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Pink salmon, the most abundant Pacific salmon, have an obligate 2-year life cycle that leads to reproductively isolated even- and odd-year lineages. Using new and existing data, we examined the genetic structure of both lineages across their distributional range by genotyping 16 681 single-nucleotide polymorphisms for 383 individuals originating from seven pairs of even- and odd-year populations. Distinct differences in standing pools of genetic variation were identified between the lineages; we observed higher levels of heterozygosity, allelic richness, and significantly more private alleles in the odd-year lineage. However, the patterns of population structure were concordant between lineages: the Asian and northern Alaska populations displayed little differentiation but differed significantly from populations in southcentral Alaska and the Pacific Northwest. Our population structure results, in the context of known paleoecological information, suggest that both lineages occupied a northern Beringial refugium as well as a Cascadian refugium in North America during the Last Glacial Maximum. These results highlight the influence of historical patterns of habitat availability on contemporary population structure and support the hypothesis of a pre-glacial origin of the lineages. Le saumon rose, le plus abondant des saumons du Pacifique, a un cycle biologique fixe de deux ans qui se traduit par des lignees d'annees paires et impaires isolees les unes des autres du point de vue de la reproduction. En utilisant des donnees nouvelles et existantes, nous avons examine la structure genetique des deux lignees a la grandeur de leur aire de repartition en genotypant 16 681 polymorphismes mononucleotidiques pour 383 individus issus de sept paires de populations d'annees paires et impaires. Des differences claires dans les bassins de variation genetique existants ont ete cernees entre les lignees; nous avons observe des degres plus eleves d'heterozygotie et de richesse allelique et significativement plus d'alleles particuliers dans la lignee d'annees impaires. Les motifs de structure des populations concordent toutefois entre les deux lignees; les populations asiatiques et du nord de l'Alaska presentent peu de differenciation, mais sont significativement differentes des populations du centre-sud de l'Alaska et du Pacific Northwest. Nos resultats sur la structure des populations, dans le contexte d'information paleoecologique connue, donnent a penser que les deux lignees ont occupe un refuge beringien septentrional ainsi qu'un refuge cascadien en Amerique du Nord durant le dernier maximum glaciaire. Ces resultats soulignent l'influence de motifs de disponibilite d'habitat passes sur la structure actuelle des populations et appuient l'hypothese d'une origine preglaciaire des lignees. [Traduit par la Redaction], Introduction An enduring goal in evolutionary biology is to describe the dynamics that result in population structure, species distribution, and genetic diversity. Groups of organisms that use the same habitat [...]

Poleward species range shifts have been predicted to result from climate change, and many observations have confirmed such movement. Poleward shifts may represent a homogeneous shift in distribution, seasonal northward movement of specific populations, or colonization processes at the poleward edge of the distribution. The ecosystem of the Bering Sea has been changing along with the climate, moving from an arctic to a subarctic system. Several fish species have been observed farther north than previously reported and in increasing abundances. We examined one of these fish species, Pacific cod, in the northern Bering Sea (NBS) to assess whether they migrated from another stock in the eastern Bering Sea (EBS), Gulf of Alaska, or Aleutian Islands, or whether they represent a separate population. Genetic analyses using 3,599 single nucleotide polymorphism markers indicated that nonspawning cod collected in August 2017 in the NBS were similar to spawning stocks of cod in the EBS. This result suggests escalating northward movement of the large EBS stock during summer months. Whether the cod observed in the NBS migrate south during winter to spawn or remain in the NBS as a sink population is unknown. [ABSTRACT FROM AUTHOR]