The alien invader plant Parthenium hysterophorus is a Category 1 weed in South Africa, where it poses a serious threat to indigenous vegetation in particular, and to biodiversity in general. In addition to its competitive ability, it is hypothesized that the successful invasiveness of P. hysterophorus is linked to the allelopathic potential of the plant. One compound in particular, parthenin, is alleged to play a major role in this allelopathic potential. Interference between P. hysterophorus and three indigenous grass species (Eragrostis curvula, Panicum maximum, Digitaria eriantha) was investigated on a site with a natural parthenium infestation at Skukuza, Kruger National Park. The trial was conducted over two growing seasons on exclosure plots which eliminated mammal herbivory. P. maximum displayed best overall performance and was eventually able to completely overwhelm P. hysterophorus. Eragrostis curvula and D. eriantha grew more favourably in the second season after becoming better established but were clearly not well adapted to the trial conditions. Although P. maximum was the supreme interferer, all grasses were able to significantly interfere with P. hysterophorus growth in the second season. The ability of P. maximum to interfere with P. hysterophorus growth so efficiently that it caused mortalities of the latter species, indicates that P. maximum exhibits high potential for use as an antagonistic species in an integrated control programme. An investigation on the production dynamics of parthenin in the leaves of P. hysterophorus indicated that high levels of this compound are produced and maintained in the plant up until senescence. The high resource allocation priority of the plant towards this secondary metabolite even in the final growth stages may indicate the use of residual allelopathy to inhibit or impede the recruitment of other species. Studies on the persistence of parthenin in soil revealed that parthenin is readily degraded in soil and that microbial degradation appears to play a predominant role. Significant differences between parthenin disappearance-time half-life (DT50) values were observed in soils incubated at different temperatures and in soils with different textures. Exposure of the three grass species to pure parthenin showed that, in terms of their early development, the order of sensitivity of the grasses was: Panicum maximum>Digitaria eriantha>Eragrostis curvula. It may therefore prove challenging to establish P. maximum from seed in P. hysterophorus stands during the execution of an integrated control programme due to the sensitivity of this grass species to parthenin. From the research findings it appears possible that P. hysterophorus can inhibit or impede the recruitment of indigenous vegetation under natural conditions. At least one mechanism through which this alien species can exert its negative influence on other plant species is the production and release of parthenin. / Dissertation (MSc (Agric) Agronomy)--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

In 1985 the Diama Dam was built near the mouth of the Senegal River to regulate flows during the rainy season and prevent the intrusion of seawater during the dry season. This created ideal conditions upstream of the dam wall for invasion by two highly invasive aquatic weeds, first by water lettuce Pistia stratiotes Linnaeus (Araceae) in 1993, and then by salvinia Salvinia molesta D.S. Mitchell (Salviniaceae) in 1999. This study was focused on the management of P. stratiotes and S. molesta. Following successes that were achieved elsewhere in the world, biological control programmes involving two weevil species were inaugurated against both weeds and research was focused on several aspects. These included pre-release studies to determine the weevils' host-specificity and impact on the plants in the laboratory, their subsequent mass-rearing and releases at selected sites and post-release evaluations on their impact on the weed populations in the field. Both programmes, which reprepresented the first biocontrol efforts against aquatic weeds in Senegal, proved highly successful with severe damage inflicted on the weed populations and complete control achieved within a relatively short time span. A laboratory exclusion experiment with N. affinis on P. stratiotes showed that in treated tubs, the weevil strongly depressed plant performance as measured by the plant growth parameters: mass, rosette diameter, root length, number of leaves and daughter plants whereas control plants were healthy. Field releases started in September 1994 and water coverage by P. stratiotes at Lake Guiers was reduced by 25% in January 1995 and 50% in April 1995. A general decline of 65% in water coverage by P. stratiotes was observed in June 1995 and by August 1995, eight months after releases P. stratiotes mats were destroyed. Further, although no releases were made there, good results were obtained within 18 months at Djoudj Park water bodies, located 150 km NW from Lake Guiers indicating the potential of the weevil to disperse long distances. In 2005, P. stratiotes reappeared and the weevil N. affinis has located and controlled all of these P. stratiotes recurrences after new releases. In 1999, S. molesta covered an estimated area of 18 000 ha on the Senegal River Left Bank and tributaries (Senegal) and 7 840 ha on the Senegal River Right Bank (Mauritania). Military and Civil Development Committee (CCMAD) and community volunteers made an effort to control S. molesta using physical removal, but this costly and labour-intensive approach was unsustainable. Hence, biological control was adopted by Senegal and Mauritania to manage the weed. Host range tests to assess feeding by C. salviniae on S. molesta and non-target plants and carried out on 13 crop species showed that no feeding damage was observed on the latter and weevils only fed on S. molesta. Field releases of some 48 953 weevils at 270 sites were made from early January 2002 to August 2002. Within one year, weevils were established and were being recovered up to 50 km from the release sites. In a case study conducted at one of the release sites, the S. molesta infestation was reduced from 100% to less than 3% 24 months after release. These results are discussed in the context of the weeds’ negative impact on aquatic systems and riverside communities, and in the involvement of these communities in the programmes.

La diversité biologique constitue l’un des piliers du fonctionnement des écosystèmes, etun potentiel pour l’adaptation et l’évolution de la vie dans le contexte du changement climatique. Les espèces constituant cette biodiversité sont étroitement connectées de différentes façons. Une diminution de cette biodiversité peut déclencher des effets de cascade et des conséquences largement imprévisibles, bien au delà de la seule réduction apparente du nombre ou de la distribution des espèces. La grande complexité de l’organisation écologique est très souvent un cauchemar pour la prise de décision. Les difficultés commencent avec le choix d’une mesure adéquate de la biodiversité. Une telle mesure est cependant une étape nécessaire si nous voulons prioriser nos actions de gestion de la biodiversité, afin de préserver le plus de diversité possible avec des ressources limitées. Bien que cette thèse ne prétende pas produire des réponses complètes à ces problèmes complexes, elle offre quelques points de réflexion pour la gestion de la biodiversité.Elle se compose de quatre chapitres. Le premier chapitre soulève la question de la gestion d’une biodiversité mélangée, au sein de laquelle des espèces invasives peuvent également s’inviter. Ce chapitre souligne les interconnections entre la sévérité des impacts des invasions biologiques et le contexte dans lequel cette invasion intervient. Considérant les impacts des invasions comme “ambivalents” — i.e. pouvant être positifs, négatifs, ou neutres pour le système dans lequel l’invasion s’installe — nous proposons une typologie afin d’évaluer l’ambivalence des impacts, sur la base de l’identification des sources potentielles de variabilité des impacts. Pour le second chapitre, nous nous concentrons sur la mesure de la biodiversité lorsque l’on tient compte des interactions entre espèces, de façon à produire une version de la métaphore de l’Arche de Noé (Weitzman, 1998) mieux adaptée aux problèmes de conservation in situ. Nous montrons tout d’abord que, lorsque l’on tient compte d’interactions écologiques, le problème défini par Weitzman demeure une solution extrême ; et deuxièmement, qu’un renversement de la hiérarchie des espèces préservées est possible et entièrement déterminée par la catégorie des interactions. Dans le troisième chapitre, nous utilisons le cadre de coût-bénéfice in-situ développé dans le chapitre 2 afin de comparer les résultats de priorisation de deux indices de biodiversité, Weitzman et Rao. Ces deux indices combinent différemment l’information sur les probabilités autonomes de survie des espèces, les interactions écologiques et la dissimilitude entre espèces afin de mesurer la biodiversité. Nous analysons des plans simples de protection de la biodiversité pour chaque indice, et démêlons le rôle joué par les différents éléments d’information nécessaires au calcul du ranking par l’indicateur,dans un écosystème à trois espèces. Nous montrons que chaque indice réalise un compromis qui lui est propre entre ces éléments d’information, et que l’introduction d’interactions écologiques entre plus de deux espèces mène à des conclusions plus complexes. Les interactions écologiques donnent ainsi une information additionnelle importante afin de déterminer les objectifs de conservation. Notre dernier chapitre est une adaptation du cadre d’optimisation défini précédemment. Il élabore une règle de décision myope afin de déterminer quelles invasions doivent être contrôlées en priorité, en tenant compte des coûts de gestion relatifs et les impacts trophiques en cascade. Nous discutons le gradient de la fonction d’objectif composé d’une fonction de diversité W et d’une fonction d’utilité U, afin de déterminer si nous devrions conserver plusieurs ou seulement quelques espèces sous une contrainte de budget. / Biological diversity constitutes one of the major pattern of ecosystem functioning, and a potential for adaptation and evolution of life in the context of climate change. As species are in many ways tightly interconnected, biodiversity loss can trigger large cascade effects and might lead to largely unpredictable consequences, reaching far beyond the visible reduction in the number or distribution of species. The high complexity of ecological organization is often a nightmare for decision-making, starting from accurately measuring biodiversity. This is however a necessary step to take if we want to prioritize action in biodiversity management, in order to preserve as much diversity as possible under limited resources. Though this thesis does not pretend to provide complete answers to those quite complex issues, it provides some reflection points for biodiversity management. It is composed of four chapters. The first chapter raises the issue of dealing with a mixed biodiversity, in which invasive species can be guests. It highlights the interconnections between the severity of the impacts of biological invasions and the contexts in which this invasion occurs. Considering invasion impacts as inherently ''ambivalent'' - i.e. good, bad or neutral for the system in which it arrives - we propose a typology to assess ambivalence in impact, based on the identification of potential sources of impact variability. For the second chapter, we focus on the measurement of biodiversity when accounting for species interactions, which we incorporates into the Noah's Arch problem developed by Weitzman (1998). We then derive a general model for ranking in situ conservation projects. We show firstly that, when accounting for ecological interactions, the problem defined by Weitzman is still an extreme solution, and secondly, that a ranking reversal is possible and completely defined by the interaction categories. In the third chapter, we use the in situ cost-benefit framework developed in Chapter 2 to compare the outcomes of two biodiversity indices, Weitzman's and Rao's. Those two indexes combine information about species survival probability, ecological interaction and distinctiveness in a different way to measure biodiversity; We analyze simple biodiversity protection plans for each index, and disentangle the role played by the different data requirement in the rankings, in a three species ecosystem. We show that such pieces of information will come as a trade-off when considered simultaneously in the measure, and that the introduction of ecological interactions among more than two species lead to more complex conclusions. Ecological interactions thus give important additional information to determine conservation objectives. Our last chapter is an adaptation of the previously defined optimization framework for the prioritization of invasive species management. It elaborates a myopic rule to determine which invasions must be controlled in priority, taking into account relative management costs and trophic cascades impacts. We discuss the gradient of the objective function composed of a diversity function W and a utility function U, to see whether we should retain several or only a few species for management under a budget constraint.

It is well known that invasive alien plants (IAPs) pose a significant threat to natural biodiversity and human well-being. Through various pressures exerted on natural ecosystems, IAPs decrease and alter natural processes that provide important ecosystems services and livelihoods to human communities. These plants also displace and out-compete natural plant communities in the areas in which they invade. Management of IAPs is a complex issue with social, environmental and financial challenges. The long-term sustainable management of IAPs requires a management approach that monitors and measures the outcomes of current management practices, and considers the lessons learnt in future decision making. Adaptive management is such an approach and is characterised by monitoring, assessment, reflection and adaptation. In this dissertation I explore IAP management within the South African National Parks (SANParks) organisation. I focus on the quality of the available IAP clearing data for monitoring and environmental decision-making and explore how strategic adaptive management (SAM) is being applied to IAP management. Strategic adaptive management is a form of adaptive management that SANParks adopted to deal with the inherent unpredictability of the social ecological systems they manage, and is primarily a learning-by-doing approach. In chapter one I describe the various impacts that IAPs have on natural environments. I also discuss management of IAPs, the national Working for Water (WfW) programme and how SANParks control IAPs in partnership with WfW. Clearing of IAPs within the borders of SANParks is funded by the Department of Environmental Affairs‘ (DEA) Natural Resource Management programmes and carried out through the Working for Water programme, under SANParks‘ Biodiversity Social Projects programme and is done on a contract basis. Contract data are stored in the Working for Water Information Management System (WIMS) database. Although IAP clearing is well established, the efficiency of overall clearing operations within the parks, and quality and reliability of the data available in the WIMS, needs to be examined. In Chapter two, I (i) assess the status of IAP clearing and the direct clearing costs in each of the five national parks (costs are inflated to 2012 equivalents using the consumer price index), (ii) assess the accuracy of workload estimations for WfW IAP clearing, and (iii) discuss the utility of WIMS as a system to collate and store accurate data for monitoring purposes, focusing on the integrity and reliability of the data, the accuracy of density estimations and whether it can inform sound decision making. The planning of future clearing contracts lacks efficiency due to inaccuracies and unreliability of input data, specifically estimates of invasive alien plant density. The accuracy of density estimation and cost of clearing varies greatly between parks and does not appear to reflect the reality on the ground. In Chapter 3, through an interview process with IAP managers, I 1) unpack the steps in the SAM ‗cycle‘ and investigate the effectiveness of implementation of each step according to respondents; 2) assess the barriers that are currently keeping managers from implementing effective IAP management; 3) discuss whether learning and adaptation is taking place, and 4) discuss how the SAM process can be modified to promote its effectiveness.

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

The release of biological control agents into the environment is inherently risky: assessment of those risks through on-going, post-release monitoring is very important. Herbivores have the potential to inflict multiple impacts on a host plant’s performance and reproduction. Previous research demonstrates that the effects of herbivory on plants include changes to plant architecture, biomass allocation, flowering time and reproductive success, to list a few. Moreover, when herbivory significantly impacts the population ecology of a dominant community member, other species can be indirectly affected, ultimately influencing plant community ecology. Here I describe an investigation into the impacts of two introduced herbivorous biological control agents: the leaf beetle Galerucella calmariensis (Coleoptera: Chrysomelidae), and the flower-feeding weevil, Nanophyes marmoratus (Coleoptera: Brentidae) on several characteristics of the host plant species, invasive purple loosestrife (Lythrum salicaria), and its surrounding community. I collected data on 18 invaded communities from around eastern Ontario, including information on feeding damage and the density of each species of biological control, along with data on purple loosestrife’s height and biomass, inflorescence length, inflorescence number and fruit production. The history of each site’s colonization by Galerucella was also considered. I discovered that the density of both Galerucella and Nanophyes at a site was negatively associated with Lythrum fruit production. However, herbivore density was not significantly associated with Lythrum biomass, height or the species richness of the surrounding plant community. This study, conducted 20 years after the initial Ontario release of Galerucella, demonstrates that although vegetative traits of Lythrum do not appear to be significantly impacted by the presence of Galerucella or Nanophyes, reproductive traits are. Twenty years is likely too short a time period to adequately assess the impacts of the release on community species richness, although my data indicate that communities with smaller Lythrum plants tend to have higher species richness. This study covered a small geographical area and data collection was conducted for a single season only; adding additional years and/ or sites is recommended.

Pulse oximeters are used in operating rooms and recovery rooms as a monitoring device for oxygen in the respiratory system of the patient. The advantage of pulse oximeters over other methods of oxygen monitoring is that they are easy to use and they are non-invasive, which means it is not necessary break the skin to extract blood for information to be obtained. The standard for the measurement of partial pressure of CO2 and O2 is an arterial blood gas analysis (ABG). However routine monitoring using this method on a continuous basis is impractical since it is slow, painful and invasive. Measuring carbon dioxide is critical to preventing ailments such as carbon dioxide poisoning or hypoxia. The problem is, currently there is no known effective non-invasive method for accurately measuring carbon dioxide in the body to properly assess the adequacy of ventilation. The objective of this study was to experimentally use spectroscopy in the visible spectrum and the principles of operation of a pulse oximeter to incorporate a method of non-invasive real-time carbon dioxide monitoring that is as quick and easy to use.

Invasive species have caused billions of dollars in damages to their introduced environment through direct effects on wildlife and by altering their introduced habitats. For a species to be considered invasive, it must successfully navigate the stages of invasion: it must be introduced, become established, spread, and have a quantifiable impact on its introduced environment. The numbers of introductions and individuals released affects the genetic diversity of nonnative populations which, in turn, can affect their invasion success. The Mayan Cichlid (Cichlasoma urophthalmus) is endemic to the Atlantic coast of Mexico and Central America. It was first detected in the United States in 1983 in Everglades National Park. Since then, it has spread across more than 70,000 hectares throughout southern and central Florida. I have established the Mayan Cichlid to be a successful invader in Florida by quantifying per capita negative impacts of Mayan Cichlids on densities of Sheepshead Minnow (Cyprinodon variegatus), Marsh Killifish (Fundulus confluentus), and Eastern Mosquitofish (Gambusia holbrooki) over a 15-year period. I also analyzed the role of genetics in the invasion success of the Mayan Cichlid. I used a mitochondrial gene, cytochrome b, and 17 microsatellite loci to identify the sources for the Mayan Cichlid introduction into Florida. Cytochrome b data supported an introduction from Guatemala; microsatellite data suggested movement of Mayan Cichlids from the upper Yucatán Peninsula to Guatemala and introductions from Guatemala and Belize to Florida. I also found evidence of cytonuclear disequilibrium together with low genetic diversity within the Florida population which indicate a population bottleneck and admixture between two distinct lineages upon introduction, followed by rapid spread resulting in a panmictic population genetically distinct from the native range populations. I found much less genetic structure and a weaker correlation between genetic diversity and geographic distance within Florida compared with Mexico and Central America. Low number of effective alleles, heterozygosities, and FST values and the genetic similarity of Florida sites also indicate an admixed population or one that has rapidly expanded from a small initial group.

O uso de microrganismos na biotecnologia tem grande importância e interesse econômico no Brasil. Entre esses microrganismos a levedura Saccharomyces cerevisiae tem grande destaque nos processos fermentativos para produção de pães, bebidas e álcool combustível. Dimorfismo em S. cerevisiae (alteração na morfologia celular de células brotantes para estruturas filamentosas) tem sido observado em condições de deficiência de nitrogênio, carbono e presença de álcoois superiores. Isso pode ser um tipo de defesa da levedura, que ao encontrar um meio prejudicial ao seu desenvolvimento, através da alongação das células, crescimento hifal e da invasão do meio, cria novos mecanismos para encontrar alimento para o seu desenvolvimento. Neste trabalho, dezessete linhagens (haplóides e diplóides) de S. cerevisiae isoladas do processo fermentativo industrial para produção de etanol foram caracterizadas quanto à filamentação induzida por deficiência de carbono (crescimento invasivo), nitrogênio e presença de álcoois superiores, em meio de cultura sólido. Objetivou-se também avaliar a indução da filamentação por álcool isoamílico em condições de fermentação e seus efeitos sobre os parâmetros fermentativos. A maioria das linhagens apresentou filamentação em resposta aos álcoois isoamílico, butanol e isobutanol, não respondendo ao metanol, sendo mais marcante em linhagens haplóides. O álcool isoamílico foi o indutor mais eficiente em meio (YEPD), linhagens diplóides apresentaram crescimento invasivo, embora esse tipo de filamentação seja mais comum em linhagens haplóides. Resultados semelhantes foram observados quando se utilizou frutose e manose em substituição à glicose no meio de cultura. As linhagens não filamentaram em meio de cultura deficiente em nitrogênio (SLAD). A linhagem CCA193 (PE-02), extensivamente utilizada nas destilarias da região, foi escolhida para a indução da filamentação por álcool isoamílico em condições de fermentação (meio de caldo de cana e sistema de reciclo celular). A adição de 0,1% desse álcool superior afetou significativamente os parâmetros fermentativos, induzindo filamentação após o terceiro ciclo fermentativo, coincidindo com a recuperação da viabilidade celular, número de células viáveis, produção de etanol e diminuição do Brix residual, embora não se comparando aos valores alcançados ao final do sexto ciclo no tratamento sem álcool isoamílico. Os resultados obtidos indicaram que a filamentação induzida por álcoois superiores e deficiência de nutrientes (especialmente carbono) é um processo comum em linhagens industriais de S. cerevisiae e pode contribuir para a manutenção/sobrevivência das células em condições adversas. / The use of microorganisms in biotechnology is an important and economical area of interest in Brazil. Among these, the yeast Saccharomyces cerevisiae is specially remarkable in baking industry and alcohol fermentation. Dimorphism in S. cerevisiae (cell morphology alterations from budding cells to filamentous structures) has been observed in conditions of nitrogen and carbon deprivation and presence of fusel alcohoes. This can be a defense mechanism that allows the yeast to forage for nutrients through cell elongation, hyphal growth and medium invasiveness. In this work seventeen industrial strains of S. cerevisiae (haploid and diploid) isolated from the fermentative process for alcohol production were characterized for filamentation induced by carbon (invasive growth) and nitrogen deprivation and presence of fusel alcohol, in solid culture media. The induction of filamentation by isoamyl alcohol in fermentation condition was also aimed, evaluating its effects on the fermentative parameters. The majority presented filamentation induced by isoamyl alcohol, butanol and isobutanol, but not by methanol. The isoamyl alcohol was the most effective inducer in rich medium (YEPD), diploid strains showed invasive growth, although this kind of filamentous growth be common in haploid strains. Similar results were observed when fructose and mannose were utilized replacing glucose in the culture medium. In nitrogen-deficient medium (SLAD) the strains did not filament. The yeast strain CCA193 (PE-02), extensively used in the alcohol units, was chosen for filamentation induction by isoamyl alcohol in fermentation conditions (sugar cane juice medium and cell recycle system). The addition of 0.1% of this higher alcohol affected significantly the fermentative parameters, however filamentation was induced after the third fermentative cycle, coincident with the cell viability, viable cell number, ethanol production recuperation and residual Brix decrease, though the values were not comparable to the treatment without isoamyl alcohol by the sixth cycle.The results obtained indicate that the filamentation induced by higher alcohol and nutrient deprivation (specially carbon) is a common process in industrial strains of S. cerevisiae and can contribute for the cell maintenance/survival in adverse conditions.

No description available.