Genetic and phenotypic changes in an Atlantic salmon population supplemented with non-local individuals: a longitudinal study over 21 years

Abstract

While introductions and supplementations using non-native and potentially domesticated individuals may have dramatic evolutionary effects on wild populations, few studies documented the evolution of genetic diversity and life-history traits in supplemented populations. Here, we investigated yearto-year changes from 1989 to 2009 in genetic admixture at 15 microsatellite loci and in phenotypic traits in an Atlantic salmon (Salmo salar) population stocked during the first decade of this period with two genetically and phenotypically distinct source populations. We detected a pattern of temporally increasing introgressive hybridization between the stocked population and both source populations. The proportion of fish returning to the river after a single winter at sea (versus several ones) was higher in fish assigned to the main source population than in local individuals. Moreover, during the first decade of the study, both single-sea-winter and multi-sea-winter (MSW) fish assigned to the main source population were smaller than local fish. During the second decade of the study, MSW fish defined as hybrids were lighter and smaller than fish from parental populations, suggesting outbreeding depression. Overall, this study suggests that supplementation with nonlocal individuals may alter not only the genetic diversity of wild populations but also life-history traits of adaptive significance.

Evidence for long‐term change in length, mass and migration phenology of anadromous spawners in French Atlantic salmon Salmo salar

“…Populations from the Loire River and from northern France, which represent <5% of the records, were excluded from the data set for three main reasons: fishing for S. salar in the Loire River has been forbidden since 1994; S. salar catches in northern France are low; stocking practice takes place on all these rivers, which may mask ecological signals (Le Cam et al ., ).…”

Genomic consequences of a recent three‐way admixture in supplemented wild brown trout populations revealed by local ancestry tracts

“…Understanding the fitness consequences of such gene flow has become a central issue to many conservation programmes (Fraser, ; Glover et al., ; Harbicht, Wilson, & Fraser, ; Naish et al., ; Skaala et al., ; Waples, ). The impact of HMH has been classically studied using methods based on allele frequencies, highlighting neutral genetic diversity losses (Fernández‐Cebrián Araguas, Sanz, García‐Marín, & Fraser 2014; Hansen & Mensberg, ; Laikre et al., ), and altered local adaptation, fitness or reproductive success (Le Cam, Perrier, Besnard, Bernatchez, & Evanno, ; McGinnity et al., ; Muhlfeld et al., ). Genetic homogenization (i.e., loss of fine‐scale population structure) among recipient populations has also been repeatedly pointed out (Eldridge, Myers, & Naish, ; Ozerov et al., ; Valiquette, Perrier, Thibault, & Bernatchez, ).…”

StrAuto: automation and parallelization of STRUCTURE analysis

“…Inference of population structure has found application in fields as varied as human genetics (e.g., [1]) evolution and speciation [2], molecular ecology [3], landscape genetics [4], agriculture [5], forest population genomics [6], tree improvement [7], fisheries [8] and many others. The Bayesian algorithm implemented in the software STRUCTURE [9–11] is now among the most heavily used methods to infer population structure from genotype data despite the difficulties in making unbiased estimates of population structuring under various models of demograhic history [12] or when not using balanced population sampling [13].…”