Fig. 4. Association of the Alba candidate locus with wing color across the Colias phylogeny.

(A) Species tree of Colias colored by geographic region, with purple = South America, blue = North America, orange = Holarctic, and green = Eurasia and Northern Africa. (B) Read-mapping depth of an individual using whole-genome data across the 1200-bp long Alba candidate locus for each species. Separate columns depict coverage plots according to female wing color. In cases where we have sequence data for both morphs, both are shown side by side. The y axis in each row is 0 to 100 × coverage. (C) Schematic explaining our genome-wide, window-based analysis of color-associated read coverage. Data for each species are by row, with wing color indicated by a blue or orange box. For four genomic windows, the presence of read coverage in a window is indicated by a black filled box (absence of coverage an empty box). Mean value for each window for Alba samples (A_mean) and colored samples (O_mean) is then calculated, followed by their difference. (D) Histogram showing the distribution of color-associated bias in coverage (A_mean − O_mean) of 546,228 windows across the genome, with counts on the y axis plotted on a log₁₀ scale. The one window located in the Alba candidate locus is the only one that perfectly correlates with color and is indicated with a blue bar and arrow.