Aerial agility can be enhanced in the fruit fly (Drosophila melanogaster) by manipulating the expression of a single gene involved in wing development, finds a study in Nature Communications. This suggests that the wing shape of wild flies is not optimised for all flight capabilities, but probably reflects the best trade-off among competing traits.
Natural variations in the shape of insect wings confer different benefits to different individuals: for example, greater speed or greater agility allows for better predator evasion, or for greater attractiveness to a mate. Over evolutionary time, this shape variation becomes optimised in response to these different selective forces, although whether performance trade-offs exist among different characteristics is not known.
Richard Bomphrey and colleagues use a technique called RNA interference to silence a specific gene known to be important in fruit fly wing development, in order to investigate whether flight ability can be enhanced beyond the variation found naturally in the wild. They then track the flies' flight trajectories using high speed cameras. They find that flies genetically modified to have wings with a slightly higher aspect ratio (slightly more elongated from base to tip) exhibited a smaller turn radius, and greater turn rates, compared to wild flies.
However, if the wing aspect ratio is increased to more extreme values (i.e. the wings became even more elongated), then all flight performance characteristics decrease relative to the wild flies. This indicates that the shape of fruit fly wings is not optimised for agility and manoeuvrability, but is most likely constrained by other selective pressures such as flight efficiency.