Figure 7. Lifetime of the RQS state.

This schematic diagram based on Figure 5A defines the ‘boundaries’ of the transient RQS $q_{ext}(\tau )$ (red line) and $q_{sp}(\tau )$ (blue line). $q_{ext}(\tau )$ gives the value of $q$ for which the average time to extinction is equal to ${\displaystyle \tau }$ is defined similarly but for the speciation process. Average times to speciation and extinction become equal at the critical value $q_c$ at which RQS persists the longest. For $d=50$, $q_c\approx 2.4$ and this value, along with the RQS lifetime, increases with $d$.