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Microgeographic countergradient variation in the wood frog, Rana sylvatica
1School of Forestry and Environmental Studies and Department of Ecology and Evolutionary Biology, Yale University, 370 Prospect Street, New Haven, Connecticut 06511, USA. david.skelly@yale.edu
Evolution; International Journal of Organic Evolution
|April 3, 2004
Summary
Wood frogs from cooler, shaded wetlands develop faster than those from warmer, open wetlands. This countergradient variation occurs at small scales, suggesting rapid adaptation in developing populations.
Area of Science:
- Ecology
- Evolutionary Biology
- Amphibian Biology
Background:
- Macrogeographic temperature gradients drive countergradient variation in many species.
- Countergradient variation is characterized by faster growth/development in colder environments when individuals are in a common setting.
Purpose of the Study:
- To investigate if countergradient variation exists at microgeographic scales.
- To examine countergradient variation in wood frog (Rana sylvatica) embryonic development across contrasting wetland microhabitats.
Main Methods:
- A common garden experiment was conducted using wood frog embryos.
- Embryos were collected from nearby natural wetlands with contrasting canopy cover (shaded vs. unshaded).
- Embryonic development rates were compared between embryos from different microhabitats.
Main Results:
- Wood frog embryos from shaded, cooler wetlands exhibited significantly faster development rates (up to 12%) compared to those from unshaded, warmer wetlands.
- This demonstrates countergradient variation at a microgeographic scale.
Conclusions:
- Countergradient variation is relevant at microgeographic scales, extending beyond macrogeographic patterns.
- Vegetation dynamics causing wetland shading can lead to rapid divergence in embryonic development over decades.