Disentangling structural genomic and behavioral barriers in a sea of connectivity

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 whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod, by exploring a unique dataset combining whole-genome sequencing data and behavioral 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 behavioral tracking over four years revealed temporally stable s...