Phylogeography and Molecular Ecology of Selected Invasive Species in the Hawaiian Islands

Most alien (non-native) species which become naturalized are not disruptive to natural ecosystems. However, the small fraction that do spread and become invasive can have severe environmental and economic impacts. These impacts are often irreversible as control efforts normally only start after species are widespread. Molecular ecology renders a new approach to better understand invasions and can help in their management by resolving taxonomic issues, elucidating geographical source(s), detecting hybridization and introgression, and tracking dispersal and spread. Using a molecular ecological approach, some of these phenomena were investigated in this dissertation research for three different plant invaders in Hawaii. Molecular markers were developed for Pennisetum setaceum (fountaingrass), Miconia calvescens (velvet tree) and Senecio madagascariensis (fireweed) to answer ecological and management related questions. Molecular and quantitative genetic variation indicated that fountaingrass is monoclonal throughout Hawaii and furthermore, that this clone or “super-genotype” is shared globally among invasive and native ranges. This indicates phenotypic plasticity as the sole mechanism behind fountaingrass’ invasive success. Fountaingrass is unlikely to evolve resistance against successful control mechanisms. Subsequent herbicide trails indicated that grass-selective herbicides are ineffective against fountaingrass. Phylogenetic and population genetic structure showed that fireweed introduced to Hawaii originated from eastern South Africa. Effective and host-specific biological control agents against fireweed are most likely to be found in this region. The high genetic diversity found in fireweed is indicative of multiple introductions. Genetic spatial autocorrelation revealed a diffusive dispersal pattern in the Hawaiian Islands. Genetic structure indicated that bottlenecked populations of velvet tree are highly inbred in Hawaii and southern Pacific Islands. The data further suggested that invasive populations throughout northern and southern Pacific islands are genetically similar despite differential invasive success. These results indicate that invasions in both hemispheres are potentially fi-om similar geographic origin and/or that Hawaiian infestations are the result of a secondary introduction directly from Tahiti. The introduction of genotypes pre-adapted for various morphological, physiological and life history traits facilitate invasion success of velvet tree. Climatological similarities between the Society and the Hawaiian Islands indicate that Hawaiian infestations of velvet tree have not yet reached an optimum. Biological control would be the only effective control method against velvet tree with most productive control agents likely to be found in Mexico

The ecology, biogeography, history and future of two globally important weeds : Cardiospermum halicacabum Linn. and C. grandiflorum Sw.

Members of the balloon vine genus, Cardiospermum, have been extensively moved around the globe as medicinal and horticultural species, two of which are now widespread invasive species; C. grandiflorum and C. halicacabum. A third species, C. corindum, may also have significant invasion potential. However, in some regions the native status of these species is not clear, hampering management. For example, in South Africa it is unknown whether C. halicacabum and C. corindum are native, and this is a major constraint to on-going biological control programmes against invasive C. grandiflorum. We review the geography, biology and ecology of selected members of the genus with an emphasis on the two most widespread invaders, C. halicacabum and C. grandiflorum. Specifically, we use molecular data to reconstruct a phylogeny of the group in order to shed light on the native ranges of C. halicacabum and C. corindum in southern Africa. Phylogenetic analyses indicate that southern African accessions of these species are closely related to South American taxa indicating human-mediated introduction and/or natural long distance dispersal. Then, on a global scale we use species distribution modelling to predict potential suitable climate regions where these species are currently absent. Native range data were used to test the accuracy with which bioclimatic modelling can identify the known invasive ranges of these species. Results show that Cardiospermum species have potential to spread further in already invaded or introduced regions in Australia, Africa and Asia, underlining the importance of resolving taxonomic uncertainties for future management efforts. Bioclimatic modelling predicts Australia to have highly favourable environmental conditions for C. corindum and therefore vigilance against this species should be high. Species distribution modelling showed that native range data over fit predicted suitable ranges, and that factors other than climate influence establishment potential. This review opens the door to better understand the global biogeography of the genus Cardiospermum, with direct implications for management, while also highlighting gaps in current research

The effects of reverse bias on the efficiency of dye solar cells

Philosophiae Doctor - PhDDye-sensitised solar cells (DSC) have attracted much attention during the last few years due to their high efficiencies and their potentially low production costs. The technology is based on a thin layer of nano sized, high band gap (3.2 eV) TiO2 film. A Ru containing dye (from hereon called the Ru dye) is chemisorbed onto the TiO2 film. This combination acts as the working electrode. The counter electrode consists of a platinum layer which is the catalyst for the regeneration of the Iodine/Iodide electrolyte. The work that is presented here is focused on the results that were obtained during studies of the performance of the DSC under certain reverse bias conditions. When one cell in the series connection in a module is shaded, the current will pass this cell in reverse bias. In such a case the shaded cell will be subjected to a voltage in the reverse direction coming from the other lit cells in the module. This reverse voltage could permanently modify or damage the cell if it is not properly protected. Although the work is focussed on the chemical stability of the dye, various techniques were employed to determine the physical changes in the cell. It was found that a cell that was subjected to a reverse bias of 2 V for 500 min showed a 58% recovery and a cell that was subjected to 4.5 V reverse bias was irreversibly damaged. The UV-vis spectra showed a blue shift (higher energy), the Raman showed no peak at 1713 cm-1 (which indicates the absence of free carboxylate groups) and the FT-IR showed the disappearance of the NC-S absorption band at 2100 cm-1. The combined conclusion is that the - NCS ligand has been depleted and replaced with I3- ions. When measuring the impedance, the Nyquist plots showed an increase in the charge transfer resistance at the counter electrode when subjected to a reverse bias potential of 2 V. This is confirmed by the Bode plots. This indicates a partial oxidation of the Pt catalyst on the counter electrode. It can therefore be stated with confidence that the changes in the cell after being subjected to a reverse bias potential of 2 V for 500 min are changes on the -NCS bonds on the Ru dye as well as the Pt in the counter electrode.South Afric

Loyalty To SMEs: A Pipe Dream In The Current Economic Climate?

Small to medium enterprises (SMEs) plays a vital role in the growth and development of a country. It is therefore critical for any country, especially developing countries, to support and enhance the development of SMEs. Although the external support t is critical; SME’s needs to create and build its own loyal customer base for growth and sustainability. Loyal occurs when customers choose to use a particular store rather than others. A well maintained customer base can affect the SME’s profitability in a positive manner.Quantitative research was undertaken by means of a self-administered questionnaire to establish the perception of South African SME owners regarding loyalty. The study revealed that the main drive for creating loyal customers is good products and services as well as competitive prices. It is hoped that this information will help SMEs to attract and keep loyal customers as it is more cost effective to retain loyal customers than it is to obtain new customers

Water erosion risk assessment in South Africa : towards a methodological framework

Soil erosion is a major problem confronting land and water resources in many parts of the world and the spatial extent should be assessed and continually monitored. The combination of existing erosion models and remote sensing techniques within a Geographical Information System framework is commonly utilized for erosion risk assessment. In most countries, however, especially in developing countries such as South Africa, there is still an absence of standardized methodological frameworks that deliver comparable results across large areas as a baseline for regional scale monitoring. Assessment at the regional scale is often problematic due to spatial variability of the factors controlling erosion and the lack of input and validation data. Due to limitations of scale at which techniques can be applied and processes assessed, this study implemented a multi-process and multi-scale approach to support establishment of a methodological framework for South African conditions. The approach includes assessment of (i) sheet-rill erosion at a national scale based on the principles and components defined in the (Revised) Universal Soil Loss Equation, (ii) gully erosion in a large catchment located in the Eastern Cape Province by integrating eleven important factors into a GIS, and (iii) sediment migration for a research catchment near Wartburg in KwaZulu-Natal by means of the Soil and Water Assessment Tool. Case Study i illustrates that 20% (26 million ha) of South African land is classified as having a moderate to severe actual erosion risk (emphasizing sheet-rill erosion) and describes the challenges to be overcome in assessment at this scale. Case Study ii identifies severe gully erosion affecting an area of approximately 5 273 ha in the large catchment (Tsitsa valley) of the Eastern Cape Province and highlights gully factors likely to emerge as dominant between continuous gullies and discontinuous gullies. Case Study iii illustrates that a cabbage plot in the upper reaches of a research catchment near Wartburg is a significant sediment source, but is counterbalanced by sinks (river channel and farm dams) downstream. Model assumptions affecting outputs in the context of connectivity between sources and sinks are described. The factor-based nature of this multi-process and -scale approach allowed scrutiny of the role of the main factors in contributing to erosion risk. A combination of poor vegetation cover and susceptible parent material-soil associations are confirmed as the overriding factors in South Africa, and not topography and rainfall as frequently determined in the USA and Europe. A methodological framework with three hierarchical levels is then presented for South Africa. The framework illustrates the most feasible erosion assessment techniques and input datasets for which sufficient spatial information exists, and emphasizes simplicity required for application at a regional scale with proper incorporation of the most important factors. The framework is not interpreted as a single assessment technique but rather as an approach that guides the selection of appropriate techniques and datasets according to the complexity of the erosion processes and scale dependency. It is useful in determining the relative impact of different land use and management scenarios, as well as for comparative purposes under possible future climate change scenarios.Thesis (PhD)--University of Pretoria, 2012.Geography, Geoinformatics and Meteorologyunrestricte

Soil erosion prediction under changing land use on Mauritius

More than one half of the total area of Mauritius Island (1844 km2) is under intensive cultivation, mostly sugarcane. Since the sugarcane industry is currently facing tremendous economic constraints, sugarcane cultivation may be diversified into other agricultural types such as vegetables, pineapple and forestry. Increasing concern about the sugarcane industry and the consequences of agricultural diversification, necessitated the application of soil loss prediction models within a GIS framework. Modelling of the potential soil loss in the Rivierre Des Anguilles catchment (RDAC) is undertaken to understand the extent to which soil erosion is affected by different land use types or agricultural systems. Although most of the RDAC is covered with sugarcane (62%), a wide range of landforms, micro-climates and soils exist, making the catchment representative of southern catchments in Mauritius. The study integrates GIS techniques with two empirical soil loss models: The Revised Universal Soil Loss Equation (RUSLE); and The Soil Loss Estimation Model of Southern Africa (SLEMSA). Both models, as well as the GIS application termed Soil Erosion Assessment using GIS (SEAGIS), are used to investigate average annual soil loss from the catchment under key management practices. Using data on soil erodibility, rain erosivity, topography and land cover, soil loss can be estimated under different management options for cropland (sugarcane, intercropped cane, vegetables, banana and tea) and natural vegetation (scrub and forest). RUSLE is additionally used to predict soil loss for the catchment under potential crop diversification scenarios including, vegetables, pineapple and forest. Using the empirical soil loss models in conjunction with a GIS, it is possible to compile soil erosion prediction maps of the RDAC under current and future conditions. Although soil loss in the catchment varies significantly, models show a similar trend in mean soil loss rates of the cropping systems. Rates are generally highest on steep slopes (>20%) with high rainfall (2400 mm) along the river valley and upper catchment area (above the 400 contour line). Predicted soil loss results, however, indicate a strong inverse relationship with vegetation cover. Very high soil loss values (more than 80 t.ha-1.yr-1) are attained under vegetables, moderate values (13 to 20 t.ha-1.yr-11) under intercropped cane, low (10 t.ha-1.yr-1) or very low (less than 2 t.ha-1.yr-1) under sugarcane, very low (4 t.ha-1.yr-1) to moderate (16 t.ha-1.yr-1) ratings under banana plantations, very low (less than 1 t. -1.yr-1) to high rates (41 t.ha-1.yr-1) under tea plantations, and low rates (less than 10 t.ha-1.yr-1) for natural vegetation. SLEMSA, however, predicts high erosion rates (27 t.ha-1.yr-1to 59 t.ha-1.yr-1) under natural vegetation, since the model is not developed for use in natural conditions. Crop diversification will have a considerable influence on soil erosion. RUSLE predicts a mean soil loss of 42 t.ha-1.yr-1, 20 t.ha-1.yr-1, and 0.2 t.ha-1.yr-1 under vegetables, pineapple, and forest, respectively. When compared to current conditions, the mean soil loss for the catchment will double under pineapple (increase by 100%), and quadruple under vegetables (increase by 300%). Results indicate that no appreciable erosion damage will occur in the RDAC if converted to forested land. Results provide considerable information regarding soil loss under potential land use The study also improves the understanding of factors governing erosion in Mauritius, which is important in the targeting of research and soil conservation efforts. Landowners and the government can use results to promote farming systems that do not degrade land resources.Dissertation (MSc)--University of Pretoria, 2007.Geography, Geoinformatics and MeteorologyMScUnrestricte

Hydrometallurgical Simulation - A Viable Program Structure

In order to satisfy the increasingly sophisticated requirements for simulation in the metallurgical industry, this research focused on the development of data structures and algorithms general and extendable enough to accomodate all hydrometallurgical processes. The data structures' designed to describe process stream information were based on the concept of sub-streams (Britt-, 19SG) using the pi ex data structure (Evans, Joseph and Seider, 1977) inherent to the Pascal programming language. As sub-streams are combined to describe complete process streams, the data structures may be extended to describe any process stream by creating additional sub-streams as may be required. Algorithms for partitioning, tearing and ordering flow sheets based on the work of Tarjan (1972, 1973) and Lee and Rudd (1966) were designed and implemented. These algorithms are able to treat the large problem sizes associated with hydrometallurgical process flow sheets. The data structures and algorithms have been successfully combined into a powerful process simulator extendable to the general hydrometallurgical process description

Lizard epidermal gland secretions II : chemical characterization of the generation gland secretion of the sungazer, Cordylus giganteus

The original publication is available at http://pubs.acs.org/doi/full/10.1021/np1008366In lizards, the epidermal glands of the femoral and precloacal regions are involved in the production of semiochemicals. In addition to its femoral glands, the giant girdled lizard, or sungazer, Cordylus giganteus, which is endemic to South Africa, has generation glands as an additional potential source of semiochemicals. These epidermal glands are described as glandular scales that overlay the femoral glands and are included in the normal epidermal profile located in the femoral (thigh) and anterior antebrachial (fore-leg) regions of the male sungazer. GC-MS analysis of the generation gland secretions and the trimethylsilyl derivatives of some of the steroidal constituents was employed to identify 59 constituents, including alkenes, carboxylic acids, alcohols, ketones, aldehydes, esters, amides, nitriles, and steroids. The quantitative differences of the volatile constituents of the fore- and hind-leg generation glands were compared between individuals. This is the first report on the chemical composition of generation glandular material of lizards. © 2011 The American Chemical Society and American Society of Pharmacognosy.Post-prin

Water erosion risk assessment in South Africa : a proposed methodological framework

With the increase in human impacts on the environment, especially in terms of agricultural intensification and climate change, erosion processes need to be assessed and continually monitored. In many countries, but particularly in developing countries such as South Africa, standardized methodological frameworks that deliver comparable results across large areas as a baseline for regional scale monitoring are absent. Due to limitations of scale at which techniques can be applied and erosion processes assessed, this study describes a multi-process and multiscale approach for soil erosion risk assessment under South African conditions. The framework includes assessment of sheet-rill erosion at a national scale based on the principles and components defined in the Universal Soil Loss Equation; gully erosion in a large catchment located in the Eastern Cape Province by integrating 11 important factors into a GIS; and sediment migration for a research catchment near Wartburg in KwaZulu-Natal by means of the Soil andWater Assessment Tool. Three hierarchical levels are presented in the framework, illustrating the most feasible erosion assessment techniques and input datasets that are required for application at a regional scale with proper incorporation of the most important erosion contributing factors. The methodological framework is not interpreted as a single assessment technique but rather as an approach that guides the selection of appropriate techniques and datasets according to scale dependency and modelled complexity of the erosion processes.National Research Foundationhttp://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-0459hb201