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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Thermal ecology of the Glanville Fritillary butterfly (Melitaea cinxia)

Advani, Nikhil Kishore 08 October 2012 (has links)
Anthropogenic climate warming is predicted to accelerate over the next century, with potentially dramatic consequences for wildlife. It is important to understand as well as possible how different organisms will respond to this stress. This project seeks to gain a better mechanistic understanding of the thermal biology of the Glanville Fritillary butterfly (Melitaea cinxia) at the latitudinal and elevational extremes of its range. Investigation of the temperatures at which adult butterflies took spontaneous flight revealed a significant difference between populations from the elevational extremes, with insects from high elevation taking flight at lower thoracic temperatures than those from low elevation. Contrary to expectation, there was no systematic effect of latitude on takeoff temperature. If these measures represent adaptation to climate, then these effects are not simple and the influences of elevation and latitude are not the same. Investigation of thermal tolerance across all life cycle stages found no difference in larval performance between the populations tested. There was however an effect of treatment. This suggests that in M. cinxia, even populations from different extremes of the range may not differ in their thermal tolerance. The effect of treatment suggests that there is temperature-induced plasticity. The adaptive significance of this has been explored to some extent. Investigation of heat shock protein expression between the latitudinal extremes finds no difference in Hsp21.4 expression when exposed to heat stress, however both Hsp20.4 and Hsp90 were upregulated in response to heat stress. For Hsp20.4, there were significant differences in expression between the populations. Finally, a species distribution model using maximum entropy techniques was conducted for M. cinxia, predicting both the current and future (2100) distributions of the species. The model closely matches the known current distribution, and predicts a clear northward range shift in response to climate change. / text
112

Allometric structure and topology of food webs: Energetic constraints conserve food-web structure across ecosystems and space

Digel, Christoph 24 April 2014 (has links)
No description available.
113

Demography and distribution of the North Island robin (Petroica longipes) in a fragmented agricultural landscape of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctorate of Philosophy in Ecology at Massey University, Palmerston North, New Zealand

Richard, Yvan January 2007 (has links)
Habitat loss and fragmentation are recognised worldwide as contributing to declines and extinctions of species. However, the biological factors underlying the effects of fragmentation are still often poorly understood, possibly due to the diversity of scales and approaches taken by researchers. I propose in this thesis an integrative approach that can be applied to any taxa and landscape, using a metapopulation of North Island robins (Petroica longipes) inhabiting forest patches of a fragmented agricultural landscape of New Zealand. In particular, I attempt to integrate the effects of habitat fragmentation on both habitat quality and the dispersal-driven broad scale dynamics of populations. I first analysed the distribution of robins based on presence-absence data, relating presence-absence to local habitat factors as well as size and isolation of forest patches (Chapter 2). Their distribution was found to be primarily limited by the isolation of forest patches, but was also related to some habitat factors. However, habitat fragmentation was not found to affect habitat quality, as the factors found to affect survival and productivity were unrelated to size and isolation, independent from the size or isolation of forest patches (Chapter 3). Based on the radio-tracking of juvenile robins, I applied a choice analysis technique to show that robins need woody vegetation for their natal dispersal and that they are unlikely to cross stretches of pasture greater than 150 m (Chapter 4). Juveniles dispersed a median Euclidean distance of 1129 m with a maximum of 11 km, whereas I predicted from the data that they would have dispersed a median distance of 3 km in continuous forest with a maximum of 20 km (Chapter 5). The consequences of this dispersal limitation and of variations in habitat quality were assessed using a spatially-explicit individual-based metapopulation model that incorporated realistic gap-limited dispersal behaviour of juvenile robins (Chapter 6). Whereas the movement of individuals between patches is commonly assumed to improve the persistence of populations, I found that a weaker gap-crossing ability, and therefore reduced landscape connectivity, increased the metapopulation size at equilibrium. This study highlights the complex effects of habitat loss and fragmentation on the distribution of species, but also the limits of excessive model simplification.
114

Untersuchung der Lebensraumansprüche des Grauspechts Picus canus und seiner Verbreitungsgrenze in Niedersachsen / Investigating the habitat demands of the Grey-headed Woodpecker Picus canus and its distribution border in Lower Saxony

Schneider, Mareike 06 June 2018 (has links)
No description available.
115

Análise da susceptibilidade à invasão do capim-annoni-2 sobre áreas do bioma Pampa do município de Aceguá-RS

González, José David Montoya January 2017 (has links)
O Eragrostis plana Nees (capim-annoni-2 ou capim annoni) é uma gramínea exótica trazida da África do Sul nos anos cinquenta e atualmente tem presença em aproximadamente 10% da área total do bioma Pampa, sendo a espécie mais invasiva desse bioma. Tendo em conta a grande capacidade desta espécie para se estabelecer em uma ampla variedade de condições ambientais, os efeitos ambientais e econômicos negativos envolvidos, bem como sua dificuldade de erradicação, é importante identificar as áreas mais suscetíveis à invasão em um futuro próximo, para assim aprimorar os planos de manejo e evitar a expansão de áreas infestadas. O presente trabalho foi desenvolvido no município de Aceguá – RS, com o objetivo de identificar quais áreas são as mais suscetíveis à invasão. Foram aplicados os modelos de distribuição de espécies MAXENT e GARP tendo como dados de entrada as variáveis ambientais calculadas a partir imagens espectrais, modelo numérico de elevação, mapa de solos e mapa de vias. Como algumas variáveis originalmente têm resolução espacial de 250 m e outras de 30 m, foi feita uma reamostragem tanto a 30 m como a 250 m para comparar os resultados dos modelos nas duas resoluções espaciais. Para diminuir o número de variáveis de entrada foi feita uma análise de correlação para eliminar as variáveis com alta correlação. Também foi feito o teste Jackknife para avaliar quais variáveis contribuem mais na modelagem espacial da distribuição do capim annoni. Os dois modelos, tanto no treinamento como na validação, nas duas resoluções espaciais, apresentam valores médios de ajuste de AUC acima de 0,7, sendo considerado um bom ajuste. Foram empregados três métodos para calcular os limiares ótimos de corte para cada um dos modelos: 1) sensibilidade igual à especificidade; 2) soma entre a sensibilidade e a especificidade máxima; Os limiares obtidos foram 42 para MAXENT_250, 39 para MAXENT_30, 69 para GARP_250 e 68 para GARP_30. Após a aplicação dos limiares, verificou-se que o modelo GARP prediz uma área maior que o MAXENT, 33,20% em comparação com 24,60% na resolução espacial de 250 m, e 35,83% contra 27,17% na resolução espacial de 30 m. Verificou-se também que o GARP possui melhor capacidade de generalização, o qual é importante para modelar espécies invasoras. Os dois modelos predizem com presença uma área comum de 21,23% e 23,94% nas resoluções espaciais de 250 m e 30 m respectivamente. As pastagens são as classes de uso que apresentam uma maior suscetibilidade à invasão de capim anonni. Ao cruzar os resultados dos modelos de suscetibilidade à invasão de capim annoni, com resolução espacial de 30 m, e as áreas de pastagens que estão sob alta pressão de pastejo, verificou-se que o modelo MAXENT consegue predizer uma suscetibilidade à invasão em 24,51% das áreas e o modelo GARP prediz 37,95% de suscetibilidade à invasão. As comparações entre as duas resoluções espaciais demonstrou que não há muitas diferenças em termos de quantificação de área, sendo que o principal ganho foi o detalhamento espacial, o qual foi obtido com um alto custo computacional. / The Eragrostis plana Nees (South African lovegrass), is an exotic grassy plant originally from South Africa, introduced in the 50s and is currently present in approximately 10% of the total area of the Pampa biome, being the most invasive species in this biome. Considering the large capacity of the South African lovegrass establishing itself in a wide variety of environmental conditions, the negative effects, both environmental and economical that it involves, as well as its difficulty of eradication, it is important to identify the invasion most susceptible areas in the near future, in order to improve the management to prevent the spread of infested areas. This research was developed in the municipality of Aceguá – RS, with the objective of identifying which areas are most susceptible to invasion. The MAXENT and GARP models of distribution of species were applied, having as input data the environmental variables calculated from spectral images, digital elevation model, soil map and road map. As some variables originally had spatial resolution of 250m and others of 30m, a resample was done at both 30m and 250m in order to compare the models results in these two spatial resolutions. To reduce the input variables amount, a correlation analysis was performed to eliminate the high correlation variables. The Jackknife test was also used to evaluate which variables contribute most to the South African lovegrass distribution spatial modeling. Both models, at the two spatial resolutions, during the training and the validation steps, present mean values of AUC adjustment above 0.7, being considered a good fit. Three methods were used to calculate the optimal thresholds for each model: 1) the sensitivity equals to the specificity; 2) the sum between sensitivity and specificity is the maximum; 3) the distance between the ROC curve and left top corner is minimum. The calculated thresholds were 42 for MAXENT_250, 39 for MAXENT_30, 69 for GARP_250 and 68 for GARP_30. After applying these thresholds, it was verified that the GARP model predicts an area greater than MAXENT, 33.20% compared to 24.60% for the spatial resolution of 250m, and 35.83% against 27.17% in the spatial resolution of 30m. It was also verified that GARP has a better generalization capacity, which is important for modeling invasive species patterns. Both models predict a common area with susceptible to invasion of 21.23% and 23.94% in spatial resolutions of 250m and 30m respectively. The grasslands are the land cover that presents a South African lovegrass invasion greater susceptibility. Cross-referencing the susceptibility invasion models with the overgrazing areas at 30m of spatial resolution, it was verified that the model MAXENT can predict a susceptibility to invasion in 24.51% of the areas and the GARP model predicts 37.95% susceptibility to invasion. Comparisons between the two spatial resolutions showed that there are not many differences in terms of area quantification, where the main gain was spatial detailing, which was obtained with a high computational cost.
116

Effects of Climate Change and Urban Development on the Distribution and Conservation of Vegetation in a Mediterranean Type Ecosystem

January 2012 (has links)
abstract: Climate and land use change are projected to threaten biodiversity over the coming century. However, the combined effects of these threats on biodiversity and the capacity of current conservation networks to protect species' habitat are not well understood. The goals of this study were to evaluate the effect of climate change and urban development on vegetation distribution in a Mediterranean-type ecosystem; to identify the primary source of uncertainty in suitable habitat predictions; and to evaluate how well conservation areas protect future habitat in the Southwest ecoregion of the California Floristic Province. I used a consensus-based modeling approach combining three different species distribution models to predict current and future suitable habitat for 19 plant species representing different plant functional types (PFT) defined by fire-response (obligate seeders, resprouting shrubs), and life forms (herbs, subshurbs). I also examined the response of species grouped by range sizes (large, small). I used two climate models, two emission scenarios, two thresholds, and high-resolution (90m resolution) environmental data to create a range of potential scenarios. I evaluated the effectiveness of an existing conservation network to protect suitable habitat for rare species in light of climate and land use change. The results indicate that the area of suitable habitat for each species varied depending on the climate model, emission scenario, and threshold combination. The suitable habitat for up to four species could disappear from the ecoregion, while suitable habitat for up to 15 other species could decrease under climate change conditions. The centroid of the species' suitable environmental conditions could shift up to 440 km. Large net gains in suitable habitat were predicted for a few species. The suitable habitat area for herbs has a small response to climate change, while obligate seeders could be the most affected PFT. The results indicate that the other two PFTs gain a considerable amount of suitable habitat area. Several rare species could lose suitable habitat area inside designated conservation areas while gaining suitable habitat area outside. Climate change is predicted to be more important than urban development as a driver of habitat loss for vegetation in this region in the coming century. These results indicate that regional analyses of this type are useful and necessary to understand the dynamics of drivers of change at the regional scale and to inform decision making at this scale. / Dissertation/Thesis / M.S. Biology 2012
117

The ecosystem services of the Cerrado trees : modelling, distribution mapping and implications for conservation

Mesa, Christian Requena January 2017 (has links)
O interesse em valorizar os serviços ecossistêmicos fornecidos pela vegetação natural aumentou em um esforço para mitigar os efeitos da mudança do uso da terra. Nesta linha de pensamento, desenvolvemos um índice para valorar as comunidades de árvores - do ponto de vista antropocêntrico - da savana brasileira (Cerrado). O índice e a cartografia produzida servirão como ferramenta para a priorização da conservação, bem como para revelar como a colonização e a expansão da agricultura tem ocorrido. Para desenvolver o índice, foram produzidas novas camadas ambientais com resolução de 90m; A distribuição das 93 espécies mais comuns foi modelada; e a cartografia da distribuição de cada uso humano das árvores (alimentos, aromáticos, fibras, cosméticos, cortiça, etc., totalizando 20 usos) e um índice de valor total fo desenvolvido. O novo índice de valor, nomenado a Soma de Usos (SoU, Sum of Uses), representa o número esperado de usos para a montagem de espécies potenciais que poderia estar ocorrendo no lugar em condições ideais. O impacto da agricultura foi avaliado pela contabilização da área que foi convertida em lavouras. Nossos resultados indicam fortemente que a colonização humana e a expansão de terras cultivadas eliminaram as árvores de áreas que antes eram melhores prestadores de serviços ambientais. Por outro lado, observamos também que as áreas protegidas no Cerrado estão localizadas onde esperamos encontrar valor marginal para as espécies ótimas. Esses resultados nos levam a pensar que a estratégia de conservação pode estar longe de ser ideal para o maior remanescente arável do mundo. / The interest in valuing the ecosystem services provided by the natural vegetation has increased in an effort to mitigate the effects of land use change. In this line of thinking, we developed an index to value the tree communities -from an anthropocentric point of view- of the Brazilian savannah (Cerrado). The index and the cartography produced will serve as a tool for prioritization of conservation, has well as to unveil how colonization and agriculture expansion has taken place. In order to develop the index: new environmental layers at 90m resolution were produced; the most common 93 species’ distribution was modelled; and cartography for each use humans derive from the trees (food, aromatic, fiber, cosmetic, cork, etc., totaling 20 uses) and a total value index were developed. The new index of value, namely the Sum of Uses (SoU), represent the expected number of uses for the potential species assemblage that could be taking place under optimal conditions. The impact of agriculture was assessed by accounting for the area that has been converted to croplands. Our results strongly indicate that human settlement and cropland expansion have cleared the trees of areas that once were better than average ecosystem service providers. On the other hand, we also observe that protected areas in the Cerrado are located where we expect to find marginal value for the optimal communities. These results lead us to think that the conservation strategy might be far from optimal for the largest remaining arable patch in the world.
118

The Impacts of Geography and Climate Change on Magdalenian Social Networks

January 2017 (has links)
abstract: This dissertation uses a comparative approach to investigate long-term human- environment interrelationships in times of climate change. It uses Geographical Information Systems and ecological models to reconstruct the Magdalenian (~20,000- 14,000 calibrated years ago) environments of the coastal mountainous zone of Cantabria (Northwest Spain) and the interior valleys of the Dordogne (Southwest France) to contextualize the social networks that could have formed during a time of high climate and resource variability. It simulates the formation of such networks in an agent-based model, which documents the processes underlying the formation of archaeological assemblages, and evaluates the potential impacts of climate-topography interactions on cultural transmission. This research then reconstructs the Magdalenian social networks visible through a multivariate statistical analysis of stylistic similarities among portable art objects. As these networks cannot be analyzed directly to infer social behavior, their characteristics are compared to the results of the agent-based model, which provide characteristics estimates of the Magdalenian latent social networks that most likely produced the empirical archaeological assemblage studied. This research contributes several new results, most of which point to the advantages of using an inter-disciplinary approach to the study of the archaeological record. It demonstrates the benefits of using an agent-based model to parse social data from long- term palimpsests. It shows that geographical and environmental contexts affect the structure of social networks, which in turn affects the transmission of ideas and goods that flow through it. This shows the presence of human-environment interactions that not only affected our ancestors’ reaction to resource insecurities, but also led them to innovate and improve the productivity of their own environment. However, it also suggests that such alterations may have reduced the populations’ resilience to strong climatic changes, and that the region with diverse resources provided a more stable and resilient environment than the region transformed to satisfy the immediate needs of its population. / Dissertation/Thesis / Appendix_D_Sites_Dates / Appendix_E_Flowchart_Biome_Reconstruction / Appendix_H_Flowchart_ABM / Appendix_I_Flowchart_Social_Network / Appendix_J_Portable_Art_Objects / Appendix_J_Art_Characteristics / Appendix_L_Poster_Summary / Appendix_A_Prehistoric_Fauna / Appendix_B_Modern_PFT_Distribution / Appendix_C_Prehistoric_PFT_Distribution / Doctoral Dissertation Anthropology 2017
119

PADRÕES DE DISTRIBUIÇÃO DO GÊNERO Aegla Leach, 1820 (Crustacea, Decapoda, Anomura) ASSOCIADOS À COBERTURA DO SOLO / DISTRIBUTION PATTERN OF THE GENUS Aegla Leach, 1820 (Crustacea, Decapoda, Anomura) ASSOCIATED TO THE COVER LAND.

Gonçalves, Alberto Senra 16 March 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Knowing the distributional patterns and the mechanisms that lead to the actual levels of diversity and richness is a challenge given the ecosystems threats. Understanding how the threats coming from the human actions can affect this diversity is the key to protect ecosystems and species. This study toward (i) investigate the richness distribution patterns of the genus Aegla in four freshwater ecoregions in South America, as well as (ii) the mechanisms that lead to that distribution, and (iii) the human influences in these freshwater ecosystems. The study area comprised four freshwater ecoregions: Upper Uruguay, Low Uruguay, Laguna dos Patos, and Tramandaí-Mampituba. Through data from five scientific collections, UFRGS, UFSM, FZB-RS, PUC-RS, and URI-Erechim, we compiled 30 species of Aegla. We associated the species distribution in four ecoregions to the distributional patterns, conservation status, environmental and spatial variables, rugosity, and land cover. The protected area network not effectively protects the aquatic ecosystems. The species richness is associated to average values of rugosity. Finally, the species occurrence areas exhibit land cover categories of agriculture and urban areas. We consider the levels of endemism inside the protected area network are key factor to conservation of aquatic ecosystems. Historic process linked to the river network formation, in a spatial context, is an important approach to understand the distributional pattern of some freshwater groups. These patterns are associated to spatial questions, following the increasing of agriculture and urban lands, are committing the diversity in freshwater environments. / Conhecer os padrões de distribuição e os mecanismos que levam aos níveis de diversidade e riqueza atuais são desafios dado à ameaça dos ecossistemas. Entendermos como as ameaças oriundas das ações do homem podem impactar essa diversidade é a chave para conservarmos ecossistemas e espécies. Esse estudo teve como objetivo (i) investigar os padrões de distribuição da riqueza do gênero Aegla em quatro ecorregiões de água doce da América do Sul, bem como, (ii) quais os mecanismos que levaram a tal distribuição, e por fim, (iii) a influência das ações do homem nos ecossistemas de água doce. A área de estudo compreendeu quatro ecorregiões de água doce: Alto Uruguai, Baixo Uruguai, Laguna dos Patos e Tramandaí-Mampituba. Através de registros de cinco coleções científicas, UFRGS, UFSM, FZB-RS, PUC-RS e URI-Erechim, obtivemos dados de 30 espécies do gênero Aegla. Padrões de distribuição, status de conservação, variáveis ambientais e espaciais, rugosidade e cobertura do solo foram analisadas e associadas à distribuição das espécies nas ecorregiões. Ficou claro que a rede de unidades de conservação não protege efetivamente os ecossistemas aquáticos. Por sua vez, a riqueza de espécies está associada a valores médios de rugosidade do relevo. E, finalmente, as áreas de ocorrência das espécies apresentaram cobertura do solo com áreas agrícolas e urbanas. Considerarmos os níveis de endemismos dos grupos nas redes de unidades de conservação é um fator chave para proteção efetiva dos ecossistemas aquáticos. Processos históricos ligados à formação das redes de rios, no contexto espacial, é a chave para entendermos padrões de distribuição de alguns grupos de água doce. Esses padrões de distribuição associados às questões espaciais, ligados ao crescente aumento das áreas de agricultura e urbana, estão comprometendo a diversidade de ambientes dulcícolas.
120

The ecosystem services of the Cerrado trees : modelling, distribution mapping and implications for conservation

Mesa, Christian Requena January 2017 (has links)
O interesse em valorizar os serviços ecossistêmicos fornecidos pela vegetação natural aumentou em um esforço para mitigar os efeitos da mudança do uso da terra. Nesta linha de pensamento, desenvolvemos um índice para valorar as comunidades de árvores - do ponto de vista antropocêntrico - da savana brasileira (Cerrado). O índice e a cartografia produzida servirão como ferramenta para a priorização da conservação, bem como para revelar como a colonização e a expansão da agricultura tem ocorrido. Para desenvolver o índice, foram produzidas novas camadas ambientais com resolução de 90m; A distribuição das 93 espécies mais comuns foi modelada; e a cartografia da distribuição de cada uso humano das árvores (alimentos, aromáticos, fibras, cosméticos, cortiça, etc., totalizando 20 usos) e um índice de valor total fo desenvolvido. O novo índice de valor, nomenado a Soma de Usos (SoU, Sum of Uses), representa o número esperado de usos para a montagem de espécies potenciais que poderia estar ocorrendo no lugar em condições ideais. O impacto da agricultura foi avaliado pela contabilização da área que foi convertida em lavouras. Nossos resultados indicam fortemente que a colonização humana e a expansão de terras cultivadas eliminaram as árvores de áreas que antes eram melhores prestadores de serviços ambientais. Por outro lado, observamos também que as áreas protegidas no Cerrado estão localizadas onde esperamos encontrar valor marginal para as espécies ótimas. Esses resultados nos levam a pensar que a estratégia de conservação pode estar longe de ser ideal para o maior remanescente arável do mundo. / The interest in valuing the ecosystem services provided by the natural vegetation has increased in an effort to mitigate the effects of land use change. In this line of thinking, we developed an index to value the tree communities -from an anthropocentric point of view- of the Brazilian savannah (Cerrado). The index and the cartography produced will serve as a tool for prioritization of conservation, has well as to unveil how colonization and agriculture expansion has taken place. In order to develop the index: new environmental layers at 90m resolution were produced; the most common 93 species’ distribution was modelled; and cartography for each use humans derive from the trees (food, aromatic, fiber, cosmetic, cork, etc., totaling 20 uses) and a total value index were developed. The new index of value, namely the Sum of Uses (SoU), represent the expected number of uses for the potential species assemblage that could be taking place under optimal conditions. The impact of agriculture was assessed by accounting for the area that has been converted to croplands. Our results strongly indicate that human settlement and cropland expansion have cleared the trees of areas that once were better than average ecosystem service providers. On the other hand, we also observe that protected areas in the Cerrado are located where we expect to find marginal value for the optimal communities. These results lead us to think that the conservation strategy might be far from optimal for the largest remaining arable patch in the world.

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