Phylogeographic analysis of complete mtDNA genomes from Walleye Pollock (Gadus chalcogrammus Pallas, 1811) shows an ancient origin of genetic biodiversity

Abstract

Ursvik et al. compared the complete mitochondrial DNA (mtDNA) genome sequences of Walleye Pollock (Gadus ( = Theragra) chalcogrammus) from the Pacific Ocean with a pair of fish from an isolated population of Norwegian pollock in the Barents Sea. They concluded that the Norwegian population was recently introduced from the Pacific. We test this hypothesis within a temporal framework provided by a phylogeographic analysis of complete genomes from the pollocks' sister species, Atlantic Cod (Gadus morhua), and their divergence 3.5 mya. Pollock have a coalescent ancestor 189 ± 25 kya. The two Norwegian fish have a common ancestor 87 ± 7 kya, which suggests an ancient origin rather than a recent human-mediated introduction. Mitochondrial genomic biodiversity in pollock antedates the most recent glacial cycle. The clade structure of the whole-genome tree indicates that previously described single-locus mtDNA haplotypes and haplogroups are typically paraphyletic.

• Gadus chalcogrammus
• Theragra
• finnmarchica
• phylogeography, mitogenomics

Acknowledgements

The authors thank their colleagues T. Yanagimoto, A. Ursvik, and their co-workers for providing their data through NCBI, and three anonymous reviewers for comments on previous drafts of the manuscript. This work was supported by a Grants and Contract agreement to S.M.C. between the Department of Fisheries and Oceans and Memorial University.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.