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Contributed by Nils Chr. Stenseth, March 2, 2021 (sent for review January 8, 2021; reviewed by Tom Gilbert and Michael Knapp)
Significance
Both theory and experiments suggest that fishing can drive the evolution of an earlier maturation age. However, determining whether changes in the wild are the result of fisheries-induced evolution has been difficult. Temporal, genome-wide datasets can directly reveal responses to selection. Here, we investigate the genomes of two wild Atlantic cod populations from samples that pre- and postdate periods of intensive fishing. Although phenotypic changes suggest fisheries-induced evolution, we do not find evidence for any strong genomic change or loss of genetic diversity. While evolution could have occurred through undetectable frequency changes at many loci, the irreversible loss of late-maturing genotypes appears unlikely. Instead, we suggest that recovery of former phenotypes is possible with reduced fishing pressure.
Abstract
The mode and extent of rapid evolution and genomic change in response to human harvesting are key conservation issues. Although experiments and models have shown a high potential for both genetic and phenotypic change in response to fishing, empirical examples of genetic responses in wild populations are rare. Here, we compare whole-genome sequence data of Atlantic cod (Gadus morhua) that were collected before (early 20th century) and after (early 21st century) periods of intensive exploitation and rapid decline in the age of maturation from two geographically distinct populations in Newfoundland, Canada, and the northeast Arctic, Norway. Our temporal, genome-wide analyses of 346,290 loci show no substantial loss of genetic diversity and high effective population sizes. Moreover, we do not find distinct signals of strong selective sweeps anywhere in the genome, although we cannot rule out the possibility of highly polygenic evolution. Our observations suggest that phenotypic change in these populations is not constrained by irreversible loss of genomic variation and thus imply that former traits could be reestablished with demographic recovery.
Footnotes
- ↵1To whom correspondence may be addressed. Email: malin.pinsky{at}rutgers.edu, n.c.stenseth{at}mn.uio.no, or bastiaan.star{at}ibv.uio.no.
Author contributions: M.L.P., A.M.E., O.S.K., N.C.S., K.S.J., S.J., and B.S. designed research; A.T.G.-W. and B.S. performed research; M.L.P., I.R.B., P.B., C.M., H.T.B., O.S.K., J.A.G., S.J., and B.S. contributed new materials/analytic tools; M.L.P., C.H., J.M.I.B., M.M., and B.S. curated data; M.L.P. and B.S. analyzed data; M.L.P. and B.S. wrote the paper with input from A.M.E., C.H., H.T.B., M.S.O.B., O.S.K., J.A.G., J.M.I.B., M.M., N.C.S., K.S.J., and S.J.; and historical samples were provided by I.R.B., P.B., C.M., O.S.K., and J.A.G.
Reviewers: T.G., University of Copenhagen; and M.K., University of Otago.
The authors declare no competing interest.
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This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2025453118/-/DCSupplemental.
Data Availability
Analysis scripts and associated data reported in this article are archived as a Git repository through Zenodo at https://doi.org/10.5281/zenodo.4554375. Raw sequencing reads for the historical and modern samples reported in this article are available at the European Nucleotide Archive (project no. PRJEB41431).
- Copyright © 2021 the Author(s). Published by PNAS.
This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Genomic stability through time despite decades of exploitation in cod on both sides of the Atlantic
Article Classifications
- Biological Sciences
- Population Biology
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