Extended Data Fig. 6: Nucleotide divergence (d_XY) values between sequences from conspecific Sb and SB males of the six socially polymorphic fire ant species estimated using 50 kb non-overlapping sliding windows across the social chromosome.

The boundaries of the differently shaded intervals correspond to the breakpoints of the three inversions, with the inversions depicted by thick horizontal coloured lines. The x axes represent physical position along chromosome 16, with the location of gene Gp-9 indicated. For each of the six species, d_XY values between Sb and SB males were significantly higher for the region corresponding to the inversions than for the rest of the social chromosome (Mann–Whitney U-tests, all P < 0.01). The region of elevated d_XY proximal to the inversions (at ca. 8-10 Mb) appears to experience reduced recombination in S. invicta based on progeny studies;¹⁵ this area may correspond at least partly to the centomeric region or some other, unknown feature may be responsible for the reduced recombination and elevated d_XY there.