"We think we know a lot about how animals might respond to global warming, but we really have very little idea about their actual genetic response to environmental change," said Hadly, an assistant professor of biological sciences at Stanford.
In the study, she and her colleagues conducted a genetic analysis of two species of rodents commonly found in Wyoming's Yellowstone National Park the montane vole (Microtus montanus) and the northern pocket gopher (Thomomys talpoides). The researchers collected DNA from living animals and from the teeth of fossilized specimens whose remains were buried in Lamar Cave, a remote site near the northeast entrance to the park.
"The deposit in the cave is about nine yards deep and it took me seven years to excavate and identify the fossils," Hadly said. "It contains hundreds of thousands of bones and represents a continuous fossil record dating back 3,000 years. This timescale allows us to really investigate microevolution in a natural environment, the way you'd investigate it in a laboratory with something that has a much quicker generational timeline, such as bacteria or fruit flies."
Climate change and genetics
For the experiment, the research team compared DNA from voles and pocket gophers living near Lamar Cave with ancient DNA from fossilized rodents that inhabited the area at different times since 1000 B.C.
The researchers were particularly interested in animals that were alive during two recent climatic events the Medieval Warm Period (850-1350 A.D.), when the Northern Hemisphere experienced a slight warming trend; and the Little Ice Age (1350-1950), when the hemisphere cooled.