Selection and evolution of causally covarying traits

Area of Science:

• Evolutionary Biology
• Quantitative Genetics
• Ecology

Background:

• Traits influencing fitness variation are central to evolutionary biology.
• Multivariate selection gradients quantify direct trait effects on fitness, not total effects.
• Path analytic characterizations of total trait effects on fitness are not yet integrated into quantitative genetic theory.

Purpose of the Study:

• To formally define and introduce
• extended selection gradients
• to capture the total effects of traits on fitness.
• To provide a more intuitive framework for characterizing natural selection.
• To integrate total effect measures into quantitative genetic theory.

Main Methods:

• Formal definition of extended selection gradients.
• Comparison of extended selection gradients with standard selection gradients.
• Discussion of statistical assessment and data assumptions for estimation.
• Integration with multivariate phenotypic variation and genetic inference.

Main Results:

• Extended selection gradients represent the total effects of traits on fitness, distinct from direct effects.
• These new gradients differ in statistical assessment, required assumptions, and biological meaning.
• Extended selection gradients offer a more intuitive scheme for characterizing selection.

Conclusions:

• Extended selection gradients provide a more comprehensive measure of trait-fitness relationships.
• This framework enhances the prediction of microevolutionary trajectories.
• The study formally incorporates total effect path analytic characterizations into quantitative genetic theory.