Fig. 3.

Rate of change according to Eq. 9. (A and B) Spatial snapshots at indicated times, (C and D) time series of $[\mathrm{F}]$, (E and F) time series of ${\mathrm{\Delta }}_{\mathrm{F}}^{\mathrm{gain}}$, ${\mathrm{\Delta }}_{\mathrm{F}}^{\mathrm{loss}}$, (G and H) time series of the right-hand side of Eq. 9 (gain minus loss). At $t=0$, the simulation is started on the saddle (on the left, $[\mathrm{F}](0)\approx 0.2$ and on the right, $[\mathrm{F}](0)\approx 0.7$, see blue and red circles in Fig. 2). Toward the left (along $t^{+}$), a simulation that tips up and toward the right (along $t^{-}$) a simulation that tips down is shown. Parameters are shown in Table 1. Columns correspond to leftmost and rightmost vertical dashed lines in Fig. 2 ($\varphi N=0.257$ and $\varphi N=1.32$). Domain size: 100 $\times$ 100 cells.