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Sea-age variation in maiden Atlantic salmon spawners: phenotypic plasticity or genetic polymorphism?
William S C Gurney1, Philip J Bacon, Douglas C Speirs
1Department of Mathematics and Statistics, University of Strathclyde, Glasgow, G1 1XH, Scotland, UK. bill@dullatur.myzen.co.uk
Bulletin of Mathematical Biology
|August 6, 2011
Summary
Atlantic salmon exhibit a stable genetic polymorphism with different life-cycle morphs. This study reveals that riverine phase density dependencies, like competition, maintain the long-term stability and relative abundance of these sea-age morphs.
Area of Science:
- Evolutionary Biology
- Population Genetics
- Ichthyology
Background:
- Atlantic salmon (Salmo salar) display a polymorphism based on sea-phase duration and location.
- These morphs coexist in Scottish rivers, with distinct spawning run timings and locations.
- Environmental factors influence morph abundance, but the underlying stability mechanism is unclear.
Purpose of the Study:
- To understand the dynamic elements maintaining the long-term stability of Atlantic salmon polymorphism.
- To determine the factors governing the relative abundance of different sea-age morphs.
- To investigate the role of density-dependent factors in the riverine phase of salmon life-history.
Main Methods:
- Model-based synthetic study.
- Exploration of morph-specific density dependencies in the riverine phase.
- Investigation of known salmon biology mechanisms for density dependence.
Main Results:
- Identified key dynamic elements crucial for polymorphism stability.
- Demonstrated that morph-specific density dependencies in the riverine phase equalize fitness.
- Showcased the robustness of coexistence mechanisms for multiple sea-age morphs.
Conclusions:
- The coexistence of multiple sea-age morphs in Atlantic salmon is a stable genetic polymorphism.
- This stability is maintained by physical separation and/or asymmetric competition between different morphs or their offspring in the riverine environment.
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