Tesis sobre el tema "Barrières au flux de gènes"
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Burban, Ewen. "Approche génomique de la détection des barrières au flux de gènes". Electronic Thesis or Diss., Université de Rennes (2023-....), 2024. http://www.theses.fr/2024URENB007.
Texto completoCharacterizing the mechanisms that underlie reproductive isolation between diverging lineages is central in understanding the speciation process. As populations evolve, they gradually develop reproductive isolation (RI) by passing through intermediate steps, often referred to as the "gray zone of speciation". This isolation is marked by the emergence of genomic regions acting as barriers to local gene flow, distinct from the rest of the genome. Detecting these barrier loci involves identifying outlier loci with specific signatures. However, other processes can create similar patterns, which challenges barrier loci detection. In my thesis, I developed a new tool, RIDGE - Reproductive Isolation Detection using Genomic Polymorphisms, a novel free and portable tool tailored for this purpose in a comparative framework. RIDGE utilizes an Approximate Bayesian Computation model-averaging approach based on a random forest to accommodate diverse scenarios of lineage divergence. It considers heterogeneity in migration rate, linked selection, and recombination, estimates barrier proportion and conducts locus-scale tests for gene flow barriers. Simulations and analyses of published datasets in crow species pairs demonstrate RIDGE's efficacy in detecting ongoing migration and identifying barrier loci, even for recent divergence times. Furthermore, the contribution of summary statistics varies depending on the dataset, highlighting the complexity of gene flow barrier genomic signals and the interest of combining several statistics. Subsequently, I applied RIDGE to wild/domestic pairs in maize (an outcrosser), and foxtail millet (a selfer), both domesticated around 9,000 years ago. Gene flow between forms has been reported in these two systems. Consistently, models with ongoing migration and heterogeneity in migration rate were clearly dominant over other models. RIDGE also demonstrated its ability to distinguish between barrier loci and domestication loci (that experienced selective sweeps within the domestic forms). The perspectives of this work include applying RIDGE to multiple population/species pairs encompassing a large spectrum of divergence to determine the genomic pattern of RI during speciation, to test the snowball theory formulated by Orr in 1995 or to determine the nature of speciation genes
Latouche-Hallé, Céline. "Flux de gènes et structure génétique de Dicorynia guianensis en forêt tropicale humide". Paris 11, 2004. http://www.theses.fr/2004PA112003.
Texto completoDicorynia guianensis is a canopy tree, endemic to the tropical rain forest of French Guiana. All adult trees within a continuous area of 40 ha (n=157), 375 saplings, and 246 progenies from 22 mature trees, were sampled and genotyped with 6 microsatellite loci and one PCR-RFLP cpDNA combination. Level of nuclear intrapopulation diversity was lower than temperate forest trees, as other tropical species. For both genomes, genetic differentiation was more pronounced between spatial aggregates than between cohorts. Spatial structure was larger for chloroplast than nuclear markers indicating a strong asymmetry between pollen and seed flow. Moreover, the species was able to maintain high levels of intrapopulation diversity for chloroplast genome. An avoidance of fixation of haplotypes is expected in recently formed aggregates for a colonizing species or in non-equilibrium situations where aggregates are subject to rapid extinction-recolonization dynamics. At the population level, the species was mostly outcrossing but there was marked variation among individuals. One tree exhibited mixed mating confirming that the self-incompatibility barriers could be relaxed. Male mating success was only moderately related to distance between trees within the study area. It was, however, related to the diameter of the stem and to the visual assessment of flowering intensity. The majority (66%) of pollen came from outside the study stand. These data suggest that the fine-scale spatial genetic structure is mainly the consequence of restricted seed dispersal, and that pollen flow has limited impact. The mating behavior of D. Guianensis is a combination of long distance pollen flow and occasional selfing
Raufaste, Nathalie. "Barrières au flux génique et sélection dans une zone hybride : étude théorique et expérimentale chez la souris domestique". Montpellier 2, 2001. http://www.theses.fr/2001MON20145.
Texto completoCartaud, François. "Modélisation des écoulements dans les interfaces des barrières d'étanchéité composites des installations de stockage de déchets". Paris, ENMP, 2004. http://www.theses.fr/2004ENMP1229.
Texto completoComposite liner at the bottom of waste landfill is based, in France, on a geomembrane overlapping a compacted clay liner. Defects exist in geomembranes and leachates, provided by water percolation through the waste, then flow in the interface between the two components of the lining system. The present work consisted in analysis, quantification and modelling of the leakage process in the interface. The experimental study has been carried out on a one-meter scale device in laboratory and allowed to assess the role of normal stress on the flow rate in interface. The case where a geotextile is present beneath the geomembrane has been also studied. The modelling allows to take into account more accurately the geometry of the interface and ensures a better quantification of leachate flow rates than using existing methods
Chaix, Gilles. "Etude des flux de gènes dans un verger à graines d'Eucalyptus grandis à Madagascar". Phd thesis, Ecole nationale superieure agronomique de montpellier - AGRO M, 2002. http://tel.archives-ouvertes.fr/tel-01071377.
Texto completoChaix, Gilles. "Etudes des flux de gènes dans un verger à graines d'Eucalyptus grandis à Madagascar". Montpellier, ENSA, 2002. http://www.theses.fr/2002ENSA0030.
Texto completoDesaint, Stéphane. "Description des populations bactériennes telluriques dégradant le carbofuran : diversité génétique et flux de gènes". Dijon, 2000. http://www.theses.fr/2000DIJOS065.
Texto completoVigouroux, Yves. "Betteraves transgéniques et betteraves adventices : étude des flux de gènes et de leurs conséquences". Dijon, 2000. http://www.theses.fr/2000DIJOS087.
Texto completoFaure, Matthieu. "Génétique des barrières semi-perméables au flux génique dans la zone d’hybridation des moules Mytilus edulis et M. Galloprovincialis". Montpellier 2, 2007. http://www.theses.fr/2007MON20225.
Texto completoGhesquière, Alain. "Diversité génétique de l'espèce sauvage de riz, Oryza longistaminata A. Chev. Et Roehr, et dynamique des flux géniques au sein du groupe Sativa en Afrique". Paris 11, 1988. http://www.theses.fr/1988PA112380.
Texto completoA genetic evaluation of the wild perennial rice Oryza longistaminata was conducted on a living collection representing the ecogeographical variability of this species in Africa. The description of the breeding system according to populations’ types confirmed that 0. Longistaminata was an allogamous species, but partial selfcompatible plants occurring in weedy populations could arise from introgressions with cultivated rices. The analysis of isozyme polymorphism on 20 loci pointed out that electrophoretic evidences of introgressions were restricted to particular and without rhizomes forms called Obake; these plants were supposed to be hybrid derivatives from indica varieties of O. Sativa. A genetic model based on a complementary set of letal genes was previously reported to assume the reproductive isolation between O. Longistaminata and the others rice species but back cross progenies did not fit with theoretical expectations and suggested penetrance effects of genes involved in reproductive barrier; besides, the heredity of rhizomatous habit presumed a close connection between the reproductive barrier and rhizomes expression. Electrophoretically detectable events indicated that interspecific hybridizations were subjected to genetic modifications including transposable elements and led to set up a comprehensive model to assume experimental data as a whole. The mechanisms of introgressions dynamic were cleared up and the Obake state was interpreted as a syndrome of cumulative deleterious effects. The evolutive significance of interspecific relationships within the Sativa group was inferred from the effects of the migration process in Africa of the wild rices; consequently, the results emphasized the major contribution of perennial forms for introducing genetic variability in cultivated rices. The basis of an efficient utilisation in plant breeding of genetic ressources provided by 0. Longistaminata were considered
Liu, Yongbo. "Conséquences écologiques et évolutives du flux de gènes entre Brassica napus transgénique et ses apparentés sauvages". Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00584017.
Texto completoEl, Ayari Tahani. "Barrières au flux génique en Méditerranée Occidentale : étude de la différenciation génétique chez deux mollusques marins, Mytilus galloprovincialis & Stramonita haemastoma". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS226/document.
Texto completoPopulation genetics has revealed the genetic diversity of marine species is often subdivided into a mosaic of discrete patches, within which populations are genetically homogeneous, delineated by discontinuities called barriers to gene flow. The aim of this thesis was to contribute to better understand the processes explaining the origin, maintenance and location of genetic barriers at the Atlantic/Mediterranean transition zone. First, we studied the genetic structure of the mussel Mytilus galloprovincialis. In contrast to the abrupt narrow cline reported in Spain, we discovered along the Algerian coastline a 600 km wide mosaic hybrid zone eastward of the Almeria-Oran oceanic front. Second, we studied the genetic structure of a marine gastropod Stramonita haemastoma. We discovered two cryptic lineages differentially fixed for alternative mitochondrial haplogroups, and differentiated at three microsatellite markers developed in this PhD work. Surprisingly, the spatial distribution proved to be an unusual mosaic with a patch of the Atlantic lineage enclaved in the north of the Western Mediterranean Sea, bordered in the South by a hybrid zone in eastern Spain around Valencia. These two studies highlight the importance of intrinsic reproductive isolation in explaining the mosaic distribution of the marine genetic diversity. Although boundaries between patches coincide with physical barriers to dispersal or ecotones, hydrography and environment mainly explain the position of the genetic discontinuities but neither their origin nor their maintenance
Fargue, Agnès. "Maîtrise des flux de gènes chez le colza : Etude ex-ante de l'impact de différentes innovations variétales". Phd thesis, INAPG (AgroParisTech), 2003. http://tel.archives-ouvertes.fr/tel-00005713.
Texto completoPour lévaluer dans diverses situations culturales, le modèle GENESYS-COLZA a été utilisé. Différentes expérimentations ont été mises en place pour mesurer leffet de la compétitivité, du taux dautogamie et de lémission de pollen sur les flux de gènes et mesurer leur gamme de variation. Le modèle a ensuite été utilisé pour estimer leffet des paramètres génotypiques sur les flux de gènes. Les paramètres les plus pertinents semblent être lémission de pollen et lautogamie pour les flux entre parcelles et la hauteur pour la contamination des cultures suivantes.
Dautres simulations ont été effectuées pour répondre à des questions de la filière.
Fargue, Agnès. "Maîtrise des flux de gènes chez le colza : Etude ex-ante de l'impact de différentes innovations váriétales". Paris, Institut national d'agronomie de Paris Grignon, 2002. http://www.theses.fr/2002INAP0049.
Texto completoBierne, Nicolas. "Barrières au flux génique en milieu marin : sélection et dispersion larvaire dans la zone d'hybridation des moules côtières Mytilus edulis et M. galloprovincialis". Montpellier 2, 2001. http://www.theses.fr/2001MON20142.
Texto completoLakis, Ghayas. "Dynamique évolutive de la durée du cycle de mil : effet des flux de gènes et des pratiques paysannes". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112166.
Texto completoDomestication of pearl millet (Pennisetum glaucum) in the Sahel of Africa has produced a wide range of diversity in cycle duration of landraces. This diversity allows Sahelian farmers to outface the precipitation fluctuation and to ensure regularity in grain production. Due to ecological and social recent changes, modifications of farmer’s practices could be a factor promoting gene flow between the early and late flowering varieties by increasing the opportunity of neighboring and flowering overlap between them. Such a situation raises questions about the past and current evolutionary dynamics of phenological diversity in this crop.In the first part of my thesis I tried to evaluate the possibility of gene flow between pearl millet varieties in South-West Niger, through a comparative approach among contrasting situations pertaining to the spatial distribution of early and late landraces. Therefore I conducted: 1) a field study where we observed flowering periods, for two types of varieties (early type (Haïni Kiré): 75 to 95 days and late type (Somno): 105 to 125 days of cycle length) in several pearl millet fields, and in two villages 2) a molecular study that allows the assessment of the level of genetic differentiation between late and early flowering populations sampled from four villages (including the two where the field study was conducted) of the same region (Dallol Bosso), using microsatellite markers. I was able to demonstrate the occurrence of pollen flow between the two types of landraces and I also showed evidence of genetic introgression between early and semi-late landraces. Potential mechanisms that would allow for the maintenance of the phenological differentiation between these two varieties and despite the gene flow are discussed.In the second part of this work I used a candidate gene and a population genetics approach, to try to identify genes that may have contributed to the cycle length diversity in pearl millet. I focused on three flowering candidate genes, PgHd3a, PgDwarf8 and PgPHYC which have been shown to be involved in the cycle length genetic diversity in several species, in order to estimate the differentiation between wild and domestic pearl millets and between early and late landraces, on the basis of theses candidate genes. I also tried to track for the fingerprint of eventual past selective events within these candidate genes. To be able to distinguish the effects of selection from the effect of demographic events that occurred during the domestication process, I used 8 neutral STS loci and an Approximate Bayesian Computation approach.My results strongly suggest that PgHd3a and PgDwarf8 were likely targeted by selection during domestication. However, a potential role of any of the three candidate genes in the phenological differentiation between early and late landraces was not supported by our data. The Bayesian approach confirmed the idea, suggested by many authors, that the gene flow from the wild to the domestic genetic pool has contributed significantly to the genetic diversity of the domestic pearl millet
Mendes, Marianna. "Etude des facteurs qui affectent la performance des géosynthétiques bentonitiques sous flux de gaz et liquides en barrières des installations de stockage de déchets". Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00738413.
Texto completoMendes, Marianna Jacominy de Amorim. "Etude des facteurs qui affectent la performance des géosynthétiques bentonitiques sous flux de gaz et liquides en barrières des installations de stockage de déchets". Grenoble, 2010. http://www.theses.fr/2010GRENU014.
Texto completoGeosynthetic Clay Liners (GCLs) are synthetic materials composed by a core of calcium or sodium bentonite, either in powder or granular, bonded to one or more geosynthetic layers (geotextile or geomembrane, in general). These layers are usually bonded by an adhesive, needle-punching, stitch-bonding or sewing. When hydrated and confined, they fulfil functions of liquid or gas barrier with their hydraulic performance depending in most cases on the hydraulic conductivity of the bentonite. Thanks to their low permeability to water and gases, GCLs are often used in municipal solid waste landfill applications, combined to compacted clay liners (CCL) or with geomembranes (GM) as part of both bottom and cover liners. Previous studies were conducted to investigate the most important factors that influence the gas/liquid flow rate through GCLs or composite liners. Although the nature of bentonite is so important in the permeability of the GCLs there is a lack of data in the literature regarding the influence of the nature of the bentonite on the gas flow through GCLs and liquid flow through composite liners involving GCLs. That is what this thesis aims at clarifying. Furthermore, in conjunction with the nature of the bentonite, the impact of the manufacturing process of the GCL on the flow rate and transmissivity at GM-GCL interfaces was also discussed. Two studies were performed: (i) investigation of the GCL permeability to gas simulating the covering conditions of municipal solid waste landfill; (ii) investigation of liquid transfer through composite liners GM-GCL-CCL due to a defect in the geomembrane, simulating typical conditions of bottom liners in landfills. In the first study, an apparatus recently proposed, based on the falling pressure method, was used in tests to verify the GCL permeability to gas. Three stitch bonded GCLs from the same manufacturer differing by the bentonite nature (natural sodium, natural calcium and activated calcium) were tested. The results showed that the gravimetric water content of the GCL necessary to attain a certain permeability value depends on the bentonite nature, which was not observed in terms of volumetric water content. However, other factors showed to be more important than the nature of bentonite in the GCL permeability to gas: the desiccation due to the gas flow can increase significantly the permeability, which compromise the GCL performance as a gas barrier. The second study focused in investigating the influence of the GCL characteristics in the liquid flow through a composite liner under bottom liners solicitations. Four types of GCLs with two different bonding processes (stitch-bonded or needle-punched) and different bentonites (natural sodium or natural calcium) were tested. The results obtained showed no significant differences among flow rate versus time in most of the tests performed, especially after steady-state conditions of flow having been reached. An analytical solution was employed to estimate the transmissivity of the GM-GCL interfaces. This solution also allowed predictions of flow rates and radius of wetted areas for typical configurations of composite liners in the field. The results obtained showed little influence of the nature of the bentonite and the predominance of influence of the presence of preferential flow paths between the geomembrane and the GCL surface on the transmissivity of GM-GCL interfaces and flow rates through composite liners
Geocompostos bentoníticos (GCLs) são materiais sintéticos compostos por um núcleo de bentonita sódica ou cálcica, em pó ou em grânulos, unido a uma ou mais camadas de geossintéticos (geotêxtil ou geomembrana, geralmente). Essas camadas são ligadas por adesivo, agulhagem ou costura. Quando hidratados e confinados, eles cumprem função de barreira de líquidos ou gases com o seu desempenho dependendo, na maioria dos casos, da condutividade hidráulica da bentonita. Graças à baixa permeabilidade aos líquidos e gases, GCLs são comumente usados em aterros sanitários, associados a camada de argila compactada (CCL) e geomembrana (GM) para compor as impermeabilizações de cobertura e fundo dessas instalações. Estudos precedentes investigaram os fatores mais influentes no fluxo de gás/líquidos através de GCLs ou barreiras compostas. Apesar da natureza da bentonita ser tão importante para a permeabilidade dos GCLs, não há dados na literatura a respeito da influência da natureza da bentonita no fluxo de gás através de GCLs ou fluxo de líquidos através de barreiras compostas envolvendo GCLs. Isso é o tema que a presente tese quer esclarecer. Além de estudar a influência da natureza da bentonita, o impacto do processo de manufatura do GCL na vazão e na transmissibilidade na interface GM-GCL também foi discutido. Dois estudos foram conduzidos: (i) investigação da permeabilidade ao gás de GCLs simulando as condições de cobertura de aterros sanitários; (ii) investigação do transporte de líquidos através de barreiras compostas GM-GCL-CCL devido a um dano na geomembrana, sob condições típicas do fundo de aterros sanitários. No primeiro estudo, um equipamento recentemente proposto, cujo funcionamento baseia-se no método da queda de pressão, foi usado em ensaios para verificar a permeabilidade ao gás de GCLs. Três GCLs costurados do mesmo fabricante, diferindo pela natureza da bentonita (sódica natural, cálcica natural e cálcica ativada) foram testados. Os resultados mostram que o teor de umidade gravimétrica necessário para atingir certa permeabilidade depende da natureza da bentonita. O mesmo não foi observado em termos de teor de umidade volumétrica, destacando a importância da estrutura da bentonita na sua permeabilidade. No entanto, outros fatores se mostraram mais importantes do que a natureza da bentonita na permeabilidade ao gás dos GCLs: a dessecação devido ao fluxo de gás pode aumentar significativamente a permeabilidade, o que compromete o desempenho do GCL como barreira. O segundo estudo focou na investigação da influência das características do GCL no transporte de liquido através de uma barreira composta sob condições típicas da base de aterros sanitários. Quatro tipos de GCLs com dois processos de manufatura (costurado ou agulhado) e duas bentonitas diferentes (sódica natural ou cálcica natural) foram ensaiados. Os resultados obtidos mostram que não houve influência significativa de vazão versus tempo para os ensaios conduzidos, especialmente depois de atingido o regime permanente de fluxo. Uma solução analítica foi empregada para estimar a transmissibilidade da interface GM-GCL. Essa solução permitiu também a previsão de vazamento e raio da área molhada em barreiras compostas de dimensões reais. Os resultados obtidos mostram pouca influência da natureza da bentonita na vazão e a predominância de caminhos preferenciais de fluxo na interface transmissível GM-GCL
Rontein, Denis. "Métabolisme intermédiaire dans des cellules végétales : de l'expression des gènes de la phosphoénolpyruvate carboxylase à la régulation de son flux". Bordeaux 2, 2000. http://www.theses.fr/2000BOR28811.
Texto completoDesplanque, Benoît. "Betteraves mauvaises herbes et rudérales : diversité génétique, traits d'histoire de vie et flux de gènes au sein du complexe d'espèces cultivées-sauvages Beta vulgaris ssp". Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-441.pdf.
Texto completoRivet, Yannick. "Les populations de Culex pipiens (diptera : culicidae) vues au travers des gènes de résistance aux insecticides organophosphorés : étude dans la région Rhône-Alpes". Lyon 1, 1992. http://www.theses.fr/1992LYO1T107.
Texto completoDeville, Alexandra. "Suivi de terrain, expérimentations et modélisation : des approches complémentaires pour l'étude de l'impact des populations de colza hors-champ sur les flux de gènes au sein des agro-écosystèmes". Paris 11, 2004. http://www.theses.fr/2004PA112304.
Texto completoRisk assessment of (trans)gene persistence and dispersal in space and time requires a good knowledge of the vehicles spreading (trans)genes in agro-ecosystems. Feral populations of oilseed rape, located in field margins can act as relays in (trans)genes dispersal. Three complementary approaches were carried out at an agricultural-area scale (Selommes, Loir-et-Cher) to specify the role of such populations in gene dispersal. First, a field survey of all oilseed rape populations (cultivated, feral, volunteers and fallows) in the studied area was conducted for 4 years using GPS cartography. This survey was completed with (i) phenotypic and genotypic analysis of seeds from these populations and (ii) farmers surveys. Second, we identified key-parameters of the life-cycle of feral populations and studied the effect of road verges management (mowing and herbicide treatment) using a demographic study based on modelling and field surveys. Third, an experimental study was designed to evaluate the adaptation of feral populations to their environment. We demonstrate that feral populations of oilseed rape have a potentially influential impact on gene dispersal. They seem to persist through time via self-recruitment or soil seed bank In addition, hybridizations between plants of different populations appear relatively frequent. These specific data collected on feral populations of oilseed rape at a realistic space and time scale are required to refine the predictions of models of gene dispersal and improve risk assessment of gene dispersal
Robert, Thierry. "Dynamique des flux de gènes entre formes sauvages et cultivées du mil (Pennisetum typhoides Stapf et Hubb) : impact des sélections gamétophytiques". Paris 11, 1989. http://www.theses.fr/1989PA112166.
Texto completoCoulon, Aurélie. "Etude de l'influence du paysage sur la dispersion du chevreuil (Capreolus capreolus) en milieu fragmenté". Toulouse 3, 2006. http://www.theses.fr/2006TOU30144.
Texto completoDispersal is a crucial life history trait in population functioning. As most wild species live in heterogeneous landscapes, it is important to understand how the different elements constituting these landscapes influence dispersal movements and determine connectivity between resource patches. It is the goal of this study, realised on a roe deer population inhabiting a rural landscape of Haute-Garonne (south-western France), characterised by its fragmented wooded habitat. The combination of analyses of movements of 20 individuals fitted with GPS collars and of gene flow organisation within a sample of more than 1000 individuals genotyped at 11 microsatellites enabled to study in a complementary way different aspects of the question. We showed that dispersal occurs preferentially along wooded corridors and that elements associated with potential disturbances (buildings, roads) are avoided during movements. The cumulative presence of canals, a highway and the Garonne river limits dispersal movements between the two areas they delimit and affects population genetic structure. Integrating the different results of this study in a spatially-explicit individual-based model should allow interesting applications for landscape connectivity analysis and management units definition
Muller, Marie-Hélène. "Flux de gènes et domestication : l'histoire évolutive d'un complexe sauvage-cultivé. Approches expérimentale et théorique chez la luzerne pérenne (Medicago sativa L. )". Montpellier 2, 2002. http://www.theses.fr/2002MON20006.
Texto completoJuan, Thomas. "Identification de nouveaux gènes essentiels à la mise en place de la latéralité chez le poisson-zèbre". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4116.
Texto completoThe proper establishment of Left/Right (L/R) asymmetry is fundamental to normal development in bilaterians. However, the initial mechanisms involved in symmetry breaking and their conservation throughout the course of evolution remain poorly understood. In zebrafish, the L/R organizer region or Kupffer’s vesicle (KV) consists as a fluid filled cavity, whose circular counterclockwise motion is driven by the motion of motile cilia. We have observed the presence of vesicles containing the ESCRT component Chmp1b in the lumen of the KV. Hence, the diminution of their number is associated with laterality defect, suggesting a potential role for those vesicles in L/R asymmetry establishment. We also participate to show that in spite of its overall circular geometry, the KV flow can ensure the directional transport of vesicles in the organ lumen. Secondly, we are also showing that the function of the Myo1D protein, implicated in L/R asymmetry establishment in drosophila, is conserved in zebrafish. The loss of Myo1D leads to an impaired early lateralization. Moreover, Myo1D functionally interact with the protein Vangl2, a component of the PCP pathway, which controls the tilt and positioning of KV cilia. These findings are supportive of a mechanism according to which Myo1D system represents a conserved molecular machinery essential for L/R asymmetry establishment in bilaterians
Fouchet, Pierre. "Caractérisation de l'hétérogénéité de populations bactériennes par cytométrie en flux : études de paramètres physiologiques et structuraux". Compiègne, 1994. http://www.theses.fr/1994COMPD696.
Texto completoSimard, Frédéric. "Variabilité génétique et flux de gènes chez les moustiques anophèles arabiensis et anophèles gambiae, vecteurs du paludisme en Afrique. Apport des loci microsatellites". Nancy 1, 1999. http://www.theses.fr/1999NAN10147.
Texto completoMenneson, Eric. "TRANSPORT TRANSENDOTHÉLIAL DE GÈNES : ÉTUDES DYNAMIQUES DU PASSAGE SÉLECTIF DE POLYPLEXES AU TRAVERS DE L'ENDOTHÉLIUM VASCULAIRE PULMONAIRE". Phd thesis, Université d'Orléans, 2005. http://tel.archives-ouvertes.fr/tel-00011964.
Texto completoJuan, Thomas. "Identification de nouveaux gènes essentiels à la mise en place de la latéralité chez le poisson-zèbre". Electronic Thesis or Diss., Université Côte d'Azur (ComUE), 2017. http://theses.univ-cotedazur.fr/2017AZUR4116.
Texto completoThe proper establishment of Left/Right (L/R) asymmetry is fundamental to normal development in bilaterians. However, the initial mechanisms involved in symmetry breaking and their conservation throughout the course of evolution remain poorly understood. In zebrafish, the L/R organizer region or Kupffer’s vesicle (KV) consists as a fluid filled cavity, whose circular counterclockwise motion is driven by the motion of motile cilia. We have observed the presence of vesicles containing the ESCRT component Chmp1b in the lumen of the KV. Hence, the diminution of their number is associated with laterality defect, suggesting a potential role for those vesicles in L/R asymmetry establishment. We also participate to show that in spite of its overall circular geometry, the KV flow can ensure the directional transport of vesicles in the organ lumen. Secondly, we are also showing that the function of the Myo1D protein, implicated in L/R asymmetry establishment in drosophila, is conserved in zebrafish. The loss of Myo1D leads to an impaired early lateralization. Moreover, Myo1D functionally interact with the protein Vangl2, a component of the PCP pathway, which controls the tilt and positioning of KV cilia. These findings are supportive of a mechanism according to which Myo1D system represents a conserved molecular machinery essential for L/R asymmetry establishment in bilaterians
Cardenas, Leyla. "Dispersal ability and genetic structure in Concholepas concholepas (Bruguiière, 1789) : effects of historical and contemporary events". Paris 6, 2007. http://www.theses.fr/2007PA066405.
Texto completoBased on the study of the marine gastropod Concholepas concholepas, spread along the Chilean coasts, this thesis aimed at examining the correlation between biogeographic and phylogeography patterns and the role played by the present-day dispersal on the maintenance of the historical population structure. On an historical time scale, the analysis of sequences of a mitochondrial DNA gene (COI) on ca. 400 individuals from 14 localities along 4000 km of coastline revealed a rapid demographic and geographic expansion. On a contemporary time scale, the use of 11 microsatellites showed that the effective dispersal represents only a fraction of the potential larval ability previously hypothesized based on the pelagic larval duration: dispersal strongly vary according to hydro-dynamic patterns (retention zone) and habitats (fjords vs. Linear coasts). The results of this thesis have implications on management and conservations policy applied to C. Concholepas
Johanet, Aurélie. "Flux de gènes inter- et intra-spécifiques chez des espèces de vallées alluviales : cas des tritons palmés et ponctués en vallée de la Loire". Phd thesis, Université d'Angers, 2009. http://tel.archives-ouvertes.fr/tel-00477761.
Texto completoNaino, Jika Abdel Kader. "Flux de gènes et évolution des ressources génétiques du mil (Pennisetum glaucum) dans le Bassin du Lac Tchad : rôle de la diversité socio-culturelle". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS180/document.
Texto completoThe resilience of sub-Saharan farming systems to environmental and socioeconomic disturbances is partly based on the maintenance of agro-biodiversity, but also on preserving the right for farmers to reproduce and freely exchange seeds and related knowledge. However, few data are actually available on effective seed flow and on mechanisms modulating gene flow and genetic introgression between landraces grown in Sahelian farming systems. For pearl millet especially, there are only very few data on the relationship between diversity of this crop on the one hand and the socio-cultural diversity of farmers on the other hand. In the first part of my thesis, I was interested in assessing a potential relationship between ethnolinguistic diversity and population genetic structure of pearl millet in the Lake Chad Basin. Analysis of molecular polymorphisms suggests the existence of social barrier to seed flow among ethnolinguistic groups. However, these barriers are not sufficient to prevent genetic introgression between pearl millet populations cultivated by farmers belonging to different ethno-linguistic groups. In the second chapter, I focused on the role of local adaptation on gene flow. The results led me to propose the hypothesis that gene flow between early and late landraces are higher in the northern regions where rainfall is weak. Finally in the third part, I have quantified the biochemical compound of pearl millet seeds belonging to different varieties that show different uses or culinary preferences among farmers belonging to different ethnolingiuistic groups. I used a combined approach of proteomics and metabolics. Among the 1072 protein spots quantified only 7 distinguish the very photoperiodic non photoperiodic landrace. Metabolomics data suggest the presence of fungi, possibly endophytes, in some of the samples analyzed
Sester, Mathilde. "Modélisation de l'effet des systèmes de cultures sur les flux de gènes entre culture transgénique et adventice apparentée : cas de la betterave sucrière (Beta vulgaris L.)". Phd thesis, Université de Bourgogne, 2004. http://tel.archives-ouvertes.fr/tel-00080792.
Texto completoÀ cause des dimensions spatiales et temporelles du flux de gène ainsi que de la large gamme de variabilité des systèmes de culture, il est impossible d'étudier le phénomène exclusivement en expérimentation. Par conséquent, nous avons développé un modèle (GENESYS-BETTERAVE) qui quantifie les effets des systèmes de culture sur ce flux de gènes. Il est centré sur le cycle de développement des betteraves cultivées et adventices dans chaque parcelle basé sur une succession de stades clé (plantules, montées, plantes en fleurs, production semencière, stock semencier). Pour chaque stade est calculée la densité d'individus dans la parcelle ainsi que les proportions génotypiques, principalement celles des individus transgéniques. Les relations entre les stades dépendent des cultures en place dans les parcelles, des techniques utilisées pour gérer ces cultures ainsi que du génotype des betteraves. Pendant la floraison, du pollen est échangé entre les parcelles et l'importance de cette dispersion dépend du parcellaire. Une partie des informations nécessaires à la réalisation du modèle, est tirée de la littérature.
Des expérimentations sont ensuite réalisées pour étudier et quantifier les parties encore peu connues du cycle de développement. Elles ont permis de décrire et de modéliser le devenir des semences enfouies de betteraves adventices, en mesurant la mortalité in situ, les capacités de germination des semences et de croissance pré-levée des plantules en fonction des saisons. D'autres essais ont permis de modéliser toutes les étapes clé du développement des betteraves adventices et des traînantes (dynamique et taux de montaison, dynamique de floraison, production de pollen...) dans les cultures les plus fréquentes de la rotation betteravière.
Après avoir été programmé sous forme de logiciel, le modèle est alors utilisé pour des simulations simples qui montrent qu'il prend bien en compte les éléments caractéristiques des systèmes de cultures, en attendant une validation pour vérifier à plus grande échelle le réalisme de la prédiction.
Soularue, Jean-Paul. "Évolution de la phénologie des arbres à l'échelle d'un paysage forestier". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14724/document.
Texto completoTiming of bud burst (TBB) is a key adaptive trait affected by temperature variations. Predicting the evolution of natural forests undergoing environmental variations requires to understand the evolutionary dynamics that have resulted in the strong patterns of differentiation characterized for this trait. It has been shown experimentally that the TBB was strongly correlated with the timing off lowering. This suggests that trees having similar TBB tend to mate preferentially, making assortative mating at TBB the default reproduction regime within tree species. Clinal patterns of genetic differentiation have been mostly interpreted as resulting from divergent selection, however, few studies have considered the peculiar features of timing of bud burst. Through a modelling approach based on quantitative genetics models, we first demonstrate here that the sole interaction between assortative mating at TBB and pollen flow can induce a clinal differentiation among populations without any selection pressure. In a such theoretical context, assortative mating filters pollen flow in presence of environmental gradients and progressively shifts the genetic values of populations. Then, we demonstrate that assortative mating amplifies the adaptive response of populations to co-gradient selection, and constrains it in the case of countergradient selection. Finally, we show that assortative mating differentiates populations even in the case of uniform selection
Dussert, Yann. "Évolution de la durée du cycle et du contrôle de l'architecture lors de la domestication du mil (pennisetum glaucum)". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066665.
Texto completoPearl millet is a cereal cultivated in the sudano-sahelian area in Africa. Using a data set consisting of 18 microsatellites and 8 nucleotide sequences for 45 domesticated and wild populations, I showed the existence of a high differentiation between two wild genetic pools. Using the model-based Approximate Bayesian Computation (ABC) approach, I tested different domestication scenarios and showed that a single domestication in eastern Sahel is more likely than other models.There are two main types of domesticated pearl millet: early-flowering and late-flowering varieties. My results show a lack of neutral genetic differentiation between these two types, suggesting the existence of recurrent gene flow. I also studied a candidate gene, PgHd3a, belonging to the Hd3a-like family and which could be implicated in the floral transition. No selection footprint has been detected, and it is likely this gene is not involved in the phenotypic difference between early and late-flowering varieties. Expression results casted some doubt about its role during floral transition in pearl millet. I also isolated a new paralog of PgHd3a, PgHd3a-2.Finally, I studied a longitudinal frequency cline at the continental scale for the presence of a Miniature Inverted-repeat Transposable Element (MITE) located in the teosinte branched1 gene, involved in the regulation of the number of tillers in maize. By comparing differentiation levels between the MITE and 13 neutral microsatellites, and by investigating the nucleotide polymorphism in the genomic region surrounding the MITE, I showed the cline was probably caused by neutral processes
Poilleux-Milhem, Hélène. "Test de validation adaptatif dans un modèle de régression : modélisation et estimation de l'effet d'une discontinuité du couvert végétal sur la dispersion du pollen de colza". Paris 11, 2002. http://www.theses.fr/2002PA112297.
Texto completoThis thesis framework is the spread of genetically modified organisms in the environment. Several parametric models of the individual pollen dispersal distribution have already been proposed for homogeneous experiments (plants emitting marked pollen surrounded by the same unmarked plants). In order to predict the "genetic pollution" in an agricultural landscape, a discontinuity effect on pollen flows in a cultivated area (e. G. A road crosses a field) has to be taken into account. This effect was modelled and estimated: according to the size of the discontinuity, it may correspond to a significant acceleration of the pollen flow. Graphical diagnosis methods show that the modelling of the individual pollen dispersal distribution and of the discontinuity effect, is best fitting the data when using constant piecewise functions. Prior to using parametric models to predict genetic pollution, goodness-of-fit tools are essential. We therefore propose a goodness-of-fit test in a nonlinear Gaussian regression model, where the errors are independent and identically distributed. This test does not require any knowledge on the regression function and on the variance of the observations. It generalises the linear hypothesis tests proposed by Baraud et al (Ann. Statist. 2003, Vol. 31) to the nonlinear hypothesis. It is asymptotically of level α and a set of functions over which it is asymptotically powerful is characterized. It is rate optimal among adaptive procedures over isotropic and anisotropic Hölder classes of alternatives. It is consistent against directional alternatives that approach the null hypothesis at a rate close to the parametric rate. According to a simulation study, this test is powerful even for fixed sample sizes
Dussert, Yann. "Évolution de la durée du cycle et du contrôle de l'architecture lors de la domestication du mil (pennisetum glaucum)". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066665.
Texto completoPearl millet is a cereal cultivated in the sudano-sahelian area in Africa. Using a data set consisting of 18 microsatellites and 8 nucleotide sequences for 45 domesticated and wild populations, I showed the existence of a high differentiation between two wild genetic pools. Using the model-based Approximate Bayesian Computation (ABC) approach, I tested different domestication scenarios and showed that a single domestication in eastern Sahel is more likely than other models.There are two main types of domesticated pearl millet: early-flowering and late-flowering varieties. My results show a lack of neutral genetic differentiation between these two types, suggesting the existence of recurrent gene flow. I also studied a candidate gene, PgHd3a, belonging to the Hd3a-like family and which could be implicated in the floral transition. No selection footprint has been detected, and it is likely this gene is not involved in the phenotypic difference between early and late-flowering varieties. Expression results casted some doubt about its role during floral transition in pearl millet. I also isolated a new paralog of PgHd3a, PgHd3a-2.Finally, I studied a longitudinal frequency cline at the continental scale for the presence of a Miniature Inverted-repeat Transposable Element (MITE) located in the teosinte branched1 gene, involved in the regulation of the number of tillers in maize. By comparing differentiation levels between the MITE and 13 neutral microsatellites, and by investigating the nucleotide polymorphism in the genomic region surrounding the MITE, I showed the cline was probably caused by neutral processes
De, Cauwer Isabelle. "Importance relative des flux de gènes et de la valeur sélective individuelle dans les variations de sex ratio chez une espèce gynodioïque, Beta vulgaris ssp. maritima". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10048/document.
Texto completoIn flowering plants, which exhibit a spectacular diversity of reproductive strategies, gene dispersal generally occurs through two distinct pathways: pollen for the male function, and seed for the female function. Among sexually polymorphic flowering plants, gynodioecy refers to a particular breeding system in which females and hermaphrodites co-occur in natural populations. Since females reproduce only through seeds, they apparently transmit their genes only half as frequently as hermaphrodites, which gain fitness through both seed and pollen production. This apparent evolutionary paradox has attracted the attention of evolutionary biologists as far as the mid-nineteenth century. The aim of this PhD thesis was to understand the successful maintenance of female individuals and the important spatial variations in sex ratio that are often observed in natural populations of gynodioecious Beta vulgaris ssp. maritima, in which sex is determined by interactions between cytoplasmic male sterility (CMS) genes and nuclear restorers of male fertility. Using population biology and population genetics approaches, three distinct themes were considered. (i) First, male and female fitness of the different sexual types were compared, using both measures in controlled conditions and paternity analyses in the wild. While our results only suggest a very restricted female advantage, we detected strong male fitness differences among hermaphrodites that were partially explained by the genotype of individuals and by the occurrence of a cost of restoration. (ii) The study of the distribution of genetic diversity in several natural populations and in several consecutive cohorts allowed us to quantify the relative impact of migration, founder events and genetic drift on the spatial distribution of sexes. Overall, random founder effects with spatially restricted pollen and seed flow appeared to be the primary determinants of sex ratio variations. (iii) Finally, we explore how such sex ratio variation can affect the reproductive output of hermaphrodites and females. Altogether, we show that fine-scale spatial structure, resulting from the joint action of founder events and limited gene flow, can notably modify the dynamics of gynodioecy in natural populations
Bardonnet, Clara. "Une analyse de la connectivité fonctionnelle du paysage : Etude des déplacements et des flux de gènes chez un mustélidé forestier, la Martre des pins (Martes martes)". Thesis, Reims, 2015. http://www.theses.fr/2015REIMS013/document.
Texto completoLandscape changes, generated by anthropogenic activities, are widely recognised as one of the main causes of global biodiversity decline. Leading to a loss of functional landscape connectivity, they disrupt movements and gene flow which play a primordial role for the persistence of populations. However, the relationship between these processes and landscape structure remains unclear. In this context, we studied landscape connectivity in European pine marten, a forest species present in fragmented landscapes. We evaluated landscape resistance, i.e. how landscape features impede or facilitate movements and gene flow, analysing genetic variability of groups sampled in 13 forest sites of the Champagne-Ardenne regional area, and studying individual fine-scale movements in both continuous and fragmented areas. We showed that intensive agricultural plain and certain linear infrastructures could impede movements. In addition, we showed that hedgerows facilitate movements between forest patches and we suggested that vegetation height of open habitats could play a role for these movements. This study provides important insights on movement ecology of the European pine marten and underlines the need to take into account responses of organisms in the establishment of ecological networks
Arnaud, J. F. "Importance de la dispersion dans la structuration génétique et l'évolution du système de reproduction chez une espèce gynodioique". Habilitation à diriger des recherches, Université des Sciences et Technologie de Lille - Lille I, 2008. http://tel.archives-ouvertes.fr/tel-00418811.
Texto completoGaüzère, Julie. "Effets de la dispersion du pollen à longue distance sur les capacités d'adaptation de populations de Hêtre commun le long d'un gradient altitudinal". Thesis, Montpellier, SupAgro, 2014. http://www.theses.fr/2014NSAM0028/document.
Texto completoThe rapidity of the climate change observed and predicted raises the issue of how fast species can adapt to future. In face of environmental change, populations can adapt without migrating thanks to their plastic response in a first time, and to their response to selection in the long term (genetic adaptation). In conditions of environment variable both in space and time, gene flow can enhance the spread of beneficial alleles between populations. The objective of this thesis is to experimentally measure the adaptive differentiation and the long-distance pollen dispersal along an elevational gradient of beech populations (Fagus sylvatica). In this study we investigated three beech populations located on the northern side of the Mont-Ventoux (from 900m to 1400m of elevation). Twelve potential adaptive functional traits (phenological, physiological and morphological) have been measured on 60 maternal families collected from these populations (20 mothers/population, 100 offspring/mother) and planted in nursery. The results of this thesis show that that (i) the strong pollen immigrant rate received by the populations (m = 56 %) did not their prevent adaptive differentiation, (ii) the action of natural selection erodes the genetic variance of the traits, (iii) despite significant genetic variance for all the traits, the genetic covariance between traits should affect the rate and direction of evolution in the future, and (iv) gene flow contribute to increase the total genetic variance within the populations. Finally, populations at medium and high elevations may have the potential to adapt to future climate
Monthe, Kameni Franck Stéphane. "Origine et dynamique de la diversité génétique des arbres Guinéo-Congolais du genre Entandrophragma et implications pour une gestion durable". Doctoral thesis, Universite Libre de Bruxelles, 2019. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/283779.
Texto completoDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Fulgencio, Jean-Pierre. "Effets d'un biguanide et de deux thiazolidinediones sur le métabolisme du glucose et des acides gras dans des hepatocytes de rat : des flux métaboliques à l'expression de gènes". Paris 7, 2003. http://www.theses.fr/2003PA077047.
Texto completoFrançois, Donatien. "Connectivité fonctionnelle chez Vipera berus (Linnaeus, 1758), une espèce peu dispersante et aux mœurs discrètes : caractérisation des flux de gènes à fine échelle spatiale au sein d’un paysage contrasté". Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1B002.
Texto completoFace to the impact of land-use changes on species dispersal, decisions were recently conducted at French regional scale to favour and to maintain connectivity. The aim of this work was to quantified connectivity for a model species threatened in Western Europe : the common European adder (V. berus). Its secretive behaviour required to use an indirect and individual-based approach to measure its dispersal thanks to molecular techniques. Thus, V berus gene flow were analysed at fine spatial scale (10 × 7 km²) on a study site (A0) made up of two sub-areas with contrasting landscapes (A1/A2), both by land use and their temporal stability (instable/stable). Genetic differentiation on A0 is weak and mainly associated with a strong isolation-by-distance (IBD) pattern. Dispersal is therefore spatially limited in V. berus (natal dispersal ≤ 500m) and related to males concerning adults. Moreover, gene flow is also influenced by landscape heterogeneity : (i) by meadow (A0), urbanisation (A1) and dry grassland and forests (A2), (ii) particularly at 300m around individuals among spatial extent tested (10-500m) and (iii) more by the spatial configuration than the type and quantity of habitat patches. These innovative results contribute to (i) reflection about conservation strategies for V. Berus et (ii) underly the diversity of factors to consider in studying and maintaining connectivity at a more large spatial scale (dispersal pattern and process, spatio-temporal scales)
Abadie, Pierre. "Génétique et évolution de l'isolement reproducteur entre chêne sessile (Quercus petraea (Matt.) Liebl.) et pédonculé (Q. robur L.)". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR15270/document.
Texto completoSpeciation can be defined as the range of processes that lead to the evolution of reproductive isolation among groups of individuals. Past decades have witnessed a renewal in the recognition of natural selection as a primary force in the formation of new species, in particular for ecological speciation models in conditions of sympatry. Sessile oak (Quercus petraea (Matt.) Liebl.) and pedunculate oak (Q. robur L.) are two sympatric species which exhibit large morphological and ecological differences, despite relatively high estimated rates of natural hybridization. However, very little is known about the nature and strength of reproductive barriers between those two species. The objective of this thesis was therefore to characterize their isolating barriers at phenotypic and genetic levels, in order to better understand their relative importance, their role in the process of divergence and their evolution in that species complex. A first approach based on controlled crosses has shown (i) the existence of strong barriers at the pre-zygotic level and that of significant although weaker ones at the post-zygotic level, based on observations from fitness of hybrid progenies, and (ii) a large variability for traits linked to barriers phenotypes, across genotypes and also for their expression in different micro-environments. A second approach of population genomics used 33 candidate genes to reproductive isolation and allowed to identify «speciation genes» submitted to divergent selection, the strongest divergence being observed for genes involved in the flowering pathway. The model of colonization of these oak species in natural stands was discussed in the light of these new results
Duvaux, Ludovic. "Déterminants historiques et sélectifs des échanges génétiques au cours de la spéciation chez la souris domestique : patrons de coalescence et introgression en zone hybride". Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20116/document.
Texto completoUnderstanding the speciation process requires to appraise patterns of gene flow between incipient speices as well as the role of selection in their determination. This thesis attempts to do so using two subspecies of the house mouse, Mus musculus, as a model. We inferred the history of their differentiation based on sequence polymorphism data at 60 autosomal loci. By simulating the coalescent of these loci under several historical scenarios we were able to infer, using an ABC (Approximate Bayesian Computation) method, an ancient divergence of the subspecies (1.5 MY). This was followed by a long period of isolation (1.2 MY) preceding a phase of genetic exchanges that started well before the formation of the present European hybrid zone. The isolation phase lasted long enough to explain a majority of the present genetic incompatibilities. Ancient and lasting gene flow could have favoured a behavioural reinforcement of reproductive isolation. We a lso studied the relationship between the mode of evolution of 77 autosomal genomic regions and their introgression patterns across a hybrid zone. Local recombination rates variations seem to partly account for the patterns observed at some loci with limited and symmetrical introgression. However such is not the case for 40% of the the loci showing asymmetrical introgression in on direction or the other. domesticus results from a movement of the hybrid zone from domesticus to musculus
Khimoun, Aurélie. "Histoire évolutive, contexte spatial et écologique de la divergence de deux sous-espèces d'Antirrhinum majus". Toulouse 3, 2012. http://thesesups.ups-tlse.fr/2280/.
Texto completoThis thesis sought at understanding how evolutionary and ecological processes lead to population divergence and ultimately speciation. To this aim, i integrated the different components of speciation - ecological, spatial and matting isolation - ina temporal framework to gain a better understanding of their dynamicinteraction through time. I studied the ongoing divergence of two snapdragon subspecies of Antirrhiunum majus pseudomajus and A. M striatum. I tested the relative role of historical processes of colonasation (post-glacial colonisation scenario), contemporary barriers to gene flow and local adaptation to explain the current patterns of subspecies distribution and the distribution of their genetic diversity. I also investigated the extent of gene flaw between the two subspecies in the contact zones and the role of environmental factors on the direction of gene flow and the maintenance of disjunct distributions despite gene flow. Finally, i studied the relative roles of neutral processesof dispersal and selective processes in the maintenance of a stable hybrid zone between the two subspecies
Paz, Vinas Ivan. "Distribution de la diversité génétique dans les réseaux dendritiques : patrons, processus et implications pour la conservation de la biodiversité". Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2575/.
Texto completoThe objective of this thesis is to characterize the distribution of genetic diversity in dendritic networks. First, we identify a general spatial pattern of genetic diversity on these ecosystems, as well as the effects of asymmetric gene flow, differential in effective population sizes and colonization processes on this pattern. Second, we characterize patterns of genetic diversity of four freshwater fish species (Gobio occitaniae, Squalius cephalus, Barbatula barbatula and Phoxinus phoxinus) at the Garonne river basin, so as to identify priority areas to protect. Third, we explore the effects of gene flow asymmetry on the inference of populations' demographic histories. Finally, we combine genetic and demographic approaches to evaluate the status of a threathened species (Parachondrostoma toxostoma)
Mallet, Bertrand. "Rôle des facteurs écologiques dans le processus de spéciation en milieu insulaire. Effet de l'habitat et des pollinisateurs sur la diversification du faham (Jumellea spp., Orchidaceae) aux Mascareignes". Thesis, La Réunion, 2014. http://www.theses.fr/2014LARE0020/document.
Texto completoMechanisms responsible for the establishment of reproductive isolation are little studied in island adaptive radiations. According to the theory of ecological speciation, reproductive isolation results from the ecologically-based divergent selection. By their unique characteristics, oceanic islands are ideal systems to study the role of ecological factors in the diversification of endemic lineages. This study focuses on the role of habitat and pollinators in restricting inter and intraspecific gene flow between populations of faham (Jumellea spp.), an orchid endemic to Mascarene Islands. To do this, patterns of phenotypic differentiation (floral traits), environmental differentiation (habitat, altitude, climate) and genetic differentiation (nuclear microsatellites) were compared. At the intraspecific level, the results show that gene flow restriction is mainly due to the colonization of different habitat types with no obvious role of pollinators. At the interspecific level, in addition to the role of habitat, pollinator shift seems to explain effective complete reproductive isolation. By placing these results into the continuum of speciation, it appears that reproductive isolation evolve initially in response to adaptation to different habitats and, in a second phase, would be enhanced by pollinator-driven divergent selection. Operationally, this study reviews the taxonomy of faham and proposes to define management units and priorities in terms of conservation