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A genomic island linked to ecotype divergence in A tlantic cod
Author(s) -
HemmerHansen Jakob,
Nielsen Einar E.,
Therkildsen Nina O.,
Taylor Martin I.,
Ogden Rob,
Geffen Audrey J.,
Bekkevold Dorte,
Helyar Sarah,
Pampoulie Christophe,
Johansen Torild,
Carvalho Gary R.
Publication year - 2013
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.12284
Subject(s) - ecotype , biology , gene flow , evolutionary biology , natural selection , population , divergence (linguistics) , population genomics , local adaptation , selective sweep , genomics , genome , gene , ecology , genetics , genetic variation , allele , philosophy , demography , linguistics , sociology , haplotype
The genomic architecture underlying ecological divergence and ecological speciation with gene flow is still largely unknown for most organisms. One central question is whether divergence is genome‐wide or localized in ‘genomic mosaics’ during early stages when gene flow is still pronounced. Empirical work has so far been limited, and the relative impacts of gene flow and natural selection on genomic patterns have not been fully explored. Here, we use ecotypes of Atlantic cod to investigate genomic patterns of diversity and population differentiation in a natural system characterized by high gene flow and large effective population sizes, properties which theoretically could restrict divergence in local genomic regions. We identify a genomic region of strong population differentiation, extending over approximately 20 cM, between pairs of migratory and stationary ecotypes examined at two different localities. Furthermore, the region is characterized by markedly reduced levels of genetic diversity in migratory ecotype samples. The results highlight the genomic region, or ‘genomic island’, as potentially associated with ecological divergence and suggest the involvement of a selective sweep. Finally, we also confirm earlier findings of localized genomic differentiation in three other linkage groups associated with divergence among eastern A tlantic populations. Thus, although the underlying mechanisms are still unknown, the results suggest that ‘genomic mosaics’ of differentiation may even be found under high levels of gene flow and that marine fishes may provide insightful model systems for studying and identifying initial targets of selection during ecological divergence.