Дисертації з теми "Génomique de spéciation"
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Barry, Pierre. "Rôles des contraintes génomiques et des traits d'histoire de vie dans la spéciation : une approche de génomique comparative." Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONG007.
Повний текст джерелаSpeciation is the evolutionary process through which a species splits into two lineages that diverge and accumulate reproductive barriers, until complete reproductive isolation is achieved. During this process, the diverging lineages can still exchange genes by hybridisation, but gene flow is progressively restricted by the accumulation of barriers. This results in semi-permeable genomes, whereby some loci exchange freely between lineages and remain undifferentiated while others do not introgress, thus contributing to the establishment of divergent genomic regions, called genomic islands of speciation. The study of the establishment, accumulation, erosion and maintenance of these barriers and their effects on the semipermeability of the genomes of lineages undergoing speciation helps to understand how new species are formed. The advent of high-throughput sequencing techniques has made it possible to characterise the genomic landscape of divergence in multiple lineages undergoing speciation across the tree of life. These studies have shown the influence of the demographic history and genomic architecture as major determinants of the genomic landscape of divergence. However, other factors could intervene and explain the diversity of evolutionary trajectories that may or may not lead to speciation. The main objective of this thesis is to assess the impact of species' life history traits on speciation. We have chosen to study 20 marine fish species subdivided into two lineages (Atlantic and Mediterranean), and presenting a wide diversity of degrees of divergence and life history traits. These traits are thought to impact on the intensity of genetic drift, dispersal abilities and generation time of the species. In the first chapter, we studied the determinants of genetic diversity, the substrate on which divergence is built during the initial separation of lineages. We observed that adult longevity of marine fishes is negatively correlated w ith genetic diversity, and we demonstrated that this relationship could be explained by a greater variance in reproductive success in long-lived species due to reproductive strategies specific to marine fishes (high juvenile mortality, low adult mortality and increased fecundity with age). Then, in a second chapter, we discovered a great diversity of evolutionary histories between species, characterised by a strong gradient of genetic divergence between Atlantic and Mediterranean lineages. This gradient partly reflects the level of semi-permeability of the genomes. Species with low differentiation show low reproductive isolation, whereas the most highly differentiated species show almost complete reproductive isolation. Species' life history traits partly explain this diversity in isolation levels via different mechanisms. Larval duration negatively influences genetic differentiation by modulating dispersal capacities, the effect of body size indicates a negative effect of long-term abundance on divergence, while longevity seems to impact the number of generations elapsed since ancestral separation. In conclusion, the 20 species studied show a surprising variability of evolutionary histories considering the similarities of their biogeographic history and genomic architecture. The relationships between life-history traits and the evolutionary history of the species proved to be complex, but we were nevertheless able to shed light on some of them by decomposing the involvement of traits in the different stages of speciation. The application of the comparative genomics approach developed in this thesis to other suture zones will further extend our knowledge of the determinants of the tempo and mode of speciation
Rougeux, Clément. "Génomique de la spéciation chez le Grand Corégone (Coregonus clupeaformis) : caractérisation des bases génomiques associées à la différenciation phénotypique." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34461.
Повний текст джерелаRepeated evolution of phenotypic differentiation between diverging species pairs provides an ideal context for the study of the genomic architecture of parallel speciation. The main objective of this thesis is to provide evidence concerning the genomic bases involved in phenotypic differentiation, and their influence on the evolutionary potential of species complexes belonging to two related lineages, the Lake Whitefish (Coregonus clupeaformis) and European Whitefish (C. lavaretus). Specificaly, it is necessary to elucidate the origin of the genetic polymorphism of each population from both whitefish lineages, and to which extend this polymorphism was involved in the genetic divergence and phenotypic differentiation between species pairs. A genome-wide analysis allowed to infer the divergence history combining the effects of historical demograhy and selective pressure that collectively shape the genomic landscape of differentiation between species pairs. Then, transcriptomic analyses revealed parallel polygenic bases involved in the phenotypic differentiation of species pairs, and such genes were enriched in shared ancestral polymorphism. Finaly, a parallel differential methylation level has been identified between species. Although this methylation is genomicaly based, these differentially methylated regions are associated with a transcriptional differentiation between the limnetic and benthic species. This work shows that selection is constrained by some genotypes which could lead to an independent parallel phenotypic aquisition, but also act on the maintainance of ancestral genetic polymorphism, particularly in a context of parallel speciation. This thesis allows to highlight and to contribute to the understanding of the genomic mechanisms generating biodiversity, notably by using an integrative approach.
Renaut, Sébastien. "Génomique de la spéciation chez le grand corégone (Coregonus clupeaformis) : divergence adaptive et isolement reproducteur." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27708/27708.pdf.
Повний текст джерелаGabrielli, Maëva. "Histoires évolutives et spéciation chez les Zostérops des Mascareignes (Zosteropidés)." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30055.
Повний текст джерелаUnderstanding how new species arise is a longstanding question in evolutionary biology. With the recent and major progress in sequencing technologies, this question can now be addressed using genome-wide data. The identification of genomic regions under positive selection and that may act as barriers to gene flow is of particular importance as these regions might be involved in the build-up of reproductive isolation, ultimately leading to speciation. Mascarene white-eyes provide an outstanding system to unravel the processes leading to the formation of new species. In particular, the Reunion grey-white eye, a small passerine bird endemic to the small volcanic island of Reunion in the Mascarene archipelago, comprises four geographic forms that differ strikingly in their plumage colouration and are parapatrically distributed within the island. This system is ideal to try identifying the genomic regions differentiating at the onset of divergence. Using data from genome-wide Single Nucleotide Polymorphism (SNP) markers in hundreds of individuals, we first investigate the evolutionary history of the different geographic forms of the Reunion grey white-eye using phylogenetic inferences. Our results provide strong support in favour of within-island diversification, and highlight a role of both strong selection and low dispersal in driving divergence. We then use complete genome sequences to analyse genomic landscapes of differentiation between Reunion grey white-eye geographic forms and between the Reunion grey white-eye and closely related species. Our findings show that incorporating recombination rate information improves the detection of islands of differentiation in the Reunion grey white-eye that may reflect ongoing selection. Finally, we investigate the impacts of geological and climatic events on the evolutionary trajectories of three Mascarene white-eyes. Our findings suggest that local events in Mauritius or Reunion may be the main driver of demographic trajectories in this system. Overall, this thesis furthers our understanding of the origin of diversity in remote oceanic islands and beyond
Duranton, Maud. "Intégrer des approches expérimentales et d’évolution moléculaire en génomique de la spéciation afin d’identifier les mécanismes impliqués dans la divergence entre bar atlantique et loup méditerranéen." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG031.
Повний текст джерелаSpeciation is the evolutionary process of species formation through the progressive establishment of reproductive isolation barriers between diverging populations. Understanding what kind of loci constitute these barriers, which evolutionary forces underlie their formation and how they impact the fitness of hybrids are fundamental questions in evolutionary biology. However, studying true biological species that do not interact through genetic exchanges do not help answering these questions as many reproductive isolation barriers potentially exist, making the identification of the initial barriers a difficult task. This is why we here focus our study of speciation on the European sea bass (Dicentrarchus labrax), a marine fish species subdivided into two incipient species, which are represented by the Atlantic and Mediterranean evolutionary lineages. In order to understand how divergence built up and maintained between these two lineages, we combined several complementary approaches. First, a population genomic study of wild individuals allowed us to specify the demographic context in which divergence took place and to identify the evolutionary mechanisms that allowed genetic differentiation to unfold at the genome level. We found that chromosomal variations in recombination rate have influenced the establishment of reproductive isolation. Furthermore, genomic regions involved in reproductive isolation showed particularly high levels of sequence divergence, that we related to the presence of anciently introgressed alleles. Our findings indicate that past genetic exchanges between D. labrax Atlantic lineage and a closely related species, the spotted sea bass (Dicentrarchus punctatus), have facilitated the establishment of reproductive isolation between the two extent D. labrax lineages. Secondly, we studied molecular evolution patterns of genes involved in reproductive isolation. We showed that these genes mainly display strong evolutionary constraints and thus undergo strong purifying selection. Thirdly, we used experimental crossings to determine if backcrossed individuals have a reduced fitness, which could be expected if there is hybrid depression. We observed that backcrossed individuals had the same fitness than non-backcross Mediterranean relatives. On the contrary, Atlantic alleles are even favored for these hybrids, and this occurs at the same loci where negative selection operates against Atlantic alleles over the long-term. These results thus reveal a complex temporal dynamic of selection on foreign Atlantic haplotypes. Overall, this work challenges the classical view of allopatric speciation which is generally thought as the progressive accumulation of barriers as the by-product of divergence between two populations, facilitated by the absence of gene flow. Here, we showed that on the contrary, genetic exchanges between D. labrax Atlantic population and a third lineage have probably accelerated the emergence of reproductive isolation between the two European sea bass lineages. Furthermore, reproductive isolation is generally assumed to rely on strong selection against first-generations hybrids. However, we showed that this is probably not the case for the European sea bass in which the dynamics of selection on foreign genetic material could be more complex, involving an inversion of selective effect over generations. This thesis shows that linked selection, in interaction with local recombination rate, plays a fundamental role in the establishment and maintenance of reproductive isolation
Rougemont, Quentin. "Évolution de la divergence entre la lamproie fluviatile (Lampetra fluviatilis) et la lamproie deplaner (Lampetra planeri) inférée par approches expérimentales et de génomique des populations." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S141/document.
Повний текст джерелаThis thesis investigates the process of speciation between the European lampreys Lampetra fluviatilis and L. planeri. The two species have drastically different life history strategies: L. fluviatilis is parasitic and anadromous while L. planeri is non-parasitic and strictly freshwater resident. Yet their level of reproductive isolation and history of divergence remain poorly understood. A multidisciplinary approach including experiments, population genomics analyses and historical reconstruction was undertaken to address these issues. Experimental crosses revealed a very low level of reproductive isolation, partially mirrored by variable levels of gene flow in wild populations. Genetic analyses revealed that the two taxa were best described as partially reproductively isolated ecotypes suggesting that endogenous genetic barriers partially reduced effective migration between ecotypes. Genome wide analyses showed the importance of the current and ancient geographical context of speciation. In particular, parapatric L. planeri populations diverged mostly through drift and displayed a reduced genetic diversity . Demographic inferences suggested that divergence have likely emerged in allopatry and then secondary contacts resulted in partial parallelism between replicate population pairs. A strong heterogeneity of divergence across the genome was revealed by sympatric populations suggesting that genomic islands of differentiation were not linked to ongoing ecological divergence. Further investigations showed that the genetic diversity of L. planeri populations was weakly affected by human-induced river fragmentation. Resident populations displayed a higher diversity when gene flow was possible with L. fluviatilis populations in downstream sections of rivers. Overall this thesis showed that parasitic and non-parasitic lamprey ecotypes represent a promising model for studying speciation and notably the genomic architecture of divergence
Gauthier, Jérémy. "Génomique de l'adaptation des guêpes parasitoïdes du genre Cotesia : rôle du bracovirus." Thesis, Tours, 2017. http://www.theses.fr/2017TOUR4033.
Повний текст джерелаThe wasps from the Cotesia genus are endoparasitoids of Lepidoptera. The larvae grow inside the host body and alter its physiology to escape the host immune defenses. To achieve that, these wasps developed a particularly original strategy: virus domestication. Named Bracovirus, it originates from a free-living virus stably integrated into the wasp genome. The wasp uses this bracovirus to produce viral particles containing virulence genes, once expressed in the host, allowing larval development and parasitic success. The aim of my thesis was to uncover, using evolutionary genomic approaches, the role of the bracovirus in the evolutionary history of theses wasps. At the population level, Cotesia sesamiae, used in Africa as biocontrol agents, is structured in several populations, including one strictly associated to a single host species
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.
Повний текст джерелаUnderstanding 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
Tinaut, Alexandra. "Génétique écologique et génomique des évènements de divergence chez les complexes d’espèces en forêt tropicale humide." Thesis, Guyane, 2015. http://www.theses.fr/2015YANE0005/document.
Повний текст джерелаUnderstanding of the mechanisms driving diversification of species is a significant way to improve the management of ecosystems, predict the impacts of climate change and understand the actual and past biodiversity level. The aim of this thesis is to understand and comprehend genetic mechanisms behind the diversification of species in the presence of gene flow. This thesis is focused on the biological model Symphonia globulifera, which presents two ecotypes: the S.globulifera, specialist of seasonally flooded lowlands and S.sp1, specialist of terra firme. These two ecotypes show low genetic differentiation, despite the presence of two apparent phenotypes. A first part of this thesis was to test the presence of local adaptation of this using reciprocal transplant experiment gardens, allowing the understanding of the ecotypes distributions in their natural habitats. Then, this local adaptation in the presence of gene flow, directed me to the regulation of gene methylation in order to see the role this brand of epigenetics can have in the divergence of the ecotypes. In a third part of the thesis, new generation sequencing of the transcriptome ecotypes in reciprocal gardens transplantations allowed me to show the evidence of gene regulation to differentiate the ecotypes. This work thesis is based on phenotype records data, AFLP genotyping and high-throughput sequencing of the transcriptome, in order to show the important value of gene regulation in the divergence of the locally adapted ecotypes, and a weak role of DNA methylation in the establishment of local adaptation
Huber, Bárbara. "From wing pattern genes to the chemistry of speciation : an integrative dissection of the early stages of diversification in mimetic butterflies." Thesis, Paris, EPHE, 2015. http://www.theses.fr/2015EPHE3057/document.
Повний текст джерелаHow does biological diversification occur in the face of genetic exchange? How do reproductive barriers evolve and function? What is the role of adaptive traits in promoting diversification and speciation? These open questions in evolutionary biology are at the core of this project. In order to tackle them, we have focused on butterflies in the neo-tropical genus which are an important component of the diverse butterfly communities in the Neo-tropics. Butterflies in the genus Heliconius are unpalatable to predators, use warning colours to advertise their defences, and mimic other defended butterflies in their local communities. The genus has undergone an adaptive radiation in wing colour patterns as a result of natural selection for mimicry, and is also well known for assortative mating based on wing pattern. I have extended the current knowledge about the ecological function and the genetic basis of wing color patterns in these butterflies and explored the importance of wing coloration relative to chemical signaling in the early stages of diversification. To this aim, I have characterised the adaptive divergence between lineages at different stages of the speciation continuum, by integrating genomic, phenotypic, behavioural, chemical and ecological data. More precisely, I have studied the so-called silvaniform sub-clade of Heliconius, known for harbouring species with tiger patterns that participate in mimicry with large groups of other closely and distantly-related species. My work includes the comparative description of the genetic architecture of wing pattern adaptation in two species, H. hecale and H. ismenius, using crosses, genome-wide next-generation genotyping, and advanced morphometrics of colour patterns. I have also explored the importance of natural and sexual selection on wing-patterning loci at early stages of divergence in the genus. In particular, I have analysed the structure and maintenance of a hybrid zone between two distinctly coloured parapatric races of H. hecale by using a combination of population genetics and genomics, coupled to a phenotypic analysis of the clines and to behavioural assays on male-based mate choice. Finally, I have carried out genome-wide analyses of divergence and gene flow with whole genome sequencing data to look for evidence of introgression between coexisting, hybridising co-mimetic species. This was again coupled to experiments on mating preferences and behavior, and yielded evidence for important differences in putative pheromone signals which may mediate species recognition and the maintenance of species boundaries. Overall, my results show that although selection on wing pattern divergence have been central to the diversification of the genus Heliconius, the accumulation of other barriers to gene flow may be important for the speciation process to be completed
Ribardière, Ambre. "Isolement reproductif et architecture génomique de la différenciation chez deux espèces du complexe Jaera albifrons (isopodes marins) - Etude de populations mixtes présentant des niveaux d'isolement interspécifique contrastés." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066397/document.
Повний текст джерелаWithin the field of speciation, sympatric areas with different levels of interspecific genetic differentiation offer a good opportunity to understand the nature and evolution of reproductive barriers between species. Jaera (albifrons) albifrons and Jaera (albifrons) praehirsuta are two species of marine isopods that coexist in sympatry along the northern European coasts. Ecological, behavioral and genetic barriers efficiently isolate these two species, except in a unique region (Normandy, France) where morphological phenotypes were described in the 60's.In this thesis, microsatellites and SNPs obtained from RAD-sequencing allowed me to demonstrate that the level of interspecific isolation varies widely between sites, from introgressive hybridization to quasi-complete isolation. A comparative analysis of these sites combining sampling from natural populations, experimental crosses, and genomic analyses then allowed me to: i) demonstrate the predominant role of sexual isolation (which remains strong in introgressed populations), together with a relatively weaker post-zygotic barrier, ii) discover the presence of Wolbachia bacteria within the two species, iii) demonstrate that the coexistence of these species originate from an allopatric speciation followed by secondary contacts with varying levels of heterospecific gene flow renewal, and iv) show that gene flow varies also strongly along the genome, with an effect of sex chromosomes and rearranged chromosomes apparently limiting introgression
Nogueira, Marques João Pedro. "Utilisation des outils génomiques pour comprendre la différenciation et le mélange des espèces chez les lièvres et les souris." Thesis, Montpellier, 2022. http://www.theses.fr/2022MONTG010.
Повний текст джерелаThe present thesis has contributed, using high throughput genome sequencing, to understanding the history of divergence leading to speciation, and the causes and consequences of genetic exchanges between species, in hares and mice.First, this work has contributed to the development of the genomic resources available to study hare population genomics, by providing the first de novo assembly of a hare genome (for the mountain hare, Lepus timidus), and assessing its utility as compared to the rabbit assembly, previously available. We have also generated the first mountain hare transcriptome, and the most complete among the currently available Lepus transcriptomes. In combination with published data on the European brown hare (L. europaeus), we pinpointed candidate fixed differences between the two species that can be used to build genotyping tools to monitor gene exchange in contact zones.Second, we have contributed to the understanding of the documented massive introgression of the mitochondrial genome from the mountain hare to the Iberian hare (L. granatensis) in Iberia, by reconstructing the post-glacial demographic dynamics of the latter species using Single Nucleotide Polymorphism data. We demonstrated that this introgression occurred at the favor of the invasive replacement of the donor species by the recipient one during the last deglaciation, thus showing the importance of demographic and biogeographic history in driving introgression.Third, using whole genome sequencing, we studied genetic differentiation and admixture in Iran, the region of origin of the three described house mouse subspecies (M. m. domesticus, musculus and castaneus), source of their expansion to the rest of Eurasia, leading to their present parapatric distributions. We discovered in Central Iran a population that is differentiated from these three subspecies, and inferred that it results from an ancient admixture between M. m. domesticus (about 40%) and a population related to M. m. musculus. The domesticus and musculus lineages thus admixed extensively close to their region of origin, but appear genetically isolated after their independent geographical expansions to Europe, where they form a narrow tension zone, a pattern evocative of a ring species. This offers an exceptional model to further study the evolution and determinants of reproductive isolation between these subspecies. Our analyses also suggest a selective advantage of non-domesticus Y chromosome in this context of admixture in Central Iran.We also discovered in North Western Iran a population that is mostly of domesticus origin, with inferred admixture from its geographical neighbours (musculus and central Iran), but which has fixed a Y chromosome lineage related to that of musculus. We show that this massive Y introgression is accompanied by co-introgression of genes with functions related to male fertility, especially on the X chromosome. We tested the potential link of this Y invasion with an arms-race between the X and Y chromosomes that could bias sex-ratio, and therefore address the question of the potential role of genetic conflicts in promoting introgression. Among subspecies we found a correlation between copy numbers of Y and X ampliconic families (Sly/Slx genes) whose interaction is known to control sex chromosome transmission in a dosage dependent manner. Higher copy numbers in the musculus lineage suggest stronger distortion properties. We however argue that this X-Y conflict is not the cause of massive Y introgression, which would rather reflect an intrinsic advantage of the musculus Y lineage in zones of admixture between the subspecies. The ability of the musculus Y chromosome to invade zones where musculus admixes with other subspecies seems to be a ubiquitous pattern, observed in other geographic regions. The conflict would rather cause co-introgression or co-evolution of the X ampliconic region in admixed populations
Nogueira, Marques João Pedro. "Using genomic tools to understand species differentiation and admixture in hares and mice." Thesis, Université de Montpellier (2022-….), 2022. http://www.theses.fr/2022UMONG010.
Повний текст джерелаThe present thesis has contributed, using high throughput genome sequencing, to understanding the history of divergence leading to speciation, and the causes and consequences of genetic exchanges between species, in hares and mice.First, this work has contributed to the development of the genomic resources available to study hare population genomics, by providing the first de novo assembly of a hare genome (for the mountain hare, Lepus timidus), and assessing its utility as compared to the rabbit assembly, previously available. We have also generated the first mountain hare transcriptome, and the most complete among the currently available Lepus transcriptomes. In combination with published data on the European brown hare (L. europaeus), we pinpointed candidate fixed differences between the two species that can be used to build genotyping tools to monitor gene exchange in contact zones.Second, we have contributed to the understanding of the documented massive introgression of the mitochondrial genome from the mountain hare to the Iberian hare (L. granatensis) in Iberia, by reconstructing the post-glacial demographic dynamics of the latter species using Single Nucleotide Polymorphism data. We demonstrated that this introgression occurred at the favor of the invasive replacement of the donor species by the recipient one during the last deglaciation, thus showing the importance of demographic and biogeographic history in driving introgression.Third, using whole genome sequencing, we studied genetic differentiation and admixture in Iran, the region of origin of the three described house mouse subspecies (M. m. domesticus, musculus and castaneus), source of their expansion to the rest of Eurasia, leading to their present parapatric distributions. We discovered in Central Iran a population that is differentiated from these three subspecies, and inferred that it results from an ancient admixture between M. m. domesticus (about 40%) and a population related to M. m. musculus. The domesticus and musculus lineages thus admixed extensively close to their region of origin, but appear genetically isolated after their independent geographical expansions to Europe, where they form a narrow tension zone, a pattern evocative of a ring species. This offers an exceptional model to further study the evolution and determinants of reproductive isolation between these subspecies. Our analyses also suggest a selective advantage of non-domesticus Y chromosome in this context of admixture in Central Iran.We also discovered in North Western Iran a population that is mostly of domesticus origin, with inferred admixture from its geographical neighbours (musculus and central Iran), but which has fixed a Y chromosome lineage related to that of musculus. We show that this massive Y introgression is accompanied by co-introgression of genes with functions related to male fertility, especially on the X chromosome. We tested the potential link of this Y invasion with an arms-race between the X and Y chromosomes that could bias sex-ratio, and therefore address the question of the potential role of genetic conflicts in promoting introgression. Among subspecies we found a correlation between copy numbers of Y and X ampliconic families (Sly/Slx genes) whose interaction is known to control sex chromosome transmission in a dosage dependent manner. Higher copy numbers in the musculus lineage suggest stronger distortion properties. We however argue that this X-Y conflict is not the cause of massive Y introgression, which would rather reflect an intrinsic advantage of the musculus Y lineage in zones of admixture between the subspecies. The ability of the musculus Y chromosome to invade zones where musculus admixes with other subspecies seems to be a ubiquitous pattern, observed in other geographic regions. The conflict would rather cause co-introgression or co-evolution of the X ampliconic region in admixed populations
Plucain, Jessica. "Bases génétiques et écologiques de la diversification adaptative chez Escherichia coli." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00947803.
Повний текст джерелаBourgeois, Yann. "Génétique évolutive d'un cas extrême de polymorphisme de la coloration du plumage chez un oiseau insulaire, Zosterops borbonicus (Zosteropideae)." Toulouse 3, 2013. http://www.theses.fr/2013TOU30333.
Повний текст джерелаColor polymorphisms are of considerable interest in evolutionary biology. As they are accessible and involved in a variety of selective processes, they have contributed significantly to our understanding of biological diversity. We studied a case of polymorphism at a small spatial scale in Zosterops borbonicus, using indirect approaches such as population genetics and genomics. It appears that coloration changes are not due to genes classically described as 'evolutionary hotspots'. We also identified a locus linked to coloration on chromosome 1. This locus is not yet described as affecting feathers or hair coloration. High effective population sizes and moderate gene flow have probably favored selective effects in shaping this polymorphism. This study illustrates how indirect approaches can allow inferring the context in which phenotypic diversity occurs
Roux, Camille. "Effets de la sélection naturelle et de l'histoire démographique sur les patrons de polymorphisme nucléaire : comparaisons interspécifiques chez Arabidopsis halleri et A. lyrata entre le fond génomique et deux régions cibles de la sélection." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10157/document.
Повний текст джерелаThe dichotomous view of life has long been availed to represent the diversity observed in nature. The recent expansion of sequence data have identified large discrepancies between the phylogenies of genes and species, forming the so-called "mosaic structure" of genomes. This complex pattern is the result of different neutral and adaptive evolutionary processes shaping the diversity of life. These processes explain the shared polymorphism observed between two different species. The trans-specific polymorphism (TSP) is generated by neutral retention of ancestral polymorphism, introgression and genetic homoplasy. Functional TSP is the result of the same processes and of the effects of natural selection. Whether local adaptation of a species contributes to the reduction of TSP, natural selection may increase the TSP in the case of balancing selection.Using the pair of closely related plant species Arabidopsis halleri and A. lyrata, we compared the patterns of polymorphism observed in genomic backgrounds to those observed in the neighborhood of the target regions of balancing selection, in order to measure the relative importance of selection and demography.Demographic analysis by ABC from genomic backgrounds leads to the rejection of the hypothesis of recent migration between these two species, and support the importance of the evolution of tolerance to heavy metals in the process of speciation of A. halleri.Finally, by measuring the patterns of polymorphism around the S-locus, we showed that balancing selection affects very localy the neutral linked polymorphism
Georgiades, Kalliopi. "Phylogénomique des bactéries pathogènes." Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX20690/document.
Повний текст джерелаThe virulence of pathogenic bacteria has been attributed to virulence factors and pathogenic bacteria are considered to have more genes compared to bacteria that do not cause disease. According to the first genomic studies, removing a certain number of genes from pathogenic bacteria impairs their capacity to infect hosts. However, more recent studies have demonstrated that the specialization of bacteria in eukaryotic cells is associated with massive gene loss, especially for allopatric endosymbionts that have been isolated for a long time in an intracellular niche. Indeed, bacteria living in sympatry often have bigger genomes and exhibit greater resistance and plasticity and constitute species complexes rather than true species. Specialists, including specific pathogenic bacteria, escape these bacterial complexes and colonize a niche; thereby gaining a species name. Their specialization allows them to adopt allopatric lifestyle and experience reductive genome evolution. These observations led us to design a study to quantify the rate of gene losses during the evolution of free-living bacteria to intracellular specialists. Our objective was to verify that what characterizes the evolution of intracellular bacteria is genomic reduction, taking under consideration all possible gene gain events. Furthermore, in another neutral study comparing the 12 most dangerous pandemic bacteria to Humans to their closest non-epidemic species, we wished to identify any genomic specificities associated to the virulent capacity of pathogenic bacteria and demonstrate that, besides toxins and surprisingly, toxin-antitoxin modules, pathogenic bacteria are not characterized by more virulence factors, but rather by a loss of regulatory genes. Finally, virulent bacteria exhibit a genomic repertoire in which absent genes are as important as present ones
Dobigny, Gauthier. "Spéciation chromosomique chez les espèces jumelles ouest-africaines du genre Taterillus (Rodentia, Gerbillinae) : implications systématiques et biogéographiques. Hypoyhèses génomiques." Paris, Muséum national d'histoire naturelle, 2003. http://www.theses.fr/2002MNHN0023.
Повний текст джерелаPeluffo, Alexandre E. "The how and the why of ventral branches evolution between Drosophila santomea and Drosophila yakuba : genetic basis, natural variation and plasticity of a shape difference linked to speciation." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC100.
Повний текст джерелаThe thesis tackles the problem of the evolution of shape through the example of a shape difference in the male ventral branches linked to reproductive isolation in two sister species: Drosophila yakuba and Drosophila santomea. The goal is to identify the genes involved in the evolution of this shape difference and the evolutionary causes of such difference. In a first part, the thesis interrogates the concept of “gene” and its search. Then are scientifically characterized the “how” and “why” questions and their link with the distinction of proximal/ultimate, or evolutionary, causes; these philosophical grounds are then linked to Evo-Devo and the experimental work presented in the thesis. In a second part, through geometric morphometrics and a new high-throughput genotyping method, MSG, we identify a loci of 2.7 mega-bases located on chromosome 3L as involved in the evolution of the shape of ventral branches between D. yakuba and D. santomea. These results are linked to our quantitative analysis of shape variation in multiple natural and laboratory strains and strains reared at different temperatures which bring light into the evolutionary causes of this shape difference
Garavito-Espejo, Andrea Maria. "Inférences génétiques et génomiques pour la caractérisation du système majeur de stérilité hybride entre les riz cultivés Oryza sativa et O. Glaberrima." Montpellier 2, 2009. http://www.theses.fr/2009MON20224.
Повний текст джерелаThe two cultivated rice species O. Sativa and O. Glaberrima possess many interesting and complementary traits, such as high yield and good grain quality for the former, and several alleles for resistance or tolerance to different biotic and abiotic stresses for the latter. It would be desirable to combine these characteristics into interspecific lines. However, a strong reproductive barrier impairs the genetic exchange between the two species. This barrier is the result of the action of several loci that might interact or act separately to render the F1 hybrids pollen-sterile and partially female-fertile. Among these, the S1 locus has the strongest effect over the fertility of the hybrids. The main aim of this work is to contribute to a better understanding of the genetic bases of the reproductive barrier that separates O. Sativa and O. Glaberrima. For this purpose, we applied different genetic and genomic approaches in order to characterize the S1 locus. We made a significant advance in the understanding of the reproductive barrier between O. Sativa and O. Glaberrima controlled by the S1 locus. We were able to detect the presence of at least two additional loci, highly linked to S1, to infer the possible epistatic interactions and allelic incompatibilities between them, to develop a genetic model that explains the female semi-sterility of the hybrids, to explore the genomic region that bears these loci, into a collection of O. Glaberrima and its ancestor O. Barthii, and finally, to identify possible candidate genes for two of the loci (S1 and S1A). The knowledge generated by this work will contribute to the establishment of new strategies to introgress more efficiently useful genes from O. Glaberrima to O. Sativa, allowing breeders to take advantage of the genetic diversity present in the cultivated African rice species
Saintagne, Caroline. "Distribution des régions génomiques différenciant deux espèces proches : le chêne sessile (Quercus petraea) et le chêne pédonculé (Q. robur)." Nancy 1, 2003. http://docnum.univ-lorraine.fr/public/SCD_T_2003_0059_SAINTAGNE.pdf.
Повний текст джерелаSessile (Quercus petraea) and pedunculate (Q. Robur) oak which are two inter-fertile species colonising the same space, display similar genomes, whereas maintain ecological and morphological specific differences. Two complementary approaches have been applied to study the molecular origin of phenotypic differences: (i) Location of QTL, controlling characters which differentiate the two species, in a genetic linkage map of pedunculate oak; (ii) estimation, in natural mixt stand, of the inter-specific differentiation coefficient (GST) for different types of molecular markers, already mapped in the same map. The both approaches suggests that genome regions involved in inter-specific differentiation are dispersed across the genome, although with a tendency to within-linkage group clustering in small distance. Our results suggest that species differentiation is mainly due multi-locus effects maintained by selective pressure strong enough to prevent gene flow from disrupting them
Portier, Perrine. "Sélection d'écotypes bactériens pathogènes et non-pathogènes par la plante en relation avec la différenciation en espèces génomiques chez Agrobacterium spp." Phd thesis, Université Claude Bernard - Lyon I, 2004. http://tel.archives-ouvertes.fr/tel-00350502.
Повний текст джерелаGagnon-Hébert, François Olivier. "Développement et utilisation d'une puce de capture d'exons pour l'étude à large spectre de régions génomiques divergentes entre populations sympatriques de grand Corégone (Coregonus clupeaformis)." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29802/29802.pdf.
Повний текст джерелаThe fundamental process of speciation allows the emergence of an astonishing diversity on Earth. One of the main challenges in evolutionary biology is to understand and document the fundamental molecular mechanisms underlying this diversity observed in nature. The establishment of these mechanisms can be extremely rapid when a species colonizes new environments, which gives birth to niche specialization. On the genetic level, this population divergence appears by the emergence of heterogeneous barriers to gene flow in the genome. Lake Whitefish species pairs in North America represent a good model to study the ongoing process of speciation given its particular evolutionary situation. Various lakes in northeastern North America harbor sympatric populations of dwarf (limnetic) and normal (benthic) whitefish showing clear signs of morphological and genetic divergence. In this study, we have taken advantage of recent biotechnological developments in order to identify and document genomic regions of divergence between whitefish ecotypes. The objectives were to i) develop an exon capture chip, ii) enrich and capture genomic regions from multiple samples in natural populations, iii) assemble and annotate a maximum of captured genes and, ultimately, iv) document the extent of genetic differentiation between whitefish ecotypes. This new approach available with the technology of sequence capture allowed us to specifically capture and assemble 2,728 genes (~10% of the genome) to document on a large scale the extent of genetic differentiation between both ecotypes. In total, 267 SNP loci, located in 210 genes, were significantly divergent. This vast array of genes associated to many different biological processes potentially and partly explains the ecological divergence between whitefish ecotypes. Results suggest a greater role of regulation of gene expression and the role of many changes, each of small effect, as explaining early divergence between dwarf and normal whitefish, compared to functional mutations in the protein coding regions.