Determinants of hierarchical genetic structure in Atlantic salmonpopulations: environmental factors vs. anthropogenic influences

• Published in: Molecular Ecology
• Main Authors: Perrier, Charles, C., Guyomard, René, R., Baglinière, Jean-Luc, J.-L., Evanno, Guillaume, G.
• Other Authors: Écologie et santé des écosystèmes (ESE), Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST, Génétique Animale et Biologie Intégrative (GABI), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, INRA; Region Basse-Normandie; European Atlantic Salmon Arc Project
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: Atlantic salmon; genetic structure; introgression; stocking; MICROSATELLITE DNA VARIATION; BROWN TROUT POPULATIONS; ALLELE FREQUENCY; DATA; SALAR L; LOCAL ADAPTATION; LANDSCAPE GENETICS; NATURAL-SELECTION; LIFE-HISTORY; BALTIC SEA; REPRODUCTIVE ISOLATION; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; Salmo salar
• Online Access: https://hal.science/hal-01004630; https://doi.org/10.1111/j.1365-294X.2011.05266.x

Disentangling the effects of natural environmental features and anthropogenic factors on the genetic structure of endangered populations is an important challenge for conservation biology. Here, we investigated the combined influences of major environmental features and stocking with non-native fish on the genetic structure and local adaptation of Atlantic salmon (Salmo salar) populations. We used 17 microsatellite loci to genotype 975 individuals originating from 34 French rivers. Bayesian analyses revealed a hierarchical genetic structure into five geographically distinct clusters. Coastal distance, geological substrate and river length were strong predictors of population structure. Gene flow was higher among rivers with similar geologies, suggesting local adaptation to geological substrate. The effect of river length was mainly owing to one highly differentiated population that has the farthest spawning grounds off the river mouth (up to 900 km) and the largest fish, suggesting local adaptation to river length. We detected high levels of admixture in stocked populations but also in neighbouring ones, implying large-scale impacts of stocking through dispersal of non-native individuals. However, we found relatively few admixed individuals suggesting a lower fitness of stocked fish and/or some reproductive isolation between wild and stocked individuals. When excluding stocked populations, genetic structure increased as did its correlation with environmental factors. This study overall indicates that geological substrate and river length are major environmental factors influencing gene flow and potential local adaptation among Atlantic salmon populations but that stocking with non-native individuals may ultimately disrupt these natural patterns of gene flow among locally adapted populations.