Prior distributions of the parameters used in the ABC analyses.

Note:Nanc.: effective population size (Ne) of the ancestral population. NBus.: Ne of the Busia population. NRuk.: Ne of the Rukomeshi population. NIAEA: Ne of the IAEA colony. Ncol.Bus.: Ne of the unsampled colony of Busia origin. Ncol.Ruk.: Ne of the unsampled colony of Rukomeshi origin. NBcol.Bus.: Ne of the colony of Busia origin (IAEA in scenario 4 and unsampled in scenario 6) during the bottleneck associated with its establishment that started in 1975 lasted BDcol.Bus. generations. NBcol.Ruk.: Ne of the colony of Rukomeshi origin (IAEA in scenario 5 and unsampled in scenario 6) during the bottleneck associated with its establishment that started at Tcol.Ruk. and lasted BDcol.Ruk. generations. NBcont.: Ne of the Busia population during the bottleneck associated with the tsetse control that started in 1991 and lasted BDcont. generations. Tanc.: number of generations between present and the merge of the two potential source populations an unsampled ancestral population. Tadmix.: date of the admixture. ar: admixture rate. GSM: Generalized Stepwise Mutation model. SNI: Single nucleotide indel mutations.*: see Supplementary file S2 (Table S7 in Supplementary file S2) for a rationale.