Interactive effects of temperature and geography on emigration behavior of Drosophila melanogaster: climatic and island factors.

Abstract

These studies were desgned to detect geographic variation in emigration behavior, at various temperatures, of newly collected wild strains ofDrosophila melanogaster. Natural populations from various geographic regions showed three basic emigration response patterns to temperature: linear, threshold, and optimum-temperature response types. The emigration activity of northern mainland populations increased in the range of 15–20°C, whereas the activity of comparable southern populations increased linearly with increasing temperatures. The northern island populations showed the optimum-temperature response type, and the comparable southern island populations showed all three emigration patterns. In most cases emigration activity on islands was generally reduced compared with that on the adjacent mainland. The northern island populations, however, showed a higher emigration activity at 25°C than the adjacent mainland populations. Here the different sensitivities to temperature seemed to be related to differences in both climatic conditions and insular conditions.