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Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon
Due to the mediating role of body size in determining fitness, the “bigger‐is‐better” hypothesis still pervades evolutionary ecology despite evidence that natural selection on phenotypic traits varies in time and space. For Pacific salmon (genus Oncorhynchus), most individual studies quantify select...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7463379/ https://www.ncbi.nlm.nih.gov/pubmed/32908600 http://dx.doi.org/10.1111/eva.12957 |
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author | Ulaski, Marta E. Finkle, Heather Westley, Peter A. H. |
author_facet | Ulaski, Marta E. Finkle, Heather Westley, Peter A. H. |
author_sort | Ulaski, Marta E. |
collection | PubMed |
description | Due to the mediating role of body size in determining fitness, the “bigger‐is‐better” hypothesis still pervades evolutionary ecology despite evidence that natural selection on phenotypic traits varies in time and space. For Pacific salmon (genus Oncorhynchus), most individual studies quantify selection across a narrow range of sizes and ages; therefore, uncertainties remain concerning how selection on size may differ among diverse life histories. Here, we quantify the direction and magnitude of natural selection on body size among age‐classes of multiple marine cohorts of O. nerka (sockeye salmon). Across four cohorts of seaward migrants, we calculated standardized selection differentials by comparing observed size distributions of out‐migrating juvenile salmon to back‐calculated smolt length from the scales of surviving, returning adults. Results reveal the magnitude of selection on size was very strong (>90th percentile compared to a database of 3,759 linear selection differentials) and consistent among years. However, the direction of selection on size consistently varied among age‐classes. Selection was positive for fish migrating to sea after two years in freshwater (age 2) and in their first year of life (age 0), but negative for fish migrating after 1 year in freshwater (age 1). The absolute magnitude of selection was negatively correlated to mean ocean‐entry timing, which may underpin negative selection favoring small age‐1 fish, given associations between size and timing of seaward migration. Collectively, these results indicate that “bigger is not always better” in terms of survival and emphasize trade‐offs that may exist between fitness components for organisms with similarly diverse migratory life histories. |
format | Online Article Text |
id | pubmed-7463379 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-74633792020-09-08 Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon Ulaski, Marta E. Finkle, Heather Westley, Peter A. H. Evol Appl Original Articles Due to the mediating role of body size in determining fitness, the “bigger‐is‐better” hypothesis still pervades evolutionary ecology despite evidence that natural selection on phenotypic traits varies in time and space. For Pacific salmon (genus Oncorhynchus), most individual studies quantify selection across a narrow range of sizes and ages; therefore, uncertainties remain concerning how selection on size may differ among diverse life histories. Here, we quantify the direction and magnitude of natural selection on body size among age‐classes of multiple marine cohorts of O. nerka (sockeye salmon). Across four cohorts of seaward migrants, we calculated standardized selection differentials by comparing observed size distributions of out‐migrating juvenile salmon to back‐calculated smolt length from the scales of surviving, returning adults. Results reveal the magnitude of selection on size was very strong (>90th percentile compared to a database of 3,759 linear selection differentials) and consistent among years. However, the direction of selection on size consistently varied among age‐classes. Selection was positive for fish migrating to sea after two years in freshwater (age 2) and in their first year of life (age 0), but negative for fish migrating after 1 year in freshwater (age 1). The absolute magnitude of selection was negatively correlated to mean ocean‐entry timing, which may underpin negative selection favoring small age‐1 fish, given associations between size and timing of seaward migration. Collectively, these results indicate that “bigger is not always better” in terms of survival and emphasize trade‐offs that may exist between fitness components for organisms with similarly diverse migratory life histories. John Wiley and Sons Inc. 2020-04-09 /pmc/articles/PMC7463379/ /pubmed/32908600 http://dx.doi.org/10.1111/eva.12957 Text en © 2020 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Original Articles Ulaski, Marta E. Finkle, Heather Westley, Peter A. H. Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title | Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title_full | Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title_fullStr | Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title_full_unstemmed | Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title_short | Direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating Pacific salmon |
title_sort | direction and magnitude of natural selection on body size differ among age‐classes of seaward‐migrating pacific salmon |
topic | Original Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7463379/ https://www.ncbi.nlm.nih.gov/pubmed/32908600 http://dx.doi.org/10.1111/eva.12957 |
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