Experiments on Sexual Isolation in Drosophila

Abstract
From laboratory and field expts. possible reasons for a probable absolute sexual isolation between D. pseudoobscura and D. persimilis under natural conditions but never complete isolation in the laboratory may be due to differences in activity rhythms, food preferences, environmental preferences, intraspecific preferences during mating, the sterility of the F1 hybrid males and a breakdown of the viability observed in the backcross progeny.