FIG. 5.—
Plot of CLRT P values with Ka. (A) Drosophila miranda: The pooled loci of both this study, as well as the randomly selected genes of Bachtrog et al. (2009), are shown. (B) Drosophila pseudoobscura: The pooled loci of homologous genes across the X chromosome. The dotted line indicates the 5% significance cutoff for the CLRT. The solid line indicates the significant correlation between the observed divergence measure Ka and the calculated P value of this polymorphism-based test statistic. Results indicate a significant correlation between this polymorphism-based test of selection and this divergence-based measure, in both species—despite roughly an order of magnitude difference in effective population size. This result suggests that at least a portion of the correlation observed in figure 4 owes to hitchhiking effects.