Relatedness in trait group models of social evolution

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Population genetics

Background:

• Genetic relatedness is fundamental to social evolution, historically based on genealogy but now encompassing broader genetic similarity.
• Group-structured populations are common in nature and models, influencing trait evolution.
• Traits affecting group fitness are often categorized as 'whole-group' or 'other-only', but this distinction is rarely clear.

Purpose of the Study:

• To examine and differentiate genetic relatedness in group-structured populations for two trait types: whole-group and other-only.
• To analyze how these trait types influence selection pressures and evolutionary outcomes.
• To clarify apparent contradictions and limitations in existing literature on social evolution.

Main Methods:

• Analysis of genetic relatedness within group-structured populations.
• Partitioning total relatedness into structural and assortative components.
• Comparing the mathematical properties and influencing factors of relatedness for whole-group versus other-only traits.

Main Results:

• Average relatedness differs between whole-group and other-only traits, impacting selection.
• Positive relatedness requires positive assortment for other-only traits but not whole-group traits.
• Negative relatedness is possible for other-only traits but not whole-group traits; group size impacts whole-group traits, while non-random assortment affects other-only traits more.

Conclusions:

• Distinguishing between whole-group and other-only traits is crucial for accurate evolutionary predictions.
• This distinction resolves inconsistencies in the literature and refines theoretical models of social evolution.
• The findings provide a clearer framework for understanding the evolution of cooperation and altruism in structured populations.