Natural selection in experiments with population inversions

Conclusions

• 1. Our data show that the karyotypic differentiation ofDrosophila funebris populations into urban and rural races, the diminution of inversion frequency in the towns destroyed by the war, and the changes in inversion frequencies with the months of the seasonal cycle, must all be regarded as vivid manifestations of the action of natural selection on the evolution of the karyotype.

• 2. Our material for the first time gives direct experimental evidence of the effect of natural selection on the karyotypic structure of populations. The experiments on hibernation show the differential survival of different karyotypic structures which are widespread in populations in nature. Different inversions react differently to the same experimental conditions.

• 3. This work has therefore discovered a new trend in the genetics of populations. It will become possible to apply natural selection as a method of direct experimental analysis for the solution of the several principal problems of the evolution of populations.