Figure 2.

Scaled conditional mean fixation time, ${\upsilon }_c={\overline{T}}_c/2N$ for a co-dominant mutant under weak selection in slowly changing, on-average neutral environment in which the selection coefficient $s(t)=\sigma \hspace{0.17em}\text{sin}(\omega t+\theta )$. The parameter $\alpha =N|s(0)|$ was varied with selection amplitude σ, keeping the population size N and the initial phase $\theta =\pi /4$ (for positive α) and $5\pi /4$ (for negative α) fixed. The inset shows the variation of the conditional mean fixation time with dominance in static environment (solid) and slowly varying environment for initial phase $\theta =\pi /4$ (dotted) and $5\pi /4$ (dashed), and $\sigma =0.000158$. In both plots, $N=2\times {10}^3$ and $N\omega =0.08$, and the lines show the analytical expressions (9) and (10) and the points show the numerical solution of (4)–(7).