Academic literature on the topic 'Délimitation moléculaire'
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Dissertations / Theses on the topic "Délimitation moléculaire":
Montecinos, Alejandro. "Species delienation and hybridization in the brown seaweed Ectocarpus complex." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066328/document.
The genus Ectocarpus Lyngbye (Ectocarpales, Phaeophyceae) comprises marine filamentous algae characterized by an alternation between two independent multicellular organisms of different ploidy. The general objective of the thesis was to study species delineation and speciation within this genus. We started clarifying the number of cryptic species using two unlinked loci (COI-5P and ITS1) and an integrative approach associating barcode gap detection analyses with phylogenetic reconstructions. We showed the presence of at least 15 species partitioned within a monophyletic group composed of E. crouaniorum (Ecro) and two closely related species and a paraphyletic assemblage composed of the remaining 12 other species including E. siliculosus (Esil). Second, Rad sequencing and phylogenomics analyses allowed to resolve the relationships within the paraphyletic assemblage. The different species becomes well separated into two divergent clades (Ecro and Esil). A diversity of taxa with various levels of divergence was revealed within the clade Esil and hybridization between the closest and sympatric species was suggested. Finally, the importance of reproductive isolation among the two commonest but most divergent species Esil and Ecro was studied using species-specific nuclear and cytoplasmic markers jointly with 9 microsatellites. We showed that meiosis acts as a strong reproductive barrier among these two species and demonstrates that the species of the genus Ectocarpus are excellent systems to study evolutionary consequences of hybridization and introgression for the maintenance or breakdown of species because of their haploid diploid life cycle
Rejaud, Alexandre. "Origine et diversité des Amphibiens d'Amazonie." Thesis, Toulouse 3, 2021. http://www.theses.fr/2021TOU30161.
With more than six million square kilometers, Amazonia hosts the largest tract of lowland tropical rainforest in the world and a large portion of the global terrestrial diversity. However, the temporal and spatial origins of this diversity remain poorly understood and need to be better comprehended to identify the processes responsible for this tremendous diversification. Amphibians are a particularly adequate group for investigating patterns of biogeographical history within Amazonia because they extensively diversified within the region and present important disparities in habitat use and dispersal abilities across groups. We first investigated the historical biogeography of the terra-firme genus Allobates and identified western Amazonia as an important source of diversification between 14 and 10 million years ago (Mya). This spatio-temporal pattern was coinciding with the existence of the Pebas system, a mega-wetland system that occupied most of western Amazonia during this period, that was unsuitable for terra-firme species. The Pebas system discharge was likely followed by an extension of terra-firme forests that likely fostered Allobates diversification. Our results also suggested that western Amazonia rivers might have subsequently (after 10 Mya) promoted diversification, by acting as semi-permeable barriers allowing speciation by dispersal and isolation. Secondly, we investigated the biogeographical history of the Pristimantis conspicillatus group which, instead, presented a continuous diversification throughout Neogene. This group displays a striking spatial pattern of diversification with four ancient clades that have diversified concomitantly in distinct areas in Amazonia and the Atlantic Forest, with much fewer dispersal events between areas than in Allobates. These differences suggest that amphibian species display differences in dispersal abilities that can be related to their life history traits. Finally, we compared the biogeographic histories of six frog clades, including the two aforementioned ones, that share comparable crown ages and span the Amazonian frog diversity in terms of life history traits, taxonomy, habitat use and reproduction modes. We identified western Amazonia as the principal source of diversification for Amazonian amphibians, although it acted as such only after 10 Mya for the groups that have adapted to various types of habitats; and only between 10 and 5 Mya for the ecologically conservative groups. This suggest that species with lower habitat availability reach niche filling more rapidly than ecologically adaptive species, resulting in shorter diversification phases. Our results also suggest that riverine barrier effect seems to have affected solely conservative groups particularly when the river course is stable over time. While these results were obtained by considering only a fraction of Amazonian diversity, they provide interesting insights on the influence of niche conservatism upon Amazonian evolutive trajectories, which will hopefully foster further and more ample research in this direction
Geoffroy, Alexandre. "Diversité génétique et délimitation d'espèces par des approches conjointes de barcoding et de génétique des populations : application à l'identification d'espèces d'algues marines nouvellement cultivées." Paris 6, 2012. http://hal.upmc.fr/tel-01115945.
Bichain, Jean-Michel. "La systématique des bythinelles revisitée : apport des outils moléculaires et morphométriques à la délimitation des espèces du genre Bythinella Moquin-Tandon, 1856 : Mollusca, Caenogastropoda, Amnicolidae." Paris, Muséum national d'histoire naturelle, 2007. http://www.theses.fr/2007MNHN0006.
In order to clarify the alpha-taxonomy of the genus Bythinella, we performed several molecular and morphometric methods and applied delimitation criteria derived from an unified species concept framework. Our results challenge the knowledge of the group. Whereas traditional taxonomy recognized all morphs as good species, we showed that even the least discussed shell characters do not reflect true species boundaries. Thus it seems that traditional alpha-taxonomy led to an overestimation in epigean habitats and to an underestimation of the genus alpha-diversity in underground habitats. Morphometric analyses revealed that these evolutionary lineages fixed morphological characters such as the global shell shape. But, inter-specific differences are partly biased by intra-specific variability. Our results allow to give the first diagnostic tools, molecular and morphometric, to identify these different nominal taxa
Théry, Thomas. "Systématique du genre Essigella (Hemiptera : Sternorrhyncha) au moyen de données moléculaires." Thèse, 2018. http://hdl.handle.net/1866/20780.