Biology subjects

Dallaire, X.

Publications and source records attributed to Dallaire, X..

5 recordsLinked to original sources

bioRxiv2025

Conservation units for anadromous Arctic Char (Salvelinus alpinus) in the Canadian Arctic informed by genetic structure, population connectivity and adaptive genomic variation

Intraspecific genetic diversity is a crucial aspect of biodiversity conservation as it preserves evolutionary potential and enhances resilience to environmental change. Genomic-informed delineation of Conservation Units (CUs) offers ways of subdividing species into groups based on historical isolation and adaptive differentiation, to develop biologically relevant conservation and management policies. CUs have been defined in many species of harvested anadromous salmonids, but broad scale data remains lacking in the Canadian Arctic, where anadromous Arctic Char (Salvelinus alpinus) dominates catches in Indigenous-led subsistence and commercial fisheries. In this study, we use low-coverage whole-genome data from 30 Canadian populations of Arctic Char to define CUs based on population structure and connectivity, as well as adaptive genetic variation. We highlight two main genetic groups, each of which comprises three subgroups, or candidate CUs: the North (above the 67th parallel), including the North Baffin Island, Kitikmeot, and Inuvialuit Settlement Region CUs; and the South (below the 67th parallel), including the South Baffin Island, Ungava Bay, and Hudson Bay CUs. This delimitation is supported by areas of low effective migration between candidate CUs, as well as isolation-by-environment, which suggests adaptive differentiation. Finally, we discuss opportunities and caveats relating to linkage when identifying adaptive genetic variation from whole genome sequencing data through genome scans and Gene-Environment Associations.

evolutionary biology↗

bioRxiv2024

Leveraging whole genomes, mitochondrial DNA, and haploblocks to decipher complex demographic histories: an example from a broadly admixed arctic fish

The study of phylogeography has transitioned from mitochondrial haplotypes to genome-wide analyses, blurring the line between this field and population genomics. Whole-genome sequencing offers the opportunity to join use both and provides the density of markers necessary to investigate genetic linkage and recombination along the genome. This facilitates the unraveling of complex demographic histories of admixture between divergent lineages, as is often the case in species evolving in recently deglaciated habitats. In this study, we sequenced 1120 Arctic Char genomes from 33 populations across Canada and Western Greenland to characterize patterns of genetic variation and diversity, and how they are shaped by hybridization between the Arctic and Atlantic glacial lineages. Several lines of evidence supported mito-nuclear discordance in lineage distribution, with all Canadian populations under the 66th parallel being characterized by introgression from the Atlantic lineage, leading to higher nuclear genetic diversity. By scanning the genome using local PCAs, we identified putative low-recombining haploblocks as local ancestry tracts from either lineage and described the impacts of recombination on the introgression landscape in admixed populations. Finally, we inferred conflicting origins of recolonization using whole genomes vs. ancestry tracts for the Arctic lineage, suggesting that haplotypes sheltered from introgression by low recombination could enlighten complex post-glacial histories. Overall, we argue that Whole-Genome Sequencing, even at low depths of coverage, provides a versatile approach to the study of phylogeographic dynamics.

evolutionary biology↗

bioRxiv2023

Widespread deviant patterns of heterozygosity in whole-genome sequencing due to autopolyploidy, repeated elements and duplication

Most population genomic tools rely on accurate SNP calling and filtering to meet their underlying assumptions. However, genomic complexity, due to structural variants, paralogous sequences and repetitive elements, presents significant challenges in assembling contiguous reference genomes. Consequently, short-read resequencing studies can encounter mismapping issues, leading to SNPs that deviate from Mendelian expected patterns of heterozygosity and allelic ratio. In this study, we employed the ngsParalog software to identify such deviant SNPs in whole-genome sequencing data from four species: Arctic Char (Salvelinus alpinus), Lake Whitefish (Coregonus clupeaformis), Atlantic Salmon (Salmo salar), and the American Eel (Anguilla rostrata), with low (2X) to intermediate (6X) coverage. The analyses revealed that deviant SNPs accounted for up to 62% of all SNPs in salmonid datasets and approximately 10% in the American Eel dataset. These deviant SNPs were particularly concentrated within repetitive elements and genomic regions that had recently undergone rediploidization in salmonids. Additionally, narrow peaks of elevated coverage were ubiquitous along all four reference genomes, encompassed most deviant SNPs and could be partially attributed to transposons and tandem repeats. Including these deviant SNPs in genomic analyses led to highly distorted site frequency spectra, apparent homogenization of populations and underestimating pairwise FST values. Considering the widespread occurrence of deviant SNPs arising from a variety of source, their important impact in estimating population parameters, and the availability of effective tools to identify them, we propose that excluding deviant-SNPs from WGS datasets is required to improve genomic inferences for a wide range of taxa and sequencing depths. Significance: Genomes can be very repetitive and hard to assemble into a reference, which can lead to biases when genotyping genetic markers in complex genomic regions. Here, we draw attention to this issue in various whole-genome datasets and validate a method to identify problematic SNPs at low coverage. We also explore processes creating such SNPs and their consequences on common population genomics analyses.

genomics↗

bioRxiv2021

Long distance migration is a major factor driving local adaptation at continental scale in Coho Salmon

Inferring the genomic basis of local adaptation is a long-standing goal of evolutionary biology. Beyond its fundamental evolutionary implications, such knowledge can guide conservation decisions for populations of conservation and management concern. Here, we investigated the genomic basis of local adaptation in the Coho salmon (Oncorhynchus kisutch) across its entire North American range. We hypothesized that extensive spatial variation in environmental conditions and the species homing behavior may promote the establishment of local adaptation. We genotyped 7,829 individuals representing 217 sampling locations at more than 100,000 high-quality RADseq loci to investigate how recombination might affect the detection of loci putatively under selection and took advantage of the precise description of the demographic history of the species from our previous work to draw accurate population genomic inferences about local adaptation. Results indicated that genetic differentiation scans and genetic-environment association analyses were both significantly affected by variation in recombination rate as low recombination regions displayed an increased number of outliers. By taking these confounding factors into consideration, we revealed that migration distance was the primary selective factor driving local adaptation and partial parallel divergence among distant populations. Moreover, we identified several candidates SNP associated with long distance migration and altitude including a gene known to be involved in adaptation to altitude in other species. The evolutionary implications of our findings are discussed along with conservation applications.

evolutionary biology↗

bioRxiv2020

Population structure and genomic evidence for local adaptation to freshwater and marine environments in anadromous Arctic Char (Salvelinus alpinus) throughout Nunavik, Canada

Distinguishing neutral and adaptive genetic variation is one of the main challenges in investigating processes shaping population structure in the wild, and landscape genomics can help identify signatures of adaptation to contrasting environments. Arctic Char (Salvelinus alpinus) is an anadromous salmonid and the most harvested fish species by Inuit people, particularly so in Nunavik (Canada), one of the most recently deglaciated region in the world. Unlike most other anadromous salmonids, Arctic Char occupy coastal habitats near their overwintering rivers during their marine phase. The main objective of this study was to document the putative neutral and adaptive genomic variation of anadromous Arctic Char populations in Nunavik (Quebec, Canada) and bordering regions. A second objective was to interpret our results in the context of fisheries management in Nunavik. We used genotyping-by-sequencing (GBS) to genotype 18,112 filtered single nucleotide polymorphisms (SNPs) for 650 individuals sampled in 23 locations (average sample size per location = 28) along >2,000 km of coastline. Our results reveal a hierarchical genetic structure, whereby neighboring hydrographic systems harbour distinct populations grouping within major oceanographic basins, namely the Hudson Bay, Hudson Strait, Ungava Bay and Labrador Sea. We found genetic diversity and differentiation to be consistent with both the expected post-glacial recolonization history and patterns of isolation-by-distance reflecting contemporary gene flow. Furthermore, using three gene-environment association (GEA) methods we found genomic evidence for local adaptation to freshwater and marine environmental components, especially in relation to sea-surface and air temperatures during summer, as well as salinity. Our results support fisheries management at a regional level, and other implications on hatchery projects and adaptation to climate change are discussed.

genomics↗