Bases génomiques de la divergence adaptative et de la mortalité en mer chez le saumon atlantique (Salmo salar)

Authors: Bourret, Vincent
Advisor: Bernatchez, LouisDionne, Mélanie
Abstract: The historical significance of Atlantic salmon and its contemporary exploitation have made this species a central focus in conservation biology. This thesis addresses a number of questions linked to important challenges for this species’ conservation and management. Moreover, by emphasizing a genomic approach, we aimed to systematically disentangle neutral and adaptive genetic divergence. First, we documented temporal changes in the genetic make up of a wild Atlantic salmon population following introgression from farmed escapees. Although our results did not show any significant temporal changes in allelic richness and gene diversity, introgression has resulted in significant alterations of the genetic integrity of the native population, including a possible loss of adaptation to wild conditions. Then, we participated in the development and testing of a SNP-array and conducted the most extensive population genetic study on Atlantic salmon to date. We found three major regional genetic groups in Europe and secondary contact zones between those groups. These zones were associated with putative endogenous and exogenous barriers, rendering the interpretation of environmental influence on potentially adaptive divergence equivocal. In this context, the next objective was to improve our understanding of links between the environment and genetic divergence of Atlantic salmon populations. Our results provide valuable insight into the links between environmental variation and both neutral and potentially adaptive genetic divergence. In particular, we have shown that climate and geological characteristics were significantly associated with both potentially adaptive and neutral genetic divergence. Finally, we explored the genomic bases for sea mortality of Atlantic salmon. Using a novel multilocus approach, we observed a pattern of genetically-based selective mortality at sea, which was repeated over time. These results support the hypothesis that selection mainly causes small changes in allele frequencies among many co-varying loci rather than a small number of changes in loci with large effects. Overall, this thesis has significantly improved our knowledge of many critical aspects of Atlantic salmon population genetics, which are tightly linked to conservation and management.
Document Type: Thèse de doctorat
Issue Date: 2014
Open Access Date: 20 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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