Genetical Relationship and Isolating Mechanisms in the Species SubgroupAnanassae(Sophophora, Drosophila) VI. Interspecific Cytological Divergence in the Three Species of theAnanassaeSpecies Subgroup

Abstract

The chromosome complement of D. bipectinata and D. malerkotliana comprises four pairs of V-shaped elements, two of which are large, one medium and one small. The karyotype of D. ananassae differs from those of D. bipectinata and D. malerkotliana with respect to one member of the medium pair of Vs, which is replaced by a J-shaped element. The X chromosome is represented by a medium V-shaped element in all the three species. Whereas the Y chromosome is morphologically indistinguishable from the X in D. bipectinata and D. malerkotliana, it is represented by a J-shaped element in D. ananassae. An analysis of the salivary chromosomes of the hybrid between D. bipectinata and D. malerkotliana indicates that the difference in the chromosomes of these two species lies in two inversion complexes one of which is in II L and the other in III R. The direct comparison of the band pattern in the salivary chromosome maps of D. ananassae and D. bipectinata reveals that six inversions, one translocation and a few transpositions mark the cytological difference between the two species.