Representation of three final competing scenarios tested with approximate Bayesian computation (ABC). This analysis was based on a matrix including individuals displaying a probability of belonging to one of the two clusters over 0.9 (STRUCTURE software). N
corresponds to effective population size of each cluster, and T
corresponds to the time expressed in numbers of generations since divergence. The following conditions were considered: T1 < T2, T2 < T3, with 0 being the sampling date. Abbreviations are as follows: C; Central cluster, N; Northern cluster, PP; Posterior probability and their associated 95% confidence interval.