Schematic diagram representing the different coalescence phases in the history of lineages sampled from a deme belonging to a non-equilibrium meta-population. Each phase and related parameters are represented by a colour. Parameters influencing the coalescence rate in each phase are: the effective size of the deme (NDEME) and the migration rate (m) for the scattering phase; the number of migrants exchanged per generation (Nm) and the number of demes (d) for the collecting phase; and the ancestral effective size (NANC) for the ancestral phase.