Distribution of young duplicate genes on chromosomes. (A) Species-specific duplicates on chromosome 2 and 3. (B) Lineage-specific duplicates of D. pseudoobscura-D. persimilis pair on chromosome 3. (C) Duplicates of complex expansions occurring in 11 species on chromosome 2. Black lines represent observations, while black bands and red lines (red dots) show confidence intervals and average numbers of genes in corresponding windows. Dashed lines indicate the shared hotspot regions between the species. Dgri: D. grimshawi, Dpse: D. pseudoobscura, Dper: D. persimilis, Dsec: D. sechellia, Dsim: D. simulans, Dwil: D. willistoni, Dyak: D. yakuba; 2L: chromosome 2L, 2R: chromosome 2R, 3L: chromosome 3L, 3R: chromosome 3R.