Fig 1E shows the histogram of iHS values across the CHRNA5-A3-B4 locus on chromosome 15. The summary statistics are given in Table 1. None of the three populations showed a proportion of extreme iHS values that was significantly different than predicted by permutation. In addition, none of the SNPs with extreme values included any of the SNPs previously found to be associated with nicotine dependence (Table 2). The presence of a significant enrichment of extreme Tajima’s D values in this region, however, suggests that if positive selection in this region occurred, it may have occurred long enough ago such that the long haplotypes required for iHS have broken down by recombination.
