Spatial predictions of, and contributing variables to, mtDNA differentiation using GDM. Spatial predictions of genetic differentiation based on mtDNA diversity (pairwise differences) using environmental variables and distance (A and C) and environmental variables, distance and rivers (B and D). Colors between maps are not comparable. Within maps, areas with similar colors along color gradients are predicted to be more similar genetically. Panels C and D represent the relative importance of the selected variables that significantly contribute to the models. Each panel explains the map directly above it.