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: Correlations between allele frequencies and salinity (‰), temperature (°C) and oxygen concentration at surface and at spawning depth (table 3) were investigated using a landscape genomic approach (BAYENV 2.0). Significant association (median log10(BF) > 1 and q < 0.01) with at least one environmental variable was detected in 234 (2.6%) of the 8,809 examined SNP loci, distributed across all LGs except LG6 (supplementary fig. S3 and table S4, Supplementary Material online). The pattern and the number of SNPs with correlation to each environmental variable varied (fig. 5a–f). An association with salinity and oxygen level at spawning depth is clearly observed at a genome-wide scale, and in particular toward the end of LG2, whereas temperature shows a weak correlation in LG12 (fig. 5). There is a strong correlation between SNPs associated with salinity and oxygen, whereas SNPs associated with temperature are not strongly correlated with salinity or oxygen SNPs (fig. 5).Fig. 5.—
Affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway.