Dissertationen zum Thema „Génétique des populations – Épidémiologie – Modèles mathématiques“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-25 Dissertationen für die Forschung zum Thema "Génétique des populations – Épidémiologie – Modèles mathématiques" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
Saubin, Méline. „Effets des variations démographiques sur la structure génétique de populations, dans le cadre d'une maladie émergente“. Electronic Thesis or Diss., Paris, AgroParisTech, 2022. http://www.theses.fr/2022AGPT0013.
Der volle Inhalt der QuelleThe demography and genetic structure of a population are closely linked. The study of this interplay is crucial, especially for organisms with frequent demographic fluctuations such as pathogen species responsible for emerging diseases. Classical population genetics models have been used to explore this link for simplified demographic processes. In this thesis, I further investigate the interplay between demography and genetic evolution in pathogen species that display complex life cycles. For this purpose, I focus on two ecological systems that strongly deviate from demographic equilibrium, each of which allows for realistic modelling assumptions. The first ecological system focuses on a major selection event with the temporal dimension being of prime importance. The second system reports recurrent colonisation events in which the spatial aspect is decisive.In the first part, I study an event of resistance overcoming by a pathogen population. Firstly, a modelling approach is used to establish the conditions for observing resistance overcoming and to identify the determinants of resistance durability. The results highlight the antagonistic effect of the proportion of resistant hosts deployed in the agricultural landscape, which decreases the probability of overcoming but increases the speed of overcoming when it occurs. Secondly, this model is implemented to account for genetic evolution at neutral loci. The results identify three demographic scenarios associated with distinct genetic signatures during resistance overcoming: 1) small variations in population sizes and small changes in genetic structures, 2) a strong founder event on the resistant host that in turn creates a genetic structure on the susceptible host, and 3) an evolutionary rescue event that results in a strong founder event on the resistant host, preceded by a bottleneck on the susceptible host. Finally, this theoretical framework of demogenetic analysis is applied to empirical data to infer the parameters underlying the overcoming of resistant RMlp7 poplars by the pathogen Melampsora larici-populina. Two parameters are particularly well estimated and the inferred values are in agreement with our biological knowledge: a high proportion of resistant hosts in the landscape (more than 80%) and an initial frequency of virulent alleles in the pathogen population between 5 and 10%.In the second part, I study colonisation and its genetic consequences. These analyses focus on the recurrent invasion of the Durance River valley by Melampsora larici-populina. Firstly, a mechanistic-statistical model is coupled to epidemiological data to infer the parameters underlying the pathogen's expansion dynamics. This approach shows that colonisation results from frequent long-distance dispersal events, with an average dispersal distance of more than two kilometres. Secondly, the characterisation of several annual colonisation events highlights a similar genetic structure which amplitude however varies greatly between years. Two extremes are identified: in 2011, strong conservation of the initial genetic diversity along the colonised domain; in 2004, rapid erosion of genetic diversity. The inter-annual variations in these structures can be explained by variations in the frequency of long-distance dispersal events.This work highlights the importance of contextualised models that take into account demogenetic variations for a better understanding of biological systems. The information obtained is then crucial for developing relevant control strategies against pathogen populations responsible for emerging diseases
Sibert, Alexandre. „Héritabilité non génétique de la fécondité : effets sur le polymorphisme“. Paris, Muséum national d'histoire naturelle, 2002. http://www.theses.fr/2002MNHN0017.
Der volle Inhalt der QuelleThe transmission of fertility from one generation to the next is well documented. Several population genetics models integrate this phenomenon, assuming a genetic basis. Nevertheless, non-genetic inherance of fertility was described in some Human populations, whose subtle effects on genetic diversity are unknown. The present work describes an extension of the Wright-Fisher model for axesual populations, suitable for the simulation of any kind of fertility inherance. The probability of fertility is introduced as a key notion, and an algorithm for the simulation of fertility transmission from parents to their offspring is developed for a constant size population. The demographic and genealogical properties of this model show that the effects of fertility inheritance cannot be compared with any of the various models studied until now (selection, size variations, ect. ). The careful study of genetic diversity confirms these results and paradoxically shows that current neutrality tests do not allow one to distinguish between fertility inheritance and some types of selection or population expansion. Therefore, the detection of fertility inheritance from observed polymorphism data remains an open question
Ravaz, Nathalie. „Croissance de populations levuriennes mixtes : effet Killer : analyse et modélisation“. Toulouse, INPT, 1992. http://www.theses.fr/1992INPT058G.
Der volle Inhalt der QuelleTiret, Mathieu. „Approche multilocus du génome dans les modèles de génétique des populations“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLA002/document.
Der volle Inhalt der QuellePopulation genetics is the study of the evolution of allelic frequencies within a population and the influence of evolutionary pressures on these frequencies. Within this field, one could develop population models and measures to explain and predict genetic data. However, as technologie evolves new types of data are available, and it becomes essential to develop new models and new measures to reflect these new genetic marker data, increasingly richer and denser thanks to the advent of new techniques such as the Next Generation Sequencing. To this end, we propose in this thesis to develop new measures with the so-called multilocus approach, which considers the genome as a whole rather than an agglomerate of independent loci. We have first tried to build a theoretical basis for the multilocus approach in population genetics. Then, we have illustrated this multilocus approach with the case studies of identity by descent, ancestral recombination graphs and autocorrelograms in population genetics models. Through these different studies, we tried to identify the main issues and questions that the multilocus population genetics raises
Frichot, Eric. „Modèles à facteurs latents pour les études d'association écologique en génétique des populations“. Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENS018/document.
Der volle Inhalt der QuelleWe introduce a set of latent factor models dedicated to landscape genomics and ecological association tests. It includes statistical methods for correcting principal component maps for effects of spatial autocorrelation (spFA); methods for estimating ancestry coefficients from large genotypic matrices and evaluating the number of ancestral populations (sNMF); and methods for identifying genetic polymorphisms that exhibit high correlation with some environmental gradient or with the variables used as proxies for ecological pressures (LFMM). We also developed a set of open source softwares associated with the methods, based on optimized C programs that can scale with the dimension of very large data sets, to run analyses of population structure and genome scans for local adaptation
Henry, Benoit. „Processus de branchements non Markoviens en dynamique et génétique des populations“. Electronic Thesis or Diss., Université de Lorraine, 2016. http://www.theses.fr/2016LORR0135.
Der volle Inhalt der QuelleIn this thesis we consider a general branching population. The lifetimes of the individuals are supposed to be i.i.d. random variables distributed according to an arbitrary distribution. Moreover, each individual gives birth to new individuals at Poisson rate independently from the other individuals. The tree underlying the dynamics of this population is called a splitting tree. The process which count the number of alive individuals at given times is known as binary homogeneous Crump-Mode-Jagers processes. Such processes are known, when properly renormalized, to converge almost surely to some random variable. Thanks to the study of the underlying splitting tree through the tools introduced by A. Lambert in 2010, we show a central limit theorem associated to this a.s. convergence. Moreover, we suppose that individuals undergo mutation at Poisson rate under the infinitely many alleles assumption. We are mainly interested in the so called allelic frequency spectrum which describes the frequency of sizes of families (i.e. sets of individuals carrying the same type) at fixed times. Thanks to the methods developedin this thesis, we are able to get approximation results for the frequency spectrum. In a last part, we study some statistical problems for size constrained Galton-Watson trees. Our goal is to estimate the variance of the birth distribution. Using that the contour process of such tree converges to a Brownian excursion as the size of the tree growth, we construct estimators of the variance of the birth distribution
Varro, Richard. „Algèbres de Bernstein périodiques“. Montpellier 2, 1992. http://www.theses.fr/1992MON20256.
Der volle Inhalt der QuelleMathieu, Éric. „Structures génotypiques multidimensionnelles : simulations, modélisations, analyses“. Montpellier 2, 1990. http://www.theses.fr/1990MON20176.
Der volle Inhalt der QuelleSedki, Mohammed. „Échantillonnage préférentiel adaptatif et méthodes bayésiennes approchées appliquées à la génétique des populations“. Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2012. http://tel.archives-ouvertes.fr/tel-00769095.
Der volle Inhalt der QuelleGervais, Camille. „Evolution de l'auto-incompatibilité : modélisation des conditions de maintien et de diversification en populations finies“. Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10180/document.
Der volle Inhalt der QuelleSelf-incompatibility is a widespread genetic system, which enables hermaphrodite plants to avoid self-fertilization and mating with close relatives. It is based on the pistil's capacity to recognize and reject pollen when they express cognate specificities. Specificities are encoded by alleles at the self-incompatibility gene complex (known as the S-locus), composed of two linked genes, one expressed in pollen and the other expressed in pistils. During my PhD, I studied the maintenance and evolution of self-incompatibility from a theoretical standpoint, using a modeling approach. The first part of my thesis examined the co-evolution of self-incompatibility and inbreeding depression in finite populations, focusing on the conditions for maintenance of self-incompatibility when self-compatible mutants were repeatedly introduced in the population by recurring mutations. Our results showed that the maintenance of self-incompatibility is associated with high inbreeding depression, and is facilitated by high rates of self-pollination. The second part of my thesis explored the conditions for evolution of novel self-incompatibility alleles (S alleles), which we have studied both analytically in infinite populations and in finite populations via computer simulations. Our results showed that the conditions for diversification at the S locus are much less stringent in finite than in infinite populations, and that there is more diversification at this locus when few S alleles are present in the population
Henry, Benoit. „Processus de branchements non Markoviens en dynamique et génétique des populations“. Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0135/document.
Der volle Inhalt der QuelleIn this thesis we consider a general branching population. The lifetimes of the individuals are supposed to be i.i.d. random variables distributed according to an arbitrary distribution. Moreover, each individual gives birth to new individuals at Poisson rate independently from the other individuals. The tree underlying the dynamics of this population is called a splitting tree. The process which count the number of alive individuals at given times is known as binary homogeneous Crump-Mode-Jagers processes. Such processes are known, when properly renormalized, to converge almost surely to some random variable. Thanks to the study of the underlying splitting tree through the tools introduced by A. Lambert in 2010, we show a central limit theorem associated to this a.s. convergence. Moreover, we suppose that individuals undergo mutation at Poisson rate under the infinitely many alleles assumption. We are mainly interested in the so called allelic frequency spectrum which describes the frequency of sizes of families (i.e. sets of individuals carrying the same type) at fixed times. Thanks to the methods developedin this thesis, we are able to get approximation results for the frequency spectrum. In a last part, we study some statistical problems for size constrained Galton-Watson trees. Our goal is to estimate the variance of the birth distribution. Using that the contour process of such tree converges to a Brownian excursion as the size of the tree growth, we construct estimators of the variance of the birth distribution
Miró, Pina Verónica. „Equilibrium patterns of genetic diversity shuffled by migration and recombination“. Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS253.
Der volle Inhalt der QuelleThis thesis presents two different models to study how recombination and migration shuffle genetic diversity. In the first model, recombination is the only evolutionary force. At time 0, each individual has her unique chromosome painted in a distinct color. By the blending effect of recombination, the genomes of the descending individuals look like mosaics of colors, each color representing the genetic material inherited from a different ancestral individual. Each segment of the same color is called an identical-by-descent (IBD) segment. We have been able to characterize the sizes and positions of the segments that are IBD to a given locus in the chromosome of a randomly sampled individual in the population. The second model is devoted to the study of the effects of geographic structure, migration, mutation and recombination in the genetic composition of a metapopulation. The metapopulation is modelled as a graph where vertices correspond to subpopulations and edges are associated to migration rates. The idea behind this project is to study speciation: when two subpopulations accumulate enough genetic differences they may become separate species. We have been able to characterize the distribution of the genetic distances between subpopulations in a low mutation - low migration regime, depending on the geographic structure, and to show that some geographic configurations can promote speciation
Rünneburger, Estelle. „Évolution de la canalisation génétique dans un modèle quantitatif de réseau de régulation“. Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS547/document.
Der volle Inhalt der QuelleGenetic canalization is defined as the capacity of an organism to undergo a normal development even when the genome is altered by mutations. Currently, three main hypotheses are prone to explain the apparition of such a process: evolutionary, congruent and intrinsic. To test these hypotheses, I chose to study gene regulatory networks. To this end, I used a theoretical model, ran in silico simulations, and analyzed the genetic architecture by using quantitative genetics tools. I first studied the evolutionary behavior of the model, and its capacity to respond to stabilizing selection. In addition to the sensitivity analysis to model parameters, I evidenced the absence of mutation-selection-drift equilibrium after several thousand generations, which reveals the evolution of canalization. I also showed that networks submitted to frequent and large mutations, and/or selected toward extreme phenotypic optima are more prone to evolve genetic canalization. This result leads us to propose a two-fold mechanism able to explain the evolution of canalization in gene regulatory networks: shrinkage of mutational targets and redundancy in genetic regulation. At the end of this manuscript, I propose some possible future studies, such as the study of canalization towards environmental perturbations, and use of alternative models
Raoul, Jérôme. „Utilisation d'un panel SNPs très basse densité dans les populations en sélection de petits ruminants“. Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0128/document.
Der volle Inhalt der QuelleBreeding programs aim to transfer high genetic value breeding stock to the industry. The knowledge of molecular markers of individual’s genome and causal mutations allow to conceive new breeding program designs. Based on deterministic and stochastic simulations, the technical and economic benefits of using a very low density molecular markers panel were assessed in sheep and goat populations. Following results were obtained: i) using such a panel to increase female paternal filiations in case of incomplete pedigree is not always profitable, ii) a method of optimization has been used to derive the maximal profits of managing ovulation genes, and practical management giving profits close to the maximal profits have been determined, iii) at similar cost, a genomic design based on a very low density panel is more efficient than the current design based on progeny testing
Poncet, Bénédicte N. „Modèles de distribution d’allèles pour la détection de la variabilité génétique adaptative chez une espèce non modèle, Arabis alpina“. Grenoble, 2010. http://www.theses.fr/2010GRENV034.
Der volle Inhalt der QuelleUnderstanding the molecular basis of adaptation is a major task in evolutionary biology. Local adaptation is the pattern of genotype distributions driven by the natural selection that tends to differentiate populations living in different environments. Genetically, local adaptation results in allele frequencies varying along selection gradients. Our objective is to infer the contribution of allele distribution models in the study of local adaptation through the case of the alpine plant Arabis alpina (Brassicaceae) in the wild. First, a genome scan of 825 AFLP markers genotyped on 678 plants from 198 sites in French and Swiss Alps has been completed and has required the development of a semi-automatic method to select the markers. The effects of this selection on the estimation of genetic structure and variability have been explored. Second, ecologically relevant loci were identified as potentially submitted to selection. Their allele distributions are significantly correlated with environmental variables and topographical conditions. The confounding effects (admixture and isolation by distance) were assessed and discarded in our study case. Some ecologically relevant loci have been sequenced to identify candidate genes and genomic regions potentially selected using the synteny between the genomes of A. Alpina and the model species Arabidopsis thaliana. Finally, the correlative approach to detect selection was compared with more traditional approaches of population genomic. These results suggest that the allele distribution models are a first step before the relevant functional ecology studies to better understand the adaptation to different environmental conditions
Blanc, Emmanuelle. „Modélisation des conséquences évolutives de la compétition pour la lumière dans des populations composites de blé“. Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASB013.
Der volle Inhalt der QuelleIntra-specific diversity, mobilized at the scale of the field (cultivar mixtures and composite populations) should play an important role in the agroecological transition, contributing to the adaptation and resilience of low input cropping systems, more prone to stresses. However, many questions are raised by the complex plant-to-plant interactions occurring in such heterogeneous canopies, and there is a growing need to develop modelling approaches to improve their design and management. Thus, our study focuses on the use of functional-structural plant modelling to study the impact of the aerial architecture of plants on the performance and the evolution of heterogeneous wheat populations. The thesis project is based on WALTer : a pre-existing functional-structural plant model that simulates the development of a wheat field from sowing to maturity and the plasticity of tillering (i.e. branching) in response to competition for light. In a first step, modifications were made to WALTer to reduce the computational cost of simulations, enhance its realism and improve its ability to simulate complex heterogeneous stands. The functioning of this new version of WALTer was then characterized by analysing the impact of stochasticity on the simulations and by performing a sensitivity analysis on homogeneous plots. Furthermore, on the basis of field observations, an automatic calibration method, which is rarely developed for this type of model, was applied to WALTer in order to estimate the values of the parameters previously identified as important by the sensitivity analysis. Thanks to a sensitivity analysis of balanced binary mixtures, WALTer was then used to identify the traits of the aerial architecture (described by their mean values in the mixture and the values of the differences between the 2 varieties) that have the most impact on the performance of the plots. The analysis thus revealed the preponderant role of tillering capability and dimensions of the leaves as determinants of the performance of the simulated mixtures. Thanks to an optimization phase, the combinations of traits that are the most favourable for the performance of the simulated mixtures were identified. The results of the simulations highlighted the importance of carefully selecting combinations of traits to associate in mixtures, showing the potential interest of a diversity of architecture in heterogeneous stands, but also the possible adverse effects of such diversity. Finally, WALTer was coupled to a population genetics model to simulate the evolution of heterogeneous wheat stands along generations of resowing. The coupling was used to simulate the dynamic management of a population presenting a large diversity of plant height. The genetic and phenotypic evolution of the population over 20 generations of resowing could thus be compared with experimental data to confirm the good functioning of the coupling. This thesis allowed the development of methods and tools for the functional-structural modelling of heterogeneous wheat stands. The simulations carried out have also improved our understanding of the impact of the aerial architecture on the competition for light in these stands. Ultimately, this work will be useful for the design and management of heterogeneous wheat stands adapted to farmers' needs
Lanchier, Nicolas. „Systèmes de particules multicolores“. Rouen, 2005. http://www.theses.fr/2005ROUES019.
Der volle Inhalt der QuelleMost mathematical models in the biological literature that describe inherently spatial phenomena of interacting populations consist of systems of ordinary differential equations obtained under global dispersion assumptions, thus leaving out any spatial structure. Interacting particle systems are Markov processes with state space FS where F is a finite set of colors and where S is a spatial structure, typically Zd. They are ideally suited to study the consequences of the inclusion of a spatial structure in the form of local interactions. We investigate the mathematical properties (stationary distribution, geometry of the configurations, phase transitions) of various multicolour particle systems defined on Zd. Each of these systems is intended to model local interactions within a spatially structured community of populations. More precisely, the biological processes we investigate are ecological succession, allelopathy or competition between an inhibitory species and a susceptible species, multi-species host-symbiont interactions, and persistent gene flow from transgenic crops to wild relatives through pollination in a heterogeneous environment. The mathematical techniques are probabilistic, including coupling, duality, multiscales arguments, oriented percolation, asymptotic properties of random walks, and large deviations estimates
Saccareau, Mathilde. „Modélisation épidémiologique et génétique des parasites gastro-intestinaux au sein d’un troupeau d’ovins“. Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0116/document.
Der volle Inhalt der QuelleGastro-intestinal parasitism is one of the most pervasive challenge for health and welfare in grazing small ruminants, leading to consequent production loss. Its control through the use of anthelminthic treatments is no longer sustainable due to the development of parasitic resistance to anthelmintics, but also due to environmental and consumer concerns. A substantial research effort proposed different supplementary control strategies to the massive use of anthelmintics: host nutrition, pasture management, breeding for resistance. Modelling approach allows for multiple scenarios to be considered without having to resort to experimentation in order to find the best integrated control strategies of parasitism. The epidemio-genetic model previously developed by the Roslin Institute modelling a growing lamb flock infected by the parasite T. circumcincta help to study the impact of rational use of anthelmintics, host nutrition and resistance on the flock level of infection and production. The researches of the current PhD thesis aimed to modify this model in order to add adult ewes modelling, especially around parturition where the nutritional requirements are very high. This modelling was improved by taking into account flock replacement in order to have a persistent flock with matings, reforms and reproductions. In this way, our model allows to study several control strategies of parasitism on long term perspective. In order to ensure adequacy of the model outputs to data, the infection level was compared to published data of ewes infected around parturition. However, some parameters were idiosyncratic to the modelling and then they were not be directly estimated from experiments. So a sensitivity analysis was also performed to highlight the parameters which mostly contribute to the infection level variations. Among the most prevalent parasites in sheep, T. circumcincta and H. contortus are the two main parasites. H. contortus is the most virulent parasite est le plus virulent parasite in hot and wet climates, so it is helpful to develop a similar model for this parasite. Beforehand, a meta-analysis of the published studies on infections with the H. contortus parasite was performed to estimate the main life history traits of its parasitic phase. Then, these estimations were used to change the epidemio-genetic model with H. contortus infections. However, some parameters remained unknown because they were not directly estimable. So, the three main unknown parameters (previously highlighted by the sensitivity analysis of the model with T. circumcincta infections) were estimated by minimizing the worm burden differences between published data of H. contortus trickle infection ([25]) and the corresponding model outputs. In this PhD thesis, models were developed in order to evaluate, in a long term perspective, several control strategies of two gastro-intestinal nematodes (T. circumcincta et H. contortus) infections in sheep flock. Notably, the model on H. contortus infections could be used to predict the impact of breeding for resistance to parasitism at the flock level (number of necessary treatments, infection level of the sheep)
Taing, Cécile. „Dynamique de concentration dans des équations aux dérivées partielles non locales issues de la biologie“. Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS077.
Der volle Inhalt der QuelleThis thesis focuses on the dynamics of Dirac mass concentrations in non-local partial differential and integro-differential equations motivated by evolutionary biology. We consider population models structured in phenotypical traits and, taking into account adaptation and mutation phenomena, we aim to describe the selection of the fittest traits in a given environment. The mathematical modeling of these biological problems leads to nonlinear and nonlocal equations, with a small parameter that induces two time-scales. The asymptotic solutions to these equations are population distributions on the traits space and concentrate in Dirac masses located on the dominant traits. In the first part, we study the Dirac mass dynamics in a chemostat model, using a Hamilton-Jacobi formulation. The chemostat model is a system of equations describing the dynamics of consumers and nutrients in a bioreactor. In a second part, we investigate a competition model structured in age and phenotypical traits. By means of an appropriate factorization, we obtain the asymptotic limit of the solution as a decomposition into two profiles, one in age, the other in traits. When mutations are introduced, a Hamilton-Jacobi equation arises and we prove a uniqueness result of the solution to this equation in the framework of viscosity solutions. The last part is devoted to sexual population models. These models under investigation include asymmetric trait heredity or asymmetric trait-dependent fecundity between the parents: each individual inherits mostly its traits from the female
Abi, rizk Lara. „Ondes progressives et propriétés de propagation pour un problème d’épidémiologie évolutive non-local“. Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0244.
Der volle Inhalt der QuelleIn this thesis we study the existence of a travelling wave solutions for an integro-differential system of equations from evolutionary epidemiology. We use ideas from dynamical system ideas theory coupled with estimates of the asymptotic behaviour of profiles. We prove that the wave solutions have a rather simple structure. This analysis allows us to reduce the infinite dimensional travelling wave profile system of equations to a four dimensional ODE system. The latter is used to prove the existence of travelling wave solutions for any wave speed larger than a minimal wave speed c?, provided that the epidemic threshold R0, which is expressed as a function of the principal eigenvalue of a certain integral operator, is strictly greater than 1. This same threshold condition is also used to prove that any travelling wave connects two determined stationary states. In the second part, we study the propagation properties of the solutions for the same spatially distributed system of equations, when the initial density of infected plants is a compactly supported function with the space variable x. When R0 > 1, we prove that spreading occurs with a definite spreading speed that coincides with the minimal speed c? of the travelling wave solutions discussed in the first part. Moreover, the solution of the Cauchy problem asymptotically converges to some specific function for which the moving frame variable x and the phenotype one y are separated
Gil, Marie-Ève. „Analyse d'équations intégro-différentielles et d'EDP non locales issues de la modélisation de dynamiques adaptatives“. Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0346.
Der volle Inhalt der QuelleThis manuscript is devoted to the mathematical analysis of integro-differential models from population genetics. Both models are reaction-dispersion equations of the form ∂tp(t,m) = UD[p](t,m)+ f[p](t,m). They describe the dynamics of fitness distribution in an asexual population under the effect of mutation and selection. These two processes are represented by the nonlocal terms UD[p](t,m) and by f[p](t,m) respectively. The difference between the models rests on the mutation term. Indeed, in the first model, the mutation effects on fitness do not depend on the fitness of the parent. Thus, the mutation term is a standard convolution product: D[p](t,m) =RR J(m−y)p(t,y)dy −p(t,m). When a mutation occurs, the function J(m − y) represents the density of probability for an individual with fitness y to have an offspring with fitness m. The mutation rate is given by the constant U. In the second model, the mutation effects on fitness depend on the fitness of the parent. In this case, an individual with fitness y has an offspring with fitness m with a probability density Jy(m−y). This type of dependence naturally arises when the existence of an optimal fitness (or a phenotypic optimum) is assumed. For both models, we first establish existence and uniqueness results as well as decay properties of the solution. The decay property allows us to define the cumulant generating function (CGF). The CGF obeys a nonlocal transport equation. In the first model, we compute the analytical solution of this transport equation and thus, we obtain a complete description of the distribution p(t,m) through its moments. Then, we study the stationary states for both models, and establish sufficient conditions for the existence and non-existence of a concentration phenomenon corresponding to an accumulation of individuals with best possible phenotype. The results are compared to the results of stochastic individual based models which represent the same kind of evolutionary dynamics
Bah, Boubacar. „Le modèle du Look-down avec sélection“. Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4711/document.
Der volle Inhalt der QuelleThe purpose of the dissertation is to study the look-down model with selection in the case of a population composed only two alleles, one of them has a selective advantage. In this thesis, this selective advantage is modelled by a death rate for the wild-type allele. In the first part, we are interested in the case of a population of infinite size. We show the model is well defined. We show convergence in probability, as the population size tends to infinity, towards the Wright-Fisher diffusion with selection. In the second part we study a variant of the simplest look-down with selection where the size of the population is finite and fixed. We propose two methods of convergence of this finite model towards the Wright-Fisher diffusion with selection. Finally, another approach is considered. We study the look-down model with selection when we replace the usual reproduction model, which is dual to Kingman's coalescent by a population model dual to the Lambda-coalescent in the case of a population of infinite size. We first show this model is well defined. We show that the proportion of one of the two types converges in probability, as the population size N tends to infinity, towards the solution of a stochastic differential equation driven by a Poisson point process. Finally, we show that one of the two types fixate in finite time if and only if the Lambda-coalescent comes down from infinity
Coste, Christophe. „The costs of reproduction in evolutionary demography : an application of Multitrait Population Projection Matrix models“. Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC259/document.
Der volle Inhalt der QuelleCosts of reproduction are pervasive in life history theory. Through this constraint, the reproductive effort of an organism at a given time negatively affects its later survival and fertility. For life historians, they correspond mostly to a physiological trade-off that stems from an allocative process, occurring at each time-step, at the level of the individual. For evolutionary demographers, they are essentially about genetic trade-offs, arising from a genetic variance in a pleiotropic gene acting antagonistically on early-age and late-age fitness components. The study, from an evolutionary demographic standpoint, of these mechanisms and of the relative, cross and joint effects of physiological and genetic costs, is the aim of this thesis. The close examination of Williams (1966)’s original definition of the physiological costs of reproduction led us to produce a theoretical design of their apparatus that accounts for both their mechanistic and evolutionary mechanisms. This design allowed us to make predictions with regards to the strength of costs of reproduction for various positions of organisms on three life-history spectra: slow-fast, income-capital breeders and quality-quantity. From Stearns (1989b)’s tryptic architecture of life history trade-offs –that divides their structure into the genotypic level, the intermediate structure and the phenotypic level – we devised a general framework, which models the possible cohabitation of both physiological and genetic costs. From this, we inferred differing detectability patterns of both types of costs according to the environmental conditions, their variance and individual stochasticity. We could also establish that both costs buffer environmental variations, but with varying time windows of effect. Their dissimilarity emerges also from the differences between mathematical projection models specific to each cost. A new family of evolutionary models is therefore required to implement both physiological and genetic trade-offs. We then describe the vector-based construction method for such a model which we call Multitrait Population Projection Matrix (MPPM) and which allows incorporating both types of costs by embedding them as traits into the matrix. We extend the classical sensitivity analysis techniques of evolutionary demography to MPPMs. Most importantly, we present a new analysis tool for both life history and evolutionary demography: the Trait Level Analysis. It consists in comparing pairs of models that share the same asymptotic properties. Such ergodic equivalent matrices are produced by folding, an operation that consists in reducing the number of traits of a multi-trait model, by averaging transitions for the traits folded upon, whilst still preserving the asymptotic flows. The Trait Level Analysis therefore allows, for example, to measure the evolutionary importance of costs of reproduction by comparing models incorporating them with folded versions of these models from which the costs are absent. Using classical and new methods to compute fitness moments – selection gradient, variance in reproductive success, environmental variance - in models with and without the costs, we can show their effects on various demographic and evolutionary measures. We reveal, in this way, the combined effects of genetic and physiological costs on the vital rates of an age-structured population. We also demonstrate how physiological costs affect both components of effective selection, as they flatten the slope of selection gradients and increase the effective size of a population. Finally, we show how their buffering of environmental and demographic variance confer greater resilience to populations experiencing physiological costs of reproduction
Gryspeirt, Aiko. „Impact des plantes Bt sur la biologie de Plodia interpunctella: évaluation de l'efficacité de la stratégie agricole "Haute dose - refuge" pour la gestion de la résistance des insectes ravageurs aux plantes Bt“. Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210542.
Der volle Inhalt der QuelleMon projet de recherche s’inscrit dans le cadre de l’évaluation de l'efficacité de cette stratégie et s’articule en deux phases :une phase expérimentale et une phase théorique. La première se concentre sur la caractérisation en laboratoire de l'impact des toxines Cry sur la biologie d'un ravageur. Cette phase constitue un support au volet théorique :la mise au point d’un modèle mathématique évaluant l'efficacité de la stratégie HD/R. L'originalité de ce projet repose entre autre sur l'interactivité entre ces deux volets.
Volet expérimental. Impact des toxines Cry sur la biologie de Plodia interpunctella. Nous évaluons séparément l'impact d'une gamme de concentrations de deux toxines Cry (CryXX et CryYY) sur une série de paramètres comportementaux et biologiques d'un insecte commun des denrées stockées: Plodia interpunctella (Hübner) (Lepidoptera :Pyralidae). Ces paramètres sont sélectionnés car leur variation pourrait avoir un impact sur l'efficacité de la stratégie HD/R dans le contrôle de la résistance. Il est donc pertinent de les quantifier pour intégrer dans le modèle des ordres de grandeur réalistes et générer des résultats qui ne sont pas uniquement basés sur des spéculations théoriques.
Volet théorique A. Efficacité de la stratégie HD/R pour des plantes Bt synthétisant une ou deux toxines simultanément. La stratégie 'HD/R' a été développée pour prévenir la résistance envers les plantes Bt synthétisant une seule toxine. Or, depuis 2003, de nouvelles variétés de coton Bt synthétisant simultanément deux toxines Cry sont commercialisées (BollgardII® et WidestrikeTM). Nous évaluons, grâce au modèle que nous avons développé, l'efficacité de cette stratégie lors d'une utilisation exclusive de plantes Bt synthétisant une ou deux toxines.
Volet théorique B. Impact du ralentissement du développement des insectes sur les plantes Bt sur l'efficacité de la stratégie HD/R. Le volet expérimental met en évidence un allongement de la durée du développement des larves se nourrissant sur une diète contaminée en toxine Cry. Ce ralentissement induit une séparation temporelle entre l'émergence des adultes de la zone Bt et de la zone refuge et perturbe une hypothèse principale de la stratégie HD/R: le croisement aléatoire entre adultes, indépendamment du génotype et de la zone d'origine. Dans ce troisième chapitre, nous étudions l'impact de la perturbation du croisement aléatoire sur l'efficacité de la stratégie HD/R. Nous testons également deux options pour optimiser la stratégie en cas d'asynchronie: l'utilisation de plantes Bt synthétisant une faible concentration en toxine (atténuant le décalage entre l'émergence des adultes) ou l'augmentation de la taille de la zone refuge (favorisant la survie des individus porteurs d'allèle de sensibilité et donc optimisant la dilution de la résistance à la génération suivante).
Ce travail s'intègre dans une problématique actuelle et utilise des outils de biologie théorique (théories de la dynamique et de la génétique des populations) ainsi que le développement d'un modèle mathématique. Il apporte des éléments de réponse et de réflexion sur l'optimisation de la gestion de la résistance des insectes mais c'est aussi une illustration de la complémentarité entre la biologie expérimentale et théorique.
/
On the market since 1996, genetically modified plants synthesizing an insecticidal toxin (Cry toxin) stemmed from Bacillus thuringiensis, called Bt plants, target several insect pests (Lepidoptera or Coleoptera). Bt crops cover increasingly larger areas and control important pest populations The Insect Resistance Management Strategy (IRM) strategy currently recommended in the U.S.A. to limit the development of resistant populations is the High Dose / Refuge zone (HD/R) strategy. This pre-emptive strategy requires a refuge zone composed by non-Bt plants, usable by the target insect and in close proximity of the Bt zone synthesizing a high toxin concentration.
My research project contributes to the effectiveness assessment of this HD/R strategy. It is structured on two main parts: an experimental, and a theoretical section. The first part characterizes the impact of Cry toxins on the biology of an insect pest. It is the basis of the theoretical part: the implementation of a mathematical model, which evaluates the effectiveness of the HD/R strategy.
The originality of this project is based on the interactivity of these two components.
Experimental section. Impact of the Cry toxins on the biology of Plodia interpunctella. We assess the impact of a range of concentrations of two Cry toxins (CryXX et CryYY) on several behavioural and biological parameters of a common pest of stored products: Plodia interpunctella (Hübner) (Lepidoptera :Pyralidae). These parameters are selected because their variation could influence the effectiveness of a HD/R strategy. So, it is important to quantify these parameters so that realistic values can be integrated in our model. The results of the model are thus not based on theoretical assumptions alone.
Theoretical section A. Effectiveness of a HD/R strategy with Bt plants synthesizing one or two toxins. Initially, the HD/R strategy has been developed to limit the resistance towards Bt plants synthesizing one toxin. However, since 2003, new Bt cotton varieties synthesize two toxins simultaneously (BollgardII® et WidestrikeTM). We assess, with our model, the effectiveness of this strategy for Bt plants synthesizing one or two toxins.
Theoretical section B. Impact of the slowing down of the insect development reared on Bt plants on the effectiveness of the HD/R strategy. The experimental part demonstrates that larvae reared on a Bt diet have a protracted development duration. The consequence of this is a temporal separation between adult emergence in the two zones (Bt zone and refuge zone). This could affect the main assumption of the HD/R strategy, i. e. random mating independently of the genotype and of the native zone. In this third chapter, we study the impact of random mating disruption on the effectiveness of a HD/R strategy. We test two options to optimise the strategy in case of asynchrony: the use of Bt plants synthesizing a lower toxin concentration (limiting emergence asynchrony) or increasing the refuge zone size (favouring the survival of insect carrying one or two susceptible allele and thus optimising the dilution of resistance at the next generation).
This work is applied to a current issue. It uses some of the tools of theoretical biology (theories of population dynamics and population genetics) and develops a mathematical model. It provides some responses and some elements of thought about insect resistance management. It is also an illustration of the complementarity between experimental and theoretical biology.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Goussen, Benoit. „Analyse par modélisation mécanistique des réponses microévolutives d'une population de Caenorhabditis elegans exposée à un stress métallique radioactif“. Phd thesis, AgroParisTech, 2013. http://pastel.archives-ouvertes.fr/pastel-01012072.
Der volle Inhalt der Quelle