New publication: Genome architecture enables local adaptation of Atlantic cod despite high connectivity

By Julia M.I. Barth*, Paul R. Berg*, Per R. Jonsson, Sara Bonanomi, Hanna Corell, Jakob Hemmer-Hansen, Kjetill S. Jakobsen*, Kerstin Johannesson, Per Erik Jorde*, Halvor Knutsen*, Per-Olav Moksnes, Bastiaan Star*, Nils Chr. Stenseth*, Henrik Svedäng, Sissel Jentoft*, and Carl André in Molecular Ecology

Abstract

Adaptation to local conditions is a fundamental process in evolution; however, mechanisms maintaining local adaptation despite high gene flow are still poorly understood. Marine ecosystems provide a wide array of diverse habitats that frequently promote ecological adaptation even in species characterized by strong levels of gene flow. As one example, populations of the marine fish Atlantic cod (Gadus morhua) are highly connected due to immense dispersal capabilities but nevertheless show local adaptation in several key traits. By combining population genomic analyses based on 12K single-nucleotide polymorphisms with larval dispersal patterns inferred using a biophysical ocean model, we show that Atlantic cod individuals residing in sheltered estuarine habitats of Scandinavian fjords mainly belong to offshore oceanic populations with considerable connectivity between these diverse ecosystems. Nevertheless, we also find evidence for discrete fjord populations that are genetically differentiated from offshore populations, indicative of local adaptation, the degree of which appears to be influenced by connectivity. Analyses of the genomic architecture reveal a significant overrepresentation of a large ~5 Mb chromosomal rearrangement in fjord cod, previously proposed to comprise genes critical for the survival at low salinities. This suggests that despite considerable connectivity with offshore populations, local adaptation to fjord environments may be enabled by suppression of recombination in the rearranged region. Our study provides new insights into the potential of local adaptation in high gene flow species within fine geographical scales and highlights the importance of genome architecture in analyses of ecological adaptation.


Molecular Ecology
Accepted manuscript online: 19 June 2017
DOI: 10.1111/mec.14207
Publication webpage

* Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, UiO, Oslo, Norway.
See the publication webpage for full author information.

Tags: Molecular Ecology;
Published July 5, 2017 10:30 PM - Last modified July 5, 2017 10:30 PM