Charles Perrier | Centre National de la Recherche Scientifique / French National Centre for Scientific Research (original) (raw)
Papers by Charles Perrier
Urban Evolutionary Biology
The field of urban ecology has provided many fascinating examples of organisms that display novel... more The field of urban ecology has provided many fascinating examples of organisms that display novel biological features in urban environments compared to natural habitats. Quantitative genetics provides a framework that can be used to investigate whether this phenotypic differentiation between urban and natural habitats is adaptive and is the result of heritable changes in response to divergent selection. New generation sequencing tools offer unique opportunities to expand our understanding of the genes and genetic mechanisms implicated in evolution in urban environments. This chapter first reviews quantitative genetics studies investigating the mechanisms of evolution in the city. It then reviews pioneering genomic studies that have shed light on the genes and genetic mechanisms implicated in urban microevolution. The authors discuss how further use of cost-effective high-resolution genomic approaches may improve the comprehension of both genomic and epigenomic mechanisms implicated ...
International Journal of Biometeorology
Evolutionary Applications
Understanding the effect of human induced landscape fragmentation on gene flow and evolutionary p... more Understanding the effect of human induced landscape fragmentation on gene flow and evolutionary potential of wild populations has become a major concern. Here, we investigated the effect of riverscape fragmentation on patterns of genetic diversity in the freshwater resident brook lamprey (Lampetra planeri) that has a low ability to pass obstacles to migration. We also tested the hypotheses of i) asymmetric gene flow following water current and ii) admixture with the closely related anadromous L. fluviatilis ecotype having a positive effect on L. planeri genetic diversity. We genotyped 2472 individuals, including 225 L. fluviatilis, sampled in 81 sites upstream and downstream from barriers to migration, in 29 West-European rivers. Linear modelling revealed a strong positive relationship between the distance to the source and genetic diversity, consistent with expected patterns of decreased gene flow into upstream populations. However, the presence of anthropogenic barriers had a mode...
Long-term field studies coupled with quantitative genomics offer a powerful means to understand t... more Long-term field studies coupled with quantitative genomics offer a powerful means to understand the genetic bases underlying quantitative traits and their evolutionary changes. However, analyzing and interpreting the time scales at which adaptive evolution occurs is challenging. First, while evolution is predictable in the short term, with strikingly rapid phenotypic changes in data series, it remains unpredictable in the long term. Second, while the temporal dynamics of some loci with large effect on phenotypic variation and fitness have been characterized, this task can be complicated in cases of highly polygenic trait architecture implicating numerous small effect size loci, or when statistical tests are sensitive to the heterogeneity of some key characteristics of the genome, like recombination rate variations. After introducing these aforementioned challenges, we discuss a recent investigation of the genomic architecture and spatio-temporal variation in great tit bill length, w...
Evolutionary Applications
How environmental and anthropogenic factors influence genetic variation and local adaptation is a... more How environmental and anthropogenic factors influence genetic variation and local adaptation is a central issue in evolutionary biology. The Mexican golden trout (Oncorhynchus chrysogaster), one of the southernmost native salmonid species in the world, is susceptible to climate change, habitat perturbations and the introduction of exotic rainbow trout (O. mykiss) for aquaculture. The present study aimed to explore the effect of both genetic introgression from O. mykiss and riverscape variables on the genetic variation of O. chrysogaster. Genotyping-by-sequencing (GBS) was applied to generate 9 767 single nucleotide polymorphisms (SNPs), genotyping 270 O. chrysogaster and aquaculture trout. Population genomics analyses were combined with riverscape genetics approaches. A small degree of admixture was identified between aquaculture and native trout, and significant effects of riverscape variables on genetic diversity were detected, as well as evidence of isolation by riverscape resist...
Evolutionary Applications
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Evolutionary Applications
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Molecular Ecology, 2016
Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among r... more Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among replicate ecotype pairs remains an important challenge in speciation research. We investigated the genomic divergence between the anadromous parasitic river lamprey (Lampetra fluviatilis) and the freshwater-resident nonparasitic brook lamprey (Lampetra planeri) in nine population pairs displaying variable levels of geographic connectivity. We genotyped 338 individuals with RAD sequencing and inferred the demographic divergence history of each population pair using a diffusion approximation method. Divergence patterns in geographically connected population pairs were better explained by introgression after secondary contact, whereas disconnected population pairs have retained a signal of ancient migration. In all ecotype pairs, models accounting for differential introgression among loci outperformed homogeneous migration models. Generating neutral predictions from the inferred divergence scenarios to detect highly differentiated markers identified greater proportions of outliers in disconnected population pairs than in connected pairs. However, increased similarity in the most divergent genomic regions was found among connected ecotype pairs, indicating that gene flow was instrumental in generating parallelism at the molecular level. These results suggest that heterogeneous genomic differentiation and parallelism among replicate ecotype pairs have partly emerged through restricted introgression in genomic islands.
Conservation Genetics Resources, 2011
Atlantic salmon and brown trout frequently cooccur in the same habitats and juveniles of both spe... more Atlantic salmon and brown trout frequently cooccur in the same habitats and juveniles of both species are difficult to discriminate. Hybridization between the two taxa has also been widely documented especially in endangered populations hence the need for species-specific molecular markers. Here we show that the microsatellite marker SsAD486 has two species-specific alleles allowing the identification of Atlantic salmon, brown trout, and their hybrids throughout the European range of these species. Since this marker is polymorphic in Atlantic salmon populations from Western Atlantic, it could also help discriminating between North American and European salmon.
Http Www Theses Fr, 2010
This thesis investigates the genetic structure among Atlantic salmon populations from France. We ... more This thesis investigates the genetic structure among Atlantic salmon populations from France. We focused on the influence of environmental factors and stocking on the spatial distribution of genetic diversity. We genotyped 1739 individuals from 34 rivers at 17 microsatellite markers. Samples were collected in old (1965-1987) and recent (1998-2006) cohorts. Clustering analyses revealed the existence of five genetically and geographically distinct groups. Distance among estuaries and river length were strong predictors of population structure. Local adaptation to upstream migration difficulty linked to the large distance from the sea to the spawning grounds is suggested in the Loire-Allier population given the large body size of fish, their particular run timing, and the high differentiation of this population. Comparing recent and old samples revealed a general reduction of differentiation among populations and high introgression by stocking strains in some populations most probably resulting from stocking. In some depopulated rivers were no stocking was performed we observed natural recolonization by individuals from neighbouring and distant stocks. We developed an approach using temporally explicit simulations to quantify the impact of stocking on some populations. This study suggested a lower fitness of stocked fish compared to wild individuals. In parallel to genetic analyses, we carried out microchemistry analyses of otoliths from individuals collected in stocked populations. Coupling genetic and microchemistry analyses on the same individuals allowed identifying river-born fish with hatchery pedigrees, discriminating them from hatchery-born fish with similar genetic characteristics.
Understanding genomic signatures of divergent selection underlying long-term adaptation in popula... more Understanding genomic signatures of divergent selection underlying long-term adaptation in populations located in heterogeneous environments is a key goal in evolutionary biology. In this study, we investigated neutral, adaptive and deleterious genetic variation using 7,192 SNPs in 31 Lake Trout (Salvelinus namaycush) populations (n = 673) from Qu ebec, Canada. Average genetic diversity was low, weakly shared among lakes, and positively correlated with lake size, indicating a major role for genetic drift subsequent to lake isolation. Putatively deleterious mutations were on average at lower frequencies than the other SNPs, and their abundance relative to the entire polymorphism in each population was positively correlated with inbreeding, suggesting that the effectiveness of purifying selection was negatively correlated with inbreeding, as predicted from theory. Despite evidence for pronounced genetic drift and inbreeding, several outlier loci were associated with temperature and found in or close to genes with biologically relevant functions notably related to heat stress and immune responses. Outcomes of gene–temperature associations were influenced by the inclusion of the most inbred populations, in which allele frequencies deviated the most from model predictions. This result illustrates challenge in identifying gene–environment associations in cases of high genetic drift and restricted gene flow and suggests limited adaptation in populations experiencing higher inbreeding. We discuss the relevance of these findings for the conservation and management, notably regarding stocking and genetic rescue, of Lake Trout populations and other species inhabiting highly fragmented habitats.
Understanding the emergence of species through the process of ecological speciation is a central ... more Understanding the emergence of species through the process of ecological speciation is a central question in evolutionary biology which also has implications for conservation and management. Lake trout (Salvelinus namaycush) is renowned for the occurrence of different ecotypes linked to resource and habitat use throughout North America. We aimed to unravel the fine genetic structure of the four lake trout ecotypes in Lake Superior. A total of 486 individuals from four sites were genotyped at 6822 filtered SNPs using RADseq technology. Our results revealed different extent of morphological and genetic differentiation within the different sites. Overall, genetic differentiation was weak but significant and was on average three times higher between sites (mean F ST = 0.016) than between ecotypes within sites (mean F ST = 0.005) indicating higher level of gene flow or a more recent shared ancestor between ecotypes within each site than between populations of the same ecotype. Evidence of divergent selection was also found between ecotypes and/or in association with morphological variation. Outlier loci found in genes related to lipid metabolism and visual acuity were of particular interest in this context of ecotypic divergence. However, we did not find clear indication of parallelism at the genomic level, despite the presence of phenotypic parallelism among some ecotypes from different sampling sites. Overall, the occurrence of different levels of both genomic and phenotypic differentiation between ecotypes within each site with several differentiated loci linked to relevant biological functions supports the presence of a continuum of divergence in lake trout.
Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among r... more Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among replicate ecotype pairs remains an important challenge in speciation research. We investigated the genomic divergence between the anadromous parasitic river lamprey (Lampetra fluviatilis) and the freshwater-resident nonparasitic brook lamprey (Lampetra planeri) in nine population pairs displaying variable levels of geographic connectivity. We genotyped 338 individuals with RAD sequencing and inferred the demographic divergence history of each population pair using a diffusion approximation method. Divergence patterns in geographically connected population pairs were better explained by introgression after secondary contact, whereas disconnected population pairs have retained a signal of ancient migration. In all ecotype pairs, models accounting for differential introgression among loci outperformed homogeneous migration models. Generating neutral predictions from the inferred divergence scenarios to detect highly differentiated markers identified greater proportions of outliers in disconnected population pairs than in connected pairs. However, increased similarity in the most divergent genomic regions was found among connected ecotype pairs, indicating that gene flow was instrumental in generating paral-lelism at the molecular level. These results suggest that heterogeneous genomic differentiation and parallelism among replicate ecotype pairs have partly emerged through restricted introgression in genomic islands.
Repeated adaptive ecological diversification has commonly been reported in fish and has often bee... more Repeated adaptive ecological diversification has commonly been reported in fish and has often been associated with trophic niche diversity. The main goal of this study was to investigate the extent of parallelism in the genomic and phenotypic divergence between piscivorous and planktivorous lake trout ecotypes from Laurentian Shield lakes, Canada. This was achieved by documenting the extent of morphological differentiation using geometric morphometrics and linear measurements as well as the pattern of genomic divergence by means of RADseq genotyping (3925 filtered SNPs) in 12 lakes. Our results indicate that the two ecotypes evolved distinct body shape and several linear measurements in parallel. Neutral genetic differentiation was pronounced between all isolated populations (Mean F ST = 0.433), indicating no or very limited migration and pronounced genetic drift. Significant genetic differentiation also suggested partial reproductive isolation between ecotypes in the two lakes where they are found in sympatry. Combining different outlier detection methods, we identified 48 SNPs putatively under divergent selection between ecotypes, among which 10 could be annotated and related to functions such as developmental processes and ionic regulation. Finally, our results indicate that parallel morphological divergence is accompanied by both parallel and nonparallel genomic divergence, which is associated with the use of different trophic niches between ecotypes. The results are also discussed in the context of management and conservation of this highly exploited species throughout northern North America.
Effective population size over a generation (Ne) or over a reproductive cycle (Nb) and the adult ... more Effective population size over a generation (Ne) or over a reproductive cycle (Nb) and the adult census size (Nc) are important parameters in both conservation and evolutionary biology. Ne provides information regarding the rate of loss of genetic diversity and can be tracked back in time to infer demographic history of populations, whereas Nb may often be more easily quantified than Nc for short-term abundance monitoring. In this study, we propose (1) an empirical context to Waples et al. (2014) who introduced a correction to bias due to overlapping generations, and (2) a mathematical relationship between Ne and Nb for direct application in Atlantic salmon populations in Québec, Canada. To achieve this, we investigate the relationships between Ne, Nb and Nc in 10 Atlantic salmon populations, Canada, for which we genotyped 100 randomly sampled young-of-the year individuals for 5 consecutive years. The results show a positive correlation between Ne, Nb and Nc, suggesting that Nb is an indicative parameter for tracking effective population size and abundance of Atlantic salmon. However, our model allows predicting Nc from Nb values at 27% that can be partly explained by high variance in Nb/Nc both among populations (37%) and among years (19%). This result illustrates the need for thorough calibration of Nb/Nc before using Nb in monitoring programs, as well as a full understanding of the limits of such an approach. Finally, we discuss the importance of these results for the management of wild populations.
Urban Evolutionary Biology
The field of urban ecology has provided many fascinating examples of organisms that display novel... more The field of urban ecology has provided many fascinating examples of organisms that display novel biological features in urban environments compared to natural habitats. Quantitative genetics provides a framework that can be used to investigate whether this phenotypic differentiation between urban and natural habitats is adaptive and is the result of heritable changes in response to divergent selection. New generation sequencing tools offer unique opportunities to expand our understanding of the genes and genetic mechanisms implicated in evolution in urban environments. This chapter first reviews quantitative genetics studies investigating the mechanisms of evolution in the city. It then reviews pioneering genomic studies that have shed light on the genes and genetic mechanisms implicated in urban microevolution. The authors discuss how further use of cost-effective high-resolution genomic approaches may improve the comprehension of both genomic and epigenomic mechanisms implicated ...
International Journal of Biometeorology
Evolutionary Applications
Understanding the effect of human induced landscape fragmentation on gene flow and evolutionary p... more Understanding the effect of human induced landscape fragmentation on gene flow and evolutionary potential of wild populations has become a major concern. Here, we investigated the effect of riverscape fragmentation on patterns of genetic diversity in the freshwater resident brook lamprey (Lampetra planeri) that has a low ability to pass obstacles to migration. We also tested the hypotheses of i) asymmetric gene flow following water current and ii) admixture with the closely related anadromous L. fluviatilis ecotype having a positive effect on L. planeri genetic diversity. We genotyped 2472 individuals, including 225 L. fluviatilis, sampled in 81 sites upstream and downstream from barriers to migration, in 29 West-European rivers. Linear modelling revealed a strong positive relationship between the distance to the source and genetic diversity, consistent with expected patterns of decreased gene flow into upstream populations. However, the presence of anthropogenic barriers had a mode...
Long-term field studies coupled with quantitative genomics offer a powerful means to understand t... more Long-term field studies coupled with quantitative genomics offer a powerful means to understand the genetic bases underlying quantitative traits and their evolutionary changes. However, analyzing and interpreting the time scales at which adaptive evolution occurs is challenging. First, while evolution is predictable in the short term, with strikingly rapid phenotypic changes in data series, it remains unpredictable in the long term. Second, while the temporal dynamics of some loci with large effect on phenotypic variation and fitness have been characterized, this task can be complicated in cases of highly polygenic trait architecture implicating numerous small effect size loci, or when statistical tests are sensitive to the heterogeneity of some key characteristics of the genome, like recombination rate variations. After introducing these aforementioned challenges, we discuss a recent investigation of the genomic architecture and spatio-temporal variation in great tit bill length, w...
Evolutionary Applications
How environmental and anthropogenic factors influence genetic variation and local adaptation is a... more How environmental and anthropogenic factors influence genetic variation and local adaptation is a central issue in evolutionary biology. The Mexican golden trout (Oncorhynchus chrysogaster), one of the southernmost native salmonid species in the world, is susceptible to climate change, habitat perturbations and the introduction of exotic rainbow trout (O. mykiss) for aquaculture. The present study aimed to explore the effect of both genetic introgression from O. mykiss and riverscape variables on the genetic variation of O. chrysogaster. Genotyping-by-sequencing (GBS) was applied to generate 9 767 single nucleotide polymorphisms (SNPs), genotyping 270 O. chrysogaster and aquaculture trout. Population genomics analyses were combined with riverscape genetics approaches. A small degree of admixture was identified between aquaculture and native trout, and significant effects of riverscape variables on genetic diversity were detected, as well as evidence of isolation by riverscape resist...
Evolutionary Applications
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Evolutionary Applications
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Molecular Ecology, 2016
Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among r... more Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among replicate ecotype pairs remains an important challenge in speciation research. We investigated the genomic divergence between the anadromous parasitic river lamprey (Lampetra fluviatilis) and the freshwater-resident nonparasitic brook lamprey (Lampetra planeri) in nine population pairs displaying variable levels of geographic connectivity. We genotyped 338 individuals with RAD sequencing and inferred the demographic divergence history of each population pair using a diffusion approximation method. Divergence patterns in geographically connected population pairs were better explained by introgression after secondary contact, whereas disconnected population pairs have retained a signal of ancient migration. In all ecotype pairs, models accounting for differential introgression among loci outperformed homogeneous migration models. Generating neutral predictions from the inferred divergence scenarios to detect highly differentiated markers identified greater proportions of outliers in disconnected population pairs than in connected pairs. However, increased similarity in the most divergent genomic regions was found among connected ecotype pairs, indicating that gene flow was instrumental in generating parallelism at the molecular level. These results suggest that heterogeneous genomic differentiation and parallelism among replicate ecotype pairs have partly emerged through restricted introgression in genomic islands.
Conservation Genetics Resources, 2011
Atlantic salmon and brown trout frequently cooccur in the same habitats and juveniles of both spe... more Atlantic salmon and brown trout frequently cooccur in the same habitats and juveniles of both species are difficult to discriminate. Hybridization between the two taxa has also been widely documented especially in endangered populations hence the need for species-specific molecular markers. Here we show that the microsatellite marker SsAD486 has two species-specific alleles allowing the identification of Atlantic salmon, brown trout, and their hybrids throughout the European range of these species. Since this marker is polymorphic in Atlantic salmon populations from Western Atlantic, it could also help discriminating between North American and European salmon.
Http Www Theses Fr, 2010
This thesis investigates the genetic structure among Atlantic salmon populations from France. We ... more This thesis investigates the genetic structure among Atlantic salmon populations from France. We focused on the influence of environmental factors and stocking on the spatial distribution of genetic diversity. We genotyped 1739 individuals from 34 rivers at 17 microsatellite markers. Samples were collected in old (1965-1987) and recent (1998-2006) cohorts. Clustering analyses revealed the existence of five genetically and geographically distinct groups. Distance among estuaries and river length were strong predictors of population structure. Local adaptation to upstream migration difficulty linked to the large distance from the sea to the spawning grounds is suggested in the Loire-Allier population given the large body size of fish, their particular run timing, and the high differentiation of this population. Comparing recent and old samples revealed a general reduction of differentiation among populations and high introgression by stocking strains in some populations most probably resulting from stocking. In some depopulated rivers were no stocking was performed we observed natural recolonization by individuals from neighbouring and distant stocks. We developed an approach using temporally explicit simulations to quantify the impact of stocking on some populations. This study suggested a lower fitness of stocked fish compared to wild individuals. In parallel to genetic analyses, we carried out microchemistry analyses of otoliths from individuals collected in stocked populations. Coupling genetic and microchemistry analyses on the same individuals allowed identifying river-born fish with hatchery pedigrees, discriminating them from hatchery-born fish with similar genetic characteristics.
Understanding genomic signatures of divergent selection underlying long-term adaptation in popula... more Understanding genomic signatures of divergent selection underlying long-term adaptation in populations located in heterogeneous environments is a key goal in evolutionary biology. In this study, we investigated neutral, adaptive and deleterious genetic variation using 7,192 SNPs in 31 Lake Trout (Salvelinus namaycush) populations (n = 673) from Qu ebec, Canada. Average genetic diversity was low, weakly shared among lakes, and positively correlated with lake size, indicating a major role for genetic drift subsequent to lake isolation. Putatively deleterious mutations were on average at lower frequencies than the other SNPs, and their abundance relative to the entire polymorphism in each population was positively correlated with inbreeding, suggesting that the effectiveness of purifying selection was negatively correlated with inbreeding, as predicted from theory. Despite evidence for pronounced genetic drift and inbreeding, several outlier loci were associated with temperature and found in or close to genes with biologically relevant functions notably related to heat stress and immune responses. Outcomes of gene–temperature associations were influenced by the inclusion of the most inbred populations, in which allele frequencies deviated the most from model predictions. This result illustrates challenge in identifying gene–environment associations in cases of high genetic drift and restricted gene flow and suggests limited adaptation in populations experiencing higher inbreeding. We discuss the relevance of these findings for the conservation and management, notably regarding stocking and genetic rescue, of Lake Trout populations and other species inhabiting highly fragmented habitats.
Understanding the emergence of species through the process of ecological speciation is a central ... more Understanding the emergence of species through the process of ecological speciation is a central question in evolutionary biology which also has implications for conservation and management. Lake trout (Salvelinus namaycush) is renowned for the occurrence of different ecotypes linked to resource and habitat use throughout North America. We aimed to unravel the fine genetic structure of the four lake trout ecotypes in Lake Superior. A total of 486 individuals from four sites were genotyped at 6822 filtered SNPs using RADseq technology. Our results revealed different extent of morphological and genetic differentiation within the different sites. Overall, genetic differentiation was weak but significant and was on average three times higher between sites (mean F ST = 0.016) than between ecotypes within sites (mean F ST = 0.005) indicating higher level of gene flow or a more recent shared ancestor between ecotypes within each site than between populations of the same ecotype. Evidence of divergent selection was also found between ecotypes and/or in association with morphological variation. Outlier loci found in genes related to lipid metabolism and visual acuity were of particular interest in this context of ecotypic divergence. However, we did not find clear indication of parallelism at the genomic level, despite the presence of phenotypic parallelism among some ecotypes from different sampling sites. Overall, the occurrence of different levels of both genomic and phenotypic differentiation between ecotypes within each site with several differentiated loci linked to relevant biological functions supports the presence of a continuum of divergence in lake trout.
Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among r... more Understanding the evolutionary mechanisms generating parallel genomic divergence patterns among replicate ecotype pairs remains an important challenge in speciation research. We investigated the genomic divergence between the anadromous parasitic river lamprey (Lampetra fluviatilis) and the freshwater-resident nonparasitic brook lamprey (Lampetra planeri) in nine population pairs displaying variable levels of geographic connectivity. We genotyped 338 individuals with RAD sequencing and inferred the demographic divergence history of each population pair using a diffusion approximation method. Divergence patterns in geographically connected population pairs were better explained by introgression after secondary contact, whereas disconnected population pairs have retained a signal of ancient migration. In all ecotype pairs, models accounting for differential introgression among loci outperformed homogeneous migration models. Generating neutral predictions from the inferred divergence scenarios to detect highly differentiated markers identified greater proportions of outliers in disconnected population pairs than in connected pairs. However, increased similarity in the most divergent genomic regions was found among connected ecotype pairs, indicating that gene flow was instrumental in generating paral-lelism at the molecular level. These results suggest that heterogeneous genomic differentiation and parallelism among replicate ecotype pairs have partly emerged through restricted introgression in genomic islands.
Repeated adaptive ecological diversification has commonly been reported in fish and has often bee... more Repeated adaptive ecological diversification has commonly been reported in fish and has often been associated with trophic niche diversity. The main goal of this study was to investigate the extent of parallelism in the genomic and phenotypic divergence between piscivorous and planktivorous lake trout ecotypes from Laurentian Shield lakes, Canada. This was achieved by documenting the extent of morphological differentiation using geometric morphometrics and linear measurements as well as the pattern of genomic divergence by means of RADseq genotyping (3925 filtered SNPs) in 12 lakes. Our results indicate that the two ecotypes evolved distinct body shape and several linear measurements in parallel. Neutral genetic differentiation was pronounced between all isolated populations (Mean F ST = 0.433), indicating no or very limited migration and pronounced genetic drift. Significant genetic differentiation also suggested partial reproductive isolation between ecotypes in the two lakes where they are found in sympatry. Combining different outlier detection methods, we identified 48 SNPs putatively under divergent selection between ecotypes, among which 10 could be annotated and related to functions such as developmental processes and ionic regulation. Finally, our results indicate that parallel morphological divergence is accompanied by both parallel and nonparallel genomic divergence, which is associated with the use of different trophic niches between ecotypes. The results are also discussed in the context of management and conservation of this highly exploited species throughout northern North America.
Effective population size over a generation (Ne) or over a reproductive cycle (Nb) and the adult ... more Effective population size over a generation (Ne) or over a reproductive cycle (Nb) and the adult census size (Nc) are important parameters in both conservation and evolutionary biology. Ne provides information regarding the rate of loss of genetic diversity and can be tracked back in time to infer demographic history of populations, whereas Nb may often be more easily quantified than Nc for short-term abundance monitoring. In this study, we propose (1) an empirical context to Waples et al. (2014) who introduced a correction to bias due to overlapping generations, and (2) a mathematical relationship between Ne and Nb for direct application in Atlantic salmon populations in Québec, Canada. To achieve this, we investigate the relationships between Ne, Nb and Nc in 10 Atlantic salmon populations, Canada, for which we genotyped 100 randomly sampled young-of-the year individuals for 5 consecutive years. The results show a positive correlation between Ne, Nb and Nc, suggesting that Nb is an indicative parameter for tracking effective population size and abundance of Atlantic salmon. However, our model allows predicting Nc from Nb values at 27% that can be partly explained by high variance in Nb/Nc both among populations (37%) and among years (19%). This result illustrates the need for thorough calibration of Nb/Nc before using Nb in monitoring programs, as well as a full understanding of the limits of such an approach. Finally, we discuss the importance of these results for the management of wild populations.