Dissertations / Theses: 'Indirect interactions'

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da, Silva Milton Barbosa. "Indirect interactions structuring ecological communities." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:4a093748-6192-4bbc-bf0f-854e909b47c0.

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Ecological communities are collections of species bound together by their influences on one another. Community structure, therefore, refers to the way in which these influences are organised. As a result, ecologists are mainly interested in the factors driving the structure, functioning, and persistence of communities. The traditional focus, however, has been on the feeding relationships among species (direct trophic interactions), whereas relationships mediated by a third species or the environment (indirect interactions) have been largely overlooked. I investigated the role of indirect interactions in structuring communities through a series of field experiments in a diverse assemblage of arthropods living on a Brazilian shrub species. I experimentally reduced the abundance of the commonest galler on the shrub and found that the perturbation resonated across the food web, affecting its structure and robustness. Since there was no potential for these effects to be propagated directly or indirectly via the documented trophic links, the effects must have spread non-trophically and/or through trophic links not included in the web. Thus, I investigated non-trophic propagation of effects in the system. I demonstrate that hatched galls of the commonest galler, which serve as habitat for other species, can mediate non-trophic interactions that feedback to the galler modifying its interactions with parasitoids and inquiline aphids. I performed further manipulative experiments, excluding ants, live galls and hatched galls, to reveal mechanisms for the non-trophic interaction modifications observed in this system. Finally, I explored how non-trophic interaction modification could affect the structure and stability of a discrete ecological community in the field. I investigated how the densities of certain pairs of groups relate to each other, and how their relationship changes in relation to a third group. Then, I assembled an "effect network" revealing, for the first time in an empirical community, a hidden web of non-trophic indirect interactions modifying the direct interactions and modifying each other. Overall, the thesis presents evidence that communities are strongly interconnected through non-trophic indirect interactions. This is one of the first empirical demonstrations of the context-dependent modification of interactions via non-trophic interactions. However, determining the mechanisms behind such interaction modifications may be unfeasible. Understanding how the observed effects relate to community structuring requires shifting our focus from bipartite interaction networks to a more holistic approach.

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Morris, Rebecca Jane. "Indirect interactions in insect communities." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392402.

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Rott, Anja Sibylle. "Indirect interactions in host-parasitoid communities." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243731.

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Dionysiou, Ioanna. "Dynamic and composable trust for indirect interactions." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Summer2006/i%5Fdionysiou%5F072406.pdf.

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Lemos, Felipe de. "Indirect interactions in tomato attacked by Tetranychus evansi." Universidade Federal de Viçosa, 2015. http://www.locus.ufv.br/handle/123456789/8352.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Plantas apresentam inúmeras estratégias de defesa direta e indireta contra herbívoros. As defesas diretas atuam sobre os herbívoros enquanto as defesas indiretas beneficiam os inimigos naturais dos herbívoros. Para maximizar o seu fitness, plantas sob ataque de herbívoros fazem uso de ambas estratégias de defesa simultaneamente. No entanto, alguns herbívoros têm se adaptado para lidar com as defesas de plantas e o ácaro vermelho Tetranychus evansi é um exemplo. Esse herbívoro é capaz de manipular a defesa direta de plantas de tomate em seu próprio benefício. Nesta tese, foram investigados aspectos das interações indiretas entre plantas de tomate atacadas por T. evansi e os inimigos naturais de T. evansi, embora algumas interações diretas entre plantas e herbívoros e herbívoros e predadores também foram estudadas. No primeiro capítulo, foi investigado a influência da planta hospedeira na inadequação de T. evansi como alimento para o ácaros predador Phytoseiulus persimilis. Observou-se que a inadequação de T. evansi como alimento para esse predador não está relacionada com a planta hospedeira do herbívoro. No entanto, o efeito negativo da dieta de T. evansi no desempenho do ácaro predador foi reversível, indicando a ausência de um efeito tóxico ao longo prazo. No segundo capítulo, estudou-se como T. evansi poderia interferir com a defesa indirera de tomateiros pela indução de voláteis e atração de ácaros predadores. Foi observado que T. evansi induz a produção de compostos voláteis que são diferentes dos presentes na mistura produzida por plantas atacadas por Tetranychus urticae. Entretanto, a atratividade dos ácaros predadores (P. persimilis, Phytoseiulus longipes and Phytoseiulus macropilis) por odores de tomateiros atacados por T. evansi foi variável com a densidade de infestação de herbívoros. No terceiro capítulo desta tese, explorou-se a capacidade do ácaro predador P. macropilis em aprender a associar odores de plantas atacadas por T. evansi com a qualidade da presa. Juvenis de P. macropilis não se desenvolveram até a fase adulta, quando alimentados com ovos de T. evansi. No entanto, adultos de P. macropilis não evitaram voláteis de plantas atacadas por T. evansi mesmo após quatro dias consecutivos de experiência com essa presa de baixa qualidade. Em conclusão, estes resultados confirmam a notável capacidade de T. evansi em manipular a defesa de sua planta hospedeira e contornar a ameaça de inimigos naturais. A interação indireta entre ácaros predadores e plantas de tomateiro infestados com T. evansi é prejudicada pela indução diferencial de voláteis que enganam os ácaros predadores.
Plants employs an array of direct and indirect strategies of defence against herbivores. Direct defence acts upon the herbivores, while indirect defence benefits the natural enemies of the herbivores. To maximize their fitness, plants under attack of herbivores are predicted to simultaneously make use of both direct and indirect defence. However, some herbivores have adapted to cope with plant defences. The red spider mite Tetranychus evansi was found to manipulate the direct defence of tomato plants to their own benefit. In this thesis, I focus on investigating indirect interactions between tomato plants attacked by T. evansi and their natural enemies, although some direct interactions between plants and herbivores and herbivores and predators were also studied. First, I studied the influence of host plant on the unsuitability of T. evansi as food for the predatory mite Phytoseiulus persimilis. I observed that this unsuitability was not related with the herbivore’s host plant. The negative effect of T. evansi on the performance of predatory mites was reversible, indicating the absence of long- term toxic effects of prey on the predator. In the second chapter, I studied how T. evansi interferes with the indirect defence of tomato plants through induction of volatiles and attraction of predatory mites. I observed that damage by T. evansi induces the production of volatile organic compounds that are different from those present in the attractive blend of volatiles induced by Tetranychus urticae. The attractiveness of odours from tomato plants infested with T. evansi to predatory mites (P. persimilis, Phytoseiulus longipes and Phytoseiulus macropilis) varied with the density of mites on the plant. In the third chapter of this thesis, I explored the capacity of the predatory mite P. macropilis to learn to associate odours from plants infested with T. evansi with prey quality. Juveniles of P. macropilis were show to perform poorly when fed with eggs of T. evansi. However, adults of P. macropilis did not avoid odours from plants infested with T. evansi, even after four consecutive days of experience with the poor quality prey. In conclusion, these results confirm the remarkable ability of T. evansi to manipulate the plant defence and circumvent the threat of natural enemies. The indirect interaction between predatory mites and tomato plants infested with T. evansi is impaired by the differential induction of volatiles that mislead the predatory mites.

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Baker, Christopher CM. "Complexity in Mutualisms: Indirect Interactions With Multiple Parties." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845506.

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Ant-plants provide ants with rewards such as housing and food in exchange for protection from herbivores. These protection mutualisms are complex webs of both direct interactions, such as ants feeding on host plant extrafloral nectar, and indirect interactions mediated by 'third party' species, such as ants consuming exudates from hemipterans feeding on the host plant. While some indirect interactions are well understood, in many cases our understanding is hindered by an incomplete picture of the relevant third-party species. In this dissertation, I explore third-party interactions of three obligately phytoecious ant species on the African ant-plant Vachellia drepanolobium (formerly Acacia drepanolobium) - Crematogaster mimosae, C. nigriceps and Tetraponera penzigi. First, I examine relationships between ants and fungi. I show behavioral differences towards fungi among the three ant species, and then use multiplexed amplicon sequencing to characterize their associated fungal communities. Each ant species harbors its own distinctive fungal community, and these communities are similar for each species even at two field sites separated by 200 kilometers. The ants may vector fungi when they colonize new host trees. T. penzigi most likely uses fungi as a food source, and fungi may also have nutritional or other growth implications for the host plant. Second, I investigate relationships between ants and 'myrmecophiles' - i.e. 'ant loving' arthropods that live alongside ants in the domatia. I show that myrmecophile communities differ among the three ant species, but are also highly context dependent, differing strongly between locations and sampling periods. Surprisingly, several species of myrmecophilous Lepidoptera are herbivorous, but are more commonly associated with the 'better' ant mutualists, C. mimosae, whose workers defend more effectively against browsing mammalian herbivores. My results show that plant ants shape both fungal communities and myrmecophile communities in domatia of their V. drepanolobium host plants. These third-party species may be viewed as 'extended phenotypes' of the ants, and are essential elements whose effects need to be incorporated into our understanding of the ant-plant protection mutualism.
Biology, Organismic and Evolutionary

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Barber, Nicholas A. "Tritrophic interactions in forests direct and indirect interactions between birds, insect herbivores, and oaks /." Diss., St. Louis, Mo. : University of Missouri--St. Louis, 2009. http://etd.umsl.edu/r3561.

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Valbuena-Gonzalo, Carlos. "The Importance of Trait Mediated Indirect Interactions in Marine Ecosystems." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-163445.

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The importance of Trait Mediated Indirect Interactions (TMII) is increasingly being recognized. TMII are interactions between two species via a change in trait (behavioural, morphological, but not numerical) over a third one, which together cause ecological dynamics. Marine food webs have complex interactions, but TMII have not yet received great appreciation or application in marine conservation and management models. This article is a review about the different ways in which TMII can affect marine ecological dynamics. I summarize known examples of Behaviourally Mediated Indirect Interactions, Physiologically Mediated Indirect Interactions, and other types of indirect interactions such as initiated or mediated by parasites, in order to provide a better understanding about their functioning. I found that TMII are omnipresent in marine ecosystems and occur at all trophic levels, spanning from macro- to microorganisms. Furthermore, it includes many different taxa and guilds, and the mechanisms are highly diverse. Some of them enhance Density Mediated Effects, while others counteract them. Sometimes this results in the effects opposite of those expected, and often they extend further in the food web. Understanding of TMII is likely to be beneficial for marine conservation and management, due to the role of humans causing them or suffering its effects.

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Stenberg, Johan. "Trophic, Indirect, and Evolutionary Interactions in a Plant–Herbivore–Parasitoid System." Doctoral thesis, Umeå universitet, Ekologi, miljö och geovetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1490.

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The aim of this thesis project was to elucidate patterns and processes associated with the biotic interactions in a natural plant–herbivore–parasitoid food web characterized by spatial and temporal heterogeneity with regard to species composition. The system examined is based on island populations of the perennial herb Meadowsweet (Filipendula ulmaria, Rosaceae), located in the Skeppsvik Archipelago. The area is subject to isostatic rebound, amounting to 0.85 cm per year; this makes it possible to calculate the age of the rising islands. Meadowsweet colonizes new islands when they are about 100 years old. Meadowsweet is consumed by two major herbivores in the study area: Galerucella tenella and Altica engstroemi (Coleoptera: Chrysomelidae). Both herbivores overwinter in the topsoil and successful colonization occurs when the islands reach a height that prevents the beetles from being removed or killed as a result of wave wash during the winter. I found that both herbivores significantly reduced individual plant fitness and population growth rate. A “cafeteria experiment” with Galerucella showed that this beetle discriminated between plants from different islands, avoiding plants from old islands which contained high concentrations of putative defence compounds, while readily accepting plants from younger islands which contained lower concentrations of these chemicals. Further, the plant species exhibited a trade-off between growth and production of the putative defence compounds. Taken together, these results were interpreted as providing evidence of herbivore-driven evolution of resistance in Meadowsweet. Further, laboratory studies suggested that Galerucella gradually includes a less preferred host plant (Rubus arcticus, Rosaceae) in its diet as Meadowsweet resistance increases. This implies that Galerucella drives its own host-breadth enlargement by selectively inducing a ‘rent rise’ in the original host, Meadowsweet. In a number of field studies I showed that the oligophagous parasitoid Asecodes mento (Hymenoptera: Eulophidae) has a strong positive effect on Meadowsweet seed set by removing large numbers of G. tenella larvae. This top-down effect is, however, altered by the presence of a close relative of G. tenella, namely G. calmariensis, which is monophagous on Purple loosestrife (Lythrum salicaria, Lythraceae). G. tenella experiences associational susceptibility when coexisting with G. calmariensis since the latter supports a higher and more fit pool of shared parasitoids and because Meadowsweet attracts a higher proportion of the shared parasitoid females than Purple loosestrife. This implies that G. tenella densities are very low in coexisting populations and that Meadowsweet experiences associational resistance and produces more seeds when co-occurring with Purple loosestrife. Thus, selection for increased resistance in Meadowsweet is likely to be relaxed in populations mixed with Purple loosestrife. I conclude that the evolution of plant resistance is likely to depend on the length of time and intensity of selection. When Meadowsweet colonizes new islands it experiences a period of enemy-free space; followed by a midlife and ageing with selection by herbivores. The intensity of this selection does, however, depend on the presence of additional plant and herbivore species.

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Stenberg, Johan A. "Trophic, indirect, and evolutionary interactions in a plant-herbivore-parasitoid system /." Umeå : Department of Ecology and Environmental Science, Umeå University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1490.

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White, Evelyn M. "Indirect interactions between alien and native Senecio species as mediated by insects." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16580/.

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The studies described in this thesis investigate the role of indirect effects in invasion biology. The Introduction provides a brief overview of indirect effects and an outline of the thesis structure. The role of indirect effects in the context of invasion biology is addressed in an in-depth published literature review that comprises the second chapter, providing a theoretical background for the subsequent empirical studies. Chapters Three to Six are comprised of manuscripts that have been published or are under review or in press, which describe studies that investigate the importance of indirect effects in invasion biology using a model system consisting of the alien Asteraceae Senecio madagascariensis, a closelyrelated native, Senecio pinnatifolius, and the insect species with which they interact. Senecio madagascariensis and S. pinnatifolius occur in a similar geographic range in eastern Australia and these studies were conducted in mixed and pure populations of the two species. The herbivore and floral visitor assemblages of the two Senecio species at seven field sites in South-east Queensland were compared using sweep-net sampling, manual searching and floral visitor observation techniques. The floral visitor assemblages were similar between the two species, comprised largely of species of Syrphidae and the European honeybee, Apis mellifera. Herbivore assemblages, however, were highly variable both between species and between sites, with greater herbivore abundance and diversity recorded on the native S. pinnatifolius than its alien congener. The most commonly recorded herbivores were sap-sucking species such as Myridae. The magpie moth, Nyctemera amica was the most common folivore on both Senecio species and laboratory studies demonstrated a clear preference by ovipositing females and feeding larvae of this species for the native Senecio species, over the alien. Field surveys supported these findings, recording greater leaf damage on the native species than the invader. Herbivory levels were lower, rather than higher, in mixed populations than in pure populations, thus there was no evidence that the presence of one species enhanced herbivory in the other. Field pollination trials were conducted to determine whether competition for pollinators or facilitation of pollination occurred in mixed Senecio populations. The presence of the native S. pinnatifolius affected pollinator visitation rates to the alien Senecio; bee visits to S. madagascariensis were significantly reduced by the presence of S. pinnatifolius, whilst syrphid visits increased. However, altered visitation rates were not reflected in seed set. The presence of the alien species had no impact on pollinator visits to the native. Surprisingly, S. pinnatifolius seed set was higher in mixed populations than in pure populations. This might be due to abiotic factors, lower rates of herbivory at these sites or transfer of pollen between species resulting in the production of hybrid seed (if S. madagascariensis has greater male fitness). Hybridisation in the field was investigated using AFLP techniques. No mature hybrid plants were recorded in mixed populations, but hybrid seeds were produced by both species. Senecio pinnatifolius maternal parents produced higher numbers of hybrid seed than expected based on the relative frequencies of the two species, whilst hybridisation in S. madagascariensis was lower than expected. This may indicate greater male fitness of the invader. A range of complex indirect interactions can occur between invasive and native species, with these interactions having the potential to influence the success or failure of the invader and its impacts on co-occurring natives. The Discussion addresses the findings of the studies described here in the context of invasion biology theory.

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Rothenberg, Daniel (Daniel Alexander). "Fundamental aerosol-cloud interactions and their influence on the aerosol indirect effect on climate." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108963.

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Thesis: Ph. D. in Atmospheric Science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 173-189).
The influence of anthropogenic aerosol emissions on the optical properties of clouds and the radiative forcing arising from these interactions, known as the aerosol indirect effect on climate, constitutes a fundamental uncertainty in our understanding of 2 0 th century climate change. In this dissertation, we investigate the role of a keystone physical process, droplet activation, in contributing to this uncertainty. The first half of the ensuing work focuses on the parameterization of this process in global model, assessing both existing schemes and developing a novel one. The second half then quantifies the influence of activation by using a suite of aerosol-climate models which include a complete description of the physics which give rise to the indirect effect. Parameterizations of droplet activation perform well for idealized single-mode aerosol populations, but show systematic biases in high-pollution, weak-updraft regimes. These are exacerbated when the aerosol in question is a complex mixture. We show that estimates of droplet nucleation are highly sensitive to changes in the accumulation mode size and number concentration; this mode is itself sensitive to anthropogenic aerosol emissions, which potentially further biases modeled cloud droplet number. Using a model emulation technique, we develop a framework for building efficient metamodels of activation, which greatly reduce the mean error in droplet number predicted across regimes. The biases in these parameterizations raise questions the influence of activation on the indirect effect. Using different schemes, we calculate a spread of 1 W m- 2 in the indirect effect, which we show is equal to the spread computed from an independent suite of global models with different aerosol and physics modules. The estimated indirect effect scales more strongly with the baseline cloud droplet number concentration simulated by each model than by its change from pre-industrial to present day, indicating a strong saturation effect. While present-day estimates of aerosol-cloud interactions derived from satellite-based instruments are inadequate at constraining the pre-industrial cloud droplet burden, we show that process-based measurements could overcome this problem.
by Daniel Alexander Rothenberg.
Ph. D. in Atmospheric Science

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Ghanawi, Joly Karim. "Direct and indirect ecological interactions between aquaculture activities and marine fish communities in Scotland." Thesis, University of Stirling, 2018. http://hdl.handle.net/1893/27258.

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Presence of coastal aquaculture activities in marine landscapes is growing. However, there is insufficient knowledge on the subsequent ecological interactions between these activities and marine fish communities. The overall aim of this thesis was to evaluate the direct and indirect ecological effects of aquaculture activities on marine fish communities in Scotland. A combination of empirical and modelling approaches was employed to collect evidence of how aquaculture activities affect marine fish communities at the individual, population and ecosystem levels around coastal sea cages. The two fish farms evaluated in this research provided the wild fish sampled near the sea cages with a habitat rich in food resources which is reflected in an overall better biological condition. Results of the stomach content analysis indicated that mackerel (Scomber scombrus), whiting (Merlangius merlangus) and saithe (Pollachius virens) sampled near sea cages consumed wasted feed which was also reflected in their modified FA profiles. The overall effects of the two fish farms were more pronounced in young whiting and saithe than in mixed aged mackerel sampled near the sea cages. The phase space modelling approach indicated that the overall potential for fish farms to act at the extremes as either population sources (a habitat that is rich in resources and leads to an overall improved fitness) or ecological traps (a habitat that appears to be rich in resources but is not and leads to an overall poor fitness) are higher for juvenile whiting than for mackerel. Based on the empirical evidence and literature the two fish farms are more likely to be a population source for wild fishes. Using an ecosystem modelling approach indicated that fish farming impacts the food web in a sea loch via nutrient loading. Mussel farming relies on the natural food resources and has the potential to affect the food web in a sea loch via competing with zooplankton for resources which can affect higher trophic levels. The presence of both activities can balance the overall impact in a sea loch as compared to the impact induced if each of these activities were present on their own. Both activities have the potential do induce direct and indirect effects on the wild fish and the entire sea loch system. The results of this PhD identified several gaps in data and thus could be used to improve future sampling designs. It is important to evaluate the cumulative effect of the presence of aquaculture activities in terms of nutrient loading and physical structure in the environment. Using a combination of empirical and modelling approaches is recommended to gain further insight into the ecological impacts of aquaculture activities on wild fish communities. Results of this PhD study could lead to more informed decisions in managing the coastal aquaculture activities. Establishing coastal fish farms as aquatic sanctuaries can be of an advantage to increase fish production and conserve species that are endangered provided that no commercial and recreational fishing is allowed nearby. It would be useful to have long term monitoring of the fish stocks around the cages and if there is any production at the regional level. Additionally, information on behaviour, migration patterns should be collected to understand the impacts of aquaculture activities on fish stocks. From an aquaculture perspective, ecologically engineered fish farms in addition to careful site selection in new aquaculture developments may improve nutrient loading into the ecosystem.

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Jones, Matthew D. "Indirect, plant mediated interactions of meristem miners on flower head feeders, a case for non-independence?" Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3313.

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A long standing, dominant paradigm in the biological control of weeds is the independence of insect herbivore guilds' effects on their host plant. Recent work has shown stronger interactions among insect herbivore guilds than was previously expected. My research focuses on damage to apical meristems of tall thistles (Cirsium altissimum) by stem mining insects and the direct effects of this damage on plant architecture as well as the indirect, plant-mediated effects of this damage on flower head feeding insects and the arthropod predator community associated with tall thistle in south-central Kansas. Three questions are addressed; 1) What is the natural history of the predatory arthropod – tall thistle interaction in south-central Kansas? 2) Does apical meristem damage by insect herbivores influence host plant architecture, flower head damage and/or predatory arthropod densities? 3) Does plant architecture affect flower head damage and/or predatory arthropods? Two experiments were used to address those questions. The first experiment compared bolting tall thistles whose apical meristems were protected with insecticide with tall thistles whose apical meristems were not protected and were subject to herbivory. Damage to the apical meristem creates a plant that is shorter and has more flower heads than plants with the apical meristem intact and marginally increases primary branching. The second experiment modified the architecture of a bolting tall thistle with apical meristem damage back to a “pre-damaged” state by clipping lateral branches of the main stem. Neither experiment showed any significant difference in flower head damage severity or frequency, nor any differences in predatory arthropod densities among treatments. Through an overcompensation mechanism in the plant, meristem mining insects indirectly influence flower head feeding insects mediated by tall thistle. My results do not support the importation of multiple biological control agents for weed control.
Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Biological Sciences.

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Jenkins, Maggie F. "Indirect Food Web Interactions: Sea Otter Predation Linked to Invasion Success in a Marine Fouling Community." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/2000.

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Humans have caused grave ecological and economic damage worldwide through the introduction of invasive species. Understanding the factors that influence community susceptibility to invasion are important for controlling further spread of invasive species. Predators have been found to provide biotic resistance to invasion in both terrestrial and marine systems. However, predators can also have the opposite effect, and facilitate invasion. Therefore, recovery or expansion of native predators could facilitate the spread of invasive species. Needles et al. (2015) demonstrated that the threatened southern sea otter (Enhydra lutris nereis) facilitated the invasion of an exotic bryozoan, Watersipora subatra. However, the underlying mechanism was not fully understood. We tested the hypothesis that sea otter predation on Romaleon antennarium crabs indirectly facilitated the abundance of W. subatra. To do this, we collected weekly data on sea otter foraging and quantified the abundance of crabs in the sea otter diet. We also conducted a caging experiment, where we experimentally manipulated crab densities and limited otter access using exclusion cages on pier pilings in Morro Bay, CA. We used photoQuad image processing software to calculate the abundance of W. subatra on PVC panels within each treatment group. We found that crabs were the second most abundant prey item in Morro Bay, comprising 25.1% of the otter diet. Through the caging experiment, we found that W. subatra abundance significantly increased as crab densities decreased. Our results indicated that sea otters indirectly facilitated the invasion of W. subatra by reducing R. antennarium crab densities and sizes. Removal of crabs may release W. subatra from the disturbance caused by crab foraging behavior. Understanding the impacts of top predators in invaded ecosystems has important management implications, as recovery of predator populations could unintentionally benefit some non-native species. Therefore, management should focus first on prevention and second on early detection and eradication of invasive species likely to benefit from predator recovery.

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McDaniel, Tana. "Direct and indirect interactions between two ranid frogs, pickerel frogs (Rana palustris) and leopard frogs (Rana pipiens )." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0016/MQ55693.pdf.

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Anderson, Kathryn Michele. "Algal-herbivore interactions in a high carbon world : direct and indirect effects through individuals, populations, and communities." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63385.

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Consumer-resource interactions play an important role in determining the structure and function of ecological communities. Thus, herbivores may buffer or magnify the impacts of environmental change. In this thesis, I examine the ways in which herbivory mediates the effects of one of the most important facets of environmental change in marine ecosystems: ocean acidification (OA). Responses to OA by invertebrate herbivores are wide ranging, typically negative, and depend on species traits (e.g. reliance on calcification), population dynamics, and shifts in interspecific interactions. My goal was to conduct research across levels of biological organization to better understand the main pathways by which OA and associated increases in carbon dioxide (CO₂) will drive ecological change in herbivore-dominated systems. In Chapter 2, I examine the effect of CO₂ on herbivore growth and size-specific changes in feeding rate. I found that CO₂ had no impact on the size-specific feeding rates of the four-herbivore species I examined. However, changes in growth and body size in response to increased CO₂ may drive an overall reduction in the feeding rates of highly-calcified herbivores (e.g. urchins and gastropods), but not less calcified, crustacean herbivores. In Chapter 3, I used amphipod herbivores with short generation times to test the effects of CO₂ on per capita and abundance driven changes in herbivory. Again, I found no evidence for per capita changes in herbivory rate of this less calcified species, however increases in amphipod abundance lead to an increase in total herbivory. Finally, In Chapter 4, I manipulated both the abundance of gastropod herbivores and CO₂ in experimental tidepool communities in situ. I found that the indirect effects of CO₂ via the reduction of calcified herbivore pressure had a larger impact on tidepool community than CO₂ had directly. These results show that changes in herbivore pressure in response to OA will be driven primarily through changes in individual body size and herbivore abundance. Further, these changes in herbivory pressure can be more important in determining community structure under conditions of high CO₂ than other species-specific responses.
Science, Faculty of
Zoology, Department of
Graduate

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Watkins, Jason Derrick. "X-ray structures of P22 c2 repressor-DNA complexes the mechansism of direct and indirect readout /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26709.

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Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Loren D. Williams; Committee Member: Donald Doyle; Committee Member: Nicholas V. Hud; Committee Member: Roger Wartell; Committee Member: Stephen Harvey. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Beveridge, Oliver S. "Swimming in hot water : direct and indirect effects of temperature on protist behaviour, feeding interactions and population dynamics." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531127.

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King, Malcolm Anthony Wallace. "Indirect substrate and surface state mediated interactions at surfaces : a case study of ethene adsorption on Cu{111}." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615101.

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Rice, Kevin Barry. "Cascading Ecological Impacts of Emerald Ash Borer: Tritrophic Interactions Between Prickly Ash, Giant Swallowtail Butterfly Larvae, and Larval Predators." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366373364.

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Johnson, Evan Wesley. "Resonant Interactions of Dark Matter Particles Using Effective Field Theory." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563412934740044.

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Walsh, Matthew Robert. "Influence of the direct and indirect effects of interspecific interactions on life history evolution in a Trinidadian Killifish (Rivulus hartii)." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=87&did=1874863461&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1270247969&clientId=48051.

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Frost, Carol Margaret. "Spillover and species interactions across habitat edges between managed and natural forests." Thesis, University of Canterbury. Biological Sciences, 2013. http://hdl.handle.net/10092/8989.

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We are currently faced with the global challenge of conserving biological diversity while also increasing food production to meet the demands of a growing human population. Land-use change, primarily resulting from conversion to production land, is currently the leading cause of biodiversity loss. This occurs through habitat loss, fragmentation of remaining natural habitats, and resulting edge effects. Land-sparing and land-sharing approaches have been discussed as alternative ways to engineer landscapes to mitigate biodiversity loss while meeting production objectives. However, these represent extremes on a continuum of real-world landscapes, and it will be important to understand the mechanisms by which adjacent land use affects natural remnant ecosystems in order to make local land-management decisions that achieve conservation, as well as production, objectives. This thesis investigates the impact of juxtaposing production and natural forest on the community-wide interactions between lepidopteran herbivores and their parasitoids, as mediated by parasitoid spillover between habitats. The first and overarching objective was to determine whether herbivore productivity drives asymmetrical spillover of predators and parasitoids, primarily from managed to natural habitats, and whether this spillover alters trophic interactions in the recipient habitat. The study of trophic interactions at a community level requires understanding of both direct and indirect interactions. However, community-level indirect interactions are generally difficult to predict and measure, and these have therefore remained understudied. Apparent competition is an indirect interaction mechanism thought to be very important in structuring host-parasitoid assemblages. However, this is known primarily from studies of single species pairs, and its community-wide impacts are less clear. Therefore, my second objective was to determine whether apparent competition could be predicted for all species pairs within an herbivore assemblage, based on a measure of parasitoid overlap. My third objective was to determine whether certain host or parasitoid species traits can predict the involvement of those species in apparent competition. My key findings were that there is a net spillover of generalist predators and parasitoids from plantation to native forest, and that for generalists, this depends on herbivore abundance in the plantation forest. Herbivore populations across the edge were linked by shared parasitoids in apparent competition. Consequently, an experimental reduction of herbivore density in the plantation forest changed parasitism rates in the natural forest, as predicted based on parasitoid overlap. Finally, several host and parasitoid traits were identified that can predict the degree to which host or parasitoid species will be involved in apparent competition, a finding which may have extensive application in biological control, as well as in predicting spillover edge effects. Overall, this work suggests that asymmetrical spillover between production and natural habitats occurs in relation to productivity differences, with greater movement of predators and parasitoids in the managed-to-natural forest direction. The degree to which this affected species interactions has implications for landscape design to achieve conservation objectives in production landscapes.

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Barahona, Donifan. "On the representation of aerosol-cloud interactions in atmospheric models." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41169.

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Anthropogenic atmospheric aerosols (suspended particulate matter) can modify the radiative balance (and climate) of the Earth by altering the properties and global distribution of clouds. Current climate models however cannot adequately account for many important aspects of these aerosol-cloud interactions, ultimately leading to a large uncertainty in the estimation of the magnitude of the effect of aerosols on climate. This thesis focuses on the development of physically-based descriptions of aerosol-cloud processes in climate models that help to address some of such predictive uncertainty. It includes the formulation of a new analytical parameterization for the formation of ice clouds, and the inclusion of the effects of mixing and kinetic limitations in existing liquid cloud parameterizations. The parameterizations are analytical solutions to the cloud ice and water particle nucleation problem, developed within a framework that considers the mass and energy balances associated with the freezing and droplet activation of aerosol particles. The new frameworks explicitly account for the impact of cloud formation dynamics, the aerosol size and composition, and the dominant freezing mechanism (homogeneous vs. heterogeneous) on the ice crystal and droplet concentration and size distribution. Application of the new parameterizations is demonstrated in the NASA Global Modeling Initiative atmospheric and chemical and transport model to study the effect of aerosol emissions on the global distribution of ice crystal concentration, and, the effect of entrainment during cloud droplet activation on the global cloud radiative properties. The ice cloud formation framework is also used within a parcel ensemble model to understand the microphysical structure of cirrus clouds at very low temperature. The frameworks developed in this work provide an efficient, yet rigorous, representation of cloud formation processes from precursor aerosol. They are suitable for the study of the effect of anthropogenic aerosol emissions on cloud formation, and can contribute to the improvement of the predictive ability of atmospheric models and to the understanding of the impact of human activities on climate.

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François, Candice. "Intégration des interactions sensori-motrices et affectives dans le comportement d'achat." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALS017.

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Cette thèse propose de nouvelles méthodologies permettant de mesurer de façon indirecte et quantitative les composantes affectives du consommateur. Dans une première série d’études, nous avons observé que des variables socio-affectives influencent la perception de l’espace. Plus particulièrement, des variables comme l’estime de soi et l’anxiété sociale modèrent la façon dont les individus perçoivent une ouverture. Nos résultats suggèrent que ce type de tâche pourrait être, à terme, utilisée pour évaluer l’effet socio-affectif d’un produit porté. Dans une seconde série d’étude, nous avons analysé le mouvement de la souris lorsque des consommateurs devaient réaliser une tâche de catégorisation dichotomique. Cette méthode semble permettre d’identifier et de hiérarchiser certaines caractéristiques relatives à l’identité d’une marque. Ces résultats suggèrent que cette méthode pourrait être, à terme, utilisée afin de prédire les comportements d’achats. En conclusion, ces travaux proposent de nouvelles mesures indirectes, basées sur des variables sensori-motrices, pour l’étude du consommateur
His thesis proposes new methodologies to measure indirectly and quantitatively the consumer’s emotional components. In a first series of studies, we observed that socio-affective variables influence the perception of space. More specifically, variables such as self-esteem and social anxiety moderate the way individuals perceive width of an aperture. Our results suggest that this type of task could eventually be used to evaluate the socio-affective effect of product usage. In a second series of studies, we analyzed mouse movement when consumers were asked to perform a dichotomous categorization task. This method seems to identify and prioritize certain characteristics related to a brand's identity. These results suggest that this method could eventually be used to predict purchasing behavior. In conclusion, this work proposes new indirect measures, based on sensory-motor variables, for consumer studies

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Altfeld, Laura F. "Herbivore Abundance in Simple and Diverse Habitats: The Direct and Indirect Effects of Plant Diversity and Habitat Structure." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000062.

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Kohl, Michel T. "The Spatial Ecology of Predator-Prey Interactions: A Case Study of Yellowstone Elk, Wolves, and Cougars." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7441.

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The loss of large apex predators, and their subsequent reintroduction, has been identified as a substantial driver on the structure and function of ecological communities through behavioral mediated trophic cascades (BMTCs). The reintroduction of wolves (Canis lupus) to Yellowstone National Park (YNP) has served as foundational case study of BMTCs. In our system, it has been suggested that wolves have established a ‘landscape of fear’ in which the primary prey, elk (Cervus elaphus), now avoid risky places, which ultimately led to the recovery of the vegetation community. Although this case is frequently cited as a well-understood example of a landscape of fear, researchers never quantified whether elk avoided risky places, a critical component of the BMTC hypothesis. Thus, I employed numerous quantitative approaches to evaluate the role of wolves and cougars on elk habitat selection in northern Yellowstone. The results from this work suggest that the daily activity schedule of wolves provide a temporally predictable period of risk that allows elk to use risky places during safe times. As such, diel predator activity flattened (i.e., made less risky) the landscape of fear for 16 hours per day, 7 days a week, which permitted elk to forage on deciduous woody plants despite the presence of wolves. Thus, suggests that any trophic cascade in northern Yellowstone is likely driven by the consumptive effects of wolves on elk. In addition, my results suggest that daily activity patterns are an important component of predation risk, and as such, provide a predictable avenue for elk to avoid predators despite residing in an environment spatially saturated with wolves and cougars. Thus, the ability of elk to avoid predators through fine-scale spatial decisions provides support for my findings that the current spatial distribution of prey is largely driven by the consumptive effects of predators on the prey population, rather than a landscape of fear. In combination, these results suggest that the landscape of fear, and more generally, fear effects, may be of less relevance to conservation and management than direct killing within free-living, large landscapes.

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Russell-Mercier, Jake L. "A Study of the Impact of an Introduced Herbivore on Pollinator-mediated Interactions and Female Fitness in 'Lythrum salicaria'." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24007.

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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.

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O'Connell, Heather Adele. "The Role of Ecological Interactions in Polymicrobial Biofilms and their Contribution to Multiple Antibiotic Resistance." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/biology_diss/13.

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The primary objectives of this research were to demonstrate that: 1.) antibiotic resistant bacteria can promote the survival of antibiotic sensitive organisms when grown simultaneously as biofilms in antibiotics, 2.) community-level multiple antibiotic resistance of polymicrobial consortia can lead to biofilm formation despite the presence of multiple antibiotics, and 3.) biofilms may benefit plasmid retention and heterologous protein production in the absence of selective pressure. Quantitative analyses of confocal data showed that ampicillin resistant organisms supported populations of ampicillin sensitive organisms in steady state ampicillin concentrations 13 times greater than that which would inhibit sensitive cells inoculated alone. The rate of reaction of the resistance mechanism influenced the degree of protection. Spectinomycin resistant organisms did not support their sensitive counterparts, although flow cytometry indicated that GFP production by the sensitive strain was improved. When both organisms were grown in both antibiotics, larger numbers of substratum-attached pairs at 2 hours resulted in greater biofilm formation at 48 hours. For biofilms grown in both antibiotics, a benefit to spectinomycin resistant organism’s population size was detectable, but the only benefit to ampicillin resistant organisms was in terms of GFP production. Additionally, an initial attachment ratio of 5 spectinomycin resistant organisms to 1 ampicillin resistant organism resulted in optimal biofilm formation at 48 hours. Biofilms also enhanced the stability of high-copy number plasmids and heterologous protein production. In the absence of antibiotic selective pressure, plasmid DNA was not detected after 48 hours in chemostats, where the faster growth rate of plasmid-free cells contributed to the washout of plasmid retaining cells. The plasmid copy number per cell in biofilms grown without antibiotic selective pressure steadily increased over a six day period. Flow cytometric monitoring of bacteria grown in biofilms indicated that 95 percent of the population was producing GFP at 48 hours. This research supports the idea that ecological interactions between bacteria contribute to biofilm development in the presence of antibiotics, and demonstrates that community-level multiple antibiotic resistance is a factor in biofilm recalcitrance against antibiotics. Additionally, biofilms may provide an additional tool for stabilizing high copy number plasmids used for heterologous protein production.

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Kere, Eric Nazindigouba. "Analyse économétrique des décisions de production des propriétaires forestiers privés non industriels en France." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0052/document.

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La production de bois intègre notamment des enjeux économiques, climatiques et énergétiques. En France, selon les données de l'Institut National de l'Information Géographique et Forestière, l'accroissement biologique de la forêt est largement supérieur aux prélèvements de bois. C'est pourquoi l'État français a fixé l'objectif de prélever 21 millions de m3 supplémentaires de bois d'ici 2020 (Grenelle de l'environnement, 2007). Cependant, la forêt française appartient majoritairement à des propriétaires forestiers privés qui ont des préférences à la fois pour le revenu issu de la vente de bois et pour les aménités non-bois. Les politiques visant à accroître la production de bois doivent donc intégrer ces aspects. L'objectif de ce travail de thèse est de comprendre les déterminants de la production jointe de bois et d'aménités non-bois en France. Pour ce faire, nous nous sommes d'abord intéressés aux déterminants individuels et régionaux de l'offre de bois. Nous montrons que le comportement d'offre de bois d'un propriétaire peut varier en fonction du comportement de production de bois constaté chez ses pairs (effets sociaux). Ensuite, nous mettons en évidence un comportement de mimétisme dans les décisions de production jointe de bois et d'aménités des propriétaires forestiers privés. Enfin, nous analysons les arbitrages inter-temporels réalisés par les propriétaires entre aménités non-bois et revenu de la vente de bois en prenant en compte explicitement les anticipations de prix et de croissance. Nous évaluons à 23e par an la valeur que les propriétaires de notre échantillon accordent à 1m3/ha de bois supplémentaire laissé sur pied par rapport au niveau de stock des propriétaires industriels afin d'avoir des aménités plus importantes.Un des enjeux de ce travail est d?offrir des pistes pour mobiliser la ressource forestière ne faisant pas l'objet d'une offre, faute d'implication des propriétaires privés, soit par manque de connaissance ou d'intérêt pour leur forêt, soit parce que d'autres aspects sont privilégiés (services d'aménités non-bois par exemple). Dans cette thèse, nous montrons que les effets de mimétisme et d'entrainement social (effets sociaux) peuvent être utilisés pour amener les propriétaires forestiers à produire plus de bois. Nous montrons également, qu'une hausse du prix du bois ou la mise en place d'une taxepeut favoriser la prise de la décision de coupe de bois et augmenter l'intensité de la récolte
Timber production is related to economic, climate and energy issues. In France,according to data from the National Institute of Geoinformation and Forestry, thebiological growth rate of the forest is greater than the timber harvest rate. Thus, theFrench government has set a target of harvesting an additional quantity of 21 millioncubic meter of timber by 2020 ("Grenelle de l'environnement, 2007"). However, theFrench forest is majority owned by private forest owners who have preferences forboth income from timber trade and from non-timber amenities. The policies toincrease timber production must include these aspects. The objective of this thesisis to understand the determinants of joint production of timber and non-timberamenities in France.Therefore, we first analyze private forest owners' timber supply, taking into accountindividual and regional determinants. Afterwards, we investigate whether thedrivers of forest owners behavior differ within and between these different levels.We show that similar timber supply behavior can be observed when regional characteristicsor those of peers are similar. Then, we highlight a mimicry behavior injoint production decisions of timber and amenities made by private forest owners.Finally, we analyze inter-temporal trade-offs made by the owners from non-timberamenities and income from the sale of wood. We explicitly take into account theprice expectations and growth. Our estimations show that the willingness to pay fornon-timber amenities is e23 for our case study. This value is the difference betweenthe value they could have earned if they tried to maximize timber revenue and therevenue of their actual logging.Mainly beacause of a lack of involvement of private owners, either through a lackof knowledge or interest in their forest, or because other aspects are privileged (nontimberamenities, e.g.), a part of forest ressource is not subject to a commercial offer.Providing ways to mobilize this ressource is one of the challenges of this work. Weshow that the mimetic effects and the contextual effects can be used to encourageforest owners to produce more timber. An effective policy could be a combinationof these two effects. We also show that an increase in the price of timber or theadoption of a tax may be an incentive for timber harvesting

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Kopf, Martina Simone. "Discours interactionnel entre apprenants dans le cadre de l’enseignement secondaire : L’utilisation de stratégies communicatives en français langue étrangère par des apprenants anglophones." Thesis, Högskolan Dalarna, Franska, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:du-34257.

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L'objectif de la présente étude était d'examiner l'utilisation des stratégies communicatives (SC) dans les interactions verbales entre apprenants de français langue étrangère dans le secondaire. À cette fin, un corpus contenant les interactions verbales de 36 apprenants de français de quatre écoles secondaires différentes du Royaume-Uni a été sélectionné et analysé pour les SC, en s'appuyant sur la taxonomie de Dörnyei et Scott (1997) utilisant une optique interactionniste. Les résultats révèlent que les apprenants ont utilisé principalement des stratégies indirectes, notamment des mots de remplissage et des auto-répétitions, afin de gagner du temps pour réfléchir et maintenir la conversation. Des stratégies directes ont également été fréquemment utilisées, en particulier l'auto-correction et le passage à une première langue (L1) partagée. L'auto-correction a principalement servi à ajuster le message pour atteindre et améliorer le sens partagé, tandis que le passage à la L1 était généralement utilisé pour atténuer les difficultés de communication et établir une relation avec les interlocuteurs sur la base d'une L1 partagée. Il est à noter que les stratégies interactionnelles, en particulier les questions en langue seconde (L2), n’étaient pas souvent présentes dans les interactions. Cela met en évidence la nécessité d'un enseignement plus explicite, en particulier en ce qui concerne des stratégies interactionnelles, afin que les apprenants soient capables de négocier le sens en posant des questions et en clarifiant le problème, de parvenir à un sens partagé et de soutenir une conversation en L2 sans avoir à recourir à la L1.
The aim of the current study was to examine the use of communication strategies in verbal interactions between secondary students of French as a Foreign language. To this end, a corpus containing the verbal interactions of 36 secondary students of French from four different high schools in the UK, was selected and scanned for communication strategies, drawing on Dörnyei and Scott’s taxonomy (1997) employing an interactionist lens. Findings reveal that students used mostly indirect strategies, notably filler words and self-repetitions in order to gain time to think and to maintain the conversation. Direct strategies were also employed frequently, in particular self-correction and code-switch, the change to a shared first language (L1). Self-correction served mainly the purpose of adjusting the message to achieve and enhance shared meaning, while the switch to the L1 was usually employed to alleviate communication difficulties and establish a relationship with the speaking partners based on a shared L1. It is noteworthy that interactional strategies, especially questions in the second language (L2), did not feature highly in the interactions. This points to a need for more explicit instruction, particularly in interactional strategies, so that students are able to negotiate meaning by asking questions and clarifying issue, achieve shared meaning and can sustain a conversation in the L2 without having to resort to the L1.

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Nasseri, Nabil. "Investigating The Effects Of Ant-Hemipteran Mutualisms On The Invertebrate Community Structure And Their Host Plant, Honey Mesquite (prosopis Glandulosa)." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/971.

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Ants are ubiquitous in most communities and many form opportunistic mutualisms with honeydew-producing hemipterans (e.g. treehoppers). Hemipterans excrete honeydew, a carbohydrate rich substance, that ants harvest and, in return, ants protect their honeydew-producing partners from parasitoids, predators, and competitors. Given the efficacy of tending ants in removing hemipteran antagonists, and the strong roles that ants play within their communities as predators, competitors, and seed dispersers, surprisingly little is known of the effects of ant-hemipteran mutualisms (AHM) on the invertebrate communities in which they are embedded or on the plants that host AHM. Using observational and manipulative field experiments, I examined the long-term effect of AHM on their host plant’s, honey mesquite (Prosopis glandulosa), reproductive potential and quality. In addition, I measured how the presence of AHM affects the abundance, richness, diversity, and composition of the invertebrate communities living on honey mesquite. Plants hosting AHM may indirectly benefit (through the removal of herbivore arthropods) or suffer (through the loss pollinators) due to the defensive behavior of tending ants. To determine the effects of AHM on their host plant, I established a four-year press experiment in which I removed AHM from 50 randomly trees, while leaving 50 as controls. In addition, I marked and followed 30 trees from which AHM were naturally absent. To assess if mesquite quality differed between trees hosting AHM and trees in which AHM were naturally absent, in 2012 I assayed foliar condensed tannin concentrations, a secondary defense compound, and, in 2015, I measured foliar nitrogen, phosphorous, potassium, magnesium, and iron as they are essential for growth and reproduction. I compared the reproductive potential between AHM present and removed trees by counting flowers and fruits across all 4 years of the study. Mesquite that hosted AHM contained significantly less condensed tannins and significantly higher concentrations of N%, Mg, and Fe. Furthermore, over the duration of the study mesquite hosting AHM contained significantly more flowers than those from which AHM were removed or naturally absent. My results indicate that AHM select trees of high quality and their continued presence is associated with high levels of reproductive potential. Most studies that have evaluated community-level effects of AHM compare total abundance and species richness in communities (or host plants) with and without AHMs. However, both measures are dependent on sampling effort, complicating comparisons across different studies. To examine the effects of AMH on the arthropod community in mesquite, I first compared family richness and alpha diversity using standardized rarefaction and extrapolation curves. I then measured beta diversity and turnover in community composition from one year to the next. The removal of AHM increased invertebrate diversity and significantly altered community composition. Although treatments did not statistically differ in turnover rates, replacements occurred among treatments at the family level which may be biologically meaningful. Furthermore, herbivore and predator populations increased, and pollinator populations decreased following the removal of AHM. These results suggest that the presence of AHM can alter the composition of arthropod communities and food-web dynamics. However, these effects were significant in some years and not others, suggesting the importance of temporal variation in drivers of communities. Overall, my work demonstrates that AHM can be drivers of community composition and illustrate the importance of examining their effects across multiple seasons.

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Clementz, Stefan. "Effects of Dark Matter in Astrophysical Systems." Licentiate thesis, KTH, Teoretisk partikelfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202956.

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When studying astrophysical structures with sizes ranging from dwarf galaxies to galaxy clusters, it becomes clear that there are vast amounts of unobservable gravitating mass. A compelling hypothesis is that this missing mass, which we call dark matter, consists of elementary particles that can be described in the same manner as those of the standard model of particle physics. This thesis is dedicated to the study of particle dark matter in astrophysical systems. The solar composition problem refers to the current mismatch between theoretical predictions and observations of the solar convection zone depth and sound speed profile. It has been shown that heat transfer by dark matter in the Sun may cool the solar core and alleviate the problem. We discuss solar capture of a self-interacting Dirac fermion dark matter candidate and show that, even though particles and antiparticles annihilate, the abundance of such a particle may be large enough to influence solar physics. Currently, direct and indirect methods are employed in searches for dark matter. In this context, we study inelastic dark matter, where a small mass splitting separates two dark matter particles and scattering takes one into the other. This affects the scattering kinematics, which in turn affects direct detection and solar capture rates. We also discuss the information contained in a direct detection signal and how it can be used to infer a minimal solar capture rate of dark matter. When comparing simulated dark matter halos with collisionless dark matter with dark matter halos inferred from observations, problems appear in the smallest structures. A proposed solution is self-interacting dark matter with long range forces. As the simplest models are under severe constraints, we study self-interactions in a model of inelastic dark matter.

QC 20170309

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Hanoteaux, Sven [Verfasser], and Katja [Akademischer Betreuer] Tielbörger. "The role of indirect plant-plant interactions via shared pollinators : a combined experimental and theoretical study in species-rich temperate grasslands / Sven Hanoteaux ; Betreuer: Katja Tielbörger." Tübingen : Universitätsbibliothek Tübingen, 2014. http://d-nb.info/1162971436/34.

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Kuczyk, Josephine [Verfasser], Klaus [Akademischer Betreuer] Fischer, Klaus [Gutachter] Fischer, and Caroline [Gutachter] Müller. "Plant-herbivore interactions in a changing world - Indirect effects of climate change on the butterfly Pieris napi / Josephine Kuczyk ; Gutachter: Klaus Fischer, Caroline Müller ; Betreuer: Klaus Fischer." Greifswald : Universität Greifswald, 2020. http://d-nb.info/1205069429/34.

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Hannusch, Lisa [Verfasser], Gerhard [Akademischer Betreuer] Rödel, Gerhard [Gutachter] Rödel, Kai [Akademischer Betreuer] Ostermann, and Tilo [Gutachter] Pompe. "A Novel SCP-RICM Assay Application: Indirect Detection of Analytes by Modulation of Protein-Protein Interactions / Lisa Hannusch ; Gutachter: Gerhard Rödel, Tilo Pompe ; Gerhard Rödel, Kai Ostermann." Dresden : Technische Universität Dresden, 2021. http://d-nb.info/1239729294/34.

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Wilson, Alexsis Jane. "Insect frugivore interactions : the potential for beneficial and neutral effects on host plants." Queensland University of Technology, 2008. http://eprints.qut.edu.au/17023/.

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Frugivorous insects, specialised herbivores that consume fruit and seeds, are considered detrimental to host plant fitness. Their direct link to genetic fitness via consumption of plant reproductive tissue, and their negative socioeconomic association with agriculture exacerbates their harmful status. However, empirical testing of insect frugivore effects on host plants, and ecological research on the contribution of insect frugivores to multitrophic frugivory systems, is lacking. In the current study, direct effects of a non-mutualistic, insect frugivore/host plant system were tested and results showed variable effects. Beneficial, detrimental, but predominantly neutral effects on germination and seed production were observed between the Queensland fruit fly (Bactrocera tryoni) and tomato and capsicum plants. Significant effects on seed production were unexpected because infestation occurs after seed set. It was also found that eggplant, although a recorded host of B. tryoni, is inconsistent in its ability to sustain B. tryoni larvae through to its final instar. These results confirmed a simplification and presumption associated with insect frugivore (specifically fruit fly)/host plant interactions. Larval movement, infestation-induced fruit decay, pulp removal and germination were then investigated. For all hosts (tomato, apple and paw paw), treatments infested by B. tryoni decayed significantly quicker and to a greater extent than uninfested treatments, with obvious but variable changes to the texture and appearance. The movement of B. tryoni larvae, pattern of infestation-induced decay and pulp removal was unique and host dependent for all hosts. Only seeds from infested tomato were shown to germinate during the experiment. This indicated that host fruit characteristics are responsible, in part, for variable direct effects on host plant fitness by insect frugivores. Variable direct effects between insect frugivores and host plants, combined with the more rapid decay of infested fruits is likely to have implications for seed dispersal and seed predation by a third trophic level. The characteristics of fruit that are changed by infestation by an insect frugivore were then tested for their effect on a vertebrate frugivore, to illustrate the importance of recognising multitrophic interactions and indirect effects in frugivory. Specifically, seed predating rodents were incorporated into the study and their response to infested and uninfested fruits were recorded, as well as their reaction to the changes in fruit caused by insect frugivores (i.e. texture, smell, larvae presence and sound). Apple and pear infested with B. tryoni larvae were found to attract rodents, while infested tomato and paw paw had a neutral effect on the native rats. This differed from the predominant finding in the literature, which was a deterrent effect on avian seed dispersers. Vertebrate response to fruit infested with insect frugivores therefore, is variable. Assessing the indirect effect of insect frugivores on host plant fitness by attracting or deterring another trophic level requires knowledge of the direct effect between the introduced trophic level and the host plant. For example, the attraction of a seed predator may be as detrimental to host plant fitness as the deterrence of a seed disperser. This illustrates the complexity associated with assessing insect frugivore effects on host plant fitness. Results also indicated that differences in pulp texture, caused by infestation, have a significant effect on rodent preference for infested or uninfested treatments. Pulp texture is likely to effect rodent foraging efficiency, whereas the presence of B. tryoni larvae was observed to be inconsequential to rodent response to fruits. For rodents, and indeed any trophic level motivated by foraging efficiency, this finding raises the issue that for long lived fruiting plants, outside factors such as food abundance and competition for food, may cause a variable response to fruits infested by insect frugivores. From these investigations it has become apparent that insect frugivores are not consistently harmful to host plant fitness, as suggested by their negative stigma, but are likely to contribute variable effects, directly and indirectly, on multiple components of plant fitness and multitrophic frugivory systems.

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Blanc, Lori A. "Experimental study of an avian cavity-nesting community: nest webs, nesting ecology, and interspecific interactions." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28420.

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Cavity-nesting communities are structured by the creation of and competition for cavities as nest-sites. Viewing these communities as interconnected webs can help identify species interactions that influence community structure. This study examines cavity-nesting bird community interactions within the fire-maintained longleaf pine (Pinus palustris) ecosystem at Eglin Air Force Base, Florida. In chapter 1, I provide a background review of the ecology of my study system. In chapter 2, I use nest webs to depict the flow of cavity-creation and use at Eglin. I identified 2 webs into which most species could be placed. One web contained 6 species associated with pines. The second web contained 5 species associated with hardwoods. Red-cockaded woodpeckers (Picoides borealis) and northern flickers (Colaptes auratus) created most cavities used by other species within this community. In chapter 3, I describe snag densities and nest-site selection of the cavity-nesting bird community at Eglin. Large, mature pine snags were abundant, exceeding other reported densities for southern pine forests. Pine snags were heavily-used, despite the abundance of available red-cockaded woodpecker cavities in living pine. Hardwood snags accounted for 10% of nests found, and were used by 12 of 14 species. Diameters of nest-trees and available snags were below the range of optimal nest-snag diameters reported in other studies, indicating the need for site-specific snag management guidelines. In chapter 4, I combine a study of basic ecological principles with endangered species management to examine interactions within the cavity-nesting bird community at Eglin. I used a nest web to identify a potential indirect interaction between the red-cockaded woodpecker and large secondary cavity-nesters, mediated by the northern flicker. I used structural equation modeling to test a path model of this interaction. By experimentally manipulating cavity availability, I blocked links described in the model, confirming cavity creation and enlargement as mechanisms that influence this indirect relationship. I demonstrated that a red-cockaded woodpecker cavity-management technique could disrupt this indirect relationship by affecting northern flicker behavior, and provided an empirical example of how, in interactive ecological communities, single-species management can have indirect effects on non-target species.
Ph. D.

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Araujo, Guilherme David. "Jogos evolucionários de reciprocidade indireta via interações opcionais." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-02052016-111205/.

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Em uma perspectiva evolutiva, a emergência e a manutenção de comportamentos altruísticos e de cooperação não é de fácil entendimento. O impulso por ajudar um indivíduo desconhecido não pode significar um prejuízo na capacidade reprodutiva, o que muitas vezes parece ser o mais óbvio. Muito se tem feito no sentido de compreender os ganhos indiretos da cooperação, ou o que se espera em retorno por este comportamento. A espera por reciprocidade é um dos modos de se tornar a cooperação atraente. Os seres humanos possuem uma capacidade singular de expandir a reciprocidade para interações organizadas em que não necessariamente se recebe a retribuição de um favor, mas sim o favor de um terceiro indivíduo. Para estes sistemas, de reciprocidade indireta, são necessários elaborados processos cognitivos que sustentam uma capacidade para linguagem, julgamentos morais e organização social. Entende-se que esta forma de cooperação é um fator essencial para a evolução do intelecto e da estrutura social atuais dos seres humanos. A teoria dos jogos evolucionária é uma ferramenta matemática muito utilizada na sistematização analítica dos problemas envolvendo cooperação e processos evolutivos no geral. A capacidade reprodutiva é traduzida em termos de funções matemáticas, sendo possível realizar dinâmicas populacionais que modelam a pressão seletiva. Neste trabalho, utilizamos métodos de teoria dos jogos evolucionária para explorar modelos de reciprocidade indireta, expandindo o tratamento de um modelo para interações opcionais envolvendo estratégias de cooperadores condicionais. Mostramos que a presença de cooperadores incondicionais ameaça a estabilidade da cooperação e que erros de execução podem ser uma solução.
At an evolutionary perspective, the emergence and maintenance of altruistic and cooperative behaviours is of no easy understanding. The impulse of helping an unrelated individual cannot mean a loss of reproductive fitness, as many times may seem the obvious. Much has been done in the way of knowing the indirect benefits of cooperation, or what to expect in retribution for this behaviour. To expect reciprocity is one way of looking at cooperation as more attractive. Human beings have a singular capacity of expanding reciprocity to organized interactions where retribution of a favour is not necessary, but one can expect the favour of a third-party. For these systems, of indirect reciprocity, elaborate cognitive processes are necessary, ones that maintain the capacity for language, moral judgements and social organization. One can understand this form of cooperation as an essential factor for the evolution of humans nowadays´ intellect and social structure. Evolutionary game theory is a mathematical tool that is largely used in the analytical systematization of problems involving cooperation and evolutionary processes in general. Reproductive fitness is understood in terms of mathematical functions, making possible the work on population dynamics that model selective pressure. In this work, we use methods in evolutionary game theory to explore models of indirect reciprocity, expanding the treatment of a model for optional interactions involving conditional cooperators strategies. We show that the presence of unconditional cooperators threatens the stability of cooperation and that execution errors might be a solution.

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Reichstein, Birte. "Ontogenetic bottlenecks : effects on intraguild predation systems and ecosystem efficiency." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105759.

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Size-dependent differences between individuals in size-structured organisms have fundamental effect on population and community dynamics. Intraguild predation (IGP) is one specifically interesting constellation that often arises when two size-structured populations interact. Ontogenetic bottlenecks that determine population size-structure are affected by both population intrinsic as well as population extrinsic factors, and are therefore context-dependent. Surprisingly, size-structured IGP systems have mainly been investigated theoretically and especially long-term empirical studies are widely lacking. In this thesis I investigate empirically how habitat complexity, interaction strength, and stage-specific resource availabilities affect population processes and their effects on the dynamics of a size-structured IGP system. I conducted multi-generation experiments in a size-structured IGP system, with the Least Killifish (Heterandria formosa) as IG prey and the Common Guppy (Poecilia reticulata) as IG predator. With no alternative resource next to the shared resource, IG predator and IG prey could not coexist. Weak interactions only increased IG prey and IG predator persistence times and observed exclusion patterns depended on habitat complexity. An alternative resource for either the juvenile IG predator or the juvenile IG prey on the other hand promoted coexistence. However, this coexistence was context-dependent. Ontogenetic bottlenecks played a central role in the dynamics of the size-structured IGP system in general. In the final study I show that an ontogenetic bottleneck can, through changes in stage-specific resource availabilities, be affected in a way that leads to increased trophic transfer efficiency with potential effects on higher trophic levels. Overall, the results emphasize importance of the broader context in which size-structured communities are embedded. Especially, when managing natural communities it is important to account for the combined effects of size-structure, stage-specific resource availabilities, and habitat structure. Specifically, when managing species that connect habitats or ecosystems all life-stages’ environmental conditions must be consider in order to ensure strong predictive power of tools used for ecosystem management planning.

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Éthève, Loic. "Étude de l’assemblage, de la mécanique et de la dynamique des complexes ADN-protéine impliquant le développement d’un modèle « gros grains »." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1242/document.

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Les interactions ADN-protéine sont fondamentales dans de nombreux processus biologiques tels que la régulation des gènes et la réparation de l'ADN. Cette thèse est centrée sur l'analyse des propriétés physiques et dynamiques des interfaces ADN-protéine. À partir de l'étude de quatre complexes ADN-protéine, nous avons montré que l'interface ADN-protéine est dynamique et que les ponts salins et liaisons hydrogène se forment et se rompent dans une échelle de temps de l'ordre de la centaine de picosecondes. L'oscillation des chaînes latérales des résidus est dans certains cas capable de moduler la spécificité d'interaction. Nous avons ensuite développé un modèle de protéine gros grains dans le but de décomposer les interactions ADN-protéine en identifiant les facteurs qui modulent la stabilité et la conformation de l'ADN ainsi que les facteurs responsables de la spécificité de reconnaissance ADN-protéine. Notre modèle est adaptable, allant d'un simple volume mimant une protéine à une représentation plus complexe comportant des charges formelles sur les résidus polaires, ou des chaînes latérales à l'échelle atomique dans le cas de résidus clés ayant des comportements particuliers, tels que les cycles aromatiques qui s'intercalent entre les paires de base de l'acide nucléique
DNA-protein interactions are fundamental in many biological processes such as gene regulation and DNA repair. This thesis is focused on an analysis of the physical and dynamic properties of DNA-protein interfaces. In a study of four DNA-protein complexes, we have shown that DNA-protein interfaces are dynamic and that the salt bridges and hydrogen bonds break and reform over a time scale of hundreds of picoseconds. In certain cases, this oscillation of protein side chains is able to modulate interaction specificity. We have also developed a coarse-grain model of proteins in order to deconvolute the nature of protein-DNA interactions, identifying factors that modulate the stability and conformation of DNA and factors responsible for the protein-DNA recognition specificity. The design of our model can be changed from a simple volume mimicking the protein to a more complicated representation by the addition of formal charges on polar residues, or by adding atomic-scale side chains in the case of key residues with more precise behaviors, such as aromatic rings that intercalate between DNA base pairs

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Laurent, Lisa. "Apports d’une approche écosystémique à l’étude de la dynamique des communautés végétales forestières : vers une prise en compte des interactions écologiques multiples." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2050/document.

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Un des principaux challenges pour prédire la composition, la structure et la dynamique des communautés végétales est de déterminer comment l’environnement biotique et abiotique va modifier la direction et l’amplitude des interactions entre plantes. L’objectif de ma thèse est de mettre en évidence le rôle prépondérant des interactions complexes (impliquant plus de deux compartiments biotiques) dans la dynamique forestière et plus particulièrement dans la dynamique de régénération des ligneux d’intérêt sylvicole tel que le chêne sessile. Les résultats soulignent l’importance de prendre en compte : (i) l’effet des cervidés sur les patrons de réponses des interactions entre plantes le long des gradients de ressources, (ii) les interactions indirectes et notamment la facilitation indirecte, (iii) des paramètres démographiques différents en relation avec la phénologie des espèces en présence, (iv) la séparation des mécanismes sous-jacents à une interaction écologique multiple via un suivi des conditions environnementales. Ainsi, ma thèse appuie l’idée que les gestions se focalisant sur une unique pression et ignorant les autres pressions ne sont pas capables de maintenir des populations d’espèces cibles car elles ne tiennent pas compte des interactions multiples. Ceci souligne l’importance d’utiliser des stratégies complémentaires pour permettre la pérennité des écosystèmes forestiers et notamment une régénération suffisante dans le cadre des changements globaux que sont le changement climatique et la surabondance de cervidés
One of the main challenges to predict vegetation dynamics and plant community composition is to identify how biotic and abiotic factors modify the nature and magnitude of plant-plant interactions. The objective of my thesis is to highlight the leading role of multiple interactions (involving more than two biotic compartments) in forest understory dynamics and more specifically regeneration dynamics of target species such as sessile oak. The results emphasize the importance of: (i) effects of deer on response patterns of plant-plant interactions along resource gradients, (ii) indirect interactions, in particular indirect facilitation, (iii) demographic parameters in relation to species phenology, (iv) distinguishing among underlying mechanisms of multiple interactions thanks to environmental monitoring. Thus, my thesis supports the idea that management practices focusing on a single pressure, while ignoring others, are unable to conserve populations of target species because they don’t consider multiple interactions. This highlights the importance to use complementary management strategies to achieve sustainability in the context of global changes (climatic change and deer overabundance)

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McKinney, Amy Marie. "Pollinator-mediated interactions between the invasive shrub Lonicera maackii and native herbs: The roles of shade, flowering phenology, spatial scale, and floral density." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276309342.

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Ghimenton, Anna. "ACQUISITION PLURILINGUE CHEZ UN JEUNE ENFANT DE VÉNÉTIE : ÉTUDE DE LA FRÉQUENCE D'USAGE DES LANGUES ET DES INDICES PRAGMATIQUES LORS DES INTERACTIONS FAMILIALES." Phd thesis, Grenoble 3, 2008. http://tel.archives-ouvertes.fr/tel-00466372.

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Cette thèse porte sur le développement langagier d'un enfant de Vénétie (nord-ouest de l'Italie), Francesco, suivi entre 17 et 30 mois. Dans cette région se côtoient quotidiennement l'italien et des variétés dialectales. Nous examinons les patrons des choix langagiers de cet enfant et nous les mettons en relation avec ces mêmes patrons dans la parole qu'il perçoit directement et indirectement de ses interlocuteurs. Deux types de situations constituent ce corpus : des échanges dy-triadiques entre l'enfant et ses parents (15h07, soit 6.430 énoncés transcrits) et des interactions multipartites entre l'enfant et les membres de sa famille élargie (19h50, soit 12.084 énoncés transcrits). En prenant appui sur les approches basées sur l'usage (Tomasello, 2003) et le modèle de compétition de MacWhinney (2005), nous tentons d'élucider les processus acquisitionnels concernant les choix de langues dans un contexte où ils sont fortement variables. Trois aspects définissent la spécificité de ce travail : 1/ il a été conduit dans une situation de contact où les variétés des répertoires se répartissent au long d'un continuum et où l'enfant doit apprendre à effectuer des choix codiques appropriés au contexte interactionnel ; 2/ l'exploration des productions dans différents types d'interactions permet de repérer divers modes d'apprentissage (statistique et pragmatique) et, 3/ les résultats documentent les rôles de l'input indirect et des enjeux pragmatiques dans la transmission de variétés minoritaires. Une approche interdisciplinaire permettra d'examiner ces trois points sous un éclairage alliant dialectologie, psycholinguistique et sociolinguistique.

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Visnevski, Dmitri. "Collective dynamics of excitons and exciton-polaritons in nanoscale heterostructures." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-00914332.

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In my thesis I will discuss some aspects of collective dynamics of excitons and exciton-polaritons in nanoscale heterostructures. In the first Chapter I will make a brief introduction to the modern semiconductor physics and willdescribe the general elements and notions which will be used further. Other four chapters would be devoted to four works in which I participated, notably, in Chapter 2 I will speak about the coherent interactions between phonons and exciton orexciton-polariton condensates, in Chapter 3 I will discuss the quantum dots lasing and its amplification by an acoustic pulse. Chapter 4 and 5 will be devoted respectively to the polariton multistability and to the condensates of indirect excitons.

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Déandreis, Céline. "Impact des aérosols anthropiques sur le climat présent et futur." Paris 6, 2008. http://www.theses.fr/2008PA066139.

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Les aérosols perturbent l’équilibre radiatif de la Terre via leurs effets directs (diffusion et absorption du rayonnement solaire) et leurs effets indirects (interaction avec les nuages). Il est aujourd’hui reconnu que le rôle des aérosols anthropiques sur l’évolution du climat est significatif par rapport aux gaz à effet de serre. Malgré l’intensification des études sur ce sujet, l’estimation du forçage radiatif des aérosols anthropiques et l’estimation de leur impact sur les variables physiques sont encore très incertaines. Des causes majeures d’incertitudes proviennent de notre mauvaise connaissance des sources d’émissions des aérosols mais aussi de leurs processus de formation, de transformation et de dépôt. De plus les modèles que nous utilisons pour étudier le changement climatique ont des échelles de temps et d’espace qui ne sont pas adaptées à la représentation des processus dans lesquels les aérosols interviennent. Aux incertitudes liées à la paramétrisation des aérosols s’ajoutent celles liées à la représentation des processus physiques et dynamiques tels que transport, cycle hydrologique et bilan radiatif. Projeter le rôle des aérosols dans l’évolution du climat futur nécessite donc de réduire l’ensemble de ces sources d’incertitudes. Dans cette étude je montre l’intérêt de simuler interactivement le cycle des aérosols dans les modèles de climat afin de mieux estimer leur effet radiatif. En particulier j’estime que le couplage de LMDZ au module de chimie INCA entraîne une modification de 60% du flux net au sommet de l’atmosphère pour la période actuelle. Je montre aussi que la représentation des émissions est une source majeure d’incertitudes en ce qui concerne les projections de l’effet radiatif des aérosols pour le moyen terme. J’évalue une différence d’environ 40% sur le forçage radiatif simulé en utilisant deux inventaires d’émissions futures différents. Ces deux inventaires correspondent à une limite haute et à une limite basse en terme d’émissions d’aérosols carbonés à l’horizon 2050.

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Demann, Felicitas [Verfasser], Mathias [Akademischer Betreuer] Wegner, and Heinz [Gutachter] Brendelberger. "Direct and indirect effects of invasive parasites on native blue mussels - Mytilicola intestinalis Steuer, 1902 affects its host Mytilus edulis Linnaeus, 1758 and modifies ecological interactions to other species in the Wadden Sea / Felicitas Demann ; Gutachter: Heinz Brendelberger ; Betreuer: Mathias Wegner." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1234981548/34.

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Sotelo, Denis Stefan Robertson. "Probing Self-Interacting Dark Matter Models with Neutrino Telescopes." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-25012018-015636/.

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In this thesis we studied dark matter models with strong self-interactions, typically known as self-interacting dark matter (SIDM). This kind of models constitute a promising solution to the tension between small scale structure observations and predictions assuming the standard case of collisionless cold dark matter (CDM) while keeping the success of the standard cosmological model, LambdaCDM, at large scales. The presence of strong self-interactions can increase the dark matter capture and annihilation in astrophysical objects like our sun, enhancing the potential of indirect detection signals. We used the high energy neutrinos produced by such annihilations to probe SIDM models. We established strong constraints on SIDM with velocity independent cross section by comparing the expected neutrino signal with the results of the IceCube-79 dark matter search. Also, we determined the sensitivity for the IceCube-DeepCore and PINGU detectors for SIDM with a velocity dependent self-interacting cross section (vdSIDM). Most of its relevant parameter space can be tested with the three years of data already collected by IceCube-DeepCore, complementing results from direct detection experiments and other indirect detection studies.
Nesta tese investigamos modelos de matéria escura com auto-interações fortes, conhecidos tipicamente como matéria escura auto-interagente (SIDM). Este tipo de modelos constituem uma solução promissora à tensão entre as observações de estrutura a pequena escala e as previsões assumindo o caso padrão de matéria escura fria não colisional (CDM), enquanto se mantêm o sucesso do modelo cosmológico padrão, LambdaCDM, a grandes escalas. A presença de auto-interações fortes podem aumentar a captura e a aniquilação da matéria escura em objetos astrofísicos como o nosso sol, aumentando o potencial de sinais de detecção indireta. Usamos o sinal de neutrinos de alta energia produzidos por essas aniquilações para explorar modelos de SIDM. Estabelecemos fortes vínculos em modelos de SIDM com seção de auto-interação independente da velocidade comparando o sinal de neutrinos esperado com os resultados de busca de matéria escura do IceCube-79. Também, determinamos a sensibilidade dos detectores IceCube-DeepCore e PINGU para modelos de SIDM com uma seção de auto-interação dependente da velocidade (vdSIDM). A maior parte do espaço de parâmetros de interesse pode ser testado com os três anos de dados já coletados pelo IceCube-DeepCore, complementando os resultados de experimentos de detecção direta e outras an análises de detecção indireta.

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Gilliot, Jérémie. "Interactions multi-points indirectes sur grands écrans." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10097/document.

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L'interaction tactile multi-points co-localisée procure un fort sentiment de contrôle direct mais introduit des problèmes d'occultation, de précision et de fatigue. Ces problèmes sont exacerbés sur les écrans de grandes dimensions, qui supportent la manipulation de grandes quantités de données, souvent en collaboration avec d'autres utilisateurs. Pour résoudre ces problèmes, cette thèse s'intéresse à l'introduction d'indirections dans l'interaction multi-points sur grands écrans. Nos travaux portent sur l'étude des facteurs qui influencent la précision dans les tâches de sélection sans prévisualisation du contact. Les résultats de deux expériences contrôlées ont ainsi permis d'estimer la précision attendue selon les caractéristiques des périphériques d'entrée et de sortie et des conditions d'utilisation. Sur la base de ces connaissances, nos travaux portent également sur le développement de nouvelles techniques d'interaction pour écrans de grandes dimensions. Nous avons d'abord proposé une technique permettant d'interagir indirectement avec une tablette tactile, en introduisant la gestion de plusieurs curseurs contrôlés relativement. Nous avons ensuite conçu une interaction reposant sur la création de plusieurs périphériques virtuels qui supportent une interaction à la fois directe et indirecte tout en permettant de réorganiser les éléments d'une interface. Parallèlement à cela, nous avons transformé un écran mural de 6*2,4m en une surface tactile multi-points afin de pouvoir tester les techniques et scénarios discutés dans ces travaux
Co-localized multi-touch interaction affords a high feeling of directness but introduces problems of occlusion, precision and fatigue. These problems are even more acute with large displays, supporting the interaction with large data sets, often in collaboration with other users. To solve these problems this thesis focuses on the introduction of indirections in multi-touch interaction on large displays. We first study factors impacting accuracy in selection tasks without contact preview. Results of two controlled experiments allowed to estimate the expected accuracy depending on input and output device characteristics and input conditions. Based on this knowledge, we developed new interaction techniques for large displays. We first introduced a technique to interact indirectly using a tactile tablet by introducing the control of several cursors using a relative mapping. Then we proposed an interaction technique based on the creation of multiple soft-devices that supports both direct and indirect interaction and allows to re-arrange the interface of legacy applications. In order to design, test and evaluate these techniques, we turned a back projected wall display (6*2,4m) into an interactive multi-touch surface

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Dissertations / Theses on the topic 'Indirect interactions'

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