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Ferchaud AL, Leitwein M, Laporte M, Boivin-Delisle D, Bougas B, Hernandez C, Normandeau É, Thibault I, Bernatchez L. Adaptive and maladaptive genetic diversity in small populations: Insights from the Brook Charr (Salvelinus fontinalis) case study. Mol Ecol 2020; 29:3429-3445. [PMID: 33463857 DOI: 10.1111/mec.15566] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/13/2020] [Accepted: 07/16/2020] [Indexed: 12/12/2022]
Abstract
Investigating the relative importance of neutral versus selective processes governing the accumulation of genetic variants is a key goal in both evolutionary and conservation biology. This is particularly true in the context of small populations, where genetic drift can counteract the effect of selection. Using Brook Charr (Salvelinus fontinalis) from Québec, Canada, as a case study, we investigated the importance of demographic versus selective processes governing the accumulation of both adaptive and maladaptive mutations in closed versus open and connected populations to assess gene flow effect. This was achieved by using 14,779 high-quality filtered SNPs genotyped among 1,416 fish representing 50 populations from three life history types: lacustrine (closed populations), riverine and anadromous (connected populations). Using the PROVEAN algorithm, we observed a considerable accumulation of putative deleterious mutations across populations. The absence of correlation between the occurrence of putatively beneficial or deleterious mutations and local recombination rate supports the hypothesis that genetic drift might be the main driver of the accumulation of such variants. However, despite a lower genetic diversity observed in lacustrine than in riverine or anadromous populations, lacustrine populations do not exhibit more deleterious mutations than the two other history types, suggesting that the negative effect of genetic drift in lacustrine populations may be mitigated by that of relaxed purifying selection. Moreover, we also identified genomic regions associated with anadromy, as well as an overrepresentation of transposable elements associated with variation in environmental variables, thus supporting the importance of transposable elements in adaptation.
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Affiliation(s)
- Anne-Laure Ferchaud
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Maeva Leitwein
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Martin Laporte
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Damien Boivin-Delisle
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Bérénice Bougas
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Cécilia Hernandez
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Éric Normandeau
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
| | - Isabel Thibault
- Direction de l'expertise Sur la Faune Aquatique, Ministère des Forêts, de la Faune et des Parcs du Québec, Québec, QC, Canada
| | - Louis Bernatchez
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, QC, Canada
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Kusche H, Côté G, Hernandez C, Normandeau E, Boivin-Delisle D, Bernatchez L. Characterization of natural variation in North American Atlantic Salmon populations (Salmonidae: Salmo salar) at a locus with a major effect on sea age. Ecol Evol 2017; 7:5797-5807. [PMID: 28808549 PMCID: PMC5550958 DOI: 10.1002/ece3.3132] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/26/2017] [Accepted: 05/10/2017] [Indexed: 12/25/2022] Open
Abstract
Age at maturity is a key life‐history trait of most organisms. In anadromous salmonid fishes such as Atlantic Salmon (Salmo salar), age at sexual maturity is associated with sea age, the number of years spent at sea before the spawning migration. For the first time, we investigated the presence of two nonsynonymous vgll3 polymorphisms in North American Atlantic Salmon populations that relate to sea age in European salmon and quantified the natural variation at these and two additional candidate SNPs from two other genes. A targeted resequencing assay was developed and 1,505 returning adult individuals of size‐inferred sea age and sex from four populations were genotyped. Across three of four populations sampled in Québec, Canada, the late‐maturing component (MSW) of the population of a given sex exhibited higher proportions of SNP genotypes 54Thrvgll3 and 323Lysvgll3 compared to early‐maturing fish (1SW), for example, 85% versus 53% of females from Trinité River carried 323Lysvgll3 (nMSW = 205 vs. n1SW = 30; p < .001). However, the association between vgll3 polymorphism and sea age was more pronounced in females than in males in the rivers we studied. Logistic regression analysis of vgll3 SNP genotypes revealed increased probabilities of exhibiting higher sea age for 54Thrvgll3 and 323Lysvgll3 genotypes compared to alternative genotypes, depending on population and sex. Moreover, individuals carrying the heterozygous vgll3 SNP genotypes were more likely (>66%) to be female. In summary, two nonsynonymous vgll3 polymorphisms were confirmed in North American populations of Atlantic Salmon and our results suggest that variation at those loci correlates with sea age and sex. Our results also suggest that this correlation varies among populations. Future work would benefit from a more balanced sampling and from adding data on juvenile riverine life stages to contrast our data.
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Affiliation(s)
- Henrik Kusche
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada.,Present address: Thünen Institute of Fisheries Ecology Hamburg Germany
| | - Guillaume Côté
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - Cécilia Hernandez
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - Eric Normandeau
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - Damien Boivin-Delisle
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - Louis Bernatchez
- Département de BiologieInstitut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
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