Geographical variation in resistance to thermal stresses in Drosophila melanogaster

Geographical variation for resistance to heat and cold stress was examined and populations of D. melanogaster collected from three highland and lowland localities. Significant geographical variation for heat knockdown time and chill coma recovery was evident in D. melanogaster.Flies from highland localities exhibited greater cold tolerance.In contrast, lowland populations have more heat knockdown time (more r esistant to heat stress) than highland population. Further, plastic responses for thermal stresses were investigated by rearing flies at 16°C and 26°C. Flies reared at 16°C were more resistant to cold stress than flies grown at 26°C. However, gr eater heat tolerance was exhibited by flies reared at 26°C. Our results suggested that genetic and plastic responses to different thermal stresses may be the reason for adaptation of D. melanogaster to climatic stresses. A B S T R A C T