Adaptation to Low Salinity Promotes Genomic Divergence in Atlantic Cod (Gadus morhua L.).
Bottom Line: Our results show that discrete regions within the Atlantic cod genome are subject to directional selection and associated with adaptation to the local environmental conditions in the Baltic- and the North Sea, indicating divergence hitchhiking and the presence of genomic islands of divergence.We report a suite of outlier single nucleotide polymorphisms within or closely located to genes associated with osmoregulation, as well as genes known to play important roles in the hydration and development of oocytes.Hence, our data suggest that adaptive responses to the environmental conditions in the Baltic Sea may contribute to a strong and effective reproductive barrier, and that Baltic cod can be viewed as an example of ongoing speciation.
Affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway.Show MeSH
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Mentions: Locus-specific FST values for all pairwise population comparisons indicate a genome-wide pattern of high FST when comparisons are made to the Baltic Sea, whereas few discrete regions of the genome show elevated FST values in the remaining comparisons (fig. 2). A total of 40 private alleles (supplementary table S2, Supplementary Material online) were detected among the populations, 38 of which were rare in frequency (<0.04). The highest number of private alleles (23) was observed in the North Sea population and the lowest number (3) was observed in the Baltic population. The two private alleles of higher frequency (0.179 and 0.232) were found in the North Sea population, in complete linkage disequilibrium (LD) with each other (ss1712302407 and ss1712304757, located 241 bp apart, in LG3). In total, 334 fixed allele frequencies were detected in any population; however, only 84 of these showed frequency differences of more than 0.1 in any pairwise comparison. Out of these, 59 were unique to the Baltic population (19 potentially under selection) whereas 11, 2 and 1 were unique to the North Sea, Kattegat and Öresund populations, respectively. In addition, 59 outlier SNPs were close to fixation (frequency > 0.95; supplementary table S2, Supplementary Material online).Fig. 2.—
Affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway.