It is now straightforward to frame all these findings under the coalescence perspective. The coalescence history of the lineages sampled from a single deme in an SST (or FIM) model can be separated for simplicity into three phases: the scattering, the collecting and the ancestral phase (Figure 7). Going backward in time, lineages will coalesce in the sampled deme with a rate according to both Nm and NDEME until all lineages either have coalesced or migrated to another deme. This is the scattering phase described in the seminal works of  (Wakeley, 1998, 1999). The scattering phase was considered instantaneous for mathematical tractability, with its outcome dependent on Nm only, but later works could disentangle the effect of NDEME and m on the shape of the gene genealogy (Mona, 2017). The collecting phase starts when the lineages which did not coalesce have migrated to other demes of the array: they will then coalesce according to a Kingman process with a rate scaled by Nm and the number of demes d of the array (Wakeley, 1999) (Figure 7). Finally, all surviving lineages (in non-equilibrium model) will reach the ancestral deme at TCOL, where they will coalesce at a rate depending only on the NANC parameter (Figure 7). The interplay between the demographic parameters (NDEME, NmNANC, d) and the historical events (TCOL and TCH) determines the length of each coalescence phase and the resulting shape of the gene genealogy of the sampled lineages (Figure 7).