Figure 1.

The distributions of Penelope (A) and Ulysses (B) within the D. virilis genome as revealed by in situ hybridization. The numbers at the left of the figures identify the six chromosomes. The triangles above the chromosomes represent the insertion sites of Penelope or Ulysses in the 12 D. virilis strains studied. The stars above the chromosomes represent the subset of these insertion sites identified in hybrid dysgenesis reference strains 160 and 9 (a total of 47 Penelope sites in strain 160 and a total of 32 Ulysses sites in strains 160 and 9 combined). The arrows below the chromosomes indicate the positions of inversion BPs previously identified in other species of the virilis group. Individual inversions are identified by lowercase letters according to the classification system of refs. 8 and 28. Unique inversions that are polymorphic in individual species of the virilis group are shown in parentheses.