Can we rely on selected genetic markers for population identification? Evidence from coastal Atlantic cod. Issue 24 (1st December 2018)

• Record Type: Journal Article
• Authors: Jorde, Per Erik; Synnes, Ann‐Elin; Espeland, Sigurd Heiberg; Sodeland, Marte; Knutsen, Halvor
• Is Part Of: Ecology and evolution. Volume 8:Issue 24(2018)
• Page Start: 12547
• Page End: 12558
• Publication Date: 2018-12-01
• Subjects: marine fishes -- natural selection -- population genetics -- population of origin -- statistical assignment; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.4648
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: The use of genetic markers under putative selection in population studies carries the potential for erroneous identification of populations and misassignment of individuals to population of origin. Selected markers are nevertheless attractive, especially in marine organisms that are characterized by weak population structure at neutral loci. Highly fecund species may tolerate the cost of strong selective mortality during early life stages, potentially leading to a shift in offspring genotypes away from the parental proportions. In Atlantic cod, recent genetic studies have uncovered different genotype clusters apparently representing phenotypically cryptic populations that coexist in coastal waters. Here, we tested if a high‐graded SNP panel specifically designed to classify individual cod to population of origin may be unreliable because of natural selection acting on the SNPs or their linked background. Temporal samples of cod were collected from two fjords, starting at the earliest life stage (pelagic eggs) and carried on until late autumn (bottom‐settled juveniles), covering the period during summer of high natural mortality. Despite the potential for selective mortality during the study period, we found no evidence for selection, as both cod types occurred throughout the season, already in the earliest egg samples, and there was no evidence for a shift during the season in the proportions of one or the other type. We conclude that high‐graded marker panels under putative natural selection represent a valid and useful tool for identifying biological population structure in this highly fecund species and presumably in others. Abstract : The use of genetic markers under putative selection in population studies carries the potential for erroneous identification of populations and misassignment of individuals to population of origin. We analyzed this problem in coastal Atlantic cod by screening temporal samples for genotypes from a high‐graded SNP panel specifically designed to separate putative cod populations. Despite sampling over early life stages with high natural mortality, and thus potential for selection, we found no evidence for selection distorting population assignment in this species.