Fig. 8. Evidence of balancing selection and introgression at the Alba locus.

The folded allele frequency spectrum of all high-confidence insertions and deletions (n = 35,282 indels) identified in a field sample of 29 C. eurytheme females. The black line indicates the 95the percentile of this distribution. The colored lines represent the estimated allele frequency of the Alba allele of four different populations in California (44) and their sample sizes (Central population = Westley, Yarmouth, and Vernalis; Northwest population = Tracy and County Line; East population = Manteca, Rippon, and Modesto; Southeast population = Patterson and Newman). The estimated frequency of Alba in these field samples is more common than expected based on the genome-wide frequency of similar indels.