The lack of evidence for coadaptation in geographic populations of Drosophila ananassae

Crosses were made between geographic races of Drosophila ananassas from different localities in India. All these strains employed in the present experiments were polymorphic for the gene arrangements in the second chromosome due to the occurrence of alpha (subterminal) inversion. After ten generations it was observed that the heterozygotes were the most superior genotype and their frequencies remained above fifty percent in all these strains which served as controls and in the hybrid populations of mixed geographic origin. Thus it was found that interracial hybridization does not lead to breakdown of heterosis. The chief conclusion from these experiments is that evidence for coadaptation is lacking in D. ananassae. This finding apparently conflicts with what has been claimed for other species.