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Phenotypic divergence along lines of genetic variance
Katrina McGuigan1, Stephen F Chenoweth, Mark W Blows
1Department of Zoology and Entomology, University of Queensland, Brisbane, Queensland, 4072, Australia. mcguigan@darkwing.uoregon.edu
The American Naturalist
|February 25, 2005
Summary
Replicated evolution is not always constrained by genetic variation patterns. Hydrodynamic adaptation in rainbow fish occurred along directions of low genetic variance, challenging previous assumptions about evolutionary constraints.
Area of Science:
- Evolutionary biology
- Quantitative genetics
Background:
- Natural populations often evolve similar traits independently.
- Genetic covariation patterns (G) may influence or constrain evolutionary trajectories.
- Understanding these constraints is crucial for predicting adaptive evolution.
Purpose of the Study:
- To investigate if replicated evolution, specifically hydrodynamic adaptation in rainbow fish, is constrained by the major axes of genetic variance.
- To determine the relationship between morphological divergence and the genetic variance-covariance matrix (G).
Main Methods:
- Used an experimental system with two rainbow fish species (Melanotaenia eachamensis and Melanotaenia duboulayi).
- Analyzed morphological divergence in replicate populations adapted to lake vs. stream environments.
- Assessed the orientation of genetic variance-covariance matrix (G) and its relation to divergence (z) and major genetic variance axes (gmax).
Main Results:
- Major axis of divergence (z) was associated with greatest genetic variance (gmax), suggesting constraint.
- Hydrodynamic adaptation, however, aligned with directions of low genetic variance, weakly related to gmax.
- Divergence within habitats and between species showed associations with eigenvectors of G.
Conclusions:
- Hydrodynamic adaptation in rainbow fish was not directionally constrained by the dominant eigenvector of G.
- Empirical studies may overestimate constraints if divergence is not partitioned by adaptive process.
- The role of genetic variance in constraining specific adaptive pathways needs careful consideration.
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