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Does predation maintain eyespot plasticity in Bicyclus anynana?
Anne Lyytinen1, Paul M Brakefield, Leena Lindström
1Department of Biological and Environmental Science, University of Jyväskylä, Finland. alyytine@bytl.jyu.fi
Proceedings. Biological Sciences
|April 3, 2004
Summary
Phenotypic plasticity in Bicyclus anynana butterflies shows seasonal adaptation. Dry seasons favor crypsis (spotless wings), while wet seasons favor eyespots for predator deflection, demonstrating natural selection
Area of Science:
- Evolutionary biology
- Animal behavior
- Ecology
Background:
- Bicyclus anynana butterflies display phenotypic plasticity, with wet-season forms having eyespots and dry-season forms lacking them.
- This plasticity is hypothesized to relate to defense mechanisms like crypsis and deflection against predators.
Purpose of the Study:
- To investigate the adaptive significance of phenotypic plasticity in Bicyclus anynana.
- To assess the roles of crypsis and deflection in the seasonal variation of butterfly wing patterns.
Main Methods:
- Comparing the visibility of eyed and spotless B. anynana phenotypes against dry (brown) and wet (green) leaf backgrounds.
- Conducting predation experiments with naive and adult bird predators to evaluate survival rates and learning.
Main Results:
- Spotless butterflies exhibited higher crypsis and lower predation by adult birds on brown backgrounds (dry season).
- Crypsis advantage diminished in wet-season habitats; both forms showed equal visibility.
- Naive birds learned to prey on spotless butterflies more readily in wet habitats, suggesting a benefit of eyespots.
- Eyespots significantly increased escape probability when attacked by naive birds, indicating a deflective function.
Conclusions:
- Natural selection favors spotless wings (crypsis) in the dry season for B. anynana.
- Eyespots may provide a selective advantage in the wet season, acting as deflective markings against predators.