Figure 4. Expression divergence is higher for the ancestral branch of the neo-X (Muller element D).

A, Per-gene, per-chromosome distributions of the length of the ancestral branch leading to the obscura sub-group (D. persimilis and D. pseudoobscura; see Figure S1) in the embryonic data divided by the sum of all branch lengths (3L is the neo-X chromosome in the obscura sub-group). B, Per-gene, per-chromosome distributions of the length of the branch leading to D. pseudoobscura in the adult data divided by the sum of all branch lengths.