The goal of this dissertation is to further our understanding of how spatially heterogeneous landscapes may impact the formation of range boundaries that then aggregate to form large-scale biodiversity patterns. These patterns have been analyzed from many different perspectives by ecologists, evolutionary biologist, and physiologists using a variety of different theoretical, statistical, and mechanistic models. For some species, there is an obvious abrupt change in the environment causing a range boundary. Other environments change gradually, and it is unclear why species fail to adapt and expand their range. The first chapter develops a novel theoretical model of how the establishment of new mutations allows for adaptation to an environmental gradient, when there is no genetic variation for the trait that limits the range. Shallow environmental gradients favor mutations that arise nearer to the range margin, have smaller phenotypic effects, and allow for proportionately larger expansions than steep gradients. Mutations that allow for range expansion tend to have large phenotypic effects causing substantial range expansions. Spatial and temporal variation in climatic and environmental variables is important for understanding species response to climate change. The second chapter uses a mechanistic model to simulate switchgrass (Panicum virgatum L.) productivity across the central and eastern U.S. for current and future climate conditions. Florida and the Gulf Coast of Texas and Louisiana have the highest predicted current and future yields. Regions where future temperature and precipitation are anticipated to increase, larger future yields are expected. Large-scale geographic patterns of biodiversity are documented for many taxa. The mechanisms allowing for the coexistence of more of species in certain regions are poorly understood. The third chapter employs a newly developed wavelet lifting technique to extract scale-dependent patterns from irregularly spaced two-dimensional ecological data and analyzes the relationship between breeding avian richness and four energy variables. Evapotranspiration, temperature, and precipitation are significant predictors of richness at intermediate-to-large scales. Net primary production is the only significant predictor across small-to-large scales, and explains the most variation in richness (~40%) at an intermediate scale. Changes in the species-energy relationship with scale, may indicate a shift in the mechanism governing species richness. / text

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Wächst eine Population und breitet sich dabei geographisch aus, so spricht man von räumlichem Populationswachstum, bzw. einer Range-Expansion. Viele Arten haben im Verlaufe ihrer evolutionären Geschichte ihr Verbreitungsgebiet ausgeweitet. Gründe hierfür können beispielsweise ein geändertes Klima oder die Verschleppung der Art in einen neuen Lebensraum sein. Während einer Range-Expansion können durch Gene-Surfing räumliche Verteilungen von neutralen genetischen Varianten entstehen, die den Folgen von selektiven Prozessen ähnlich sind. Für eine korrekte Interpretation der genetischen Daten ist daher die Kenntnis über quantitative Auswirkungen von Range-Expansions auf die genetische Vielfalt unumgänglich. In dieser Arbeit charakterisiere ich die Konsequenzen von Range-Expansions für Allelfrequenz-Spektren. Dazu generiere ich in Computersimulationen genetische Daten für unterschiedliche demographische Szenarien sowie diverse ökologische und geographische Bedingungen. Ich zeige, dass Range-Expansions innerhalb kurzer Zeit zu Allelfrequenz-Spektren führen können, die sich durch ein Potenzgesetz mit einem spezifischen Exponenten beschreiben lassen. Dieser Exponent liegt zwischen den erwarteten Exponenten für stabile und exponentiell wachsende, durchmischte Populationen. Mutationen, die während einer Range-Expansion aufgetreten sind, tragen meinen Ergebnissen zufolge weniger zu heutigen Allelfrequenz-Spektren bei, als Mutationen, die bereits in der Ursprungspopulation vorhanden waren. Allerdings eignen sich neue Mutationen besser, um Range-Expansions in genetischen Daten aufzuspüren, da sie weniger von geographischen Strukturen beeinflusst werden. Meine Resultate werden dazu beitragen, Spuren von Range-Expansions in genetischen Daten zu entdecken und Rückschlüsse auf die evolutionäre Vergangenheit von Populationen zu ziehen.

The performer's conceptualisation and perception of herself is projected through the acoustic voice and impacts upon vocal delivery in rehearsal and performance. However, in the context of performer voice training in Western theatre practice the performer's sense of self, or identity, is seldom the focus of development. Vocal development is inherently a transformational process that requires the performer to expand beyond what has become habitual selfexpression. Since vocal expression is embedded in identity, an attempt to change the voice necessitates a deeper understanding, questioning, and challenging of the performer's established sense of self. In this dissertation I posit that acoustic vocal development can be successfully achieved through an embodied and imaginative approach that investigates the performer's metaphorical voice through learning opportunities provided by a process that integrates the practices of Voice Movement Therapy (VMT) and maskwork. This dissertation presents art-based autoethnographic research into the potential value of such an integrated approach to performer vocal development. The VMT maskwork approach is fundamentally an embodied and envoiced process that provides a vastly different and heightened experience of the bodymind and invites the performer to play in the liminal realm of active imagination, which is triggered by the mask-image. The dissertation investigates the vocal development benefits of using self-made masks as a psychophysical training tool to expand the performer's understanding and experience of the bodymind. The area of archetypes and subpersonalities has been identified as a primary intersection between the two modalities and three ways of working are proposed, either taking impulses from the image (mask-image and/or imagination), the body and its movement, or the voice. These three ways of working trigger the bodymind into a process of active imagination that evokes a creative and integrated mask-voice-body exploration of archetypes and/or subpersonalities. The process gives permission to, and provides a safe container for, the amplified expression of the extremes of self and voice. This dissertation offers a tri-phase VMT maskwork process structure, and highlights key steps for the VMT practitioner-led facilitation of such a process. It positions the mask as a useful transitional object which encourages reengagement with imagination, body, voice and emotion, and thus encourages an on-going and multi-layered reflection and investigation of self and voice is possible. The research showed that the integrated approach of VMT maskwork resulted in vocal expansion in all 10 of the VMT 10 vocal components; pitch, pitch fluctuation, loudness, glottal engagement, free air, disruption, violin, register, timbre and articulation. Apart from acoustic vocal expansion, the approach fostered expansion in the performer's metaphorical voice and resulted in improved grounding and confidence in performance. These conclusions support the research statement that VMT maskwork may be a valuable approach to vocal development in the context of theatre performer voice training. As researcher practitioner I hold that the embodied learning process of VMT maskwork exposes the performer to a vastly different experience of self, which fosters a process of self-reflexivity leading to personal meaning making, self-knowledge, the challenging of vocal habits, and ultimately, vocal transformation. / Dissertation (MA)--University of Pretoria, 2016. / Drama / MA / Unrestricted

Understanding eco-evolutionary dynamics in cancer tumors, species invasions, and the human microbiome is vital for numerous health and economic applications. However, spatial structure and population heterogeneity make this challenging. This dissertation tackles these challenges using a population dynamics approach, wherein systems evolve through individual growth and dispersal. The bulk of this dissertation studies expanding populations, such as growing microbial colonies, species range expansions, and cancer tumors. In this context, I first study the effect of a directional bias in dispersal: I develop a model for the stochastic growth of left-right or chirally asymmetric cells that quantitatively reproduces experimental patterns in microbial colonies. Using the model, I demonstrate that chiral dispersal provides an evolutionary advantage and affects spatial population structure in expanding populations. Second, I investigate the impact of environmental structure affecting both dispersal and growth on expanding populations. I show that cooperative population expansions in a periodic environment can be pinned to a particular location or locked to specific velocities determined by the environmental periodicity. Third, I study the problem of a phenotypically heterogeneous population, with each phenotype differing in growth and dispersal abilities. I determine the exact velocity of an expanding population where phenotypes move ballistically and explain the connection to the explosive growth transition in experimental microtubule asters. The final chapter of the dissertation examines the challenge of assembling microbial communities for performing functions such as biofuel production, nitrogen fixation, or health remediation. Due to the exponential number of possible species combinations, bioengineers resort to heuristic search strategies to find the optimal community. I identify biological properties and develop statistical measures to help bioengineers estimate their chance of success in assembling an optimal community. / 2023-02-06T00:00:00Z

The redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae), is a non-native pest of soybeans in the Americas outside of the Carribean. Mortality of overwintering adults due to cold exposure has been implicated as a major driver of interannual fluctuations in the occurrence of P. guildinii in the southeastern United States, but formal investigations of drivers, including factors other than cold temperatures, are rare. We conducted overwintering assays with field-collected P. guildinii to quantify survival and coupled historical occurrence with climatic data to develop a species distribution model. We found that leaf litter provides substantial insulation from lethal temperatures and thus increases the potential for overwintering survival of P. guildinii. Our species distribution model indicates that the northern extent of the insect’s range is limited by winter temperatures, but that can potentially expand the range hundreds of kilometers in a growing season.

Dune grasses are integral to biogeomorphic feedbacks that create and alter foredunes and barrier island stability. In a glasshouse study, Ammophila breviligulata Fern. and Uniola paniculata L. were planted together and subjected to sand burial to quantify morphological and physiological response. Ammophila breviligulata physiological and morphological performance declined when planted with U. paniculata but U. paniculata was not affected when planted with A. breviligulata. Burial had a positive effect on A. breviligulata and U. paniculata as indicated by electron transport rate and total biomass at the end of the experiment. Due to their different growth strategies, A. breviligulata and U. paniculata form continuous versus hummocky dunes, respectively. As global temperatures rise and U. paniculata migrates into A. breviligulata dominated habitat, A. breviligulata performance may diminish, and changes in dune form could result in altered island stability via increased overwash. Foredune community structure could also change due to the shift in dominant species which could alter dune succession.

Orientador: Tânia Marcia Costa / Resumo: Organismos do entremarés são frequentemente expostos a temperaturas extremas e as alterações climáticas podem trazer consequências negativas para estes organismos. Neste trabalho, avaliamos os efeitos do aumento da temperatura e redução do pH nas respostas fisiológicas e comportamentais de caranguejos chama-maré. Leptuca uruguayensis e Leptuca leptodactyla ocorrem tipicamente em habitat vegetado e não-vegetado de regiões estuarinas, apesar de coabitarem diversas áreas dos ecossistemas do entremarés. Realizamos experimentos para obtenção das respostas fisiológicas e comportamentais de ambas espécies ao aumento da temperatura. Minuca mordax foi exposta ao aquecimento e redução do pH da água para avaliação das respostas fisiológicas. Também estimamos a futura distribuição de M. mordax em cenários de mudanças climáticas. As duas espécies de Leptuca apresentaram diferenças nas adaptações fisiológicas (em relação ao consumo de oxigênio) e nos mecanismos de termorregulação, em consonância com a seleção de habitat e distribuição geográfica de cada espécie. Leptuca uruguayensis selecionou micro-habitat com temperatura inferior enquanto L. leptodactyla estava em um substrato com maior temperatura, mas apresentou características conhecidas por promoverem a dissipação de calor e reduzirem a taxa de desidratação, como tamanho e quelípodo maiores e coloração clara. As atividades comportamentais na superfície também foram afetadas pela elevação da temperatura, aumentando o tempo dentro da t... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intertidal organisms are often exposed to extremes temperatures and may be harmed by climate change. The present study aimed to evaluate the effects of warming and pH decrease on physiology and behavior of fiddler crabs. Leptuca uruguayensis and Leptuca leptodactyla inhabit vegetated and unvegetated habitats from estuarine regions, respectively, despite cohabit some areas in intertidal ecosystems. Both species were exposed to warm to analyze the physiological and behavioral effects. Minuca mordax was exposed to warm and lower pH water. Also, we estimated the future distribution of M. mordax in climate change scenarios. Both species showed different adaptation (regarding oxygen consumption) and thermoregulatory mechanism, which reflect their habitat selection and range distribution. Leptuca uruguayensis selected less heated micro-habitat while L. leptodactyla was in a warmer substrate beside possessed larger size and major claw and whiten display that enhanced dissipation of heat and lowered desiccation rate. Higher temperature constraint surface activities, increasing refuge use and decreasing feeding, which might have impacted some physiological response (ammonia excretion and hepatosomatic index). Waving display was not affected by temperature, suggesting influence by other factors such as female and competitor presence. Warming and reduced pH altered physiological response (oxygen consumption, ammonia excretion, hepatosomatic index, and osmoregulation) of M. mordax, effect... (Complete abstract click electronic access below) / Doutor

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A cause de l’actuel déclin mondial de la biodiversité, la compréhension des conséquences de chaque menace sur la biodiversité est un élément crucial en biologie de la conservation. Les espèces exotiques envahissantes représentent une de ces menaces à l’échelle mondiale, et peuvent induire localement des dommages au sein des écosystèmes. Etudier les phénomènes régissant les effets négatifs de ces espèces, et leurs potentiels d’expansion apparaît actuellement comme un élément crucial pour déterminer leurs effets sur le long terme. Dans cette étude, nous focalisons nos efforts sur une population exotique envahissante du Xénope lisse, Xenopus laevis, en France, pour apporter de nouvelles connaissances sur les interactions de cette population avec son environnement et pour étudier les changement dans l’allocation des ressources aux traits d’histoire de vie liés à la reproduction la survie et la dispersion durant l’expansion de l’aire de répartition. Nous étudions le régime alimentaire de l’espèce en France et dans d’autres populations introduites et autochtones et concluons que cette espèce peut étendre sa répartition en consommer une faible, comme une importante diversité de proies. Nous détectons également un potentiel impact de l’espèce sur les amphibiens autochtones de France. Dans la seconde section de la thèse, nous rapportons une réduction de l’allocation des ressources à la reproduction et une augmentation de la dispersion, sur le front de colonisation. Enfin, nous étudions la dynamique des populations et détectons une faible probabilité de survie, et une faible densité en individus dans le centre de l’aire de répartition. La combinaison de ces résultats suggère que les potentiels effets négatifs sur le long terme sont importants pour cette espèce, en France, tout comme dans d’autres zones où l’espèce a été, ou sera, introduite. / Because of the current global biodiversity decline, understanding the consequences of each threat on biodiversity is crucial for conservation biology. Invasive species are among the main threats at the global scale, and can locally imply harmful damages on ecosystems. Studying the phenomena driving the effects and potential for expansion of these species appears as a crucial element to assess their long terms impacts. In this study, we focused our efforts on an invasive population of the African clawed frog, Xenopus laevis, in France, to bring insight about the interactions of this population with its environment and to study the changes in resource allocation to the life history traits, related to reproduction, survival and dispersal probabilities, during the range expansion of the population. We studied the diet in the French invasive population and in other invasive and native populations, and found that this species can expand by predating a narrow, as well as a broad, range of prey categories. We also detected an impact of X. laevis on the native amphibian community in France. In the second section of the thesis, we reported a decrease in reproductive investment, and an increased dispersal allocation of resources at the range edge. We finally studied population dynamics and detected a lower survival probability and density at the range core. All these results combined suggest that the potential for long term impacts is important in France for X. laevis as well as in other areas where the species has been, or will be, introduced.