Flounder effects and linkage disequilibria in experimental populations of Drosophila

Six laboratory populations of Drosophila paulistorum were examined for changes in gene frequencies at an enzyme locus, tetrazolium oxidase (To). In some of the populations, the alleles were introduced on over 100 independently derived chromosomes. These populations showed considerable stability in gene frequencies although they were at widely different starting frequencies. Other populations were begun with only a few (about 6) independently derived chromosomes. These populations showed significant and somewhat erratic changes in To gene frequencies. The difference in behavior of the two sets of populations was almost certainly caused by linkage effects due to sample size. The implication of these studies in understanding the role of the founder effect in natural populations is briefly discussed.