Effects on phenotypic variability of directional selection arising through genetic differences in residual...

Area of Science:

• Quantitative genetics
• Evolutionary biology
• Population genetics

Background:

• Standard quantitative trait models assume constant genetic variance.
• Genotypes can influence both the mean and the variance of a trait.
• Understanding these dual effects is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To develop models for directional selection on quantitative traits where genotypes affect both mean and variance.
• To quantify the genetic response in both mean and variance under selection.
• To explore the implications of genotype-by-environment interactions on trait variability.

Main Methods:

• Developed theoretical models incorporating additive genetic effects on both trait mean and variance.
• Derived formulae for the response to selection on mean and variance.
• Accounted for gene frequency changes and the Bulmer effect.

Main Results:

• The selective value of an allele depends on its effects on both mean and variance.
• Response to selection on mean is influenced by additive genetic variance and covariance.
• Response to selection on variance depends on additive genetic covariance and variance.
• Effects on variance are pronounced under intense selection and individual-level selection.

Conclusions:

• Genotypic differences in trait variability are significant in evolutionary models.
• Directional selection can change trait variance, with implications for adaptation.
• Selection on individual phenotypes or within-family deviations maximizes effects on variance.