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Génomique de l’hybridation anthropogénique chez les moules Mytilus spp. et valeur sélective des hybrides

Abstract : Anthropogenic activities are creating new contacts between genetically differentiated lineages, providing access to the initial phase and replicates of secondary contacts. The complex M. eduliscontains several species and lineages partially reproductively isolated, exhibiting a large diversity ofsecondary contacts and levels of gene flow. It constitutes therefore a good model for the study ofhybridisation and speciation. We took advantage of several secondary contact events, both natural,anthropogenic and experimental, to investigate their effects on genomic admixture patterns. Indeed,events of M. galloprovincialis introduction from two different lineages, implicating admixture betweenthe introduced species and the native species, have been identified in several French ports and inNorway. The introduction has first been identified with a hundred ancestry informative markers.Mussel port populations are forming fine scale contact zones between the inside of the ports andlocal populations located outside. Those port populations exhibit an important rate of introgressionfrom local lineages with which they are in contact. The comparison of those anthropogenic admixtureevents with cases implicating other lineages and experimental crosses allowed us to identify parallelisms in allele frequency distortions when similar lineages are hybridising. In the aim of investigatingthe genomic patterns produced by such events, we analysed 156 genomes of reference and admixedpopulations, showing the correlation of distorsions between events is conserved at the genomic scale.Finally, we developed a theoretical model for the prediction of hybrid fitness using the frameworkof Fisher’s geometric model. This model takes into account genome scale epistatic interactions,emerging from the co-adaptation of mutations produced during divergence between the two lineages.The model is simple and flexible and predicts many empirical observations of hybridization researchincluding segregation distortions in mussels.Finally, it explains that admixed populations retrieve high fitness levelswhile being a combination of alleles from the two parental genomes.
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Alexis Simon. Génomique de l’hybridation anthropogénique chez les moules Mytilus spp. et valeur sélective des hybrides. Sciences agricoles. Université Montpellier, 2019. Français. ⟨NNT : 2019MONTG032⟩. ⟨tel-02481299⟩

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