Dissertations / Theses on the topic 'Coevolution'
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1
Långberg, Joakim. "Coevolution and turnbased games." Thesis, University of Skövde, School of Humanities and Informatics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-958.
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Artificial intelligence plays an increasingly important role in modern computer games. As the complexity of the games increase, so does the complexity of the AI.
The aim of this dissertation is to investigate how AI for a turnbased computer game can coevolve into playing smarter by combining genetic algorithms with neural networks and using a reinforcement learning regime.
The results have shown that a coevolved AI can reach a high performance in this kind of turnbased strategy games. It also shows that how the data is coded and decoded and which strategy that is used plays a very big role in the final results
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Morgan, Andrew. "Experimental host-parasite coevolution." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424864.
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SungYong, Um. "The coevolution of digital ecosystems." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/388976.
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Business Administration/Management Information SystemsPh.D.
Digital ecosystems are one of the most important strategic issues in the current digital economy. Digital ecosystems are dynamic and generative. They evolve as new firms join and as heterogeneous systems are integrated into other systems. These features digital ecosystems determine economic and technological success in the competition among digital platform systems. However, how these ecosystems evolve over time is not yet clearly known. I describe three empirical essays in order to understand the underlying mechanism of the evolution of a digital ecosystem: 1) the underlying architecture of a digital ecosystem, 2) the evolutionary pattern of a digital ecosystem, 3) and the co-evolution of a digital ecosystem. To explore these topics, I focus on the underlying generative structure of the ecosystem and its evolutionary pattern of WordPress, which is the world largest blog platform system. I collected a comprehensive set of information about the WordPress ecosystem including over 23,000 plug-ins from January 2004 to December 2014. To analyze the data, I apply a network approach to capture the generative nature of digital technology that assumes a fractal-like structure in which digital components such as Application Programming Interfaces (API) cluster into groups that generate other groups over time. As such, I can effectively capture the hierarchical structure of a network by exploring the topological structure of sub-networks that represent the fractal-like evolutionary dynamic system mechanism. The network approach, together with the conventional statistical approach, allows me to understand the unique nature of a digital ecosystem that is different from the boundary of a decomposable system, as the generative nature of system-agnostic digital components builds on a developmental combinable system. I also discuss underlying theory, methodology, data, result, and implications and conclude by highlighting the contributions of this study and the direction of future research to further explore the evolution of digital ecosystems.
Temple University--Theses
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Service, Travis. "Co-optimization: a generalization of coevolution." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Service_09007dcc804e2264.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 26, 2008) Includes bibliographical references (p. 65-68).
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Dobbie, Samuel Thormond. "Ecological perspectives on host-parasite coevolution." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48681/.
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It is a truth universally acknowledged that polymorphism at host immunity loci and corresponding parasite antigenicity loci, maintained by coevolution in pathosystems, is common and can persist for millions of years. Such polymorphisms and how they persist or break down are both fundamentally interesting and important for human health and agriculture. Examples include the major histocompatibility complex in vertebrates and the gene-for-gene (GFG) relationships in plants and their parasites. GFG systems are well-understood genetically and an important source of disease resistance for plant breeders. Therefore considerable effort has gone into studying their evolutionary dynamics in natural pathosystems and modelling the conditions under which long-term polymorphism persists or breaks down. Polymorphism in GFG systems is common and in many cases ancient in wild pathosystems. Conversely, in agriculture the introduction of a resistance gene normally results in the matching parasite avirulence gene rapidly becoming locally extinct. Simple genetic models of GFG coevolution do not produce stable polymorphism. Various more complex models do but are difficult to analyse. Recent work has shown a factor common to stable models is negative direct frequency-dependent selection, so at least one genotype becomes less fit as it grows more common regardless of genotype frequencies in the other species. This selection is not present in simplified models, but is generated in real pathosystems by various ecological and epidemiological factors. Here I expand on previous work by demonstrating that realistic demography, specifically density-dependent regulation of parasite incidence, can generate negatively self-regulating stabilising pressure. This is loosely analogous to negative frequency-dependent selection and, similarly, can stabilise polymorphism in GFG pathosystems. I show this density-dependent regulation can stabilise both non-spatial deterministic and spatial stochastic systems. I also study how this stabilising factor interacts with the complicating biological factors of limited dispersal and resultant spatial structure in populations, variable host density and the presence of a second parasite.
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Yoshida, Takeo, and Peter A. Troch. "Coevolution of volcanic catchments in Japan." COPERNICUS GESELLSCHAFT MBH, 2016. http://hdl.handle.net/10150/617400.
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Present-day landscapes have evolved over time through interactions between the prevailing climates and geological settings. Understanding the linkage between spatial patterns of landforms, soils, and vegetation in landscapes and their hydrological response is critical to make quantitative predictions in ungaged basins. Catchment coevolution is a theoretical framework that seeks to formulate hypotheses about the mechanisms and conditions that determine the historical development of catchments and how such evolution affects their hydrological response. In this study, we selected 14 volcanic catchments of different ages (from 0.225 to 82.2 Ma) in Japan. We derived indices of landscape properties (drainage density and slope–area relationship) as well as hydrological response (annual water balance, baseflow index, and flow–duration curves) and examined their relation with catchment age and climate (through the aridity index). We found a significant correlation between drainage density and baseflow index with age, but not with climate. The intra-annual flow variability was also significantly related to catchments age. Younger catchments tended to have lower peak flows and higher low flows, while older catchments exhibited more flashy runoff. The decrease in baseflow with catchment age is consistent with the existing hypothesis that in volcanic landscapes the major flow pathways change over time from deep groundwater flow to shallow subsurface flow. The drainage density of our catchments decreased with age, contrary to previous findings in a set of similar, but younger volcanic catchments in the Oregon Cascades, in which drainage density increased with age. In that case, older catchments were thought to show more landscape incision due to increasing near-surface lateral flow paths. Our results suggests two competing hypotheses on the evolution of drainage density in mature catchments. One is that as catchments continue to age, the hydrologically active channels retreat because less recharge leads to lower average aquifer levels and less baseflow. The other hypothesis is that the active channels do not undergo much surface dissection after the catchments reach maturity.
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Savel, Daniel M. "Towards a Human Genomic Coevolution Network." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1524241451267546.
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Chen, Kun. "Modeling distributed coevolution : NKP on a cluster /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18941.pdf.
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Liljestrand, Rönn Johanna. "Male-female Coevolution in Bruchid Seed Beetles." Doctoral thesis, Uppsala universitet, Zooekologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-98162.
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Male-female coevolution is at the heart of biology. It is responsible for much of the diversity we see in behaviour and morphology, and it is thought to be an important engine of speciation. The pattern of intersexual coevolution is well established in many taxa, yet understanding of the processes responsible for male-female coevolution remains incomplete. By studying interspecific variation within a closely related group of species, we can gain important information about how traits and behaviours have evolved. In the work done for this thesis, we studied a group of seed beetle species. Our results show that male-female coevolution has been a strong force in shaping both behaviour and morphological traits that are associated with mating and reproduction such as, morphology of male and female genitalia and remating behaviour. The evolution of harmful male genitalia has often been suggested to be a product of sexually antagonistic coevolution, but understanding of these extraordinary adaptations is limited. By combining comparative and experimental methods we show that as seed beetle males evolve more spiny genitalia, harm to females is elevated. We provide evidence for the correlated evolution between these antagonistic adaptations in males, and a female counter adaptation (the amount of connective tissue in the copulatory duct). We also demonstrate that imbalance of relative armament of the sexes affects evolution of the costs and benefits of reproduction. As males evolve genitalia that are more harmful relative to the level of female counteradaptation, costs associated with mating for females increase and population fitness is depressed. Our results unveil a coevolutionary arms race between the sexes and are consistent with a proposed link between sexual conflict, species’ viability and the risk of extinction.
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Best, Alex. "The evolution and coevolution of host defence." Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521900.
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Joshi, Vikas Vasudeo. "The coevolution of technology firms and founders." Thesis, University of Pennsylvania, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10158558.
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Prior research cannot explain the surprising fact that some technology firms attain spectacular growth with seemingly inexperienced founders at the helm. Informed by a cognitivist perspective, prior research in entrepreneurship explores founders' epistemology, such as knowledge and skills, and investigates their interaction with firms to explain their influence on firm growth. This framing misses the reciprocal influence between firm growth and founder development. In contrast, informed by a sociocultural perspective, my research investigates the founder’s ontology and the mutual constitution of the founder and the firm. My research draws on practice theory and uses habitus as a sensitizing concept. I build a theory that explains how the dispositional toolkit of a founder evolves with, and contributes to, firm growth. Based on three in-depth case studies of technology companies, I show how technology firms and their founders coevolved. These firms influenced the development of their founders when they used founders as resources in different aspects of business and placed them in changing relationships with others. In turn, tech founders influenced the growth trajectory of their firms when they performed day-to-day practices of business. My grounded theory suggests that founders and firms coevolve in a mutually constitutive relationship. Firm growth changes the conditions under which business practices occur. The founder develops by becoming the resource the changing contexts demand. Furthermore, a growing firm deposits new dispositions in the founder. In practice, situational cues activate a specific disposition, regulating how the founder improvises. The founder’s improvisation in turn influences firm growth. My study advances entrepreneurship research, accounting for structural influences as well as human agency, thus contributing to a previously missing understanding of the coevolution of founders and firms. My study also contributes to practice by producing insights into founder development and firm growth that are relevant for entrepreneurs, board members, and educators.
Keywords: entrepreneurial learning, entrepreneurship, firm growth, founder development, habitus, high technology venture, leadership, leadership development, organizational development, practice theory, startup.
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Ignazzi, Cosmo Antonio. "Coevolution in the brazilian system of cities." Thesis, Paris 1, 2015. http://www.theses.fr/2015PA010652.
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Cette thèse analyse le système de villes brésilien en se reposant sur une base de données construite en collectant des données démographiques, afin d’étudier l’évolution de la population de l’ensemble des agglomérations brésiliennes depuis le premier recensement de la population en 1872 jusqu’à celui de 2010. Le plus grand pays d’Amérique du Sud, qui a achevé sa transition urbaine lors du siècle dernier, est caractérisé par un contraste majeur entre le grand nombre de petites villes parsemant son territoire immense, et d’immenses aires métropolitaines dominant le système de villes. Des données économiques ont été intégrées à la base de données dans le but de tester la validité des lois d’échelle dans le cas brésilien et effectuer des analyses statistiques robustes afin d’explorer la différenciation fonctionnelle des villes, leur performance économique et le processus d’autocorrélation spatiale qui les caractérisent. Le résultat majeur est la caractérisation de la hiérarchie urbaine brésilienne sur un temps long et la mesure de l’accroissement des inégalités de taille des villes. Par ailleurs, l’intégration de données démographiques et économiques est essentielle à l’identification des imbrications entre population et croissance économiques au sein d’un des pays les plus urbanisés du mondeThis thesis analyses the urban system in Brazil adopting an advanced database that have been constructed collecting demographic data in order to examine the evolution of the population of all Brazilian agglomerations since the first Brazilian official census carried out in 1872 until 2010. The largest country of South America has already completed its urban transition during the last century and is characterised by the contrast between a larger number of small towns througout the immense territory and enormous metropolitan areas dominating the system of cities. Despite its georgraphical and historical peculiarities, this system shares with others in the world the same properties of hierarchical differenciation and urban growth processes (Zipf’s law and Gibrat’smodel)
Esta tese analisa o sistema urbano do Brasil utilizando um banco de dados avançado que foi construído para examinar a evolução populacional de todas as aglomerações brasileiras, desde o primeiro censo oficial realizado em 1872 até 2010. O maior país da América do Sul completou sua transição urbana no século passado. O sistema urbano é caracterizado por um contraste : Por um lado, há um grande número de pequenas cidades distribuídas em todo o território nacional e, por outro lado, existem algumas metrópoles enormes dominando o sistema de cidades. Apesar das peculiaridades geográficas e históricas, este sistema de cidades compartilha características similares a outros sistemas urbanos no mundo, como a mesma propriedade de diferenciação hierárquica e o processo de crescimento urbano (lei de Zipf e modelo de Gibrat). Os dados econômicos relativos aos diferentes parâmetros foram integrados na base de dados com o objetivo de testar a validade da lei de escala e a análise estatística profunda da realidade do país, a fim de explorar a diferenciação funcional das cidades brasileiras, os seus desempenhos econômicos e os processos de autocorrelação espacial que ocorrem entre elas. O resultado mais interessante investigado foi a caracterização da hierarquia urbana brasileira a longo prazo, medindo o crescimento desigual do tamanho das cidades. Além disso, o suporte paralelo de dados demográfico e econômico é essencial para identificar a conexão entre crescimento populacional e econômico em um dos países mais urbanizado do mundo
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Suzuki, Reiji, Masanori Kato, and Takaya Arita. "Cyclic coevolution of cooperative behaviors and network structures." American Physical Society, 2008. http://hdl.handle.net/2237/11274.
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Bloom, Filip. "Competitive Coevolution for micromanagement in StarCraft: Brood War." Thesis, Blekinge Tekniska Högskola, Institutionen för kreativa teknologier, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15377.
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Context. Interest in and research on neural networks and their capacity for finding solutions to nonlinear problems has increased greatly in recent years. Objectives. This thesis attempts to compare competitive coevolution to traditional neuroevolution in the game StarCraft: Brood War. Methods. Implementing and evolving AI-controlled players for the game StarCraft and evaluating their performance. Results. Fitness values and win rates against the default StarCraft AI and between the networks were gathered. Conclusions. The neural networks failed to improve under the given circumstances. The best networks performed on par with the default StarCraft AI.
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Blair, Linsey. "Snail-schistosome interactions : implications for coevolution and control." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409725.
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Craven, Kelly D. "COEVOLUTION AND GENETIC DIVERSITY IN GRASS-ENDOPHYTE SYMBIOSES." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_diss/431.
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Symbioses between cool-season grasses (Subfamily Pooideae) and endophytic fungi in the genera Epichlo and Neotyphodium straddle a continuum of interactions from antagonistic to highly mutualistic. Although these two genera of endophytes are closely related, Neotyphodium endophytes are strictly seed-transmitted and provide many physiological and defensive benefits to their hosts, while Epichlo spp. have an obligately sexual contagious stage wherein host inflorescences are replaced by fungal sexual structures (stromata), effectively sterilizing the plant. Between these two extremes of interactions are Epichlo spp. with a mixed strategy, where some grass tillers are sterilized while others develop normally and yield healthy endophyte-infected seeds. These symbioses offer a unique opportunity to dissect evolutionary mechanisms that may drive movement along this continuum. The research presented characterizes distinct hybridization processes in endophytes and grasses that result in the generation of astounding genetic diversity for the symbiosis. Interspecific hybridization via hyphal anatomosis is a common feature of Neotyphodium endophytes, and may promote mutualism by combining suites of defensive alkaloid genes and ameliorating the adverse evolutionary effects of an asexual lifestyle. My results demonstrate that several genetically distinct hybrid endophytes infect grass species in tribe Poeae. Further, I show that a highly mutualistic asexual endophyte infecting tall fescue (=Festuca arundinaceum Schreb.), Neotyphodium coenophialum, also infects two closely related and interfertile relatives of this host. My findings suggest that this seed-borne endophyte may have been introgressed into these grasses through sexual grass hybridization events. These findings highlight interspecific hybridization as a means of generating tremendous genetic variability in both endophytes and their hosts, thus magnifying the adaptive evolutionary potential of these symbioses. Further, I establish a phylogenetic framework for grasses naturally harboring Epichlo and Neotyphodium endophytes. I show that patterns of genetic divergence among grass lineages are emulated by those of their fungal symbionts. These results suggest that endophytes have co-evolved with grasses in subfamily Pooideae, and may have played a critical role in the evolutionary success and radiation of this group of grasses.
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Fazakerley, Claire. "Molecular coevolution between developmental genes in insect species." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/34410.
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Changes in the regulatory sequences of the genes involved in development are thought to be important in the evolution of morphology. However, molecular coevolution between functionally interacting genetic elements allows sequence divergence to be tolerated whilst the functional interaction is maintained. Molecular coevolution can lead to species-specificity in the sequence basis underlying molecular interactions. The concentration-dependent activation of hunchback (hb) expression in the anterior half of the Drosophila melanogaster embryo by the gradient of bicoid (bcd) protein represents a primary step in the elaboration of pattern along the anterior- posterior axis, and this interaction is conserved in the housefly, Musca domestica. In order to investigate the possibility that the molecular basis of this interaction may have coevolved, the bed and hb genes have been partially sequenced from M. domestica and compared to those of D. melanogaster. Analysis of the putative M. domestica hb regulatory region identified three candidate bed binding sites, with a consensus sequence of TTTAATCC, rather than the TCTAATCC of D. melanogaster. Comparison of the bed sequences revealed 5 changes within the 60 amino acids of the homedomain. Hence, it is possible that M. domestica bcd may have a subtly altered binding specificity, pointing towards the possibility that the coordinated changes in the binding site sequences have elicited compensatory changes in the M. domestica bed homeodomain. Preliminary analyses have been made of the functional significances of the observed differences. Although the functional significance of the observed differences in the bed and hb genes is not fully understood, the possibility remains that the molecular nature of the interaction between bed and hb has diverged between M. domestica and D. melanogaster.
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Mcclean, Luke Alexander. "Coevolution between brood-parasitic honeyguides and their hosts." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/32856.
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Obligate brood parasites lay their eggs in the nests of other species, foisting the costs of parental care onto the host parents. The success of the parasite and host are then at odds, with both parties evolving defences and countermeasures in an evolutionary arms race. This reciprocal influence of acting upon both species' evolution — a process known as coevolution — has forged the natural world around us. Avian brood parasites and their hosts are now model systems for studying such coevolutionary interactions between species, providing striking examples of the adaptations that arise when the life histories of two species become entangled. In this thesis I highlight the adaptations that have arisen in response to coevolutionary selection pressures in a group of understudied avian brood parasites, the honeyguides (Indicatoridae), and their hosts. This study focuses on the greater (Indicator indicator) and lesser (I. minor) honeyguides, and their respective primary hosts, the little bee-eater (Merops pusillus) and the black-collared barbet (Lybius torquatus). The interactions between honeyguides and their cavity-nesting hosts of the Old World tropics are evolutionarily ancient, contrasting with the majority of studies of avian brood parasitism which have predominantly focused on temperate brood-parasitic species targeting open cup-nesting hosts. Therefore, honeyguides and their hosts are an ideal study system in which look for novel adaptations that have not evolved in other systems. Using field observations and experimental manipulations at each stage of the parasitic life cycle — before parasitism, during egg-laying, during incubation, and during chickrearing — I examine how honeyguides and their hosts have evolved in response to the selection pressures they exert on each other. First, in chapter two, I consider whether the nest structure of the little bee-eater – host to the greater honeyguide – can act as a defence against brood parasitism. Experimental manipulation of the size of bee-eater nest tunnels demonstrates that bee-eaters with narrower nest tunnels are less likely to be parasitized by greater honeyguides than those bee-eaters whose nests have wider nest tunnel entrances. This study provides the first experimental evidence of a host nest functioning as a frontline defence against brood parasitism. In chapter three, I take a comparative approach and use a phylogenetic framework to investigate, across multiple avian brood parasite species, the evolutionary drivers of rapid egglaying. This trait is shared by most brood-parasitic birds, but not by non-parasitic birds. I find strong evidence that the egg-laying speed of avian brood parasites is ecologically and physiologically constrained, but find no evidence that variation in the costs incurred duringparasitism events have driven variation in the rapidity of egg-laying among brood-parasitic species. In chapter four, I examine whether there are costs associated with the virulent egg puncturing behaviour of greater honeyguides, and whether honeyguides can adjust their level of virulence in accordance with these costs. I find strong support for the idea that virulence is costly to honeyguides, as bee-eater hosts are more likely to reject clutches that contained eggs punctured by honeyguides. Such punctured clutches are also more likely to be predated. Honeyguides appear to adjust how much they puncture host eggs in accordance with the severity of these costs, providing the first evidence of an avian brood parasite moderating its virulence in response to the associated costs. In chapter five, I examine egg rejection behaviour in the black-collared barbet, a common host of the lesser honeyguide. I consider whether the (smaller) size of a parasitic egg could be used as a cue for egg rejection inside the dark environment of a cavity nest. Through observations of natural parasitism events, and experimental parasitism of host nests using different sized eggs, I demonstrate that barbets are more likely to reject a clutch of eggs when they detect a small egg within the nest. This seems to be achieved through a process of true recognition, a mechanism that involves a specific innate or learnt template of what size eggs a host should reject. Barbets do not appear to rely on discordancy – comparing all eggs within their clutch in order to reject the odd one out – in order to make rejection decisions. Finally, in chapter six I explore whether honeyguides elicit additional provisioning from their foster parents by using vocal mimicry, and investigate why such extra food would be required. I demonstrate that both greater and lesser honeyguides mimic the sound of a brood of chicks of their respective hosts in order to receive higher levels of provisioning from their foster parents. I establish that greater and lesser honeyguides do this for contrasting reasons. Greater honeyguides require higher levels of provisioning to support their fast growth rate to a size much larger than their host siblings, whereas lesser honeyguides require more food in order to offset a sub-optimal diet provided to them by their foster parents.
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Quque, Martin. "Coevolution of sociality and ageing in animal societies." Doctoral thesis, Universite Libre de Bruxelles, 2020. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/316028.
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In order to improve our knowledge of the mechanisms of ageing in animals, the main objective of the thesis was to understand the modulation of such mechanisms by the individual social role, within different social organisations. This objective thus addresses two main questions: i) describing the covariation of the degree of social complexity with ageing patterns; ii) highlighting the underlying cellular and molecular processes. Thanks to complementary and diversified studies (behavioural observations, dosage of the oxidative balance, qPCR measurement of telomere length, proteomics, metabolomics), the present thesis showed that sociality plays a role on ageing at many levels. In the zebra finch, social stress caused by aggression of the conspecifics induces oxidative stress and reduces telomere length in adults. In the sociable weaver, the social environment is of crucial importance during pre- and post-hatch development on the medium term survival of the chicks. Finally, in ants, we were able to show a positive relationship between the degree of sociality and maximum potential life span: this link was caste specific, being only significant for the most social queens. This is inline with a recent review by Lucas and Keller (2020) which concluded that the benefits of sociality are most sensitive for high levels of sociality and particularly in reproductive individuals. With regard to the molecular mechanisms of ageing,we were able to establish a causal chain between social stress, oxidative response and telomere erosion in zebra finches.The role of telomeres as a predictor of offspring survival has been confirmed (over at least 5 years) in the sociable weaver,a cooperative breeder bird. However, this link was not true in queen ants where the longest lived were those with the shortest telomeres. The co-evolution of anti-cancer mechanisms and longevity seems to be conserved since similar strategies are found in taxa as diverse as ants and rodents. On the other hand, and contrary to previous studies conducted on ants, we found that oxidative stress might be a marker of individual ageing. We suggest that the proxies of oxidative stress used so far in ants have been misleading or at least incomplete. Thus, understanding the physiological ageing particularities of ants and other social insects might require finding new relevant and specific markers. Finally, the sirtuins and mTOR signalling pathways, key precursors of which we have detected in ants, are molecular crossroads capable of activating or inhibiting cellular metabolism depending on the cell energy state. According to the studies carried out to date, these signalling pathways are among the first to be able to slow down the effects of ageing and extend life expectancy.However, specific studies need to be carried out to understand their fine regulation and thus assess the universality of these mechanisms in animal ageing. Based on our findings, we propose three points to be further addressed to better understand the mechanisms of ageing in social insects: i) the setup of experiments testing the effectiveness of energy trade-offs involving immunity or digestion metabolism; ii) measuring the telomerase activity among castes of various species in order to explore the telomere and telomere independent roles played by this enzyme in ageing; iii) the need to think about individual longitudinal follow-up and to study wild populations, after the first necessary stages in laboratory.Doctorat en Sciences
Un résumé grand public en français est disponible au début du manuscrit, juste après les remerciements.
info:eu-repo/semantics/nonPublished
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Glorieux, Emile. "Constructive cooperative coevolution for optimising interacting production stations." Licentiate thesis, Högskolan Väst, Avd för automationssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-7685.
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Engineering problems have characteristics such as a large number of variables, non-linear, computationally expensive, complex and black-box (i.e. unknown internal structure). These characteristics prompt difficulties for existing optimisation techniques. A consequence of this is that the required optimisation time rapidly increases beyond what is practical. There is a needfor dedicated techniques to exploit the power of mathematical optimisation tosolve engineering problems. The objective of this thesis is to investigate thisneed within the field of automation, specifically for control optimisation ofautomated systems.The thesis proposes an optimisation algorithm for optimising the controlof automated interacting production stations (i.e. independent stations thatinteract by for example material handling robots). The objective of the optimisation is to increase the production rate of such systems. The non-separable nature of these problems due to the interactions, makes them hard to optimise.The proposed algorithm is called the Constructive Cooperative CoevolutionAlgorithm (C3). The thesis presents the experimental evaluation of C3, bothon theoretical and real-world problems. For the theoretical problems, C3 istested on a set of standard benchmark functions. The performance, robustness and convergence speed of C3 is compared with the algorithms. This shows that C3 is a competitive optimisation algorithm for large-scale non-separable problems.C3 is also evaluated on real-world industrial problems, concerning thecontrol of interacting production stations, and compared with other optimisation algorithms on these problems. This shows that C3 is very well-suited for these problems. The importance of considering the energy consumption and equipment wear, next to the production rate, in the objective function is also investigated. This shows that it is crucial that these are considered to optimise the overall performance of interacting production stations.
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Baker, Frazier N. "Mining and Visualization of Amino Acid Coevolution Data." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1571061614939124.
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Hamerlinck, Gabriela. "Coevolution of Rhagoletis hosts and their parasitic wasps." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1849.
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Phytophagous (plant-feeding) insects are extremely species-rich and typically display tight host associations (meeting and mating on or near their host plant) with one or a small number of hosts. This specialized lifestyle can promote diversification through assortative mating, ultimately leading to genetically differentiated host races (host associated differentiation; HAD). It has been shown that HAD can cascade up to the parasitic wasps (parasitoids) that utilize the phytophagous insects as hosts. Cascading HAD occurs when there is genetic differentiation among parasitoids as a result of differential host plant use by their host insects. Thus, host switching can promote parasitoid diversification as well.
Here, I present three studies designed to help understand aspects of parasitoid shifts to novel hosts and environments. All of the studies in this dissertation utilize the Rhagoletis complex of flies and their associated parasitoids. Specifically, I address i) the role of subtle trait variation and environmental context in predicting successful parasitoid host shifts; ii) whether parasitoid host discrimination (a trait that can influence host shifts) is an innate or learned behavior; and iii) whether contemporary patterns of host shifts among parasitoids are echoed by historical host shifts in cophylogenetic analyses of host and parasitoid genera?
Towards my first aim, I present a phenomenological model developed to predict successful host shifts by parasitoids. The simulations of the model explore how environmentally mediated traits can affect successful parasitoid colonization of a new host. For my second aim, I hypothesize that behaviors impacting parasitoid host plant preferences host shifts will be genetically based rather than a learned behavior. Shifting to a new host plant has been shown to cause reproductive isolation in phytophagous insects because of strong fidelity with their host plant. Parasitoids, however, have no direct contact with the host plant as they develop entirely within the host insect. The differences in life history traits could result parasitoid host shifts being driven by random changes in host preferences. I present preliminary results suggesting that parasitoids preferentially respond to their ancestral host plant’s olfactory cues, suggesting that host preferences have a genetic basis. Finally, I present a cophylogenetic analysis of Rhagoletis hosts and their parasitoids. I find that cospeciation is the most common coevolutionary event, although there is evidence of recent host shifting that contributes to current parasitoid species diversity. The results of these studies can help us understand how host shifts can act as a potential mechanism driving diversification in parasitoids.
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Stenberg, Christofer. "Co-evolving niches in virtual Plant species : Exploring the niche forming capabilities of coevolving plants in a virtual environment." Thesis, Högskolan i Skövde, Institutionen för kommunikation och information, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-6379.
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Smart, Lesley. "Asymmetric interactions between ants, aphids and plants." Thesis, University of Bath, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292848.
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Sandberg, Johan. "Digital Capability : Investigating Coevolution of IT and Business Strategies." Doctoral thesis, Umeå universitet, Institutionen för informatik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-88722.
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This dissertation investigates the role of information technology (IT) in organizational strategy. Specifically, it examines how organizations can persist in turbulent competitive landscapes characterized by IT innovations. Underlying premises for this dissertation are that: (1) ubiquitous IT implies constant disruptions from digital innovation, (2) IT and practice are becoming fused, and (3) organizational strategies are dynamically linked with practice, i.e. they are reciprocally related through what organizations do rather than have. To investigate such IT strategizing processes, I outline a conceptual framework for analyzing how organizations can generate digital capability, i.e. a collection of routines for strategizing by leveraging digital assets to create differential value. Digital assets here refer to the complement of available resources and competencies for IT design and implementation. Based on the notion of dynamic capability and evolutionary theory, this framework emphasizes the importance of sensing, seizing and transforming abilities for generating digital capability. As organizational practices are becoming fused with IT scholars have argued that attempting to disentangle them analytically is futile. In a similar vein, organizational strategy is increasingly reliant on available IT resources for both formulation and execution. In the IS field it is widely acknowledged that IT has both enabling and inhibiting consequences for organizations. Drawing on the resource-based view of the firm and theory on organizational capabilities, the notion of IT capability has been widely used as a conceptual tool for analyzing these dual strategic effects of IT. Considering the explosive advances in computing, network and interaction that have resulted in IT being ubiquitous and deeply embedded in contemporary practices, recent research argues for the need to move beyond the functional view of technology implicit in the IT capability notion. A key aspect to address for such broadening of the perspective is the coevolution of IT and business practices, i.e. who (or what) leads, who or what follows, and whether such a causal distinction is meaningful. Grounded in the outlined conceptual framework, this dissertation examines how organizations can build digital capability to both enable large variation and complexity of feasible competitive actions, and reduce inhibiting effects of IT. The empirical investigation is situated in three distinct domains: boundary spanning IT innovation, transformation of existing IT resources, and hybridization of technology through digitalization of production equipment. These investigations are presented in five research papers. The dissertation contribute to knowledge of IT strategy by: (1) explicating the construct of digital capability, (2) providing a framework for coevolutionary strategizing processes, (3) presenting an empirical illustration of the coevolution of IT and business strategies, and (4) offer specific insights on design and orchestration of processes for digital capability generation.
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Dimitriu, Tatiana. "The coevolution of gene mobility and sociality in bacteria." Phd thesis, Université René Descartes - Paris V, 2014. http://tel.archives-ouvertes.fr/tel-00993436.
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Bacteria are social organisms which participate in multiple cooperative and group behaviours. They moreover have peculiar genetic systems, as they often bear mobile genetic elements like plasmids, molecular symbionts that are the cause of widespread horizontal gene transfer and play a large role in bacterial evolution. Both cooperation and horizontal transfer have consequences for human health: cooperative behaviours are very often involved in the virulence of pathogens, and horizontal gene transfer leads to the spread of antibiotic resistance. The evolution of plasmid transfer has mainly been analyzed in terms of infectious benefits for selfish mobile elements. However, chromosomal genes can also modulate horizontal transfer. A huge diversity in transfer rates is observed among bacterial isolates, suggesting a complex co-evolution between plasmids and hosts. Moreover, plasmids are enriched in genes involved in social behaviours, and so could play a key role in bacterial cooperative behaviours. We study here the coevolution of gene mobility and sociality in bacteria. To investigate the selective pressures acting on plasmid transfer and public good production, we use both mathematical modelling and a synthetic system that we constructed where we can independently control public good cooperation and plasmid conjugation in Escherichia coli. We first show experimentally that horizontal transfer allows the specific maintenance of public good alleles in a structured population by increasing relatedness at the gene-level. We further demonstrate experimentally and theoretically that this in turn allows for second-order selection of transfer ability: when cooperation is needed, alleles promoting donor and recipient abilities for public good traits can be selected both on the plasmid and on the chromosome in structured populations. Moreover, donor ability for private good traits can also be selected on the chromosome, provided that transfer happens towards kin. The interactions between transfer and cooperation can finally lead to an association between transfer and public good production alleles, explaining the high frequency of genes related to cooperation that are located on plasmids. Globally, these results provide insight into the mechanisms maintaining cooperation in bacteria, and may suggest ways to target cooperative virulence.
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Kirby, Kris Thomas. "Coevolution and costly resistance in an insect-virus system." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417751.
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Green, Jennifer Elaine. "Coevolution of plasmids and host bacteria in lakewater sediments." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414854.
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SIMAO, LEONARDO MENDES. "REFINERY SCHEDULING OPTIMIZATION USING GENETIC ALGORITHMS AND COOPERATIVE COEVOLUTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5969@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEsta dissertação investiga a aplicação de Algoritmos Genéticos e de Co-Evolução Cooperativa na otimização da programação da produção em refinarias de petróleo. Refinarias de petróleo constituem um dos mais importantes exemplos de plantas contínuas multiproduto, isto é, um sistema de processamento contínuo gerador de múltiplos produtos simultâneos. Uma refinaria, em geral, processa um ou mais tipos de petróleo, produzindo uma série de produtos derivados, como o GLP (gás liquefeito de petróleo), a nafta, o querosene e o óleo diesel. Trata- se de um problema complexo de otimização, devido ao número e diversidade de atividades existentes e diferentes objetivos. Além disso, neste problema, algumas atividades dependem de que outras atividades já tenham sido planejadas para que possam então ser planejadas. Um caso típico é o das retiradas de produtos de uma unidade de processo, que dependem de que a carga já tenha sido planejada, assim como em qual campanha a unidade estará naquele instante. Por isso, o uso de modelos revolucionários convencionais, como os baseados em ordem, pode gerar muitas soluções inválidas, que deverão ser posteriormente corrigidas ou descartadas, comprometendo o desempenho e a viabilidade do algoritmo. O objetivo do trabalho foi, então, desenvolver um modelo evolucionário para otimizar a programação da produção (scheduling), segundo objetivos bem definidos, capaz de lidar com as restrições do problema, gerando apenas soluções viáveis. O trabalho consistiu em três etapas principais: um estudo sobre o refino de petróleo e a programação da produção em refinarias; a definição de um modelo usando algoritmos genéticos e co-evolução cooperativa para otimização da programação da produção e a implementação de uma ferramenta para estudo de caso. O estudo sobre o refino e a programação da produção envolveu o levantamento das várias etapas do processamento do petróleo em uma refinaria, desde o seu recebimento, destilação e transformação em diversos produtos acabados, que são então enviados a seus respectivos destinos. Neste estudo, também foi levantada a estrutura de tomada de decisão em uma refinaria e seus vários níveis, diferenciando os objetivos destes níveis e explicitando o papel da programação da produção nesta estrutura. A partir daí, foram estudadas em detalhes todas as atividades que normalmente ocorrem na refinaria e que são definidas na programação, e seus papéis na produção da refinaria. A decisão de quando e com que recursos executar estas atividades é o resultado final da programação e, portanto, a saída principal do algoritmo. A modelagem do algoritmo genético consistiu inicialmente em um estudo de representações utilizadas para problemas de scheduling. O modelo coevolucionário adotado considera a decomposição do problema em duas partes e,portanto, emprega duas populações com responsabilidades diferentes: uma é responsável por indicar quando uma atividade deve ser planejada e a outra é responsável por indicar com quais recursos essa mesma atividade deve ser realizada. A primeira população teve sua representação baseada em um modelo usado para problemas do tipo Dial-A-Ride (Moon et al, 2002), que utiliza um grafo para indicar à função de avaliação a ordem na qual o planejamento deve ser construído. Esta representação foi elaborada desta forma para que fosse levada em conta a existência de restrições de precedência (atividades que devem ser planejadas antes de outras), e assim não fossem geradas soluções inválidas pelo algoritmo. A segunda população, que se responsabiliza pela alocação dos recursos para a execução das atividades, conta com uma representação onde os operadores genéticos podem atuar na ordem de escolha dos recursos que podem realizar cada uma das atividades. Finalmente, des
This work investigates the use of Genetic Algorithms and Cooperative Coevolution in refinery scheduling optimization. Oil refineries are one of the most important examples of multiproduct continuous plants, that is, a continuous processing system that generates a number of products simultaneously. A refinery processes various crude oil types and produces a wide range of products, including LPG (liquefied petroleum gas), gasoline, kerosene and diesel. It is a complex optimization problem, mainly due to the number of different tasks involved and different objective criteria. In addition, some of the tasks have precedence constraints that require other tasks to be scheduled first. For example, in order to schedule a task that transfers one of the yields of a certain crude distillation unit, both the task that feeds the crude oil into the unit and the task that sets the unit`s current operation mode must already be scheduled. Therefore, applying traditional evolutionary models, like the order- based ones, can create many infeasible solutions that will have to be corrected or rejected later on, thereby jeopardizing the algorithm performance and feasibility. The main goal was the development an evolutionary model satisfying well-defined objectives, which would optimize production scheduling and address the various constraints entailed in the problem, thus generating only feasible solutions. This work consisted on three main steps: a survey on crude oil refining and refinery scheduling; the development of a cooperative coevolutionary model to optimize the refinery scheduling and the development of a software tool for case studies. The study about refining and scheduling involved gathering information about the existent processes in a refinery, starting from the arrival of crude oil, its distillation and transformation into several products and, finally, the delivery of these products to their respective destination. The levels of decision making in a refinery were surveyed too, in order to identify the main goals for each one, and how the scheduling level fits into the structure as whole. Then, all the routine scheduling tasks and their roles in a refinery were carefully studied. The decision of when and how to assign those tasks is the final output of the scheduling task, so it must be the main output of the algorithm too. The development of the evolutionary model consisted of a survey on some of the most common evolutionary approaches to scheduling. The adopted coevolutionary model breaks the problem down into two parts, thus using two species with different responsibilities: One is responsible for deciding when a task should be scheduled, while the other is responsible for assigning a resource for this task. The first species representation was based on a model used for the Dial-a- Ride (Moon et al, 2002) kind of problems, and uses a graph to help the fitness evaluation function find the right order in which to schedule the tasks. This representation was devised in such a way that the precedence constraints were satisfied and no infeasible solutions were generated. The representation of the second species, which assigns resources for the tasks, let genetic operators change the selection order when picking a resource for a task. Finally, a software tool was developed to be used for implement this model and for performing a case study. This case study should comprise all the needed characteristics, in order to test the quality of the representation as well as evaluate the results. A simple refinery was designed, containing all equipment types, tasks and constraints found in a real-world refinery. The constraints mentioned are the precedence constraints, handled by the graph used by the first species, plus other operational constraints found in refinery scheduling. It was possible, then, to see the decoding of chromosomes into feasible solutions, always satisfying all the constraints. Several tests
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Medeiros, Lucas Paoliello de. "Coevolution in mutualistic networks: gene flow and selection mosaics." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/41/41134/tde-17102017-154829/.
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Ecological interactions such as predation, competition, and mutualism are important forces that influence species evolution. Coevolution is defined as reciprocal evolutionary change in interacting species. The Geographic Mosaic Theory of Coevolution (GMTC) provides a theoretical framework to explain how collections of populations should coevolve across space. Two fundamental aspects of the GMTC are gene flow among populations and the presence of selection mosaics, which are collections of localities with particular selection regimes. Several studies have explored how phenotypic trait matching between species evolves in pairs or small groups of species. However, ecological interactions frequently form large networks that connect dozens of species present in a given community. In networks of mutualisms, for instance, the organization of interactions may affect ecological and evolutionary processes. A next step in understanding the coevolutionary process is to investigate how aspects of the GMTC affect the evolution of species embedded in interaction networks. In this dissertation, we tried to fill this gap using a mathematical model of coevolution, complex networks tools, and information on empirical mutualistic networks. Our numerical simulations of the coevolutionary model allow us to draw three main conclusions. First, gene flow affects trait patterns generated by coevolution and may favor the emergence of trait matching depending on the selection mosaic. Second, the organization of mutualistic networks influences coevolution, but this effect may vanish when gene flow favors trait matching. Intimate mutualisms, such as protection of host plants by ants, form small and compartmentalized networks that generate higher trait matching than large and nested networks typical of mutualisms among free-living species, such as pollination. Third, habitat fragmentation resulting in the disruption of gene flow should reduce the reciprocal adaptations between interacting species and at the same time promote adaptations to the local abiotic environment. In conclusion, we show that a complex interplay between gene flow, the geographic structure of selection, and the organization of ecological networks shapes the evolution of large groups of species. Our results therefore allow predictions of how environmental impacts such as habitat fragmentation will modify the evolution of species interactionsInterações ecológicas como predação, competição e mutualismo são importantes forças que influenciam a evolução de espécies. Chamamos de coevolução a mudança evolutiva recíproca em espécies que interagem. A Teoria do Mosaico Geográfico da Coevolução (TMGC) fornece um arcabouço teórico para entender como conjuntos de populações coevoluem ao longo do espaço. Dois aspectos fundamentais da TMGC são o fluxo gênico entre populações e a presença de mosaicos de seleção, isto é, conjuntos de locais com regimes de seleção particulares. Diversos estudos exploraram como o acoplamento entre fenótipos de diferentes espécies evolui em pares ou pequenos grupos de espécies. Entretanto, interações ecológicas frequentemente formam grandes redes que conectam dezenas de espécies presentes em uma comunidade. Em redes de mutualismos, por exemplo, a organização das interações pode influenciar processos ecológicos e evolutivos. Um próximo passo para a compreensão do processo coevolutivo consiste em investigar como aspectos da TMGC influenciam a evolução de espécies em redes de interações. Nesta dissertação, tentamos preencher esta lacuna usando um modelo matemático de coevolução, ferramentas de redes complexas e informação sobre redes mutualistas empíricas. Nossas simulações numéricas do modelo coevolutivo apontam para três principais conclusões. Primeiro, o fluxo gênico influencia os padrões fenotípicos gerados por coevolução e pode favorecer a emergência de acoplamento fenotípico entre espécies dependendo do mosaico de seleção. Segundo, a organização de redes mutualistas influencia a coevolução, mas este efeito pode desaparecer quando o fluxo gênico favorece acoplamento fenotípico. Mutualismos íntimos, como proteção de plantas hospedeiras por formigas, formam redes pequenas e compartimentalizadas que geram um maior acoplamento fenotípico do que as redes grandes e aninhadas típicas de mutualismos entre espécies de vida livre, como polinização. Por fim, a fragmentação de habitat, ao extinguir o fluxo gênico, pode reduzir as adaptações recíprocas entre espécies e ao mesmo tempo tornar cada espécie mais adaptada ao seu ambiente abiótico local. Em suma, mostramos que interações complexas entre fluxo gênico, estrutura geográfica da seleção e organização de redes ecológicas moldam a evolução de grandes grupos de espécies. Dessa forma, podemos traçar previsões sobre como impactos ambientais como a fragmentação de habitat irão alterar a evolução de interações ecológicas
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Baer, Kimberly Kay. "Protein Coevolution and Coadaptation in the Vertebrate bc1 Complex." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1994.pdf.
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Hoso, Masaki. "Handedness coevolution : predator-prey interaction drives speciation in snails." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136933.
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Friberg, Urban. "Sexual conflict and male-female coevolution in the fruit fly." Doctoral thesis, Umeå : Department of Ecology and Environmental Science, Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-735.
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Jackson, Andrew. "The application of phylogenetic reconciliation to the study of coevolution." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403742.
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Stapley, Linsey Anne. "The coevolution of ants and Acacia trees in East Africa." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624422.
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Nooney, Colleen. "Statistical analysis of coevolution in protein structure and in ecology." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/16337/.
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In this thesis we explore the theory of coevolution. Yip et al. (2008) define coevolution to be the change in one biological object as a result of the change in one or more associated objects. The process of coevolution has been observed at many biological levels; from microscopic to macroscopic. We explore coevolution at the molecular level by studying protein sequences and their corresponding structures to determine how correlated areas of multiple sequence alignments and structures have coevolved. At the species level, we assess how coevolution drives ecological systems of interacting phylogenetic trees. Determining the three-dimensional structure of proteins is of interest because the structure of a protein is constrained by its function. Proteins carry out vital functions in every cell and are arguably the most important biological molecule found in organisms. Multiple sequence alignments of protein families contain evolutionary information on these functional constraints. In the first part of this thesis, we aim to develop a method to identify correlated mutations within multiple sequence alignments. These correlated positions are used to predict residues that are in close proximity in three-dimensional space. In turn these structural constraints can be used in ab initio protein structure prediction. Currently the most accurate way to determine protein structure is using experimental techniques such as Nuclear Magnetic Resonance (NMR) and X-ray Crystallography. These techniques are expensive and take time. As a result, the proteins that are chosen to have their structures determined may be subject to selection bias. Initially, we focus on a preliminary analysis of the trypsin protein family. We align trypsin structures from a variety of species using a multiple structural alignment algorithm, to determine how the structure of the family has evolved. Basic summary statistics of the aligned distance matrices reveal a set of residues where the distance between these specific residues and every other residue in the structure is highly conserved across all of the structures in the protein family. We label these residues as ‘anchor residues’ because they appear to hold the structure of the trypsin protein family in place like anchors. Following this, we develop a regularised logistic regression model to detect correlated mutations in multiple sequence alignments. We successfully apply our method to a number of small artificial test alignments. When applied to real Pfam datasets, our method has varying success at identifying coevolving columns that are close in physical proximity. In the second part of this thesis we develop a new method to test efficiently for cospeciation in multitrophic ecological systems. Our method can be applied to bitrophic and tritrophic systems, with the potential to generalise to higher order systems and networks. We utilise methods from electrical circuit theory to reduce higher order systems into two vectors of electrically equivalent patristic distances that can be compared using Spearman’s rank correlation coefficient. Compared to existing methods, our method has equal or higher performance at both trophic levels. To test our method, interacting systems of phylogenetic trees were simulated by generating random trees, and separately, their interaction matrices. Simulating the systems in this way does not take into account how the systems might have evolved. We propose a more realistic simulation method that evolves over time. The algorithm starts with one species per lineage, that are assumed to have an ecological interaction. The joint evolution of these species is simulated by sampling the time at which evolutionary events occur from an exponential distribution. We explore speciation events, and gaining and losing ecological interactions. Each of these events are controlled by rate parameters. By experimenting with these parameters, a wide range of systems with different cospeciation properties can be simulated. We show that a wide range of systems that can be produced using our method.
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Aversa, Rossella. "Coevolution of supermassive Black Holes and Galaxies across cosmic times." Doctoral thesis, SISSA, 2015. http://hdl.handle.net/20.500.11767/4852.
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Understanding how supermassive black holes (SMBHs) and galaxies coevolve within their host dark matter (DM) halos is a fundamental issue in astrophysics. This thesis is aimed to shed light on this topic. As a rst step, we employ the recent wide samples of far-infrared (FIR) selected galaxies followed-up in X-rays, and of X-ray/optically selected active galactic nuclei (AGNs) followed-up in the FIR band, along with the classic data on AGN and stellar luminosity functions at redshift z & 1:5, to probe different stages in the coevolution of SMBHs and their host galaxies. The results of this analysis indicate the following scenario: (i) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium, at an almost constant rate, over a timescale . 0:5 1 Gyr, and then abruptly declines due to quasar feedback; (ii) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions, at a rate proportional to the star formation, and is temporarily stored into a massive reservoir/proto-torus, wherefrom it can be promptly accreted; (iii) the black hole (BH) grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit (L=LEdd . 4), particularly at the highest redshifts; (iv) the ensuing energy feedback from massive BHs, at its maximum, exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (v) afterwards, if the gas stored in the reservoir is enough, a phase of supply-limited accretion follows, whose rate exponentially declines with a timescale of 3 e-folding times. We also discuss how the detailed properties and the speci c evolution of the reservoir can be investigated via coordinated, high-resolution observations of starforming, strongly lensed galaxies in the (sub-)mm band with ALMA, and in the X-ray band with Chandra and the next generation of X-ray instruments. According to the scenario described above, we further investigate the coevolution of galaxies and hosted SMBHs throughout the history of the Universe by applying a statis- tical, model-independent approach, based on the continuity equation and the abundance matching technique. We present analytical solutions of the continuity equation with- out source term, to reconstruct the SMBH mass function (BHMF) at different redshifts from the AGN luminosity function. Such an approach includes the physically-motivated AGN lightcurves we have tested and discussed, which describe the evolution of both the Eddington ratio and the radiative efficiency from slim- to thin-disc conditions. We nicely reproduce the local estimates of the BHMF, the AGN duty cycle as a function of mass and redshift, along with the Eddington ratio function and the fraction of galaxies hosting an AGN with given Eddington ratio. We employ the same approach to reconstruct the observed stellar mass function (SMF) at different redshifts, starting from the ultraviolet (UV) and FIR luminosity functions associated to star formation in galaxies. Our results imply that the buildup of stars and BHs in galaxies occurs via in-situ processes, with dry mergers playing a marginal role, at least for stellar masses . 3 1011M⊙ and BH masses . 109M⊙, where the statistical data are more secure and less biased by systematic errors. In addition, we develop an improved abundance matching technique, to link the stellar and BH content of galaxies to the gravitationally dominant DM component. The re- sulting relationships constitute a testbed for galaxy evolution models, highlighting the complementary role of stellar and AGN feedback in the star formation process. They may also be operationally implemented in numerical simulations to populate DM ha- los, or to gauge subgrid physics. Moreover, they can be exploited to investigate the galaxy/AGN clustering as a function of redshift, stellar/BH mass, and/or luminosity. The clustering properties of BHs and galaxies are found to be in full agreement with current observations, so further validating our results from the continuity equation. Finally, our analysis highlights that: (i) the fraction of AGNs observed in the slim-disc regime, where anyway most of the BH mass is accreted, increases with redshift; (ii) already at z & 6, a substantial amount of dust must have formed, over timescales . 108 yr, in strongly starforming galaxies, making these sources well within the reach of ALMA surveys in (sub-)millimeter bands.
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Betts, Alexander. "The effects of parasite diversity on eco-evolutionary dynamics." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:219e3908-94bb-4fec-897f-cf918cdb37f8.
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Virtually all interacting species (such as hosts and parasites) are embedded within diverse communities. However, evolutionary interactions are typically considered in a pairwise species framework. Although coevolutionary theory suggests that multiple species interactions may provide greater opportunities for diversification, the impacts of community diversity on coevolution have not been directly tested. In this thesis I synthesize the findings from recent experimental work to assess the effects of increased species diversity on the patterns and processes of host and parasite evolution. I then investigate the effects of parasite diversity on host-parasite population dynamics and evolution using the pathogen Pseudomonas aeruginosa and five lytic bacteriophage parasites in a brief evolution experiment. Parasite diversity was manipulated by assembling phage communities with different number of species. Phage communities suppressed host populations more rapidly but also showed reduced phage density, likely due to inter-phage competition. The evolution of resistance allowed rapid bacterial recovery that was greater in magnitude with increases in phage diversity. These results were then followed up via longer term experimental coevolution of the same host and parasite communities. Here the data showed that greater parasite diversity accelerates coevolutionary arms races and drives more diversification among lineages. Coevolution between hosts and parasite communities drove more successive increases in host resistance coupled with increasingly frequent selective sweeps at the genomic level. Consistent with this, the most rapidly evolving host genes under coevolution with parasite communities were those involved in various host resistance strategies. These results demonstrate, at phenotypic and genomic levels, how areas of high community diversity may be hotspots for rapid evolution in interacting, antagonistic species. Finally, In the face of escalating antibiotic resistance, there is now an urgent need to develop alternative antimicrobials, these results may be relevant to the application of phages as therapeutics and they are discussed in that context.
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Pamuk, Bahar. "Coevolution Based Prediction Of Protein-protein Interactions With Reduced Training Data." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610389/index.pdf.
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Protein-protein interactions are important for the prediction of protein functions since two interacting proteins usually have similar functions in a cell. Available protein interaction networks are incompletebut, they can be used to predict new interactions in a supervised learning framework. However, in the case that the known protein network includes large number of protein pairs, the training time of the machine learning algorithm becomes quite long. In this thesis work, our aim is to predict protein-protein interactions with a known portion of the interaction network. We used Support Vector Machines (SVM) as the machine learning algoritm and used the already known protein pairs in the network. We chose to use phylogenetic profiles of proteins to form the feature vectors required for the learner since the similarity of two proteins in evolution gives a reasonable rating about whether the two proteins interact or not. For large data sets, the training time of SVM becomes quite long, therefore we reduced the data size in a sensible way while we keep approximately the same prediction accuracy. We applied a number of clustering techniques to extract the most representative data and features in a two categorical framework. Knowing that the training data set is a two dimensional matrix, we applied data reduction methods in both dimensions, i.e., both in data size and in feature vector size. We observed that the data clustered by the k-means clustering technique gave superior results in prediction accuracies compared to another data clustering algorithm which was also developed for reducing data size for SVM training. Still the true positive and false positive rates (TPR-FPR) of the training data sets constructed by the two clustering methods did not give satisfying results about which method outperforms the other. On the other hand, we applied feature selection methods on the feature vectors of training data by selecting the most representative features in biological and in statistical meaning. We used phylogenetic tree of organisms to identify the organisms which are evolutionarily significant. Additionally we applied Fisher&sbquo
Ä
ô
s test method to select the features which are most representative statistically. The accuracy and TPR-FPR values obtained by feature selection methods could not provide to make a certain decision on the performance comparisons. However it can be mentioned that phylogenetic tree method resulted in acceptable prediction values when compared to Fisher&sbquo
Ä
ô
s test.
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Dorrell, Richard G. "Coevolution of plastid genomes and transcript processing pathways in photosynthetic alveolates." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/246266.
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Following their endosymbiotic uptake, plastids undergo profound changes to genome content and to their associated biochemistry. I have investigated how evolutionary transitions in plastid genomes may impact on biochemical pathways associated with plastid gene expression, focusing on the highly unusual plastids found in one group of eukaryotes, the alveolates. The principal photosynthetic alveolate lineage is the dinoflagellate algae. Most dinoflagellate species harbour unusual plastids derived from red algae. The genome of this plastid has been fragmented into small, plasmid-like elements termed “minicircles”. Transcripts of this genome receive a 3’ poly(U) tail and, in some species, undergo extensive sequence editing. Some dinoflagellates have replaced their original plastids with others, in a process termed “serial endosymbiosis”. The major non-photosynthetic alveolates are the apicomplexans, which include the malaria parasite Plasmodium. Apicomplexans are descended from free-living algae and possess a vestigial plastid, which originated through the same endosymbiosis as the ancestral red dinoflagellate plastid. This plastid has lost all genes involved in photosynthesis and does not possess a poly(U) tail addition pathway. I have investigated the consequences of the fragmentation of the red algal dinoflagellate plastid genome on plastid transcription. I have characterised non-coding transcripts in plastids of the dinoflagellate Amphidinium carterae, including the first evidence for antisense transcripts in an algal plastid. Antisense transcripts in dinoflagellate plastids do not receive poly(U) tails, suggesting that poly(U) tail addition may play a role in strand discrimination during transcript processing. I have additionally characterised transcript processing in dinoflagellate plastids that were acquired through serial endosymbiosis. I have shown that poly(U) tail addition and editing occur in the haptophyte-derived serial endosymbionts of the fucoxanthin-containing dinoflagellates Karenia mikimotoi and Karlodinium veneficum. This is the first evidence that plastids acquired through serial endosymbiosis may be supported by pathways retained from previous symbioses. Transcript editing constrains the phenotypic consequences of divergent mutations in fucoxanthin plastid genomes, whereas poly(U) tail addition plays a central role in recognising and processing translationally functional fucoxanthin plastid mRNAs. I have additionally shown that certain genes within fucoxanthin plastids are located on minicircles. This demonstrates convergent evolution in the organisation of the fucoxanthin and red algal dinoflagellate plastid genomes since their endosymbiotic acquisition. Finally, I have investigated transcript processing in the algae Chromera velia and Vitrella brassicaformis. These species are closely related to apicomplexans but are still photosynthetic and apply poly(U) tails to plastid transcripts, as with dinoflagellates. I have shown that poly(U) tails in these species are preferentially associated with translationally functional mRNAs of photosynthesis genes. This is the first plastid transcript processing pathway documented to target a specific functional gene category. Poly(U) tail addition may direct transcript cleavage and allow photosynthesis gene transcripts to accumulate to high levels. The loss of this pathway from ancestors of apicomplexans may have contributed to their transition from photosynthesis to parasitism.
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Carreno, Ramon Alexander. "Systematics of apicomplexan parasites and coevolution with definitive and intermediate hosts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35787.pdf.
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Papkou, Andrei [Verfasser]. "The influence of population size on host-parasite coevolution / Andrei Papkou." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1138979643/34.
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Hoen, Douglas. "Coevolution of transposable elements and plant genomes by DNA sequence exchanges." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107660.
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Transposable elements (TEs) are self-replicating genetic elements that comprise a large portion of all characterized nuclear genomes. Self-replication, which is catalyzed by proteins encoded by autonomous TEs, permits TEs to persist without necessarily providing immediate adaptive benefit to the organism; therefore, TEs are sometimes characterized as selfish, parasitic, or junk DNA. Nevertheless, over the course of evolution, TEs have produced diverse and vital eukaryotic adaptations. One way in which TEs coevolve with ordinary genes is by direct sequence exchange: TEs can duplicate and mobilize ordinary genes; conversely, TE-derived sequences can become conserved as ordinary genes. In this thesis, I use genome-scale bioinformatic analyses to identify direct sequence exchanges from plant genomes to TEs, and vice versa, and to characterize their functional and evolutionary consequences. After reviewing the literature, I first examine Mutator-like elements (MULEs) in rice that have duplicated and mobilized thousands of ordinary coding gene fragments, a process we term transduplication. Contrary to a previous report, these sequences do not appear to produce functional proteins, although they may have regulatory functions. Second, I examine a gene family that appears to have originated through transduplication in Arabidopsis thaliana MULEs, which is conserved within TEs, called Kaonashi (KI). KI shows that transduplication does occasionally produce functional gene duplications; however, at least in this case, the result is a not a new ordinary gene, but a new TE gene. Finally, I examine ordinary genes in A. thaliana derived from TE genes, a process termed molecular domestication. In addition to 3 previously known A. thaliana domesticated transposable elements (DTEs) families, I identify 23 candidate novel families. Together, these results support the view that, despite persisting by self-replication, TEs are not molecular parasites but are integral components of eukaryotic genomes.Les éléments transposables (ET) sont des séquences d'ADN capables de se déplacer et de s'autoreproduire dans un génome, un mécanisme appelé transposition. Ces éléments représentent l'une des composantes les plus importantes des génomes nucléaires eucaryotes. Cette capacité à s'autoreproduire, grâce aux protéines codées par les ET autonomes, a permis aux ET de persister et de peupler les génomes sans nécessairement apporter un avantage adaptatif immédiat à l'organisme hôte. À cet égard, les ET sont parfois considérés comme des éléments égoïstes ou parasites, ou de l'ADN « poubelle ». Néanmoins, les ET ont joué un rôle important au cours de l'évolution en générant diverses adaptations essentielles aux eucaryotes. Ainsi, les ET peuvent coévoluer avec les gènes du génome hôte par l'échange direct de séquence d'ADN. Les ET peuvent se dupliquer et mobiliser des gènes hôtes ; à l'inverse, des séquences d'ADN dérivées de ET peuvent avoir le même niveau de conservation que des gènes hôtes. Dans le cadre de ma thèse, j'ai utilisé des analyses bio-informatiques à l'échelle du génome afin d'identifier des échanges directs de brins de séquence d'ADN à partir de génomes de plantes vers les ET, et vice-versa, et de caractériser leurs fonctions et leurs effets évolutifs. Ma thèse débutera par une recension des diverses publications scientifiques dans le domaine. Je dresserai ensuite un portrait des éléments mobiles Mutator-like (MULE) dans le génome du riz qui ont entraîné la duplication et la mobilisation de milliers de fragments de gènes codants normaux, un procédé appelé transduplication. Contrairement à ce qui avait été rapporté dans des publications antérieures, ces séquences transdupliquées ne semblent pas produire des protéines fonctionnelles malgré le fait qu'elles puissent avoir des fonctions régulatrices. En second lieu, j'examinerai une famille de gènes, appelée Kaonashi (KI), qui proviendrait d'un événement de transduplication présent dans les MULE de l'Arabidopsis thaliana, mais également conservé dans les ET. La présence de la famille KI nous montre que le procédé de transduplication permet à l'occasion des duplications fonctionnelles de gènes. Cependant, du moins dans le cas de la KI, le procédé n'entraîne pas la création d'un nouveau gène normal, mais bien d'un nouvel élément transposable. En troisième lieu, j'examinerai les gènes hôtes présents dans le génome de la plante A. thaliana qui proviendrait de ET, un procédé appelé domestication moléculaire. En plus des trois cas de familles d'éléments transposables domestiquées (ETD) déjà connues dans l'espèce A. thaliana, j'ai identifié 23 nouvelles familles potentielles. L'ensemble de ces résultats tend à démontrer que, malgré le fait qu'ils persistent dans les génomes grâce à leur capacité d'autoreproduction, les ET ne sont pas des parasites moléculaires, mais bien des éléments clés faisant partie intégrale des génomes eucaryotes.
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Langhammer, Michael [Verfasser]. "Automated Coevolution of Source Code and Software Architecture Models / Michael Langhammer." Karlsruhe : KIT Scientific Publishing, 2019. http://d-nb.info/1193197104/34.
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Tokarchuk, Laurissa Nadia. "Fuzzy and tile coding approximation techniques for coevolution in reinforcement learning." Thesis, Queen Mary, University of London, 2005. http://qmro.qmul.ac.uk/xmlui/handle/123456789/3822.
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This thesis investigates reinforcement learning algorithms suitable for learning in large state space problems and coevolution. In order to learn in large state spaces, the state space must be collapsed to a computationally feasible size and then generalised about. This thesis presents two new implementations of the classic temporal difference (TD) reinforcement learning algorithm Sarsa that utilise fuzzy logic principles for approximation, FQ Sarsa and Fuzzy Sarsa. The effectiveness of these two fuzzy reinforcement learning algorithms is investigated in the context of an agent marketplace. It presents a practical investigation into the design of fuzzy membership functions and tile coding schemas. A critical analysis of the fuzzy algorithms to a related technique in function approximation, a coarse coding approach called tile coding is given in the context of three different simulation environments; the mountain-car problem, a predator/prey gridworld and an agent marketplace. A further comparison between Fuzzy Sarsa and tile coding in the context of the nonstationary environments of the agent marketplace and predator/prey gridworld is presented. This thesis shows that the Fuzzy Sarsa algorithm achieves a significant reduction of state space over traditional Sarsa, without loss of the finer detail that the FQ Sarsa algorithm experiences. It also shows that Fuzzy Sarsa and gradient descent Sarsa(λ) with tile coding learn similar levels of distinction against a stationary strategy. Finally, this thesis demonstrates that Fuzzy Sarsa performs better in a competitive multiagent domain than the tile coding solution.
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Gandon, Sylvain. "Evolution et coevolution dans une metapopulation dispersion, virulence et adaptation locale." Paris 6, 2000. http://www.theses.fr/2000PA066177.
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La vie dans un environnement fragmente (une metapopulation) est associee a un certain nombre de contraintes. Les tailles de populations reduites et les flux de genes limites entrainent une structuration de la variabilite genetique. Cette structuration pose de multiples problemes : la competition entre apparentes, l'augmentation de la depression de consanguinite, la diminution du potentiel evolutif. A ces problemes il faut ajouter ceux lies a la variabilite de l'environnement. La qualite de l'habitat varie dans l'espace et dans le temps et, en particulier, les ressources disponibles a un endroit donne s'epuisent plus rapidement si l'exploitation est intensive. Dans ce travail je montre comment les especes evoluent et s'adaptent a ces differentes contraintes en modifiant divers traits d'histoire de vie. Je m'interesse plus particulierement a l'evolution des parasites (transmission, virulence) et a la coevolution de leurs hotes (resistance au parasite, effort de reproduction) mais certains resultats ont une portee plus generale et concernent toutes les especes qui rencontrent le meme type de contraintes. Cette analyse theorique de l'evolution et de la coevolution dans une metapopulation genere des predictions (phenotype optimal, adaptation ou maladaptation locale) qu'il est possible de tester in natura ou experimentalement.
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LEMEL, JEAN-YVES. "Coevolution des traits d'histoire de vie dans les associations hote-parasite." Paris 6, 1998. http://www.theses.fr/1998PA066548.
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On aborde dans ce travail trois themes lies a l'evolution des traits d'histoire de vie dans les interactions hote-parasite, par une approche theorique. (1) l'effet du parasitisme sur l'evolution des traits d'histoire de vie des hotes est etudie a l'aide d'un modele integrant la dynamique ecologique de l'interaction entre l'hote et le parasite et la dynamique evolutive de l'hote. L'analyse montre que les hotes selectionnent les strategies demographiques qui maximisent la densite en parasites, independamment de la structure d'age de la population hote et du moment du cycle de vie de l'hote auquel l'infection se produit. Ce resultat apparemment paradoxal s'explique par un principe de pessimisme : la selection favorise les hotes capables de se maintenir dans le pire des mondes. (2) l'evolution des premieres lignes de defenses contre les parasites est etudiee dans le cas ou l'investissement dans la resistance se repercute negativement sur la reproduction. Une conclusion majeure est que l'evolution de la resistance a essentiellement deux issues : l'investissement dans la resistance est soit nul, soit, au contraire, eleve. L'autre conclusion importante est qu'une tres faible variation de la virulence peut entrainer une brusque modification du niveau de resistance selectionne. (3) l'hypothese qu'une augmentation de la survie des stades infectants libres des parasites entraine la selection d'une virulence accrue est testee en fonction de la nature de l'infection, simple ou multiple. Contrairement aux predictions, on montre qu'il peut exister une correlation negative entre la survie des propagules et la virulence optimale lorsque l'infection est simple et qu'il n'y a pas necessairement une correlation entre la survie des propagules et la virulence optimale lorsqu'il y a des infections multiples.
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Shi, Yong. "An Infrared View of the Coevolution of Massive Blackholes and Galaxies." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194740.
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Massive blackhole (MBH) growth is now recognized as a critical ingredient of galaxy formation and evolution. To investigate the interplay between MBH growth and galaxy evolution, we have used the capabilities of the Spitzer Space Telescope to study active galactic nuclei (AGN) and luminous infrared galaxies. We have tested the unification model for radio-loud AGN by finding that radio quasars and some FRII radio galaxies follow a correlation between low-frequency radio and the 70 um emission, two presumably isotropic indicators of nuclear radiation. We have found that mid-IR obscuration (characterized by the strength of the silicate feature) correlates with the X-ray obscuration (characterized by the HI column density), such that low HI columns correspond to silicate emission while high columns correspond to silicate absorption, for various types of AGN. We have demonstrated that in situ electron acceleration is required for both jet and lobe emission in M87. We have measured aromatic features in local AGN, demonstrated the diverse nature (star formation vs. AGN) of the far-IR emission mechanism, and constructed the star formation luminosity functions of the AGN hosts. These luminosity functions are flatter than that of field galaxies, implying that the interplay between star formation and nuclear activity enhances both processes. For luminous infrared galaxies (LIRGs), we have characterized galaxy morphologies of a complete sample of LIRGs at z~1 and found that LIRGs at z~1 are as asymmetric as local ones, implying similar conditions within galaxies lead to a LIRG level of star formation.
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Russell, Jacob Adam. "Coevolution and consequences of symbioses between aphids and maternally transmitted bacteria." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280740.
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Symbiosis is a prevalent phenomenon among organisms throughout the tree of life, including the insects which often harbor maternally transmitted bacteria. Aphids engage in symbiotic interactions with several maternally transmitted bacteria, and many are known to associate with microbes known as secondary symbionts. These bacteria are typically not essential from the aphid's perspective, and until recently little was known about their roles in aphid biology or the coevolutionary histories of these symbioses. I have addressed these mysteries in this dissertation, through use of molecular and experimental analyses. My findings reveal that secondary symbionts are diverse and infect members of numerous aphid and insect taxa. Though they are maternally transmitted, their distributions can be attributed to occasional horizontal transmission among species. Consequences of symbiosis were observed at genomic levels, with "T-" and "U-type" symbionts exhibiting accelerated evolution in their 16S rRNA sequences. The "R-type" symbiont, in contrast, has not experienced accelerated substitution rates, though it does show a recent trend toward increased AT content, as observed for other symbiotic bacteria. Molecular and phylogenetic evidence presented in this dissertation suggest that secondary symbionts are generalists, capable of infecting numerous aphid hosts. Here, I also present experimental evidence in support of this hypothesis, demonstrating that two of three horizontally transferred symbionts are passed on maternally, at high efficiency, in a novel host, Acyrthosiphon pisum. However, not all efficiently transmitted symbionts would be expected to persist in populations of A. pisum, as some reduce aphid fitness. Finally, evidence obtained from my research and previous experimental and theoretical studies suggests that secondary symbionts should improve aphid fitness, though benefits may not accrue in all environments. Here, I examine the effects of temperature on the fitness effects induced by R-, T-, and U-type symibionts, finding that the R- and T-types confer benefits in aphids exposed to high temperatures, compared to slight and even non-existent effects on A. pisum reared under permissive temperatures. The U-type reduced fitness of aphids reared under high temperatures, revealing a potential cost to symbiont infection that could help to explain intermediate infection frequencies.
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Angeles, Mary Stankovich. "Use of Dynamic Pool Size to Regulate Selection Pressure in Cooperative Coevolutionary Algorithms." NSUWorks, 2010. http://nsuworks.nova.edu/gscis_etd/78.
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Cooperative coevolutionary algorithms (CCEA) are a form of evolutionary algorithm that is applicable when the problem can be decomposed into components. Each component is assigned a subpopulation that evolves a good solution to the subproblem. To compute an individual's fitness, it is combined with collaborators drawn from the other subpopulations to form a complete solution. The individual's fitness is a function of this solution's fitness. The contributors to the comprehensive fitness formula are known as collaborators. The number of collaborators allowed from each subpopulation is called pool size. It has been shown that the outcome of the CCEA can be improved by allowing multiple collaborators from each subpopulation. This results in larger pool sizes, but improved fitness. The improvement in fitness afforded by larger pool sizes is offset by increased calculation costs. This study targeted the pool size parameter of CCEAs by devising dynamic strategies for the assignment of pool size to regulate selection pressure. Subpopulations were rewarded with a larger pool size or penalized with a smaller pool size based on measures of their diversity and/or fitness. Measures for population diversity and fitness used in this study were derived from various works involving evolutionary computation. This study showed that dynamically assigning pool size based on these measures of the diversity and fitness of the subpopulations can yield improved fitness results with significant reduction in calculation costs over statically assigned pool sizes.