The researchers found that when the fruit fly larvae were competing for food, those that did best had a version of the foraging gene that was rarest in a particular population. For example, rovers did better when there were lots of sitters, and sitters did better when there were more rovers.
"If you're a rover surrounded by many sitters, then the sitters are going to use up that patch and you're going to do better by moving out into a new patch," says Sokolowski. "So you'll have an advantage because you're not competing with the sitters who stay close to the initial resource. On the other hand, if you're a sitter and you're mostly with rovers, the rovers are going to move out and you'll be left on the patch to feed without competition."
More generally, Fitzpatrick says these results may help explain why genetic variants such as these are common in nature. "In the case of fruit flies, one variant encourages the survival of the other. In essence, there is not one best type of fly," he says. If this process is common in nature, it may offer one explanation for why individuals, in general, vary so much from one to another in almost all species.
The researchers' next step is to show that this phenomenon is also taking place in the wild. In addition, since the foraging gene is found in many animals, including honeybees, mice and humans, the researchers are examining how variations in the human foraging gene may be linked to food-related disorders.