Evaluation of current gene flow and resistance surfaces
Contemporary gene flow was estimated using BayesAss (Wilson & Rannala,
2003), which estimates directional migration rates over past generations
using multilocus genotypes and a Bayesian approach. Mixing parameters
were altered to tune
acceptance
rates within an adequate range. Aside from estimating gene flow between
populations, we adopted an estimated effective migration surfaces (EEMS)
algorithm (Petkova, Novembre, & Stephens, 2016) to visualize geographic
regions deviating from isolation by distance (IBD), i.e., to identify
areas where genetic similarity decays faster than expected for a given
geographic distance (barriers) and areas where genetic similarity decays
more slowly than expected for a given geographic distance (corridors).
Parameters for executing BayesAss and EEMS are presented in the SMM.