Seasonal changes in the resistance of a Drosophila population to low temperatures and their association with fertility

Significant genetic variation in resistance to cold was detected in samples collected from a natural Drosophila population in spring, summer, and autumn. In the summer sample, phenotypic variation was determined by genetic factors; in the summer and autumn samples, exclusively by environmental factors. Flies collected in spring had the highest longevity at low temperatures. In summer, their longevity at low temperatures was drastically reduced but it was shown to increase in autumn. Cold-resistant flies had high fertility in spring and low fertility in autumn. The seasonal differences in resistance to cold were genetically determined and are probably caused by natural selection.