CROSS-GENERATION EFFECTS FOR COLD RESISTANCE IN TROPICAL POPULATIONS OF DROSOPHILA-MELANOGASTER AND DROSOPHILA-SIMULANS

Cross-generation effects on the cold resistance of Drosophila melanogaster and D. simulans were investigated by exposing adults to different levels of cold stress and testing the resistance of female F1s and F2s. Maternal and paternal treatments had different effects on progeny resistance. Maternal effects were not detected for either species when progeny were held at 25-degrees-C, but were detected when progeny were acclimated at 13-degrees-C prior to testing. When dams were exposed to a non-lethal cold stress following acclimation, the cold resistance of their progeny was increased, particularly in D. simulans. Grandmaternal exposure to 13-degrees-C and a non-lethal stress led to a small decrease in the cold resistance of D. melanogaster, and a small increase in the resistance of D. simulans. When sires of D. melanogaster and D. simulans were exposed to a cold stress, the resistance of their progeny decreased when progeny were tested without acclimation at 13-degrees-C, but decreased only in D. melanogaster when progeny were acclimated. Paternal effects were smaller than maternal effects and were not evident in the F2 generation.