Fig. 7.

Events and configurations on an example tree. Here, we illustrate the possible events and the configurations before and after each event on a simple tree, with time going backwards from present to past. The first two lineages, are both in state blue, that is, the configuration is $(L_1=blue,L_2=blue)$, with lineage 1 being the parent lineage of 1 and 2 after relabeling. After a lineage in state red is sampled, the configuration changes, as given in the figure. A coalescent event in state blue then reduces the number of lineages in state blue to 1. A migration event then causes lineage L₁ to change state from blue to red.