A Study of an Experimental Drosophila Population in Equilibrium

An experimental population of D. pseudoobscura was maintained for four and one half years in order to study the stability of its initial chromosomal polymorphism. It was found that it took some 17 months (20 generations) for the population to achieve its final equilibrium frequencies and that the chromosomal polymorphism was then maintained for the remainder of the experiment which was a period of three years (46 generations). It was also found that the different karyotypes of the population did not exhibit any preferences for different parts of the food cups as egg laying sites. The significance of these observations in view of recent findings is discussed.