosch : Stellenbosch University, 2014-04) Grant, Paul Brian Charles; Samways, Michael J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Soft, serene insect songs add an intrinsic aesthetic value to the landscape. Yet these songs also have an important biological relevance. Acoustic signals across the landscape carry a multitude of localized information allowing organisms to communicate invisibly within their environment. Ensifera are cryptic participants of nocturnal soundscapes, contributing to ambient acoustics through their diverse range of proclamation songs. Although not without inherent risks and constraints, the single most important function of signalling is sexual advertising and pair formation. In order for acoustic communication to be effective, signals must maintain their encoded information so as to lead to positive phonotaxis in the receiver towards the emitter. In any given environment, communication is constrained by various local abiotic and biotic factors, resulting in Ensifera utilizing acoustic niches, shifting species songs spectrally, spatially and temporally for their optimal propagation in the environment. Besides the importance of Ensifera songs from an ethological point of view, the multitude of species-specific signals provide an acoustic tapestry representing species diversity across ecological gradients and over time. Acoustic inventorying and monitoring of the landscape can reflect the environmental status of ecological systems, from natural to disturbed by human influence. In contrast to traditional survey techniques, sound recording and interpretation is a non-invasive method that allows for the detection and classification of highly cryptic, yet insightful indicators of ecosystem change. Here, acoustic monitoring was used across diverse ecological gradients to improve understanding of species diversity patterns, and how they change in response to both natural gradients and in response to the human dominated landscape mosaic. This study was undertaken in three geographic locations from tropical rain forest of Brunei, Borneo, to the landscapemosaic of plantation forestry in KwaZulu-Natal, South Africa, and to the botanically rich, mountain fynbos region of the Cape Floristic Region, also in South Africa. Each region provided a diverse and particular landscape to test the value of acoustic surveys for determining local diversity patterns across natural gradients and to assess the value of the technique for assessing the impact human influence across landscapes. In tropical rainforests, an entire acoustic guild was investigated to determine how acoustic species partition their acoustic communication channels spectrally, temporally and spatially, to avoid acoustic interference. The overall assemblage showed considerable spectral partitioning. Diurnally active species showed low temporal niche overlap, whereas nocturnal species did not utilize temporal partitioning. Lack of nocturnal temporal partitioning suggests other mechanisms of acoustic avoidance are sufficient to avoid acoustic overlap, or that there are insufficient cues to partition nocturnal acoustic environments. Acoustic species also utilized spatial partitioning, with distinct acoustic assemblages at vertical heights and with elevation. Utilization of a range of different strategies allow many species to communicate with conspecifics with little or no interference from other species in a signal rich environment. Acoustic profiling was also undertaken in KwaZulu-Natal, South Africa, across a plantation forestry landscape mosaic with diverse ecological gradients containing both alien and indigenous vegetation, as well as boarding large natural protected areas. Areas covered in alien timber or non-endemic grass were devoid of acoustic signals. Managed areas that were mowed and heavily grazed were not effective in maintaining the natural complement of nocturnal acoustic species. Within natural vegetation patches inside plantations, acoustic species richness increased with plant heterogeneity and patch size. Patches of indigenous vegetation within the plantation matrix effectively reduced the contrast of transformed landscapes with surrounding natural areas, with indigenous forest patches containing a highly characteristic acoustic species assemblage. Within the botanically rich, mountain fynbos region of the Cape Floristic Region, acoustic profiling was conducted across gradients of elevation, season and vegetation. Across these gradients, katydid acoustic signals were identified and characterized for the first time. This resulted in the discovery of two new katydid species and a novel sound producing structure in a carabid beetle, a species previously unknown to produce sound. Acoustic diversity across seasonal and elevational gradients increased with increasing temperatures. Climatic variability along the elevational gradient produced variation in seasonal phenology. Katydids also utilized high frequency acoustic signals, which is probably an adaptation to overcome background noise from wind, so prevalent in this area. Furthermore, despite producing conspicuous signals for mate attraction and pair formation, katydids were found not to be part of bat-eared fox diet, an insectivorous, nocturnal predator that uses its characteristic large ears to detect sounds made by invertebrate prey. This study shows the value of using acoustic emissions from katydids to identify acoustic diversity patterns across ecological gradients and in response to human impacts on the landscape.
- ItemAcridid ecology in the sugarcane agro-ecosystem in the Zululand region of KwaZulu-Natal, South Africa(Pensoft, 2020-01-10) Bam, Adrian; Addison, Pia; Conlong, DesmondGrasshoppers and locusts are well known crop and pasture pests throughout the world. Periodically they cause extensive damage to large areas of crops and grazing lands, which often exacerbate food shortage issues in many countries. In South Africa, acridid outbreaks rarely reach economic proportions, but in sugarcane plantations, localized outbreaks of native acridid species have been reported for the last eight years with increasing frequency and intensity in certain areas. This study was undertaken from May 2012 to May 2013 to identify the economically important acridid species in the sugarcane agroecosystem in these outbreak areas, to monitor seasonal activity patterns, to assess sampling methods, and to determine the pest status of the major species through damage ratings. Five acridid species of particular importance were identified: Nomadacris septemfasciata (Serville), Petamella prosternalis (Karny), Ornithacris cyanea (Stoll), Cataloipus zuluensis Sjötedt, and Cyrtacanthacris aeruginosa (Stoll). All species are univoltine. Petamella prosternalis was the most abundant species and exhibited a winter egg diapause, while N. septemfasciata, the second most abundant species, exhibited a winter reproductive diapause. Petamella prosternalis and N. septemfasciata were significantly correlated with the damage-rating index, suggesting that these two species were responsible for most of the feeding damage found on sugarcane. This study, for the first time, identified the acridid species complex causing damage to sugarcane in the Zululand area of KwaZulu-Natal, South Africa, and documented their population characteristics and related damage. These data are important information on which to base sound integrated pest management strategies.
- ItemAdapting the Dragonfly Biotic Index to a katydid (Tettigoniidae) rapid assessment technique : case study of a biodiversity hotspot, the Cape Floristic Region, South Africa(Pensoft Publishers, 2017) Thompson, Aileen C.; Bazelet, Corinna S.; Naskrecki, Piotr; Samways, Michael J.Global biodiversity faces many challenges, with the conservation of invertebrates among these. South Africa is megadiverse and has three global biodiversity hotspots. The country also employs two invertebrate-based rapid assessment techniques to evaluate habitat quality of freshwater ecosystems. While grasshoppers (Acrididae) are known indicators of terrestrial habitats, katydids (Tettigoniidae) could be as well. Here, we adapt a South African freshwater invertebrate-based rapid assessment method, the Dragonfly Biotic Index (DBI), for the terrestrial katydid assemblage, and propose a new assessment approach using katydids: the Katydid Biotic Index (KBI). KBI assigns each katydid species a score based on a combination of: 1) IUCN Red List status, 2) geographic distribution, and 3) life history traits (which consist of mobility and trophic level). This means that the rarer, more localized, specialized and threatened katydid species receive the highest score, and the common, geographically widespread and Least Concern species the lowest. As a case study, we calculated KBI across one of South Africa’s global biodiversity hotspots, the Cape Floristic Region (CFR). We then correlated KBI/Site scores of individual ecosystems with their ecosystem threat scores. The CFR’s katydid assemblage did not differ significantly from that of the overall South African katydid assemblage in terms of its species traits, threat statuses, or distribution among tettigoniid subfamilies. Likewise, KBI/Site scores did not differ significantly among ecosystem threat statuses. This may be explained by the coarse spatial scale of this study or by the lack of specialization of the CFR katydid assemblage. Nevertheless, the KBI holds promise as it is a relatively simple and non-invasive technique for taking invertebrate species composition into account in an assessment of habitat quality. In regions where katydid assemblages are well-known, acoustic surveys and KBI may provide an efficient means for assessing habitats.
- ItemAdjuvants to improve aerial control of the citrus mealybug Planococcus citri (Hemiptera: Pseudococcidae) using entomopathogenic nematodes(Cambridge University Press - CUP, 2013-11) Van Niekerk, S.; Malan, Antoinette P.The citrus mealybug, Planococcus citri, is a highly destructive pest of citrus, occurring only in the aerial parts of plants. Humidity will be one of the key factors to consider when using entomopathogenic nematodes (EPN) as biological control agents. Different adjuvants can be added to suspensions of EPNs, to improve control as a foliar application. An aqueous suspension containing Heterorhabditis zealandica and 0.3% Zeba® significantly increased P. citri mortality by 22% at 80% relative humidity (RH) with a temperature cycle starting at 22°C for 14 h and 11°C for 11 h. The same polymer formulation was tested for Steinernema yirgalemense and mortality of P. citri increased by 21% at 60% RH and by 27% at 80% RH. The addition of Nu-Film-Pw and Zebaw to H. zealandica suspensions did not significantly retard application run-off on citrus leaves. The combination of Nu-Film-P® and Zeba®, however, was able to significantly retard sedimentation, increasing the average number of nematodes deposited on 2-cm² leaf discs by 10 nematodes. In an aqueous suspension, nematodes settle rapidly to the bottom, resulting in an uneven distribution of nematodes. Xanthan gum, at a concentration of 0.2%, was highly effective at retarding sedimentation, with 72% of the initial nematode number still in suspension after 1 h. Zeba®, at a concentration of 0.3%, despite not being as effective as Xanthan gum, nevertheless still retarded sedimentation significantly. This is the first report of the potential of Nu-Film-P® and Zeba® to improve EPN performance against P. citri when used above ground in citrus orchards.
- ItemAgrohidrologiese studies aan die Olifantsrivierbesproeiingskema, 1959-1962(Stellenbosch : Stellenbosch University, 1962) Nieuwoudt, Alexander Daneel; Sim, J. T. R.; Stellenbosch University. Faculty of AgriSciences. Department of Conservation Ecology and Entomology.No Abstract available.
- ItemAlien grass invasion of Renosterveld : influence of soil variable gradients(Stellenbosch : Stellenbosch University, 2008-12) Muhl, Sara Ann; Esler, Karen J.; Milton, S. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.This thesis examines the role of agricultural activity in the process of invasion of west coast renosterveld fragments by annual alien grass species. This highly endangered vegetation type has less than 5% remaining, it is vital to understand the mechanisms allowing invasion of annual alien grasses in order to effectively prevent the loss of the many rare and endemic species found in west coast renosterveld. This study was divided into three major components. Firstly the distribution of indigenous and alien plant species in relation to fence lines, separating active agricultural fields from untransformed vegetation, was described. Regression analysis was used to test for relationships between distances from agricultural fields and soil physical and chemical characteristics in natural vegetation. Cover by annual alien invasive grasses in untransformed vegetation decreased significantly with distance away from agricultural land. Secondly alien and indigenous grass seed banks were sampled along the transects, at the same sites, in order to establish whether the seed banks correlated with above ground cover. Results varied among sites and seed banks were correlated with the vegetation cover at only one site. It appears that there are a multitude of factors determining the distribution of annual alien grass cover. Thirdly a greenhouse experiment established the role that nitrogen plays in the success of the alien grass Avena fatua. This species was grown in competition with three indigenous species, an annual forb (Dimorphotheca pluvialis), a geophyte (Oxalis purpurea) and an indigenous perennial grass (Tribolium uniolae) at three levels of soil nitrogen. The geophyte was largely unaffected, while growth of the annual and indigenous perennial grasses was negatively affected by competition with A. fatua. Nitrogen did not seem to affect competitive interactions. Management of these renosterveld patches, in order to conserve them effectively, will require a multi-faceted approach, including prevention of further invasion and removal of invasive grasses already present.
- ItemAlien plants have greater impact than habitat fragmentation on native insect flower visitation networks(Wiley, 2018) Hansen, Simone; Roets, Francois; Seymour, Colleen L.; Thebault, Elisa; Van Veen, F. J. Frank; Pryke, James S.Aim: Habitat fragmentation and alien species are among the leading causes of biodiversity loss. In an attempt to reduce the impact of forestry on natural systems, networks of natural corridors and patches of natural habitat are often maintained within the afforested matrix, yet these can be subject to degradation by invasion of non-native species. Both habitat fragmentation and alien invasive species disrupt the complex interaction networks typical of native communities. This study examines whether an invasive plant and/or the fragmented nature of the forestry landscape influences natural flower visitation networks (FVNs), flower–visitor abundance and richness or flower/visitor species composition. Location: The species rich and diverse grasslands in the KwaZulu-Natal Midlands, South Africa is under threat from transformation, particularly by commercial forestry plantations, restricting much of the remaining untransformed grasslands into remnant grassland patches (RGPs). Remaining patches are under additional threat from the invasive Rubus cuneifolius Pursh (bramble). Sites were established in RGPs and in a nearby protected area (PA), with and without brambles present for both areas. Results: Flower abundance and flower area of native plant species were greater within RGP than in PA, but only in the absence of R. cuneifolius. Flower–visitor assemblages differed between invaded and uninvaded sites and also differed between PA and RGP sites. Both areas lost specialist flower–visitor species in the presence of brambles. Network modularity was greatly reduced by the presence of bramble, indicating a reduction in complexity and organization. The structure of FVNs was otherwise unaffected by presence of bramble or being located in RGPs or the PA. Main conclusions: The RPGs contribute to regional biodiversity conservation through additional compositional diversity and intact FVNs. Rubus cuneifolius reduces ecological complexity of both RGPs and PAs, however, and its removal must be prioritized to conserve FVNs.
- ItemAnalysis of the global warming potential of biogenic CO₂ emission in life cycle assessments(Nature Research, 2017-01-03) Liu, Weiguo; Zhang, Zhonghui; Xie, Xinfeng; Yu, Zhen; Von Gadow, Klaus; Xu, Junming; Zhao, Shanshan; Yang, YuchunBiomass is generally believed to be carbon neutral. However, recent studies have challenged the carbon neutrality hypothesis by introducing metric indicators to assess the global warming potential of biogenic CO2 (GWPbio). In this study we calculated the GWPbio factors using a forest growth model and radiative forcing effects with a time horizon of 100 years and applied the factors to five life cycle assessment (LCA) case studies of bioproducts. The forest carbon change was also accounted for in the LCA studies. GWPbio factors ranged from 0.13–0.32, indicating that biomass could be an attractive energy resource when compared with fossil fuels. As expected, short rotation and fast-growing biomass plantations produced low GWPbio. Long-lived wood products also allowed more regrowth of biomass to be accounted as absorption of the CO2 emission from biomass combustion. The LCA case studies showed that the total life cycle GHG emissions were closely related to GWPbio and energy conversion efficiency. By considering the GWPbio factors and the forest carbon change, the production of ethanol and bio-power appeared to have higher GHG emissions than petroleum-derived diesel at the highest GWPbio.
- ItemAngiostoma margaretae n. sp (Nematoda: Angiostomatidae), a parasite of the milacid slug Milax gagates Draparnaud collected near Caledon, South Africa(Springer Verlag, 2011) Ross, Jenna L.; Malan, Antoinette P.; Ivanova, Elena S.Angiostoma margaretae n. sp. (Angiostomatidae) is described from the oesophagus of the slug Milax gagates Draparnaud collected near Caledon in the Western Cape Province of South Africa. The new species closely resembles another parasite of a milacid slug, A. milacis Ivanova & Wilson, 2009, with a similar head, stoma and spicule shape, the presence of distally outstretched ovaries, coiled oviducts, the same number of caudal papillae and enlarged rectal glands. However, A. margaretae differs from the latter by having: a shorter, wider tail with a rounded vs pointed tip; the distal parts of both ovaries with a particular hook-like shape due to an expansion closely following the short initial zone; ovoviparous females; and a different arrangement of male papillae. A. margaretae is comparable with A. limacis Dujardin, 1845, A. asamati (Spiridonov, 1985), A. coloaense (Pham Van Luc, Spiridonov & Wilson, 2005) and A. stammeri (Mengert, 1953), which have a similar stoma shape and size, but can be readily differentiated by the presence of distally outstretched vs reflexed ovaries and the presence vs lack of enlarged rectal glands. The new species has a similar arrangement of the ovaries to A. kimmeriense Korol & Spiridonov, 1991 and A. zonitidis Ivanova & Wilson, 2009, but is clearly differentiated by the lack of an off-set lip region and presence of a large bowl-shaped vs tubular stoma and less numerous male caudal papillae (seven pairs vs nine in A. kimmeriense and 10 in A. zonitidis). © 2011 Springer Science+Business Media B.V.
- ItemApplying a resilience approach to flood management in rapidly changing landscapes(Stellenbosch : Stellenbosch University, 2016-12) Ilse, Kotzee; Reyers, Belinda; Esler, Karen J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Human land use activities have significantly changed the capacity of ecosystems to deliver essential service. Additional stresses brought about by climate change will require a shift in how ecosystems are managed. Global increases in the magnitude and frequency of flood events in particular have raised concerns that traditional flood management approaches may not be sufficient to deal with future uncertainties. Resilience approaches aimed at understanding and managing the capacity of social-ecological system (SES) to adapt to, cope with, and shape uncertainty and surprise offer a possible avenue to deal with these challenges. Accordingly, through the use improved systems approaches and knowledge on floods, flood regulation services and its impact on people and infrastructure this dissertation contributes towards developing and piloting of a flood resilient management strategy. Research was carried out using three flood prone municipalities in the Eden District of South Africa as a case study. The Millennium Ecosystem Assessment, in its final report, highlighted regulating services as some of the most important and degraded, but least understood ecosystem services. Regulating services moderate the flow of energy and materials and play a critical role in regulating the impacts of extreme events. The progress in research and understanding of regulating services was investigated, with a particular focus on progress on their assessment and quantification. Findings flag key research gaps in all regulating services in developing countries and globally, in specifically understudied regulation services of disease regulation and air quality regulation. Results also revealed the need to include the human dimension into the study of regulating services, which will require an increase of multi-disciplinary research using a social-ecological system approach. Based on these findings and the objectives of the study the use of an existing decision support tool SCIMAP was adapted and explored using globally available data to provide a practical and informative approach for identifying flood receiving areas at a watershed scale. Model outputs highlighted how the combined effect of natural and anthropogenic factors can aggravate or attenuate a flood event, adding valuable insights into flood generation and how it can be managed, especially in under resourced areas. In order to assess the resilience of communities to floods, a composite index and spatial analysis approach was piloted. The approach allows for a simple, yet robust index able to include an array of datasets generally available in flood prone areas with potential to disaggregate and trace variables for management and decision making. Finally, based on the methods and results developed in previous chapters of the dissertation, an approach to characterise and spatially connect the flood regulating ecosystem service flows from supply to demand is introduced and illustrated. The proposed method builds on from the thinking in flood vulnerability and incorporates landscape connections from supply to demand areas. By identifying and linking supply areas to the downstream benefitting areas of the watershed, areas directly linked to high demand can be conserved to ensure a sustainable supply of the flood regulation service. This dissertation provides new and improved approaches for building and managing flood resilient watersheds. The results have immediate applicability to landscape managers in areas where data for process-based models and the capacity to interpret model outputs may be limited.
- ItemApproaches towards a critical evaluation and update of the red list of South African Butterflies(Stellenbosch : Stellenbosch University, 2006-03) Ball, Johathan Bradford; Geertsema, H.; Samways, Michael J.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.Using the World Conservation Union’s (formerly the International Union for the Conservation of Nature) IUCN 2001 categories and criteria, the conservation status of the South African butterfly fauna has been reassessed. This study includes an assessment of the 62 globally threatened South African taxa and 1 that has a marginal distribution in this region.
- ItemArthropod communities of Proteaceae with special emphasis on plant-insect interactions(Stellenbosch : Stellenbosch University, 1989) Coetzee, J. H.(Jacobus Hendrik); Giliomee, J. H.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology & Entomology.ENGLISH ABSTRACT: Arthropod communities of five proteaceous species viz. Protea repens. P. neriifolia. P.cynaroides, Leucospermum cordifolium and Leucadendron /aureolum were studied. A faunal list of the insects was compiled according to the feeding guilds of insects. Six phytophagous guilds were recognized: flower visitors, thrips, endophages, ectophages, sap-suckers, and ants. The guild composition, species packing and seasonal distribution for the free-IMng insects, spiders and other arthropods were investigated on the different plant species. The ants, flower visitors and sap-sucking species found on the plant species, were very similar, but the number of leaf chewing species common to all the plant species was low, suggesting that some species were monophagous. Insect abundance increased during the wet winter months when the plants were in flower. Of the total number of herbivores collected, flower visitors represented 69,5%, leaf feeders 14,5% and sap-suckers 16,1 %. The chewers constituted 60,1% of the total herbivore. biomass. Leaf damage increased with age ; young leaves were practically free of herbivore damage, while older leaves were stm acceptable as food. The degree of insect damage differed amongst the plant species varying from 2% to 15%. The following leaf characteristics were investigated to determine the factors involved in defence against insect herbivory : total phenolic content, protein precipitating ability, cyanogenesis, nitrogen content, leaf toughness, woodiness and fibre content lt appears that the plant species use different mechanisms to protect their leaves. The infructescences of Protea repens were exploited by the larvae of four Coleoptera and four Lepidoptera species. The community structure of these phytophagous insects was determined largely by negative interactions. Various strategies are followed (e.g. niche segregation in time and space) to lessen interspecific competition.
- ItemArthropods associated with commercial Proteaceae in the Western Cape Province, South Africa(Stellenbosch : University of Stellenbosch, 2011-03) Sasa, Archbold; Samways, Michael J.; University of Stellenbosch. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: The commercial cultivation of Proteaceae is an important industry in the Western Cape, however, farmers are challenged with arthropod infestation which compels them to solely rely on chemical pesticides. Past studies in South Africa have shown that Proteaceae comprise a rich and diverse arthropod fauna. However, as most of these studies were conducted on wild Proteaceae, they may not be representative of cultivated proteas. Moreover, most of these species remained unidentified due to lack of identification expertise. These past studies, however, form a useful baseline for arthropod studies in proteas, e.g. the feeding guilds found in proteas. The aim of this research was to conduct an intensive and extensive survey of the arthropod-fauna associated with commercially-cultivated proteas across an entire year. Specifically, this survey was designed to document the composition of the arthropod fauna (creating a comprehensive reference collection for pest management purposes) and to assess whether the arthropod fauna differed between seasons and pesticide treatments. Infructescences, inflorescences and foliage of mainly commercial Proteaceae were sampled for arthropods seasonally for a period of twelve months by collection of plant material and direct searching. Seven commercial protea blocks, and a wild protea block (remnant patch of fynbos vegetation), were used as the sampling sites, and two sprayed blocks were used for assessing pesticide efficacy. Individual arthropods were identified as far as possible, with 37% identified to species level. A species accumulation curve showed that rare (minor) arthropod species made up of 70% of arthropods occurring in cultivated proteas. More than 8 700 individuals from more than 140 species and about 80 families were collected and identified, revealing that cultivated proteas have a rich and diverse insect fauna. These arthropods represent the full range of plant-feeding guilds: leaf miners, leaf chewers, flower bud borers, sap suckers and seed feeders. Flower visitors/free living guild was the most abundant (72%) and speciose (25%). In addition to phytophages, there was a large suite of insect predators and parasitoids. A large number of the arthropods were endemic to the Cape Floristic Region (CFR) and some (7.86%) have a pest status, in that they cause significant damage to the protea plants (for example, 60% of Safari sunset cultivar (Leucadendron salignum x L. laureolum) new flush stems and leaves were affected by Epichoristodes acerbella (Tortricidae). Capys alphaeus (Lycaenidae) and Phyllocnistis sp. (Phyllocnistidae) appear to be specialist pests, as they attack mainly Protea cynaroides and Susara cultivar (Protea magnifica x P. susannae) respectively. Arthropod abundance did not differ significantly between seasons, although significant seasonal effects were observed in species richness when the protea cultivars were examined separately. Pesticide application did not affect arthropod abundance, but did decrease species richness in sprayed blocks. Pesticides appeared to negatively affect minor (rare) species disproportionately, probably due to their lack of prior exposure to pesticides and hence sensitivity. Due to this inefficacy of pesticides in cultivated proteas, an increasing emphasis on the importance of non-chemical control measures, and our improved knowledge of the predatory and parasitic species in this system, integrated pest management strategies deserve greater research attention. Monitoring and use of threshold values for arthropod pests were suggested here, as well as the use of biological, cultural, physical and chemical (optimal use) control. For instance, in cultural control, polycropping and intercropping in proteas to increase plant diversity in the monocultures to promote a higher density of predators and parasitoids can be used. Certain flowering plants are known to provide greater temporal and spatial distribution of nectar and pollen sources, which can increase parasitoid reproductive potential and abundance of alternative hosts/prey when the pest species are scarce or at an inappropriate stage.
- ItemArtificial reservoirs complement natural ponds to improve pondscape resilience in conservation corridors in a biodiversity hotspot(Public Library of Science, 2018-09-20) Deacon, Charl; Samways, Michael J.; Pryke, James Stephen; Chapman, Maura (Gee) GeraldineNatural ponds are rich in biodiversity, contributing greatly to regional aquatic biodiversity. Artificial reservoirs used for irrigation can be significant additional features of the landscape. They infill the local natural pondscape, and are attractors for aquatic insects. Here, we determine the extent to which artificial reservoirs represent the local natural pond biota, and how they contribute to the pondscape in conservation corridors used to mitigate the impact of plantation forestry in a global biodiversity hotspot. We did this by: 1) identifying the environmental factors, including plants, that drive dragonfly, water beetle, and water bug species richness, diversity and composition, and 2) determining the value of natural ponds vs. artificial reservoirs for maintaining the population size and expanding the area of occupancy for dragonflies, beetles and bugs in conservation corridors. While vegetation cover was central for maintaining species richness and composition of the assemblages in general, many other environmental variables are necessary to encourage the full suite of local diversity. Artificial reservoirs are attractive habitats to many species, overall increasing area of occupancy for 75% of them (ranging from 62–84% for different taxa). These reservoirs provide complementary alternative habitats to natural ponds, leading to improved ecological resilience across the pondscape. We conclude that maintaining a diverse and heterogeneous pondscape is important for conserving local aquatic insect diversity, and that artificial reservoirs increase the local area of occupancy for a range of pond insects in conservation corridors, and improve the biodiversity value of these pondscapes.
- ItemAssessing the chemical ecology and shelter-seaking behaviour of the grainchinch bug, Macchiademus diplopterus (hemiptera: lygaeidae) for optimisation of trapping during aestivation(Stellenbosch : Stellenbosch University, 2016-12) Ngadze, Masimbaashe; Johnson, Shelley; Addison, Pia; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: The grain chinch bug (GCB), Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae) is a key quarantine pest of South African export fruit and is endemic to the Western Cape Province. The pest is troublesome in the drier wheat growing areas where it disperses from wheat in summer to find sheltered sites in which to aestivate. Aestivating adults can end up contaminating export fruit. The aim of the study was to gather more knowledge on the chemical ecology and shelter-seeking behaviour of the GCB. The involvement of pheromones in the aggregation behaviour of GCBs is yet to be fully elucidated. Further investigating the chemical ecology of the GCB in order to optimize its pheromone trapping was the primary focus of the first research chapter in this study. Headspace volatile compounds were identified from active bugs through gas chromatography-mass spectrometry (GC-MS) analysis. A total of 14 volatile compounds were identified from males and females in varying concentrations. For both sexes pooled, tridecane, (E)-2-hexanal and (E)-2-octenal were the three main components; (E)-2-hexenol, (E)-2-octenol, decanal and pentadecane were in medium amounts, while decanoic acid, dodecane, hexadecanal, hexanal, icosane, nonanal and tetradecanoic acid were minor components. The efficacy of synthetic lures using previously identified aggregation pheromone components, and sex pheromone volatile components (identified in present study) was studied in combination with modified traps using rubber septa dispensers in a field trial. There was no significant difference (P > 0.05) between insects caught in the sex pheromone baited traps and the aggregation pheromone baited traps. Traps caught low numbers of GCBs compared to the level of orchard infestation indicated by the amount of bugs that were found sheltering in corrugated cardboard bands tied around tree trunks. The corrugated cardboard bands showed a significant difference in the number of bugs sheltering between bands placed at bottom and top positions (0.5m and 1.5m above ground respectively) on the trees, at site 1 (P = 0.0058), site 2 (P < 0.0169) and site 4 (P < 0.0496) with the exception of site 3 (P > 0.4115). Cardboard band position influenced catches, as more bugs were found in bottom bands. This can be used advantageously in optimising innovative trap placements in the future in order to improve catches. In the second research chapter investigations into the behavioural responses of GCBs to visual objects were conducted. This was done to increase knowledge on how this behaviour can lead to the development of control measures such as the use of coloured traps of different shapes. Behavioural responses of GCBs to different shapes presented in their visual space indicated that there was a significant difference (P = 0.0001) in the choice of shape. Vertical/upright rectangular shapes had the highest number of GCB visits. GCBs responded to upright rectangles of different colours.Black and red rectangles were not significantly different (P > 0.05) from each other but were both significantly different (P = 0.0001) from green and yellow rectangles, off-target and sedentary insects. Vertical rectangles of two different colour patterns (black & white) and (red & white) did not show any significant difference (P > 0.153) in the number of GCB visits. Both black & white and red & white vertical stripes were significantly different (P = 0.0001) from off-target and sedentary insects. This indicates that GCBs were equally responsive to both colour patterns. These results indicate that GCBs exhibit a positive scototactic reaction towards dark upright surfaces. Information generated from this study will facilitate the development of pre-harvest monitoring and management measures against GCBs, using pheromone traps and physical barriers that prevent GCBs from dispersing into fruit orchards at the wheat to fruit orchard interface. This can help to reduce fruit contaminations, ultimately lowering the rejection risk of export fruit from South Africa.
- ItemAssessing the role of natural open spaces in ecosystem service provision for enhanced urban planning in the global south(Stellenbosch : Stellenbosch University, 2022-04) Wessels, Nadia; Esler, Karen J.; Sitas, Nadia; O'Farrell, Patrick; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Natural open space plays an important role in maintaining biodiversity and providing essential ecosystem services, i.e. the contributions we get from nature. Yet, natural systems within urban areas continue to be exploited and encroached upon, and are often undervalued in urban planning and management decisions, particularly within the context of the Global South where institutional constraints, and complex socio-economic and political priorities prevail. In response to these challenges, this research assessed the role of natural open space in ecosystem service provision for enhanced urban planning in the Global South, by using a case study of the Nelson Mandela Bay Municipality, situated in the Eastern Cape Province, South Africa. The research explored how understanding the benefits (ecosystem services) derived from natural open space can optimise and improve planning, which can, in turn, enable more people to benefit from the ecosystem services provided in cities. Urban natural open space systems form part of complex adaptive social-ecological systems. The realisation and optimisation of the ecosystem services provided by natural open space systems require an understanding of how land cover change affects ecosystem services, and consideration of implementation challenges and opportunities related to mainstreaming ecosystem services into urban planning, which include community and local government needs and priorities within the socio-economic and political context. Developing and implementing natural open space plans requires a transdisciplinary approach that moves beyond disciplines, such as the natural and social sciences only, to incorporate other ways of knowing and feedbacks between different knowledge systems, for example, linking practitioners’ and indigenous and local knowledge, where context-specific human needs, attitudes and values are recognised. The multidimensional outcomes of implementing urban conservation plans (or natural open space plans) are rarely critically evaluated. By providing a framework for monitoring and evaluating conservation outcomes and understanding the causal linkages and reasons for the success and failure of conservation outcomes, this research facilitates the institutionalisation of adaptive management approaches, enhancing urban planning and conservation and social outcomes. Through qualitative interviews with community members representing the city’s diverse socio- economic and ethnic variability (living near natural open space), the complex relational values with nature, and nuanced interpretations of how natural open space delivers ecosystem services were explored. Non-material services (relational benefits) were impacted by exploitative material uses, access concerns, and (mis)management. Management of natural open space also has significant implications for intra and inter-generational equity in respect of the benefits of ecosystem services, and the experience of ecosystem disservices, which require explicit consideration in municipal planning, budgeting and management. Innovative collaborative management and stewardship interventions with ecological and socio-economic benefits should be prioritised to protect the natural open space system. In the Global South the benefits of urban nature in terms of the supply and provision of ecosystem services are inequitably distributed and intertwined in complex socio-political processes. The degree to which the ecosystem services provided by natural open space are valued by local government officials, planned for, prioritised, and incorporated in decision- making, in terms of temporal and spatial implications, need to be understood. Institutional constraints of many local governments in the Global South, such as data and resource capacity, inhibit the appropriate consideration and incorporation of ecosystem services into urban planning. In such instances, expert (scientific) knowledge should be used to contribute to understanding the context-specific diverse ecosystem services provided by natural open space, and the implications of land cover changes on ecosystem service provision associated with rapid urbanisation. This expert understanding then needs to be incorporated with other knowledge systems. The research has emphasised the collective role of community members, civil society and the private sector; city officials and decision-makers; and scientists and researchers in the effective integration of ecosystem services into urban planning, in steering cities towards a sustainable trajectory. There is no panacea for effectively integrating ecosystem services into urban planning. Instead, advancing ecosystem services in urban planning requires various context-specific initiatives and approaches, which allow for collaborative governance and innovative nature-based solutions, and which give due consideration to intra and inter- generational equity. The research identifies opportunities for how to incorporate and catalyse stewardship for natural open space systems and contextually appropriate interventions that could be employed in other cities. It also highlights the need to understand the implications of trade-offs associated with the socio-economic drivers of land transformation over ecosystem service retention as cities in the Global South continue to grow and develop. The methodology followed in this research shows that an understanding of urban ecosystem services is possible without expensive and / or data-intensive decision-making tools, and similar approaches could be followed in other under-resourced cities in the Global South, which can then be used to enhance urban planning.
- ItemAssessing the values and impacts of invasive alien plants on the livelihoods of rural land-users on the Agulhas Plain, South Africa(Stellenbosch : Stellenbosch University, 2013-12) De la Fontaine, Samantha; Esler, Karen J.; Malgas, Rhoda R.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Invasive alien plants (IAPs) are known for their detrimental impacts on biodiversity and ecosystem goods and services. A substantial body of research has contributed to our understanding of their impacts on ecology. In comparison the socio-economic aspects of IAPs, are not well understood. Additionally, valuation practises have usually excluded the positive and the non-monetary impacts (benefits and uses) that IAPs hold for local livelihoods. Holistic valuation has been regarded as imperative for decision-making and managerial frameworks. A study was conducted in Elim on the southern Cape coast of the Agulhas Plain, South Africa, which aimed to explore the various impacts of IAPs on the livelihoods of rural land-users. Individual qualitative interviews were conducted face to face with landholders (referred to as farmers) (N = 12) and individuals from the economically marginalized community (referred to as marginalized community) (N = 12). The grounded theory approach to data analysis was used and results of the coding method used were displayed by means of superscripts. Results indicate that farmers were aware of broader uses of IAPs although they themselves did not utilise them as extensively as members of the marginalized communities. Invasive alien and problem plants that held value for both land-users were not perceived as being „invasive‟. Invasive alien plants were believed to have detrimental impacts on biodiversity and ecosystems goods and services which support people‟s livelihoods. Alien clearing programmes such as Working for Water (WfW) and LandCare have done much to alleviate the socio-economic burden of unemployment in this marginalized community. Aside from the social development aims set out by WfW (i.e. employment of low-income communities, poverty alleviation and skills training), knock-on social development benefits (e.g. feelings of pride, responsibility and awareness as well as conflict management skills) were also realised by individuals from the marginalized community that were previously employed by the programme. Farmers regarded alien clearing and management as a process that demands excessive time, energy and financial resources. On single occasions it was found that farmers employed methods other than the conventional clearing and management strategies (e.g. livestock that feed on IAPs and giving refuse IAP biomass from clearing and felling to neighbouring poor communities). No clear consensus was reached about regarding alien clearing and management but more support is desired from government. Working for Water relies on private landholders for alien clearing as it is required by law. This study emphasizes that stronger relationships between government and private landholders as well as more substantial incentives to clear IAPs on private land are prerequisites if required outcomes are to be achieved. Educating society at large about the detrimental impacts of IAPs is fundamental. Additionally, informing landholders on effective alien clearing methods and policies and legislation pertaining to it are key activities for the South African government. Finally, clearing and management programmes need to consider the benefits that local land-users obtain from IAPs when prioritising areas for the management of alien vegetation.