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Nine decades of decreasing phenotypic variability in Atlantic cod
Esben Moland Olsen1, Stephanie M Carlson, Jakob Gjøsaeter
1Institute of Marine Research, Flødevigen, 4817 His, Norway.
Ecology Letters
|May 21, 2009
Summary
Phenotypic variability in Atlantic cod juvenile size has decreased over 90 years, indicating stabilizing selection. This highlights the importance of studying trait diversity in wild populations for evolutionary insights.
Area of Science:
- Evolutionary biology
- Population genetics
- Ecology
Background:
- Phenotypic variability changes in natural populations are understudied compared to mean trait value shifts.
- Trait diversity is crucial for adaptive evolution and population stability.
Purpose of the Study:
- To investigate complex trait changes in Atlantic cod along the Norwegian Skagerrak coast over nine decades.
- To analyze trends in juvenile body size variability and mean size.
- To assess selection pressures on juvenile size and growth.
Main Methods:
- Utilized a unique combination of an annual beach seine survey (since 1919) for juvenile body size and abundance data.
- Employed capture-mark-recapture data to estimate selection on juvenile body size and growth.
- Analyzed nine decades of ecological and demographic data.
Main Results:
- Demonstrated a consistent decrease in juvenile size variability in Atlantic cod over nine decades.
- Found no significant trend in the mean size of juvenile Atlantic cod.
- Identified selection against both small, slow-growing and large, fast-growing individuals.
Conclusions:
- The findings suggest long-term stabilizing selection acting on Atlantic cod populations.
- Emphasizes the necessity of comprehensive studies on trait changes in wild populations.
- Underscores the importance of considering phenotypic variability alongside mean trait values in evolutionary studies.
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