(a) An isolation-with-initial-migration (IIM) model used to simulate data. The parameter values used are $θ0=0.002$ for population sizes for the thin branches and $θ1=0.01$ for the thick branches, $τR=4θ0,τS=3θ0,τT=θ0$ for species divergence times. The number of sequences is $S=4$⁠, with the sequence length $n=500$⁠. The migration rate is $M=0.1$⁠. (b) The MSci model used to analyze the data. (c) The 95% HPD CIs for parameters, with black lines indicating the true values. Estimates of $θ$ and $τ$ are multiplied by $103$⁠.