ROBERTS, SP*; FRAZIER, MR; KIRKTON, SD; HARRISON, JF: Temperature Sensitivity of Drosophila Development and Flight Performance

In Drosophila and other small dipterans, wing length and body size are inversely related to developmental temperature. It has been hypothesized that dipteran wing-loading decreases following development at low temperatures and that this is an adaptive response to enhance power and flight ability at low air temperatures, when wing-beat frequency is limited due to cooling effects on muscle performance. We tested these hypotheses using Drosophila melanogaster. For flies reared at 16, 23 or 28 C, we measured flight ability at 14, 16 and 18 C as well as the following morphological parameters: body mass, wing area and thorax mass:body mass ratio. Flight ability was significantly affected by rearing temperature and air temperature and there was a significant interaction between the two effects. At an air temperature of 14 C, no flies from the 23 and 28 C rearing groups were able to fly, although 15% of flies reared at 16 C were able to fly. At an air temperature of 16 C, approximately 50% of flies reared at 16 and 23 C could fly, but only 10% of flies reared at 28 C could fly. At an air temperature of 18 C, nearly all flies from every rearing group could fly. Female body mass and wing area was significantly greater than in males for all rearing groups, while body mass and wing area for both sexes was inversely related to rearing temperature. However, flies were not isometric across rearing temperatures, since wing-loading significantly increased with rearing temperature. Thorax mass:body mass ratio in males was significantly higher than in females, but was not affected by rearing temperature. These results support the hypothesis that this developmental plasticity is an adaptive response to flight at cold temperatures.