New publication: “Islands of Divergence” in the Atlantic CodGenomeRepresent Polymorphic Chromosomal Rearrangements

By Marte Sodeland, Per Erik Jorde*, Sigbjørn Lien*, Sissel Jentoft, Paul R. Berg*, Harald Grove, Matthew P. Kent, Mariann Arnyasi, Esben Moland Olsen, and Halvor Knutsen* in Genome Biology and Evolution

Abstract

In several species genetic differentiation across environmental gradients or between geographically separate populations has been reported to center at “genomic islands of divergence,” resulting in heterogeneous differentiation patterns across genomes. Here, genomic regions of elevated divergencewere observed on three chromosomes of the highlymobile fishAtlantic cod (Gadusmorhua) within geographically fine-scaled coastal areas. The “genomic islands” extended at least 5, 9.5, and 13megabases on linkage groups 2, 7, and 12, respectively, and coincided with large blocks of linkage disequilibrium. For each of these three chromosomes, pairs of segregating, highly divergent alleleswere identified, with little or no gene exchange between them. These patterns of recombination and divergencemirror genomic signatures previously described for large polymorphic inversions,which have been shown to repress recombination across extensive chromosomal segments. The lack of genetic exchange permits divergence between noninverted and inverted chromosomes in spite of gene flow. For the rearrangements on linkage groups 2 and 12, allelic frequency shifts between coastal and oceanic environments suggest a role in ecological adaptation, in agreement with recently reported associations between molecular variation within these genomic regions and temperature, oxygen, and salinity levels. Elevated genetic differentiation in these genomic regions has previously been described on both sides of the Atlantic Ocean, and we therefore suggest that these polymorphisms are involved in adaptive divergence across the species distributional range.

First published online: March 15, 2016
Genome Biol. Evol. 8(4):1012–1022
DOI: 10.1093/gbe/evw057

*Centre for Ecological and Evolutionary Synthesis (CEES). See the publication for full author information.
Tags: Genome Biology and Evolution;
Published May 1, 2016 2:54 AM - Last modified Sep. 23, 2016 3:03 PM