Supplementary Table 1 Band based diversity indexes found in each of the studied populations. Supplementary Table 2 General Rhost value calculated from the 2 groups distinguished by the presence of the geothermal field. AMOVA calculations were performed using a ploidy independent hierarchical AMOVA of the transformed data under the infinite allele model carried out using Genodive (Meirmans and Van Tienderen 2004). d.f. – degrees of freedom, MS – Mean square, SSQ– sum of squares, VC- variance components, % – estimated percentage of variation. AFLPs comparisons were made among groups – Geothermal field composed by Furnas and Outside Caldera composed by Vila Franca and Fajã de Baixo. Among groups within populations – within populations in each group. Supplementary Table 3 AFLPs FST pairwise comparison between all populations in the study for AFLP loci datasets: 1, with all the loci; 2, without putative loci under selection; 3, without putative loci under positive selection; 4, using only putative loci under selection and 5, using only putative loci under positive selection Probability values are given in yellow rows. Supplementary Table 4 Expected heterozygocity (He) and Shannon index values in populations calculated using different AFLPs loci datasets: 1, with all the loci; 2, without putative loci under selection; 3, without putative loci under positive selection; 4, using only putative loci under selection and 5, using only putative loci under positive selection. Supplementary Table 5 General Fst value calculated from the 2 groups distinguished by the presence of the geothermal field. AMOVA calculations were performed using Arlequin v3.5.1.2 for each different AFLP loci dataset: 1, with all the loci; 2, without putative loci under selection; 3, without putative loci under positive selection; 4, using only putative loci under selection and 5, using only putative loci under positive selection. Df – degrees of freedom, SQ– sum of squares, VC- variance components, % – estimated percentage of variation, MS – Mean square, Est. Var. – estimated variance. Mitochondrial DNA and AFLPs comparisons were made among groups – Geothermal field composed by Furnas and Outside Caldera composed by Vila Franca and Fajã de Baixo. Among groups within populations – within populations in each group. Supplementary Table 6 AFLP haplotypes (binary: 0, ausence; 1, presence) of all the individuals of the studied populations using the putative loci under positive selection.