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Analyse génétique et morphologique de l’isolement reproductif partiel dans la zone d'hybridation de Solea senegalensis et Solea aegyptiaca en Tunisie

Abstract : Hybridisation and introgression processes have an important place in the study of speciation as they allow to analyse the evolutionary consequences of genetic exchanges between partially isolated species. Here we are interested in the hybrid zone resulting from the contact between the soles S. aegyptiaca and S. senegalensis along the North Tunisian coast. First, we studied the consequences of hybridisation on phenotypic variation. This allowed us to evidence that phenotypic convergence in hybrids was accompanied by phenotypic transgression and morphological distortions for certain traits that seem to reflect a reduced condition of hybrids. Possible genetic incompatibilities between species should be responsible for the differential permeability of the genome to gene flow, thereby creating a semi-permeable barrier. To study this barrier at the genome scale, we have produced a polymorphism dataset using the RAD-seq method. This allowed us to genotype 200 individuals at 10,756 SNP markers and to characterise genomic patterns of gene flow between the two species through three complementary approaches. The first is based on a reconstruction of the demographic history of the genetic and exchanges that incorporates the effects of the semi-permeability to gene flow. The second approach focuses on the spatial evolution of allele frequencies across the hybrid zone. The last method, called genomic clines, compares the behaviour of each locus to the average introgression pattern expected under the hypothesis of neutrality. Our results indicate that S. aegyptiaca and S. senegalensis underwent ancient divergence in allopatry followed by a recent secondary contact. Only a small proportion of the genome can asymmetrically introgress across the hybrid zone, resulting in a variety of introgression patterns of which we discuss the possible origins.
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Ahmed Souissi. Analyse génétique et morphologique de l’isolement reproductif partiel dans la zone d'hybridation de Solea senegalensis et Solea aegyptiaca en Tunisie. Génétique animale. Université Montpellier; Université de Tunis El-Manar. Faculté des Sciences de Tunis (Tunisie), 2016. Français. ⟨NNT : 2016MONTT175⟩. ⟨tel-01835236⟩

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