Figure 4
From: Fixation Probabilities for Any Configuration of Two Strategies on Regular Graphs
Cooperator-defector configurations on a 4-regular graph with 8 vertices and diameter 2.
Starting from one cooperator in (a), a single cooperator is added in each subsequent panel. Although cooperation can never be favored by selection when starting from a state with a single mutant (a) or a single defector (g), it can be favored in the other states, (b–f), since the critical benefit-to-cost ratios are all finite in those panels.
