Figure 1.

Physical distribution of known Dxl genes in D. simulans, D. mauritiana, and D. sechellia. A schematic of the polytene X chromosome (top) shows location of the Dxl-containing region (Dmel r6 X:9400000–10400000). Tick marks show locations of sat359 islands conserved in all three D. simulans clade species and in the outgroup D. melanogaster; the single gray tick mark distal to Ur-Dox is a sat359 island found in the D. simulans clade species but not in D. melanogaster; the green squares show sat359 islands with a Dxl insertion; and the blue dots show protein-coding genes of interest. While Dxl insertions with the same name occupy orthologous sat359 islands in different species, the Dxl sequences are not necessarily orthologous due to the possibilities of independent, parallel insertion and ectopic exchange.