Figure 2: Evolutionary dynamics in the space of deterministic memory-one strategies, 
for two different cooperation costs.
for two different cooperation costs.From: Comparing reactive and memory-one strategies of direct reciprocity
As in Fig. 1a, the grey circles correspond to all possible homogeneous populations, and blue lines indicate evolutionary transitions; for clarity, we only show transitions from WSLS or AllD. In (a), the cost of cooperation is sufficiently low such that WSLS is evolutionary robust. In (b), mutants using AllD, Grim Trigger GT, or the strategy (0, 0, 0, 1) can invade a WSLS population; as a consequence, AllD becomes most abundant in the selection-mutation equilibrium. Parameters are the same as in Fig. 1, population size N = 100, error rate ε = 0.01, and selection strength w = 0.1.
