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? 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.