Fig 2. Fixation time is not monotone in r.
a, In an (undirected) star graph S4 on 4 nodes, one node (center) is connected to three leaf nodes by two-way edges. When the initial mutant appears at a leaf v, the fixation time Tr(S4, {v}) increases as r increases from r = 1 to roughly r = 1.023. Then it starts to decrease. b, Normalized fixation time Tr(G, {v})/Tr = 1(G, {v}) as a function of r ∈ [1, 1.3], for all 83 strongly connected graphs G with 4 nodes, and all four possible mutant starting nodes v. As r increases, the fixation time goes up for 182 of the 4 ⋅ 83 = 332 possible initial conditions. The increase is most pronounced for the so-called lollipop graph L4 and a starting node u. In contrast, for the same lollipop graph and a different starting node w, the fixation time decreases the fastest.