Empirical distribution for Dh/sd.

The empirical distribution for Dh/sd scores (horizontal axis) from the Ewens-Watterson test. The vertical axis indicates the number of loci with the corresponding Dh/sd score. The positions in the distribution of the regions that have been subject to selection in Thoroughbred are indicated by the gene symbols for the strongest candidate genes. Genes in the negative tail-end of the distribution may have been subject to positive selection. Genes in the positive end of the distribution may have been subject to balancing selection.