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Data from: Chromosome polymorphisms track trans‐Atlantic divergence and secondary contact in Atlantic salmon
Lehnert, Sarah J.; Bentzen, Paul; Kess, Tony; Lien, Sigbjorn; Horne, John B.; Clément, Marie; Bradbury, Ian R. — 2019-02-19 Pleistocene glaciations drove repeated range contractions and expansions shaping contemporary intraspecific diversity. Atlantic salmon (Salmo salar) in the western and eastern Atlantic diverged >600,000 YBP, with the two lineages isolated in different southern refugia during glacial maxima, driving trans-Atlantic genomic and karyotypic divergence. Here, we investigate genomic consequences of glacial isolation and trans-Atlantic secondary contact using 108,870 single nucleotide polymorphisms (SNPs) genotyped in 80 North American and European populations. Throughout North America, we identified extensive inter-individual variation and discrete linkage blocks within and between chromosomes with known trans-Atlantic differences in rearrangements: Ssa01/Ssa23 translocation and Ssa08/Ssa29 fusion. Spatial genetic analyses suggest independence of rearrangements, with Ssa01/Ssa23 showing high European introgression (>50%) in northern populations indicative of post-glacial trans-Atlantic secondary contact, contrasting low European ancestry genome-wide (3%). Ssa08/Ssa29 showed greater intra-population diversity suggesting a derived chromosome fusion polymorphism within North America. Evidence of potential selection on both genomic regions suggests that the adaptive role of rearrangements warrants further investigation in Atlantic salmon. Our study highlights how Pleistocene glaciations can influence large-scale intraspecific variation in genomic architecture of northern species.
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Data from: Environmental extremes drive population structure at the northern range limit of Atlantic salmon in North America
Sylvester, Emma V.A.; Beiko, Robert G.; Bentzen, Paul; Paterson, Ian; Horne, John B.; Watson, Beth; Lehnert, Sarah; Duffy, Steven; Clément, Marie; Robertson, Martha J.; Bradbury, Ian R.; Sylvester, Emma V. A. — 2018-08-23 Conservation of exploited species requires an understanding of both genetic diversity and the dominant structuring forces, particularly near range limits, where climatic variation can drive rapid expansions or contractions of geographic range. Here, we examine population structure and landscape associations in Atlantic salmon (Salmo salar) across a heterogeneous landscape near the northern range limit in Labrador, Canada. Analysis of two amplicon-based data sets containing 101 microsatellites and 376 single nucleotide polymorphisms (SNPs) from 35 locations revealed clear differentiation between populations spawning in rivers flowing into a large marine embayment (Lake Melville) compared to coastal populations. The mechanisms influencing the differentiation of embayment populations were investigated using both multivariate and machine-learning landscape genetic approaches. We identified temperature as the strongest correlate with genetic structure, particularly warm temperature extremes and wider annual temperature ranges. The genomic basis of this divergence was further explored using a subset of locations (n=17) and a 220K SNP array. SNPs associated with spatial structuring and temperature mapped to a diverse set of genes and molecular pathways, including regulation of gene expression, immune response, and cell development and differentiation. The results spanning molecular marker types and both novel and established methods clearly show climate-associated, fine-scale population structure across an environmental gradient in Atlantic salmon near its range limit in North America, highlighting valuable approaches for predicting population responses to climate change and managing species sustainability.
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Resolving fine-scale population structure and fishery exploitation using sequenced microsatellites in a northern fish
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K. S. Layton, Kara; Dempson, J. Brian; Snelgrove, Paul V.R.; Duffy, Steven J.; Messmer, Amber M.; Paterson, Ian; Jeffery, Nicholas W.; Kess, Tony; Horne, John B.; Salisbury, Sarah J.; Ruzzante, Daniel E.; Bentzen, Paul; Côté, David; Nugent, Cameron M.; Ferguson, Moira M.; Leong, Jong S.; Koop, Ben F.; Bradbury, Ian R. — 2020-01-17 <p>The resiliency of populations and species to environmental change is dependent on the maintenance of genetic diversity, and as such quantifying diversity is central to combatting ongoing wide spread reductions in biodiversity. With the advent of next-generation sequencing, several methods now exist for resolving fine-scale population structure, but the comparative performance of these methods for genetic assignment has rarely been tested. Here we evaluate the performance of sequenced microsatellites and a single nucleotide polymorphism (SNP) array to resolve fine-scale population structure in a critically important salmonid in northeastern Canada, Arctic charr (<i>Salvelinus alpinus</i>). We also assess the utility of sequenced microsatellites for fisheries applications by quantifying the spatial scales of movement and exploitation through genetic assignment of fishery samples to rivers of origin and comparing these results with a 29-year tagging dataset. Self-assignment and simulation-based analyses of 111 genome-wide microsatellite loci and 500 informative SNPs from 28 populations of Arctic charr in northeastern Canada identified largely river-specific genetic structure. Despite large differences (~4X) in the number of loci surveyed between panels, mean self-assignment accuracy was similar with the SNP panel and with the microsatellite loci (&gt;90%). Subsequent analysis of 996 fishery-collected samples using the microsatellite panel revealed that larger rivers contribute greater numbers of individuals to the fishery, and that coastal fisheries largely exploit individuals originating from nearby rivers, corroborating results from traditional tagging experiments. Our results demonstrate the efficacy of sequence-based microsatellite genotyping to advance understanding of fine-scale population structure and harvest composition in northern and understudied species.</p>

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(auteur : Horne, John B.)

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