Chromosomal variability and interracial hybridization in Drosophila bipectinata

Three paracentric inversions, In(D)2L, In(C)2R and In(H)3L, often persist in laboratory stocks of Drosophila bipectinata initiated from flies collected from natural populations. In order to test the effect of interracial hybridization on the degree of chromosomal variability, four stocks of D. bipectinata originating from different geographical localities and which were polymorphic due to the presence of three inversions, were crossed with each other. Hybrid lines as well as parental lines which served as controls were maintained in food bottles for ten generations. After ten generations, chromosomal analysis of hybrid lines as well as parental lines was undertaken. The results revealed that: all hybrid and parental lines remained polymorphic; there was a decline in the frequency of heterozygous inversions in certain hybrid populations of mixed geographical origin; and there was variation with respect to the degree of chromosomal variability in different crosses involving different inversions. These results are discussed in the light of findings reported in other Drosophila species.