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Updated: Jan 12, 2026

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Probing the Limits of Egg Recognition Using Egg Rejection Experiments Along Phenotypic Gradients
Published on: August 22, 2018
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A Quantitative Survey of Cogradient and Countergradient Variation in Nature
The American Naturalist
|October 31, 2025
Summary
Spatial covariance in environmental and genotypic effects (CovGE) is as common as gene-by-environment interactions (GxE). Our study found no specific patterns across taxa or environments, challenging existing views on gradient variation.
Area of Science:
- Evolutionary biology
- Quantitative genetics
- Ecology
Background:
- Gradient variation describes how environmental and genotypic effects covary across locations, influencing local adaptation and eco-evolutionary dynamics.
- Gene-by-environment interactions (G × E) involve nonadditive genetic and environmental influences on phenotypes.
- Debates persist on whether reaction norm patterns accurately reflect spatial covariance in environmental and genotypic effects (CovGE) and its prevalence relative to G × E.
Purpose of the Study:
- To quantitatively assess the prevalence and patterns of CovGE and G × E across diverse biological systems.
- To determine if qualitative reaction norm assessments reliably indicate CovGE.
- To investigate whether CovGE shows distinct patterns across taxonomic groups, environmental gradients, or trait types.
Main Methods:
- Conducted a quantitative survey of 556 phenotypes.
- Measured CovGE and G × E across various phenotypes, taxa, and environmental gradients.
- Compared qualitative reaction norm assessments with quantitative CovGE measurements.
Main Results:
- Qualitative assessment of reaction norms proved unreliable for identifying CovGE.
- CovGE occurred with a frequency comparable to G × E.
- No consistent patterns of CovGE were observed across environmental, taxonomic, or trait-based groups.
Conclusions:
- The findings challenge prevailing assumptions about the drivers and patterns of gradient variation.
- CovGE appears to be a general evolutionary phenomenon, not restricted to specific conditions.
- Broader application of quantitative methods for CovGE is recommended for a comprehensive understanding of its role in nature.
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