Abstract
The effects of temperature on viability of hybrids between D. melanogaster females and D. simulans males were investigated using various strains of both species. The results obtained in these experiments were: (1) At 25°C, the interspecific hybrids varied from lethal (temperature sensitive) to fully viable (resistant). (2) The temperature sensitivity of the hybrid was mainly controlled by gene(s) located on the X chromosome of D. simulans male. (3) Temperature sensitivity varied among X chromosomes within natural populations of simulans, (4) The degree of hybrid temperature sensitivity can be modified by EMS treatment in both sensitive-to-resistant and resistant-to-sensitive directions. (5) Females of D. melanogaster also have effects on the hybrid temperature sensitivity, especially in the cross with temperature-sensitive simulans males. The Oregon-R strain was most sensitive melanogaster for detection of the hybrid temperature sensitivity.
