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Temporal variation in divergent selection on spine number in threespine stickleback
1Department of Biology, University of Victoria, PO Box 3020, Victoria, British Columbia V8W 3N5, Canada. reimchen@uvic.ca
Evolution; International Journal of Organic Evolution
|February 14, 2003
Summary
Predation pressure shifts drive rapid changes in threespine stickleback spine number. These findings show how variable natural selection can maintain diversity in wild populations.
Area of Science:
- Ecology
- Evolutionary Biology
- Animal Behavior
Background:
- Natural selection fluctuates due to environmental changes, like predator-prey dynamics.
- Threespine stickleback (Gasterosteus aculeatus) exhibit spine variations influenced by different predators.
Purpose of the Study:
- To investigate temporal shifts in predation regimes and their impact on natural selection for spine number in stickleback.
- To determine if stickleback populations exhibit rapid morphological adaptation to variable predation pressures.
Main Methods:
- Analysis of a 15-year dataset on stickleback populations.
- Examination of stomach contents to infer diet and predation exposure.
- Statistical analysis of selection differentials on spine number.
Main Results:
- Juvenile stickleback showed selection for increased spine number in winter (avian predators) and decreased spine number in summer (odonate predators).
- Adult stickleback displayed variable selection, with some instances of selection for spine reduction linked to a benthic feeding niche.
- Significant selection on spine number was followed by observable changes in mean spine number in subsequent years, indicating heritability.
Conclusions:
- Temporal variation in predation pressure drives rapid, predictable morphological evolution in stickleback.
- Variable selection may be a key mechanism for maintaining genetic diversity within populations.
- Understanding predator-prey interactions is crucial for predicting evolutionary responses to environmental change.