Weak selection helps cheap but harms expensive cooperation in spatial threshold dilemmas

Area of Science:

• Evolutionary Game Theory
• Agent-Based Modeling
• Social Dynamics

Background:

• Public Goods Games (PGGs) model scenarios where individual success depends on group investment.
• Cooperation and defection dynamics are crucial in understanding social and biological systems.

Purpose of the Study:

• To investigate the impact of the strength of selection on cooperator persistence in a lattice-based Public Goods Game.
• To explore counter-intuitive outcomes arising from nonlinear benefit functions and spatial structures.

Main Methods:

• Utilized an individual-based lattice model simulating cooperating (C) and defecting (D) agents.
• Employed a highly nonlinear threshold benefit function to model PGGs.
• Developed a semi-analytical approximation to analyze the lattice model dynamics near steady states.

Main Results:

• Confirmed expected negative effects of higher cooperation costs and increased population mixing on cooperator persistence.
• Discovered a surprising, counter-intuitive effect of selection strength on the model's steady state, varying with cooperation costs.
• Observed this effect exclusively in the lattice model, suggesting the importance of spatial correlations and stochasticity.

Conclusions:

• Spatial clustering of cooperators and emergent stochastic effects in lattice models drive unexpected evolutionary dynamics.
• The strength of selection can have complex, non-monotonic effects on cooperation, contrary to simpler models.
• Findings offer insights into the biological relevance of spatial structure in maintaining cooperation.