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Why are not all chilies hot? A trade-off limits pungency
David C Haak1, Leslie A McGinnis, Douglas J Levey
1Department of Biology, University of Washington, PO Box 351800, 24 Kincaid Hall, Seattle, WA 98195-1800, USA. dhaak@indiana.edu
Proceedings. Biological Sciences
|December 23, 2011
Summary
Trade-offs in wild chilies (Capsicum chacoense) show that moisture availability shapes plant evolution. Pungency is maintained by functional integration between water-use efficiency and capsaicinoid production, constraining adaptive divergence.
Area of Science:
- Evolutionary Biology
- Plant Ecology
- Genetics
Background:
- Evolutionary constraints due to trade-offs are increasingly recognized.
- Understanding how trade-offs limit adaptive divergence in populations is crucial.
Purpose of the Study:
- Investigate how spatial moisture heterogeneity maintains polymorphism for pungency in wild chilies (Capsicum chacoense).
- Examine the functional integration between water-use efficiency and capsaicinoid production.
Main Methods:
- Studied wild chili populations along a moisture cline in Bolivia.
- Assessed the relationship between pungency, moisture availability, and seed production.
- Investigated genetic correlations between pungency and stomatal density.
Main Results:
- Pungency in Capsicum chacoense is maintained by spatial moisture heterogeneity.
- Pungency is beneficial in high moisture (fungal protection) but costly in low moisture (reduced seed production).
- A genetic correlation between pungency and stomatal density underlies reduced seed set in pungent plants under drought stress.
Conclusions:
- Trait integration, specifically between water-use efficiency and capsaicinoid production, constrains adaptive divergence in wild chili populations.
- Spatial heterogeneity in environmental factors can maintain polymorphisms by imposing differential costs and benefits of traits.
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