Genetic differentiation within and between the three granivorous ground finch species. Geospiza fortis is represented by the small and large beak-size classes and by all size classes (including intermediates) pooled. p-values for genetic differentiation are above the diagonal. Bold entries are those that remained significant after sequential Bonferroni correction. FST values are below the upper diagonal, with asterisks (*) indicating 95% confidence intervals that do not overlap with zero. RST values are below the lower diagonal.