Locomotor performance of Drosophila melanogaster: Interactions among developmental and adult temperatures, age, and geography

We explored the extent to which a phenotypic trait (walking speed) of Droso phila melanogaster is influenced by population, developmental temperature, adult temperature, and age. Our goals were to estimate the importance of th ese factors and to test the beneficial acclimation hypothesis. We measured speed of flies from two populations (the Congo and France) that developed a t different temperatures (18, 25, and 29 degreesC) and were tested at diffe rent temperatures (18, 25, and 29 degreesC) and ages (2, 7, 13 days). Not s urprisingly, speed increased strongly with test temperature. Speed was gene rally greatest for flies reared at an intermediate developmental temperatur e, contrary to the beneficial acclimation hypothesis, which predicts that s peed would be greatest when influenced by interactions involving population . For example, speed was greatest for flies from France that developed at a low temperature, but for flies from the Congo that developed at a high tem perature. The impact of developmental temperature declined with age. Surpri singly, speed actually increased with age for flies raised and maintained a t a low temperature, but decreased with age for flies raised and maintained at an intermediate or at a high temperature. Thus, walking performance is highly dynamic phenotypically, complicating potential attempts to predict r esponses to selection on performance.