The evolution of trade-offs under directional and correlational selection

Area of Science:

• Evolutionary biology
• Quantitative genetics

Background:

• Trade-offs between traits are fundamental in evolutionary biology.
• Understanding how selection shapes these trade-offs is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To develop and test predictions for the evolution of trait trade-offs under directional and correlational selection.
• To investigate how selection on an index value affects component traits within a trade-off.

Main Methods:

• Utilized quantitative genetic theory to formulate predictions.
• Employed artificial selection experiments on the fecundity-flight capability trade-off in Gryllus firmus.
• Compared empirical results with predictions derived from genetic parameters.

Main Results:

• Directional selection altered the intercept but not the slope of the trade-off function.
• Selection on an index value induced both directional and correlational selection on component traits.
• Empirical results supported theoretical predictions regarding trade-off evolution.

Conclusions:

• Selection primarily modifies the intercept, not the slope, of trade-off functions.
• Correlational selection adds complexity to trait evolution, potentially driving component traits in opposing directions.
• The study highlights the intricate nature of trade-off evolution under combined selection pressures.