Signatures of strong positive selection in an admixture graph of Atlantic cod populations

Einar Árnason, Katrín Halldórsdóttir, Alba Refoyo-Martínez, Thomas Mailund, and Fernando Racimo. 2019. Detecting signatures of strong positive selection on branches of an admixture graph of Atlantic cod populations. Poster presented at Speciation: Gordon Research Conference, Ventura, California, USA. March 10--15,  2019

Modeling historical population relationships within a species are important for understanding the operation of natural selection. We have developed a method---called Graph-aware Retrieval of Selective Sweeps (GRoSS)---for detecting signatures of strong positive selection on the branches of complex admixture graphs among a set of populations. Here, we apply the method to whole-genome sequence variation of Atlantic cod population from throughout its distributional range. We detect several regions of strong selection and putative candidate genes. We also detect large regions of differentiation due to inversions, associated with behavioral ecotypes, and we are able to pinpoint in which populations or on which branches in the history of Atlantic cod the variants originated or have been under the strongest selection. Structural chromosomal variation is important in local adaptation and speciation.