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: In the global outlier analyses comprising all four populations, we identified 123 (1.4%) and 114 (1.3%) SNPs as candidates for divergent selection (log10(Bayes factor [BF]) > 1, empirical P < 0.01), using BAYESCAN and LOSITAN, respectively. Pairwise outlier analyses using BAYESCAN, revealed 228 (2.6%) SNPs as candidates for divergent selection (supplementary fig. S3 and table S4, Supplementary Material online). However, the pattern and the number of outliers in each pairwise comparison varied (fig. 4b–g). In total, 266 SNPs (3.0%) were detected as candidates for divergent selection using global or pairwise outlier test. LG2 and 12 had the highest proportion of SNPs potentially under selection (36 and 98, respectively; supplementary table S4, Supplementary Material online). These two LGs contain large LD blocks, where most, but not all, of these outliers reside (fig. 3).Fig. 4.—
Affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway.