Fig. 4. Observed number of mating (K_obs) in each pure species (T. caespitum and T. immigrans) and for each area (North, Center, and South) in the hybrid zone.

Stars indicates a significant difference (p < 0.001) between species assessed by Mann–Whitney–Wilcoxon test. Letters indicate significant differences (p < 0.05) between areas assessed by Mann–Whitney–Wilcoxon test with a simple Bonferroni correction.