Dissertations / Theses on the topic 'Biologie des populations – Variabilité'
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Mavarez, Castillo Jesús. "Phylogéographie et biologie des populations de Biomphalaria Glabrata." Montpellier 2, 2002. http://www.theses.fr/2002MON20027.
Full textLeturque, Henri. "Evolution du sexe ratio et de la dispersion en populations structurées." Montpellier 2, 2002. http://www.theses.fr/2002MON20177.
Full textMaurice, Tiphaine. "Variabilité génétique et biologie de l'espèce Arnica montana dans un contexte de fragmentation des populations et de réchauffement climatique." Thesis, Metz, 2011. http://www.theses.fr/2011METZ043S.
Full textGlobal warming and habitat fragmentation are two major threats to rare and endangered species as Arnica montana which we compared the fragmented colline populations (500 m) of the Ardennes-Eifel region with the montane populations of the Vosges crest (1200 m) where the species is still common. We recorded the vegetation and population structure of A. montana in the colline sites (Violion caninae) and the mountains sites (Nardion strictae). However, A. montana had the same niche at the two altitudes. The study of population structure revealed a shift from sexual to clonal reproduction with increasing altitude. A study of molecular genetic variation (AFLP) indicated that populations of A. montana have preserved a relatively high amount of genetic diversity. Populations were genetically differentiated between altitudes, with a stronger isolation by distance for the fragmented colline populations, while the montane populations may be considered as a meta-population. In a common garden experiment involving gardens at two altitudes (200 m and 1200 m), we showed that A. montana had a high phenotypic plasticity and a considerable genetic variability, which could be crucial for A. montana populations to respond to predicted climate changes. A reciprocal transplant experiment between colline and montane populations showed a strong effect of the transplantation sites. Competition for light and herbivory of seedlings may be the main causes of selection. The high plasticity of A. montana might permit the seedlings to survive an increase of at least 2°C in annual temperature
Vitalis, Renaud. "Génétique des populations subdivisées : théorie et applications." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2001. http://tel.archives-ouvertes.fr/tel-00535513.
Full textLe, Corre Nicolas. "Variabilité de la connectivité et du recrutement au sein d'une métapopulation marine." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29881/29881.pdf.
Full textConnectivity of marine populations represents a key element of metapopulation demography, as it links local populations. For marine invertebrates with a bentho-pelagic life cycle, connectivity occurs during the dispersive larval stage, which is primarily driven by marine currents. The main objective of this study was to show the variability of connectivity within marine metapopulations, especially for Mytilus spp. populations in the St. Lawrence maritime estuary. The secondary objective was to further analyse the spatiotemporal variations of settlement and recruitment in this system, since these processes are essential for connectivity. (1) Different methods to assess the variability of connectivity are described, as well as their applicability to different systems. Following a description of the main factors influencing connectivity, the drivers of variability and their implications for marine metapopulations and biodiversity management are discussed. (2) In addition, field studies were conducted and revealed seasonal and inter-annual variability of Mytilus spp. settlement in the boreal St. Lawrence marine ecosystem. These observations showed that settlement, following the initial larval dispersal phase (i.e. large spatial scale), occurred during one or two short periods of time (1 to 2 weeks) during the reproductive season. Moreover, there was also evidence for a secondary post-metamorphic settlement phase (juneniles) that extended over the entire reproductive season and represented a major part of the total settlement, particularly during weeks following primary larval settlement events and storms. (3) Finally, a geostatistic method, based on the relationship between adult biomass and recruitment in different local populations, identified homogeneous demographic coupling at scales from 12-24 km over a five year study, in the direction of the main current. Overall, this study empirically confirms the importance of variations in adult biomass, settlement, and recruitment in determining the variability of connectivity in marine metapopulations and supports theoretical studies considering such fluctuations.
Lanaud, Claire. "Nouvelles données sur la biologie du cacaoyer (Theobroma cacao L. ) : diversité des populations, système d'incompatibilité, haploides spontanés : leurs conséquences pour l'amélioration génétique de cette espèce." Paris 11, 1987. http://www.theses.fr/1987PA112294.
Full textSome aspects of the biology of cocoa tree were studied for their breeding implications. Isozymes electrophoresis was developed to obtain new genetic markers. 9 polymorphic loci and 31 alleles were identified. Studies on the diversity between wild and cultivated populations from various origins revealed large species variability, particularly among Upper Amazon populations. A study on the mechanisms of incompatibility showed different levels of expression when a mixture of incompatible and compatible pollen was used, a partial inhibition of incompatibility, due to their interactions, was observed. The degree of inhibition depended both on the genetic constitution and on the relative proportions of compatible and incompatible pollen mixed on the flowers. In hybrid seeds gardens, where mixed pollinations were frequent, the use of isozymes demonstrated a high level of self-fertilized seeds in progenitors usually incompatible when only pollinated with their own pollen. The origin of spontaneous haploids depended partially on semigamy. Probably due to hamozygosity, depressive effects appeared in many characteristics for doubled haploids, but this was not transmitted in progeny. Different doubled haploid were obtained from a heterozygous genotype thus allowing the opportunity to choose better progenitors than the parent. Meanwhile the use of haploids in a breeding program was limited by a lack of efficiency to obtain them. Results obtained gave information to design new breeding schemes and to assure the multiplication of selected seeds. They emphasize the small part of the genetic diversity of cocoa tree used hitherto. Because of the originality of incompatibility system and in order to valorize cocoa breeding a rigorous control in biclonal seeds gardens must be applied. A better knowledge of population genetics was obtained and consequences for genetic resources management for this species were discussed
Boixel, Anne-Lise. "Environmental heterogeneity, a driver of adaptation to temperature in foliar plant pathogen populations?" Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASA010.
Full textEnvironmental drivers, most notably temperature, affect the biology of phyllosphere microorganisms but also induce changes in their population dynamics, even in their evolutionary trajectories. The impact of climate on foliar plant disease epidemics is usually considered in forecasting models to inform management strategies. Such models focus on averages of environmental drivers but disregard both individual variation within populations and the scale and extent of biologically relevant environmental changes. These simplifications are glossing over substantial levels of individual variation that may have important consequences on the capacity of a population to adapt to environmental changes, and thus on the dynamics of epidemics in a fluctuating or changing climate. To examine the range of validity and consequences of these simplifying assumptions, I investigated how individual variation and environmental heterogeneity jointly affect fitness, phenotypic composition and resilience of populations of a foliar pathogen (Zymoseptoria tritici) inhabiting wheat canopies. Three complementary ways of exploration were adopted in this case study. First, an in vitro high-throughput phenotyping framework was developed, validated, and used to characterise the diversity in patterns of thermal responses existing across Z. tritici populations that were sampled over contrasted scales (spatial and seasonal variation of temperature). Second, the spatio-temporal thermal variations encountered in a wheat canopy, considered as a habitat exerting fluctuating selective pressures on these differential thermal sensitivities of individuals, were investigated in depth. Third, the way selection of “thermotypes” (functional groups of individuals displaying a similar thermal sensitivity) occurs and drives dynamics of Z. tritici populations was examined. To this end, both empirical (in vitro, in planta and in natura) and theoretical (in silico) competition experiments were conducted under increasingly complex selective environments. This research work demonstrates that glossing over the natural extent of individual phenotypic diversity in a phyllosphere microbial population and over the heterogeneity of selective pressures – from phyllo- to mesoclimate – leads to underestimate the resilience of this population, and thus its adaptive potential to environmental variations. In doing so, the results of this thesis, at the interface between epidemiology, micrometeorology, and ecology, improve our understanding of how important is individual variation to population dynamics and how environmental heterogeneity allows to maintain population diversity. Finally, this thesis provides insight into how large-scale patterns and local population processes are interlinked and display a “two-tier” adaptive dynamics
Ndiwa, Titus Chemandwa. "Contribution à la connaissance des populations du tilapia du Nil (Oreochromis niloticus) vivant dans des conditions extrêmes de température et d’alcalinité." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20114/document.
Full textNile tilapia (Oreochromis niloticus) natural genetic resources are found in Africa. These resources are threatened due to modifications of the natural habitats of fishes and uncontrolled introductions of alien species or strains. Nile tilapia populations living in extreme habitats are emblematic of this situation. They represent original and potentially useful genetic resources for Aquaculture. However, the populations are threatened either by strong modifications or introduction of alien species in their habitats. Characterizing these populations constitutes the very first step of their protection and consequently their utilization in aquaculture. In our study we concentrated on two different populations of Nile Tilapia. One living in the alkaline Crocodile Lake (10,590 µS/cm, 10 pH) which is a Crater Lake located in the central Island of Lake Turkana. The second group of population inhabit the hot springs of Loboi Swamp near Lake Bogoria in Kenya. These fish are living in water characterized by high temperatures, around 36°c. All above populations (Crocodile Lake and Loboi Swamp Hot springs) may have experienced some selective pressures to cope with their challenging environments. For Crocodile Lake, fish may have found a way to excrete their nitrogenous wastes because at pH 10, excretion is not possible by simple diffusion. For the hot spring populations, most individuals should have been males as high temperature is known to induce masculinization in O. niloticus. This population may have accumulated adequate mutations to enable them overcome masculinizing effects of high water temperature. To study these populations we used geometric morphometrics and genetic markers (16 microsatellites and mtDNA) and compared them with other related populations from the region. In addition, three sex-linked genes (Cyp19a, Wt1b, amh) were analysed using SNP markers in three populations of Nile tilapia inhabiting hot springs of Loboi Swamp, and compared them to eight other populations from East Africa, Sudano-Sahelian and Ethiopian regions. Significant morphological differences were observed in all populations studied, including three closely related populations of Loboi Swamp, and two genetically related populations from Lake Turkana basin. Both genetic differences and environmental factors were responsible for the observed morphological differences. Similarly, all studied populations were genetically differentiated, and we demonstrated that populations from Loboi Swamp and Lake Baringo have been introgressed by O. leucostictus genes. Analyses of the sex-linked clustered revealed that amh gene is a candidate gene for sex determination in Nile tilapia, with 12 SNPs showing strong associations to phenotypic sex. Nevertheless there is no general pattern of sex determination, rather it seems that sex determination mechanisms are different with respect to populations, but is not characteristic or unique for the entire species
Guyader, Sébastien. "Evaluation du potentiel de variabilité du potato leafroll virus (Luteoviridae, poleovirus) et identification de quelques facteurs de sélection." Rennes 1, 2003. http://www.theses.fr/2003REN10049.
Full textGrenier, Stéphane. "Impact de la plasticité phénotypique et de la sélection sur l'évolution morphologique et génétique des populations : le cas d'une graminée pérenne, Lolium perenne L., sous défoliation." Poitiers, 2011. http://nuxeo.edel.univ-poitiers.fr/nuxeo/site/esupversions/fbc024c5-266b-444a-a7db-4f8a52f1c36c.
Full textPopulation adaptation to environmental pressures can result in morphological changes. These changes may result from two non-exclusive mechanisms, genetic selection and phenotypic plasticity. The objective of this thesis was to identify the mechanisms involved in the adaptation of a perennial ryegrass population under defoliation and to highlight the effect of these mechanisms on the morphological and genetic evolution of this population over one generation. In order to answer these questions, we studied, under two defoliation frequencies, a population consisting of 240 genotypes, derived from a cross between an individual of a turf variety and an individual of a forage variety. We demonstrated the major role of phenotypic plasticity in the morphologic evolution of the population under defoliation during one generation. This plasticity homogenised the population morphology, thus limiting the expression of the genetic variability and maintaining a cryptic genetic diversity. But this phenotypic plasticity was variable depending on the genotype and was also dependent on the initial value of the trait. We showed a genetic basis of the traits and their plasticity. Genomic selection was detected on these QTL, which led to visible and variable effects on the genetic diversity. Nevertheless, the effect of selection seemed not enough strong to be seen at the morphological level from one generation to the other. Phenotypic plasticity of traits seemed to have no effect on the fitness of individuals, which resulted to a low interaction with selection. The results of this thesis are discussed in terms of plant breeding for perennial ryegrass varieties soon in grasslands exploited under different defoliation regimes
Restoux, Gwendal. "Variabilité spatio-temporelle de la reproduction chez une espèce pérenne monoïque : le cas du sapin pectiné, Abies alba Miller, en limite sud de son aire de répartition." Aix-Marseille 3, 2009. http://www.theses.fr/2009AIX30053.
Full textThis study focuses on the spatio-temporal varibility of reproduction in silver fir (Abies alba), in its French rear edge populations in the Mont Ventoux and Lure mountain. Usually, marginal populations contrast from core populations with lower and more variable densities. In our populations of firs, we found that lower densitiy leads to higher selfing rates through a mass-action law at both population and individual levels. As a consequence, germinative abilities were lower for seeds from lower density populations, mainly because of inbreeeding depression. But this was balanced by a higher survival rates at the seedling stage. A more efficient genetic purge could explain this. However, in our populations, a lower density also induced a lower effective seed production, through an increased rate of empty seeds. This can result from pollen limi tation. Indeed, genetic analyses revealed a rather high spatial genetic structure of pollen pool, indicating a limited dispersal with a mean dispersal distance between 20 and 50m. This limited dispersal also induced a high inter-individual variability of the mating system mainly due to variations of local density and individual pollen production. Finally, we found strong inter-annual variations of the pollen pools : giving an inter-mothers differentiation of 8%, we obtained an inter-annual differenciation of 13% within mothers. The year with the higher pollen productions also presented the lower overall genetic diversity. Thus this study confirms the necessity to consider multiple years in studies on the reproduction of a perennial tree such as fir, either for theoretical concerns of for practical questions focused on the management of genetic diversity
Boissinot, Stéphane. "Phylogénie d'allèles et flux géniques dans les populations naturelles : variabilité de l'ADN mitochondrial et du chromosome Y chez la souris domestique." Montpellier 2, 1994. http://www.theses.fr/1994MON20199.
Full textGonzalo-Turpin, Héloïse. "Produire des connaissances pertinentes pour l'action en sciences de la conservation : cas de la gestion de la diversité génétique intraspécifique en restauration écologique." Phd thesis, Toulouse, INPT, 2008. http://oatao.univ-toulouse.fr/7805/1/gonzalo_turpin.pdf.
Full textBertin, Angéline. "Variabilité morphologique et sélection naturelle chez Asellus aquaticus (Crustacea, Isopoda)." Dijon, 2002. http://www.theses.fr/2002DIJOS043.
Full textCompetition between males for reproduction is supposed to favour the development of traits that improve the competitive ability of males. Indeed, a reproductive advantage of large body size in males has been reported in Asellus aquaticus. Such an advantage of large size can also be the consequence of sexual selection acting directly on a character closely correlated to body size. Therefore, we studied how morphology influences male reproductive success. Using geometric morphometric methods, we have evidenced other possible targets of sexual selection. We have also assessed the relative influence of body size and antennae size on the reproductive success of males. Our results confirm that sexual selection on antennae size is partly responsible for the observed large-male advantage in mating. However, selection regimes vary between populations. Additional results from laboratory experiments indicate that population density, though regulating the frequency of both male-male and male-female interactions, can explain the variations observed in the field
Martin, Hélène. "Processus de spéciation et impact des systèmes de reproduction dans le genre Silene : spéciation rapide chez l’espèce gynodioïque Silene nutans et labilité des chromosomes sexuels dans la section Otites." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10191/document.
Full textSpeciation reflects the origins and further development of reproductive barriers. The study of speciation thus requires answering three main questions: which processes lead to reproductive barriers; how effective these barriers are to maintain the genetic integrity of populations; and what are their genetic basis. The goal of my thesis is to attempt to answer these questions in the context of the Silene genus, and to evaluate the potential impact of breeding systems in the speciation process. In the first part, I focused on S. nutans, a gynodioecious species which exhibits two genetic lineages that differentiate in allopatry. Nowadays in secondary contact, the reproductive isolation between these lineages is almost complete. The heterogeneity of selection along the genome has shaped the heterogeneity of genetic differentiation. Therefore, I was not able to propose candidate regions of the genetic basis of the reproductive barriers. In a second part, I focused on the impact of dioecy on population divergence and species adaptation. The discovery of distinct sex determination in close species allowed me to propose to associate the genetic basis of the reproductive isolation to sex chromosome lability. My work furthers the understanding how reproductive barriers developed between two taxas and shows that taking into account the breeding system of taxa and associate genetic conflicts (sex chromosome, cyto-nuclear conflicts) can be important in the study of speciation
Meyer, Claire-Lise. "Évolution des populations métallicoles d’Arabidopsis halleri (Brassicaceae) : étude sur les traits et sur le génome en populations naturelles." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10056/document.
Full textDue to the high concentration of heavy metals and the important environmental modifications, ecological conditions of metalliferous sites are very stressing for most organisms. A few plant species, coined “metallophyte”, have acquired the capacity to grow on heavy metal contaminated soils. Among this group, the pseudometallophyte species (able to grow on contaminated as well as on non contaminated soils) constitute highly relevant models to study local adaptation and relative influence of evolutionary forces in shaping phenotypic differentiation among populations The pseudometallophyte plant Arabidopsis halleri is a model species for tolerance and hyperaccumulation of heavy metal because it is a close relative of the pre-eminent species A. thaliana. Previous studies on heavy metal tolerance and hyperaccumulation of A. halleri suggested evolution of metallicolous populations in response to high level of metal exposure. In order to investigate the evolutionary processes in neighboring metallicolous and non-metallicous A. halleri populations, we adopted population genomics and phenotyping approaches. First we explored the A. halleri genome to detect signatures of directional selection. We performed a genome-wide scan analysis using 820 AFLP markers. We identified some loci potentially under selection in metallicolous populations that constitute high-quality candidates for general adaptation to metalliferous sites. Interestingly, some candidates were population specifics, suggesting the possibility of convergent evolution or existence of different selection pressure in the different sites. Some of these candidates were mapped on A. thaliana genome to identify candidate genes. Our second objective was to evaluate the contribution of selection versus other forces in shaping distribution of zinc tolerance in A. halleri. We measured morphological and physiological traits to estimate zinc tolerance and role of selection was inferred using Qst/Fst approach. Our results suggest that, in the sampled populations, zinc tolerance has been increased in metallicolous populations through selection on standing variation within local non-metallicolous ancestral populations. The last part of this study focuses on looking for a link between genotype and phenotype of zinc tolerance
Nabholz, Benoît. "Dynamique évolutive de l'ADN mitochondrial des oiseaux et des mammifères : Mutation, Sélection et Taille des populations." Montpellier 2, 2008. http://www.theses.fr/2008MON20115.
Full textThe origin and evolution of mitochondrial genome is fascinating. Currently, it makes up less than 1% of the whole organism genome, but contains some of the most important genes. A particularly intriguing feature of the animal mitochondrial genome is its hypermutability. The first goal of this work is to progress in our understanding of the determinism of mitochondrial DNA (mtDNA) substitution rate variations by distinguishing between two classical hypotheses of evolutionary biology –the generation time hypothesis and the metabolic rate hypothesis– and an other hypothesis that comes from biomedecine, namely the longevity hypothesis. Using a phylogenetic approach, we obtained lineage-specific mitochondrial mutation rates across more than one thousand bird and mammalian species. This analysis reveals an unexpectedly high level of mitochondrial mutation rate variation between lineages. The bird/mammal comparison and a within-class analysis suggest that this variation could be linked to species longevity through a (direct or indirect) selective pressure reducing the mitochondrial mutation rate in long-lived species. In the second part of this work, we address the impact of natural selection and genetic drift on mtDNA. Recent evidence of positive selection acting on mtDNA (mostly in invertebrates) was used as a starting point. We showed that, contrary to invertebrates species, bird and mammal mtDNA evolution is mainly under purifying selection. Surprisingly, even in the absence of positive selection, population size variations have no effect on mtDNA genetic diversity, but influence the rate of non-synonymous substitutions. This result could be explained by strong stochasticity of population sizes. All these results contribute to increase our understanding of an unusually evolving genome, and also have implications for the numerous users of mtDNA as a tool to reconstruct population and species history
Henri-Dubernet, Ségolène. "Etude par électrophorèse en gradient de température de la biodiversité et des dynamiques des populations lactobacilles au cours de la transformation du lait cru en "Camembert de Normandie"." Caen, 2004. http://www.theses.fr/2004CAEN2034.
Full textŠkrabar, Neva [Verfasser]. "Phenotypic variability and genetic architecture of limbs in populations and strains of the house mouse (Mus musculus) / Neva Škrabar." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1167771001/34.
Full textTacuatiá, Luana Olinda. "Les aspects de la variabilité génétique et cytogénétique, et de la biologie reproductive chez Sisyrinchium micranthum Cav. (Iridaceae) dans le sud du Brésil." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00922984.
Full textSolano, Philippe. "Implications épidémiologiques de la variabilité génétique des populations de glossines. Cas de "Glossina palpalis" en Afrique de l'ouest." Montpellier 2, 1998. http://www.theses.fr/1998MON20169.
Full textPaparazzo, Francesco [Verfasser], and Wolfgang [Akademischer Betreuer] Stephan. "Beauveria bassiana infection in Drosophila melanogaster : survival, transcriptional response and variability among populations and host conditions / Francesco Paparazzo. Betreuer: Wolfgang Stephan." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1051777003/34.
Full textMille, Tiphaine. "Sources de variation intra-populationnelle de la morphologie des otolithes : asymétrie directionnelle et régime alimentaire." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10200/document.
Full textOtoliths are calcified structures located in Osteichthyes’ inner ear that are involved in audition and balance. Their morphology is used as an indicator of various ecological processes or properties. This application requires identifying the endogenous and exogenous factors that act simultaneously as sources of shape variation. This thesis aims at detecting and quantifying the relative contributions of directional asymmetry and diet to otolith shape variation at the intra-population level. Directional asymmetry between left and right otoliths was found in flat-fishes, the blind-side otolith being always longer and larger, whereas it was negligible in round-fishes. However, asymmetry amplitude never exceeded 18%, which suggests evolutionary canalization of otolith shape symmetry. A correlation between global diet and otolith was detected in 4 species studied in situ. Diet composition contributed more than food amount to morphological variation and affected otolith shape both globally and locally. An experimental study on sea bass (Dicentrarchus larbrax) showed that diet composition in terms of essential polyunsaturated fatty acids at larval stage affects otolith morphogenesis during juvenile stage without impacting on individuals’ somatic growth. This result suggests a direct effect of diet on otolith shape and not an indirect one through the somatic-otolith growth relationship. This effect disappeared at later stages, morphogenetic trajectories converging back to a similar shape, which suggests ontogenetic canalization of otolith shape
Gonzalo-Turpin, Héloïse Hazard Laurent Couix Nathalie. "Produire des connaissances pertinentes pour l'action en sciences de la conservation cas de la gestion de la diversité génétique intraspécifique en restauration écologique /." Toulouse : INP Toulouse, 2009. http://ethesis.inp-toulouse.fr/archive/00000815.
Full textNibouche, Samuel. "Cycle evolutif de helicoverpa armigera (hubner, 1808) (lepidoptera, noctuidae) dans l'ouest du burkina faso : biologie, ecologie et variabilite geographique des populations." Montpellier, ENSA, 1994. http://www.theses.fr/1994ENSA0025.
Full textRavelomanantsoa, Santatra Herilalaina. "Biologie des populations du complexe d'espèces Ralstonia solanacearum appliquée à l'épidémiologie de la bactériose vasculaire de la pomme de terre à Madagascar." Thesis, La Réunion, 2016. http://www.theses.fr/2016LARE0017/document.
Full textThis thesis is exploring genetic diversity, population structure and molecular epidemiology of the Ralstonia solanacearum species complex (Rssc) causing potato bacterial wilt outbreaks in Madagascar. We characterized a large collection of strains (n=1224; 75 sites) collected from potato production areas. Surprisingly, the large outbreaks were associated with IIB-1 strains (Brown rot) while a few were associated with phylotypes I and III. This is the first report of phylotype IIB-1 in Madagascar. The IIB-1 strains were genotyped based on MLVA (RS2-MLVA9). And Malagasy phylotype IIB-1 clustered with worldwide distributed strains. Fine scale genetic investigation suggested three clonal populations that were introduced and spread through latently infected tuber-seeds. Phylotype III strains were genotyped with the highly discriminatory RS3-MLVA16 scheme we developed. Genetic population analyses revealed a high genetic diversity within phylotype III strains that geographically structured into 11 clonal populations. This support the endemic character of the phylotype III population in Madagascar and suggests no transmission with potato tubers. Malagasy strains were distinct from continental African strains. A clear-cut epidemiological profile is shown between IIB-1 and III strains. Genetically, no bacterial wilt resistance properties were shown for the most popular Malagasy potato cultivars, except two cultivars: 720118 and 800934 that showed strong resistance to phylotype I-31 strain that are predominantly distributed in the Indian Ocean. This study offered tool to genotype phylotype III strains and gives an insights into population structure and epidemiology of the Rssc
Guinand, Bruno. "Rôles d'éléments de statistique multivariée dans la mise en évidence de la différenciation populationnelle : exemples et potentialités." Lyon 1, 1996. http://www.theses.fr/1996LYO10172.
Full textLedoux, Jean-Baptiste. "Biologie de la conservation du corail rouge, Corallium rubrum (Linnaeus, 1758) : impact du changement global sur l'évolution des populations infralittorales en Méditerranée Nord-Occidentale." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22096/document.
Full textAnthropic pressures act synergistically from gene to ecosystems and from polar to tropical regions, inducing a strong biological loss, which is considered by many as the sixth mass extinction. The evolution of biodiversity facing the ongoing global change is thus an open question.The present study is focused on the shallow populations (5 - 60 m) of Corallium rubrum (Octocorallia,Coralliidae) in the North Western Mediterranean Sea. The red coral is a sessile and long-lived species with a larval phase, a slow population dynamics and an important structuring role in the Mediterranean hard substrates communities. This species faces a strong harvesting pressure, and recently underwent two massmortality events linked to positive thermal anomalies putatively due to ongoing climate change. These two pressures may have deep implications on the evolution of the shallow populations of this species. Using population genetics and field ecology, the main objective of this study was to define microevolutionary processes acting between and within red coral populations, to enhance our knowledge on the biology of this species facing the environmental changes. This work extends our knowledge concerning the ecology of Corallium rubrum, and provides new toolsand data for its conservation in the context of the ongoing global change. Moreover, this work improves our understanding in the biology of sessile marine organisms with a larval phase, illustrating for example the relevance of approaches conducted at fine geographical scales to address questions regarding the evolution of these organisms
Guilloux, Thomas. "Etude de la variabilité biologique, biochimique et génétique de populations d'origines géographiques différentes de Cotesia plutellae (Kurdjumov) (hymenoptera : braconidae), parasitoi͏̈de de la teigne des Brassicacees Plutella Xylostella (L. )(lepidoptera : Yponomeutidae)." Montpellier 3, 2000. http://www.theses.fr/2000MON30066.
Full textLupoli, Roland. "Recherches sur la caractérisation intraspécifique moléculaire et biologique des pucerons en vue de son application à l'épidémiologie des virus de type non persistant." Montpellier 2, 1990. http://www.theses.fr/1990MON20101.
Full textCoulaud, Romain. "Modélisation et changements d'échelles pour l'évaluation écotoxicologique : application à deux macroinvertébrés aquatiques, Gammarus fossarum (crustacé amphipode) et potamopyrgus antipodarum (mollusque gastéropode)." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10018/document.
Full textThe regulatory framework lead to increase the assessments of the ecological risk linked to the dischaarge of chemical substances in aquatic environment with the aim to protect natural populations. However, this target level of protection cannot be used so easily to etablish a direcet link between a contamination and its effects. In order to overcome this difficulty, the multi-scale approaches based on the study of the effects of the contaminations on individual markers and then on the extrapolation of these effects at the population level with population dynamic models reprensent promising tools and start to bewell accepted in predictive processes. Yet, their use for the diagnosis of water quality remainsrare for the moment, on the one hand, because of the important varaibility of answers of individual makers in situ linked to the influence of diverse confounding environmental factors for the assessments of toxicity and, on the other hand, because pf the lack of environmental relevance of models currently proposed. Focused on the use of 2 species widely observed in European rivers and presenting contrastingecological and phylogenetic characteristics : the Grammar fossarum crutacean and the Potamopyrgus antipodarum mollusc, this doctoral degree first propose a methodology to consider the influenceof confounding factors in order to improve the reading of biological in situ tests based on the measurment of individual markers on caged organisms and second, to develop ecologically relevant population models. Thus, this work allowed to underline the importance of the consideration of confounding factors (i.e. temperature), in different in situ tests based on the measurment of individul markers on caged organisms. Moreover, population models for both species have been defined in order to test the influence of life histories and seasonal variations on demographic sensitivity of populations
Faucher, Leslie. "Histoire évolutive de deux espèces d’amphibiens pionnières, le Pélodyte ponctué et le Crapaud calamite, en milieu fortement anthropisé." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10159/document.
Full textHuman activities induce habitat loss and fragmentation that have an erosive effect on the level of intraspecific genetic diversity, decreasing the individual fitness and jeopardizing populations’ adaptive capability. Conversely, new human-made areas, such as spoil heaps of northern France, can provide suitable habitats for pioneering species. Spoil heaps being part of a highly human-fragmented landscape, the likelihood of population persistence is questioned given the scarcity of suitable habitats and the occurrence of potential barriers to dispersal. We studied the intraspecific genetic diversity of two anurans, Pelodytes punctatus and Bufo calamita, located in coalfield areas and semi-natural coastal habitats. We focused on the effects of micro-evolutionary processes of genetic drift and gene flow in shaping genetic structure. We studied (i) the biogeographical history of colonization of coalfield areas in B. calamita, (ii) the landscape connectivity using a multispecies approach, and (iii) the evolutionary determinants of variance in breeding success in B. calamita. In coalfield areas, B. calamita populations showed high levels of genetic diversity suggesting several independent colonization events. Nonetheless, marked local genetic discontinuities were observed within coalfield areas for both species, suggesting occurrence of environmental barriers impeding gene flow that may compromise population viability. Within a B. calamita population, we observed a polygynous mating system involving a possible decrease in genetic diversity. Our results suggested that variance in male mating success was linked to male-male competition and may imply distinct mating strategies
Trémouillaux-Guiller, Jocelyne. "Etude comparative des phénotypes ultrastructuraux et métaboliques d'une population de souches fixées de Choisya Ternata (rutacée) et les lignées clonales en dérivant." Tours, 1986. http://www.theses.fr/1986TOUR3801.
Full textSiah, Ali. "Distribution et polymorphisme des "mating types", variabilité du pouvoir pathogène et résistance aux strobilurines au sein d'une population française de Mycosphaerella Graminicola, agent de la septoriose du blé." Littoral, 2009. http://www.theses.fr/2009DUNK0240.
Full textMycosphaerella graminicola (anamorph : Septoria tritici) is today the most frequently occuring and the most economically damaging pathogen on wheat crops. Five hundred and ten strains of this fungus were isolated from 16 geographical locations covering most of the wheat producing areas in France. The mating type of each strain was determined by multiplex PCR. The equal distribution of the two mating types suggests regular cycles of sexual recombination within French population of the pathogen. A sequence polymorphism analysis using both PCR-RFLP-SSCP and sequencing revealed high conservation of the two mating type idiomorphs in M. Graminicola, with a more important level of polymorphism in the mat1-2 idiomorph compared to the mat 1-1 idiomorh. A sreening of 42 strains by disease level assessment showed a great variability in pathogenicity among strains. Cytological and enzymatic assays conducted in planta highlighted that M. Graminicola pathogenicity is not correlated to either rate of spore germination, mycelial growth on leaf surface or frequency of host leaf penetration, but linked to its ability to colonize the mesophyll and to produce the cell wall degrading enzyme endo-1,4-ß-xylanase during necrotrophic phase. Further investigations performed with 82 strains confirmed the widespread occurence of resistance to strobilurin fungicides within this French population of M. Graminicola and showed the presence of north-south gradient of the resistance distribution. This later study allowed the validation of four in vitro methods assessing M. Graminicola resistance to strobilurins
Baron, Étienne. "Génomique écologique de la réponse à la compétition chez Arabidopsis thaliana." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10206/document.
Full textCompetition is considered as a major factor responsible for plant communities structure, diversity and dynamics. However, the genetics underlying this local eco-evolutionary dynamics remains poorly understood. Notably, at the population scale, the natural genetic variation of response to different competition conditions, the identity of phenotypic traits under genotypic selection and of genetic basis implied in the response to competition still need to be addressed. By an ecological genomics approach using the model species Arabidopsis thaliana, the main goal of this thesis is to characterize the genetics related to the competitive ability at a local scale, according to an increasing complexity of interactions between the competitor species. First, by focusing on monospecific competition, I showed that both the competitor identity and the lag of competitor germination time promote the maintenance of the genetic and functional diversities within the target population. Based on an approach of Genome Wide Association (GWA) mapping, I detected QTLs of response to competition that were strongly dependent on the conditions of monospecific competition. Second, in the context of multispecific interactions, I demonstrated that the response of a local population to competition was highly specific to the surrounding communities considered. In addition, based on a resurrection approach, I showed that the response of a local population to competition could evolve in less than eight generations, likely in relationship to community shifts. Third, I demonstrated that the adaptive dynamic of A. thaliana was highly influenced by the competition intensity in natural conditions
Ben, Abderrazak Souha. "Variabilité génétique des populations de "Plasmodium falciparum"." Montpellier 2, 1993. http://www.theses.fr/1993MON20013.
Full textPugliese, Rosa Angela. "Mesophotic red coral population: genetic variability and connectivity." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4587/.
Full textRamakrishnan, Lakshmikantan. "Environmental variability and ecological dynamics in spatially structured populations /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004361.
Full textDutilleul, Morgan. "Réponses microévolutives et coûts adaptatifs de populations de Caenorhabditis elegans exposées à des stress environnementaux." Thèse, Montpellier 1, 2013. http://www.archipel.uqam.ca/5860/1/D2565.pdf.
Full textGalataud, Julien. "Trajectoires évolutives des populations insulaires d’Apis mellifera dans le sud-ouest de l’océan Indien : congruence des approches morphométriques et génétiques." Thesis, La Réunion, 2019. http://www.theses.fr/2019LARE0042.
Full textThe honeybee subspecies found in the islands of the southwest Indian Ocean (SOOI) is Apis mellifera unicolor. The SOOI island populations are genetically structured, with hybridization patterns observed with European lines in varying proportions depending on the islands. In order to better understand the microevolutionary processes implemented between the divergences of the 10 SOOI island populations, we studied the variability and distribution of a trait with respect to the individual genetic diversity. Thus, the wing venation pattern was characterized by using geometric morphometry (Procrustes method) on more than 1400 female workers. Multivariate approaches used, allowed us to link morphological data (wing size and conformation) to genetic data (14 microsatellite markers).First, we studied an ongoing hybridization process in Mauritius and highlighted the concordance between morphogenetic and genetic variations, and then showed that the hybridization process contributed to increasing the phenotypic variability of the population. Human introductions and beekeeping have therefore strongly influenced the evolutionary trajectory of this population.In a second step, we extended our study to the characterization of honeybees throughout the SOOI zone. The results showed, not only, that these populations were morphologically and genetically structured, but also that the variability in wing conformation reflected the evolutionary history of these populations, highlighting the influence of drift, founding effects and hybridization processes on these populations. The strong congruence observed between neutral and morphometric genetic variability does not exclude other mechanisms, such as natural selection and/or phenotypic plasticity that could have influenced the evolutionary trajectory of the SOOI honeybees
Carlesi, Lorenzo. "Genetic variability and structuring of deep Corallium rubrum (Linnaeus, 1758) populations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2613/.
Full textPacoureau, Nathan. "Influence de la variabilité climatique, de l’abondance de proies, de la densité-dépendance et de l'hétérogénéité individuelle chez des prédateurs supérieurs longévifs : de l’individu à la population." Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS026/document.
Full textA fundamental endeavor in population ecology is to identify the drivers of population dynamics. The main objective of this thesis is to determine what are the demographic and population responses of superior marine predators to the fluctuations of their prey abundance, to climatic variations, to density-dependence while taking into account inter and intra individual heterogeneity (age, experience, sex, quality or strategy). To do this, we analysed long-term individual and population-based monitoring of long-lived seabirds and phylogenetically close apical predators in two contrasting biomes: the south polar skua Catharacta maccormicki at Pointe Géologie archipelago, Antarctica, and the brown skua Catharacta lonnbergi on the sub-Antarctic Kerguelen Archipelago. We will use direct abundance of their respective prey: Adélie penguin Pygoscelis adeliae and emperor penguin Aptenodytes forsteri in Antarctica, and the blue petrel Halobaena caerulea and the thin-billed prion Pachyptila belcheri prion in Kerguelen islands. These datasets provide a unique opportunity to simultaneously disentangle and quantify the different sources of variability driving variation in natural populations occupying one of the highest trophic levels of the Antarctic and sub-Antarctic food webs. We found variation in several vital traits of both populations influenced by individual performance and latent individual heterogeneity. We discuss the mechanisms by which climatic variability, prey abundance, and population density can differentially affect the different age classes of each age class, and the potential consequences of future environmental changes
Bertrand, Bénédicte. "Analyse de la diversité moléculaire de populations d'abeilles de la lignée ouest-méditerranéenne (Apis mellifera mellifera) dans le but de la conservation." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00951288.
Full textManry, Jérémy. "De la génétique des populations à l'immunologie : les interférons chez l'homme." Paris 6, 2011. http://www.theses.fr/2011PA066158.
Full textAit, Lhaj Loutfi Ahmed. "Variabilité du régime de la reproduction au sein des populations d'Arrhenatherum elatius de milieux contrastés." Lille 1, 1987. http://www.theses.fr/1987LIL10097.
Full textDelefosse, Laurence. "Étude de la compétition chez la luzerne : comparaison de la structure génotypique de deux populations." Paris 11, 1986. http://www.theses.fr/1986PA112303.
Full textChaïb, Anissa. "Variabilité des populations naturelles de Lathyrus sylvestris L : approche morphologique, cytogénétique et génétique." Pau, 1990. http://www.theses.fr/1990PAUU3009.
Full textPilorge, Thierry. "Dynamique comparée de populations de lézards vivipares : régulation et variabilité intra- et interpopulationnelle." Paris 6, 1988. http://www.theses.fr/1988PA066481.
Full textDemanche, Christine. "Variabilité génétique et circulation des Pneumocystis dans les populations de primates non humains." Paris 12, 2003. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002110980204611&vid=upec.
Full textPneumocystis pneumonia continues to be an important opportunistic infection in immunocompromised patients. However, tremedous gaps still exist in our knowledge. In the present study, we characterized the genetic variability of Pneumocystis organisms from non human primates. We showed that the genetic divergence in primate-derived Pneumocystis organisms varied in terms of the phylogenetic divergence existing among the corresponding host species, indicating cospeciation. As monkeys-derived and human-derived Pneumocystis are closely related, simian populations should be considered as valuable models for understanding of the epidemiology of human pneumocystosis. A socially organized group of crab-eating macaques (Macaca fascicularis) was monthly examined for 2 years. We documented the constant circulation of Pneumocystis within the colony. Person-to-person transmission probably occurred but the correlation between mean precipitation rates and Pneumocystis DNA carnage supported the hypothesis of an environmental source of Pneumocystis organisms
Cury, Claire. "Analyse statistique de la variabilité anatomique de l'hippocampe à partir de grandes populations." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066021/document.
Full textStatistical shape analysis of anatomical structures is a key challenge for many applications: modeling of the normal and pathological variability, prediction of clinical or biological parameters from anatomical data... Recent years have seen the emergence of large databases in neuro-imaging, potentially increasing the statistical power of new studies. This thesis is about the statistical analysis of the anatomical variability of hippocampi in large populations. After a state of the art, the first part of the thesis focuses on the study of an anatomical variant named Incomplete Hippocampal Inversion (IHI). We developed a new robust scale for IHI assessments. We then applied the evaluation to 2000 young healthy subjects from the European database IMAGEN. Results show that IHI are frequent on healthy population, with a left side predominance. This is the first time that IHI are studied on a large database composed of healthy subjects. The second part of this thesis develops a method for the statistical analysis of shapes based on Large Diffeomorphic Deformations Metric Mapping and mathematical currents, applicable for the analysis of large datasets. In particular we have introduced a new fast approach for the estimation of anatomical templates. This approach has been validated on 1000 young healthy subjects of the IMAGEN database and on 294 subjects from the ADNI database (healthy aging subjects and patients with Alzheimer disease). Results show that the method allows the modeling of the anatomical variability of hippocampi with a reasonable number of dimensions