Dissertations / Theses on the topic 'Dynamique de population d’hôte-parasite'
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Lyoussoufi, Abderrahmane. "Bioécologie et dynamique de population du psylle du poirier Cacopsylla pyri (L. ) (Homoptera : Psyllidae). Influence de la phénologie et de la structure de l'arbre." Aix-Marseille 3, 1994. http://www.theses.fr/1994AIX30034.
Full textBrouard, Vianney. "Cell dynamics of multitype populations in oncology and Invasion probability of cooperative parasites in structured host populations." Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0037.
Full textThis thesis focuses on the study of two stochastic models related to medical problems. The first one lies on understanding infection spread of cooperating bacteriophages on a structured multi-drug resistant bacterial host population. Motivated by this example, we introduce an epidemiological model where infections are generated by cooperation of parasites in a host population structured on a configuration model. We analysed the invasion probability for which we obtain a phase transition depending on the connectivity degree of the vertices and the offspring number of parasites during an infection of a host. At the critical scaling, the invasion probability is identified as the survival probability of a Galton-Watson process. With the aim to get a biological more relevant model, we analysed a similar model where a spatial structure is added for the host population using a random geometric graph. We have shown that such spatial structure facilitates cooperation of parasites. A similar phase transition occurs where at the same critical scaling the invasion probability is upper and lower bounded by the survival probabilities of two discrete branching processes with cooperation. The second medical question deals with understanding the evolution of the genetic composition of a tumor under carcinogenesis, using multitype birth and death branching process models on a general finite trait space. In the case of neutral and deleterious cancer evolution, we provide first-order asymptotics results on all mutant subpopulation sizes. In particular such results capture the randomness of all cell trait sizes when a tumor is clinically observed, and mostly it allows to characterize the effective evolutionary pathways, providing information on the past, present, and future of tumor evolution.Moving beyond this restrictive neutral and deleterious cancer evolution framework, we provide a new method to understand the first selective mutant trait size
Boyer, Séverine. "Ecologie du copépode calanoïde Paracartia grani : implication dans le cycle de vie du parasite Marteilia refringens dans la lagune de Thau." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20147/document.
Full textIn this study, the life cycle of Paracartia grani, a calanoid copepod belonging to the Acartiidae family was determined in Thau lagoon. Indeed, the copepod involvement in the life cycle of the parasite Marteilia refringens affecting the bivalves production is suspected. Mesozooplanktonic community was monitored twice a month over two years at a fixed station in the lagoon. Sampling has identified P. grani as the acartiid dominant species in summer. From April to January, the copepod is found in the water column while from February to early April it remains in the sediment as diapausing eggs. The analysis of the population structure (size spectrum, contribution of developmental stages and sex ratio) has revealed that there are 9 generations per year. The study of the influence of three environmental parameters (temperature, salinity and chlorophyll a concentration) on the dynamic nesting species indicated that P. grani egg production was mainly governed by temperature and its rapid increase in spring could trigger the hatching of diapause eggs.The second objective of this study aimed to describe the dynamics of the parasite M. refringens in P. grani, and in the bivalves Mytilus galloprovincialis and Ruditapes decussatus in the Thau lagoon. Histological and in situ hybridization analysis allowed describing the different forms of the parasite in these three species. Research of M. refringens by PCR in P. grani copepodites revealed that the parasite DNA presence in the copepod from June to November, when new mussels appeared infected. Experiments to measure the retention efficiency of the different stages of development of P. grani by mussels have shown that all developmental stages could be involved in M. refringens life cycle, especially copepod eggs that have also shown positive results by PCR. Our study has allowed clarifying interaction between copepods, parasites and mussels but not elucidate completely M. refringens life cycle. Questions remain especially regarding way of transmission of parasite from copepods to mussels and the potential impact of the parasite on the copepod itself
Villette, Petra. "Spatial and temporal characteristics of bacterial parasite communities in outbreaking fossorial water vole (Arvicola terrestris) populations : static uniformity or dynamic heterogeneity?" Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD056/document.
Full textContext In France, during cyclic population surges, water voles, Arvicola terrestri, cause extensive damage to mountain grassland. A working group consisting of researchers from the University of Franche-Comté (UFC), INRA (Centre de Biologie et de Gestion des Populations) agricultural organizations (Fédération Régionale de Défense contre les Organismes Nuisibles de Franche-Comté, FREDON) are working on systems approach in which interactions between voles, their habitat (landscape, predators) and agricultural practices are analysed hierarchically (in space and time). One of the objectives is to highlight the largest possible number of control factors on which it is possible to act, and the scale at which these actions are relevant. These studies have helped initiate a strategy, successfully tested in Franche-Comté and in Auvergne, which promotes the integrated control of water vole populations. Nevertheless, there are still grey areas in the understanding of the cycle, particularly on the determinants of the decline phase. The role of pathogen communities (some species may even be transmitted to humans) so far remains the subject of debate in the scientific literature. The understanding of the key factors determining this phase should allow farmers to better anticipate economic impacts and to adopt optimal strategies for vole population control Objectives: (1) To test the pathogens and senescence hypotheses in order to explain the population decline. (2) To look for biological indicators (diversity of pathogens and / or immune indicators) that may predict the decline phase in order to anticipate appropriate measures to restore grasslands. (3) To assess the role of the transition between high population density phase and the decline phase for the emergence of pathogens in vole populations that may cause human diseases.General Methodology Population monitoring with regular (monthly) sampling will be made on several populations (replicates) in the period that brackets the vole population declines. Methods based on Next Generation Sequencing (NGS) makes it possible to establish extensive catalogues of pathogens (viruses, bacteria, other parasites) hosted by vole populations and to measure the prevalence
Loiseau, Claire. "Réponses au stress environnemental et à la pression parasitaire en populations naturelles : approches physiologique et génétique : Etudes chez le moineau domestique Passer domesticus." Paris 6, 2007. http://www.theses.fr/2007PA066468.
Full textGam, Meriame. "Dynamique des systèmes parasites - hôte, entre trematodes digènes et coque Cerastoderma edule : comparaison de la lagune de Merja Zerga avec le bassin d'Arcachon." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13684/document.
Full textThe global dynamics of the parasites-host systems (PHS) ‘digenean trematodes – cockle Cerastoderma edule’ was simultaneously studied in Merja Zerga (Morocco) and Arcachon Bay (France). Cockle population dynamics exhibited an intra- and inter-site variability mostly explained by temperature, predation, competition and sedimentary dynamics. In both lagoons, recruitment occurred at 19° C, with a temporal delay due to latitudinal position (April-May at Merja Zerga, and June-July at Arcachon). Growth rates were similar in both cockle populations (K=1.5 an-1) but growth performances were higher at Arcachon (F’=3.3) than at Merja Zerga (F’=3.1). Production was higher at Merja Zerga (36-65 g dry weight.m-2.yr-1). P/B was low in both sites and slighly higher at Arguin (1.1-1.5 contre 1.0-1.1 yr-1). Both sites exhibited rich parasite communities with 11 species at Merja Zerga and 13 species at Arguin, corresponding to 69 and 81% of the identified cockle parasite species richness (digeneans). Great distances and climate differences did not alter the structure of parasite communities. Structure and dynamics of PHS related to latitude showed the moderate effect of temperature, within this climate range. At Merja Zerga, temperature was not a limiting factor for parasite infestation, in contrast with what happens in northern countries. But eventually, parasite loads in adult cockles were similar in both sites. Echinostomatids and gymnophallids were the most contributive families explaining parasite- dependent mortality. Digenean impact on cockle resulted in an increasing of E/B, with a higher effect at Merja Zerga. This difference could be linked to a higher virulence in southern sites. The presence of seagrass beds, the position between subtidal and intertidal and the cockle density remained secondary factors in controlling parasite infestation
Nguyen, Huu Tri. "Echelles de temps et dynamique spatiotemporelle de populations." Aix-Marseille 2, 2007. http://theses.univ-amu.fr.lama.univ-amu.fr/2007AIX22099.pdf.
Full textAggregation of variables methods allow reducing complexity of models in population dynamics by building simplified models governing fewer variables. We first use those methods to study spatial host-parasitoids models on patches. Those models are composed of a local interaction submodel and a dispersal submodel. Dispersal consists in k events of elementary dispersal on the nearest neighbours. We study the influence of parameter k on global dynamics and persistence of the system. We then develop a model of a virus in a marine environment to study the “plankton paradox”: plankton dynamics violate the principle of competitive exclusion. The study of our system shows that the presence of a virus enables the coexistence of two different species of bacteria
Bendahmane, Mostafa. "Solutions L1 pour des systèmes de réaction-advection-diffusion intervenant en dynamique des populations." Bordeaux 1, 2001. http://www.theses.fr/2001BOR12461.
Full textLe, Rouzic Arnaud. "Modélisation de la dynamique évolutive des éléments transposables : naissance, vie et mort d'un parasite génomique." Paris 11, 2005. http://www.theses.fr/2005PA112201.
Full textTransposable elements are one of the main components of the genomes, and they can be found in almost every living organism. However, except in a few "molecular domestication" events, they seem to maintain themselves in the genomes thanks to their own multiplication ability, and they are thus generally considered as "parasitic" DNA sequences. In the present work, we have investigated, through a simulation software, a population genetics model of a transposable element family. The different stages of the "life cycle" of the element have been studied, from the very first generations following its arrival in a new species, to its long-term co-evolution with the other elements and genes in the genome. The results presented here highlight the complexity of the evolution of these genomic parasites, and several realistic evolutionary scenarios can be proposed. In the most cases, a stable equilibrium state appears to be unlikely, and the invasion of a transposable elements family seems to be a dynamic process, depending not only on the features of the element, but also on the interactions existing between the host genome and its parasitic DNA sequences
Charbonnel, Nathalie. "De la génétique à la dynamique des populations : l'exemple du gastéropode des eaux douces, Biomphalaria pfeifferi à Madagascar." Montpellier, ENSA, 2001. http://www.theses.fr/2001ENSA0018.
Full textMcCoy, Karen D. "Conséquences de la dispersion dans les systèmes hôtes-parasites : dynamique des populations, structure génétique, et adaptation locale chez un parasite d'oiseaux marins, la tique Ixodes uriae." Paris 6, 2001. http://www.theses.fr/2001PA066336.
Full textBonato, Olivier. "Dynamique des populations de l'acarien vert du manioc "Mononychellus progresivus" et de l'acarien rouge "Oligonychus gossypii" au Congo. Modélisation du sous-système acariens phytophages-manioc." Montpellier 2, 1993. http://www.theses.fr/1993MON20049.
Full textHaond, Marjorie. "Impact de la capacité de charge de l’environnement sur les dynamiques d’expansions de métapopulation : théories et applications à un système expérimental hôte-parasitoïde." Electronic Thesis or Diss., Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4017.
Full textReaction-diffusion equations are commonly used to describe population propagation dynamics. In particular, they can be used to define two types of dynamics: pulled and pushed. The pulled dynamic results from a colonization led by individuals in small numbers located at the edge of the population, the pushed dynamic results from a colonization led by larger numbers from the core of the population. Biological mechanisms underlying the pushed waves are still poorly described, however, the presence of an Allee effect (characterized by a positive correlation between growth rate and population density for small populations) is known to lead to a pushed dynamic. Other mechanisms generating a dependence between population size and the probability of colonization are also likely to generate pushed waves, but this generalization remains to be confirmed. Few studies have addressed the effects of environmental factors such as carrying capacity on population expansion rates. However, while for a pulled dynamic, the colonization of the few individuals at the front of the wave should not be influenced by the value of the carrying capacity of the environment, in the pushed case, individuals evolving at larger numbers, the carrying capacity could be a limiting factor of the expansion. We have therefore attempted to describe (i) the effects of carrying capacity on population expansion dynamics, particularly through the prism of pulled/pushed dynamics, and (ii) the diversity of demographic mechanisms that can generate high dynamics. For this purpose we used individual-centred modelling approaches and microcosm experimentation on parasitoid hymenoptera, Trichograms. We used a species with a positive density-dependent dispersion resulting in an increase in the individual probability of migrating in large populations, thus leading to potentially high colonization dynamics. Using these two approaches, we first studied the impact of carrying capacity on expansion velocity, validating our hypotheses that the dependence of expansion velocity on carrying capacity could be an indicator of the pushed/puledl nature of expansions. In a second part we studied the phenomena of Range pinning described for populations subjected to Allee effects and we tried to generalize this phenomenon to pushed dynamics in the presence of positive dependent density dispersion. In a third part we studied how a heterogeneous distribution in space of different carrying capacities would influence the dynamics of particularly high expansions
Borel, Gae͏̈tan. "Le foyer de bilharziose à Schistosoma Mansoni de l'arrière mangrove de Guadeloupe : essai de lutte biologique contre le mollusque vecteur, Biomphalaria glabrata, à l'aide du mollusque compétiteur, Melanoides tuberculata : dynamique des populations du parasite chez l'hôte réservoir, Rattus rattus." Montpellier 2, 1990. http://www.theses.fr/1990MON20208.
Full textMagalhães, Luísa Virgínia de Sousa. "Inventory, dynamics and impact of the trematodes parasites in bivalves with high economic importance." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0174/document.
Full textAmong population dynamics drivers, parasitism is significant but often neglected. Beyond inventory of the various parasites, it is urgent to understand the susceptibility of hosts, namely bivalves, to infection, and to investigate the interaction among parasites and other environmental conditions.In this way, the present study aimed to characterize and quantify the trematode macroparasites, the most abundant and prevalent in coastal waters, infecting Cerastoderma edule and Donax trunculus, which are among the most ecologically important and economically explored bivalve species in Portugal and France.The first step was to study bivalve population dynamics, evaluating the relationship between temperature and recruitment timing and the reciprocal effects of recruitment on adult biomass. For this, a large database spanning 17 years of monthly observations of a cockle population inhabiting a national protected area (Banc d’Arguin, Arcachon, France) was analysed. Long-term observations showed that the sustainability of a cockle population is recruitment-success dependent. In cockles, recruitment success showed to be partly, but not only, dependent on temperature. Hence, the sustainability of a cohort could be set earlier, i.e. by processes happening before recruitment. Following this clue, the role of parasitism on the bivalve host population dynamics was explored.Firstly, due to high pathogenicity for bivalves, special attention was given to the parasites Bucephalus minimus and Bacciger bacciger which use C. edule and D. trunculus, respectively, as first intermediate hosts (where their sporocysts parasitic stage develops). […]Then, the study focused on metacercariae infection in its bivalve second intermediate host, a relationship that is usually reported as less deleterious. […]Lastly, the susceptibility of bivalves to parasites infection when challenged by climate change related factors (salinity, temperature and pH) and contamination (Arsenic) was experimentally assessed. Main results showed that hosts exposure to stressful conditions related to global change scenarios can modify the parasite infection success and induced host biochemical response alterations.The findings presented in this thesis improved the knowledge on the effects of different constraints on bivalves, highlighting the crucial role of parasitism. If applied, these new insights can promote the sustainable management of bivalves, such an important marine resource, with greater production and economic potential
Entre os agentes que modulam a dinâmica populacional, o parasitismo é significativo masmuitas vezes negligenciado. É urgente não só inventariar as várias espécies de parasitas, bem comocompreender a suscetibilidade dos hospedeiros à infeção (nomeadamente os bivalves) e investigar ainteração entre os parasitas e outras condições ambientais. Pelo que, esta tese teve como objetivoprincipal caracterizar e quantificar os macroparasitas trematodes (os mais abundantes e prevalentesem águas costeiras) que infetam Cerastoderma edule (berbigão) e Donax trunculus (conquilha), doisdos bivalves mais importantes em Portugal e França tanto do ponto de vista ecológico comoeconómico.Primeiramente, a dinâmica populacional dos bivalves foi estudada, tendo em conta a relaçãoentre a temperatura e o período de recrutamento e os efeitos recíprocos do recrutamento nabiomassa de adultos. Para isso, foi analisada uma base de dados abrangendo 17 anos deobservações mensais de uma população de berbigões que habitam uma área nacional protegida(Banc d’Arguin, Arcachon, França). Estas observações de longa duração mostraram que asustentabilidade de uma população de berbigão é dependente do sucesso do recrutamento. Emberbigões, o sucesso do recrutamento mostrou ser em parte, mas não totalmente, dependente datemperatura. Por esta razão, a sustentabilidade de uma coorte pode estar a ser estabelecida maiscedo, isto é, por processos que acontecem antes do recrutamento. Seguindo esta pista, o verdadeiropapel do parasitismo na dinâmica populacional dos bivalves foi mais explorado.De seguida e devido à elevada patogenicidade para os bivalves, foi dada especial atençãoaos parasitas Bucephalus minimus e Bacciger bacciger que usam C. edule e D. trunculus,respetivamente, como primeiros hospedeiros intermediários (onde o estádio parasítico esporocisto sedesenvolve). […].Depois, este estudo focou-se na infeção dos bivalves por metacercariae, ou seja, quandoservem de segundos hospedeiros intermediários no ciclo de vida do parasita. […]Por fim, foi experimentalmente avaliada a suscetibilidade dos bivalves à infeção por parasitasquando desafiados por fatores relacionados com as alterações climáticas (salinidade, temperatura epH) e contaminação (Arsénio). Os resultados mostraram que a exposição dos hospedeiros acondições de stress relacionadas com cenários de alterações globais podem modificar o sucesso dainfeção parasitária e induzir alterações na resposta bioquímica do hospedeiro.As descobertas apresentadas nesta tese melhoraram o conhecimento dos efeitos dediferentes variáveis nos bivalves, salientando o papel crucial do parasitismo. Se aplicados, estesnovos pontos de vista podem promover a gestão sustentável dos bivalves, um recurso marinho tãoimportante, aumentando o seu potencial de produção e económico
Armand, Eric. "Dynamique des populations de Psylla pyri (L. ) (Homoptera-Psyllidae) en verger de poiriers dans la région d'Avignon : étude du cortège de ses parasitoi͏̈des et relations avec l'environnement." Montpellier 2, 1989. http://www.theses.fr/1989MON20040.
Full textMoyal, Pascal. "Les foreurs du maïs en zone des savanes de Côte d'Ivoire : données morphologiques, biologiques, écologiques : essais de lutte et relation plante-insecte." Paris 6, 1986. http://www.theses.fr/1986PA066488.
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