Reproductive Skew in Multimember Groups

Area of Science:

• Behavioral Ecology
• Evolutionary Biology
• Game Theory

Background:

• Reproductive skew, where reproduction is concentrated in dominant individuals, varies across cooperative societies.
• Existing models often simplify group dynamics to dominant-subordinate pairs or identical subordinates.
• Dominant individuals may offer incentives to retain subordinates, but this is poorly understood in larger groups.

Purpose of the Study:

• To develop an evolutionary stable strategy model for reproductive skew in three-member groups.
• To investigate how individual variation among subordinates affects group stability and reproductive skew.
• To determine if conclusions from two-member models generalize to larger, more complex social structures.

Main Methods:

• Developed an incentive-based evolutionary stable strategy model.
• Incorporated variation in subordinate independent reproduction opportunities, group productivity contributions, and relatedness to the dominant and other subordinates.
• Analyzed scenarios with three group members, including varying relatedness parameters.

Main Results:

• Conclusions from two-member models do not universally apply to three-member groups.
• Relatedness among subordinates can influence a dominant's decision to offer staying incentives, a factor not present in two-member models.
• Both reproductive skew and group stability are dependent on relatedness within the group and individual subordinate traits.

Conclusions:

• Group size and the relatedness structure among members are critical factors in understanding reproductive skew.
• Incentives offered by dominants are influenced by the presence and traits of multiple subordinates.
• The productivity gains from adding a third member critically determine the impact on skew and stability.