A few minutes from the University of Pennsylvania campus in Philadelphia sits a small peach orchard that’s home to some unusual experiments. Contrary to first appearances, the subjects of the experiments are not the peach trees themselves, each of which is protected by a two-meter-cubed tent of fine mesh material. Instead, researchers are interested in the hundreds of tiny fruit flies living on the trees and the even tinier bacteria living inside the insects’ guts.
The setup was designed with a deceptively simple question in mind: Do the microbes in an animal’s digestive tract help shape their host’s evolution? Washington State University evolutionary biologist Seth Rudman says that it would make sense if they did. “Microbiomes [can have] a huge effect on host fitness, and hence could have a huge effect on adaptive trajectories of populations,” says Rudman, who helped construct part of the site in 2017 while a postdoc in evolutionary ecologist Paul Schmidt’s lab at UPenn. Despite broad scientific interest in the microbiome, few researchers had tackled these kinds of evolutionary questions experimentally.
Rudman, meanwhile, has been carrying out more research in Drosophila and also plans to work with stickleback fish, a species commonly used in adaptive evolution studies, he says. Designing experiments that capture as much of a species’ ecology as possible will be particularly important, he adds, not only for understanding how microbiomes influence host genomes, but for determining the extent to which this influence matters, among all the other forces at play, in driving host evolution in the real world. “I think the jury’s out on that,” he says. “The data will hopefully guide us—and that’s the way science should go.”