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Disentangling structural genomic and behavioural barriers in a sea of connectivity
Author(s) -
Barth Julia M. I.,
VillegasRíos David,
Freitas Carla,
Moland Even,
Star Bastiaan,
André Carl,
Knutsen Halvor,
Bradbury Ian,
Dierking Jan,
Petereit Christoph,
Righton David,
Metcalfe Julian,
Jakobsen Kjetill S.,
Olsen Esben M.,
Jentoft Sissel
Publication year - 2019
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.15010
Subject(s) - biology , sympatric speciation , gadus , gene flow , reproductive isolation , sympatry , coalescent theory , local adaptation , fjord , population , evolutionary biology , ecology , atlantic cod , population genetics , genetic variation , oceanography , fishery , genetics , gene , phylogenetics , sociology , geology , fish <actinopterygii> , demography
Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod ( Gadus morhua ), by exploring a unique data set combining whole‐genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord‐type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG 12 inversion had lower fitness in the fjord environment. However, North Sea and fjord‐type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.