Social Selection and the Evolution of Maladaptation

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Behavioral ecology

Background:

• Natural selection typically drives adaptation and increases population fitness.
• Maladaptation, an evolved decrease in fitness, is possible but conditions are unclear.
• Social selection, arising from interactions with social partners, is a potential driver of maladaptation.

Purpose of the Study:

• To develop a general rule for when social selection leads to maladaptation.
• To identify conditions under which population mean fitness may decrease due to social selection.
• To explore the relationship between social selection, individual fitness, and inclusive fitness.

Main Methods:

• Development of a quantitative genetic model.
• Analysis of scenarios where social selection opposes nonsocial selection.
• Investigation of cases with negative covariance between interacting phenotypes.

Main Results:

• Maladaptation is most probable when social selection is strong relative to nonsocial selection and in an opposing direction.
• Evolution of costly social traits can outweigh individual fitness gains, reducing population mean fitness.
• Maladaptation can also occur when interacting phenotypes exhibit negative covariance.

Conclusions:

• Social selection can decrease population mean fitness if it opposes individual-level selection.
• Inclusive fitness does not decrease evolutionarily, despite potential decreases in population mean fitness.
• The study provides a framework for understanding and empirically testing maladaptation under social selection.