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Predictable patterns of disruptive selection in stickleback in postglacial lakes
1Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA. danbolnick@mail.utexas.edu
The American Naturalist
|May 3, 2008
Summary
Disruptive selection, driven by competition, is more common than thought, especially in certain lake environments. This can maintain genetic diversity and promote speciation in fish populations.
Area of Science:
- Evolutionary biology
- Ecology
- Population genetics
Background:
- Disruptive selection is often considered rare due to dynamic instability.
- Frequency-dependent interactions, like intraspecific competition, can stabilize fitness minima, potentially increasing disruptive selection's prevalence.
- Disruptive selection is crucial for maintaining genetic variation and may drive sympatric speciation.
Purpose of the Study:
- To investigate the prevalence and environmental correlates of disruptive selection on trophic morphology in three-spine stickleback.
- To determine factors influencing the strength and occurrence of disruptive selection in natural populations.
Main Methods:
- Inferred selection by measuring growth rates of three-spine stickleback (Gasterosteus aculeatus) with varying gill raker morphology across 14 Vancouver Island lakes.
- Assessed the relationship between lake size, prey availability (littoral and pelagic), and the strength of disruptive selection.
- Examined the influence of sexual dimorphism in trophic traits on disruptive selection.
Main Results:
- A general trend of weak disruptive selection on trophic morphology was observed in the studied stickleback populations.
- Selection was strongest in intermediate-sized lakes with a balanced availability of both littoral and pelagic prey.
- Sexual dimorphism in trophic traits was found to mitigate disruptive selection, aligning with theoretical predictions.
Conclusions:
- Intraspecific competition can stabilize disruptive selection, making it a more significant evolutionary force than previously assumed.
- Environmental factors, particularly lake size and resource balance, play a critical role in modulating disruptive selection.
- Understanding these factors can help predict when and where disruptive selection is likely to occur, aiding in the study of speciation and adaptation.
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