Fig. 5

Model IM-full, the most parameter-rich model (13 parameters) representing two populations from each ocean basin with an effective size that changed \({T}_{{s}_{IP}}\) and \({T}_{{s}_{AO}}\) years ago from a modern effective size (\({N}_{{mod}_{IP}}\) and \({N}_{{mod}_{AO}}\)) to an ancestral effective size (\({N}_{{anc}_{IP}}\) and \({N}_{{anc}_{AO}}\)). The two populations are connected by an asymmetrical migration rate allowed to change \({T}_{mig}\) years ago (respectively from \({m}_{{1}_{IP/AO}}\) and \({m}_{{1}_{AO/IP}}\) to \({m}_{{2}_{IP/AO}}\) and \({m}_{{2}_{AO/IP}}\)) and diverged \({T}_{div}\) years ago from an ancestral population of size \({N}_{anc}\). The remaining four models are nested within IM-full, having less migration rate parameters: IM-anc is similar to IM-full but only the ancestral migration occurs (i.e., between \({T}_{mig}\) and \({T}_{div}\)); IM-rec is similar to IM-full but only the recent migration occurs (i.e., between 0 and \({T}_{mig}\)); IM-bsc considers the migration constant from 0 to \({T}_{div}\); and IM-div is a strict divergence model with no migration