Maximum likelihood gene tree generated with PHYLIP version 3.65 using amino acid sequences for proteins SRP54 and SRP19 from various genus Drosophila species and Anopheles gambiae (Agam) as the outgroup species. Data for the tree is also provided in Additional data file 9. The tree has been artificially rooted with outgroup species (Agam). Numbers reflect the relative arm lengths from this root. Species within subgenus Drosophila (Dvir, Dmoj, Dgri) show lower overall average branch length than species within subgenus Sophophora, similar to Figure 3.