Genetic differentiation between populations. Genetic distance between pairs of populations on chromosomes X (A), 2 (B) and 3 (C). Fst estimates are shown in the top part of each graph and the corresponding P-values are shown below, in grey for A. arabiensis/A. gambiae M form comparisons, white for A. arabiensis/A. gambiae S form and in black for A. gambiae M form/A. gambiae S form. Data from immune related genes and control genes are included. Horizontal straight lines represent the significance threshold at P= 0.05, dashed lines: P = 0.05 after correction for multiple tests (Bonferroni sequential procedure). Missing data are indicated with a dot. Negative Fst values that are always not significant were represented as equal to zero. Highly significant P values (<10-4) were represented as P = 0.0001 to be shown on a logarithmic scale.