Chromosomal and cytoplasmic analysis of heat shock resistance in natural populations of Drosophila melanogaster

We evaluated genetic differences between two populations of Drosophila mela nogaster that differed in thermal tolerance. Adults of one tropical populat ion (Mali) survived heat shock (39.5 degrees C for 30 min.) at 84 %. By con trast, those from a strain collected in Denmark survived at a rate of only 53 %. The greatest effect on variation was differences in cytoplasms, but v ariation in chromosomes 2 and 1 also played a role on tolerance. Heat shock proteins, however, reside on chromosome 3 and, therefore, variation at the se sites is low or differences had little effect on results obtained from t he methods employed.