Resurrection Ecology: Bringing the Past to Life in the Lab

You don't have to visit the Galapagos Islands to see evolution in action. Sometimes, all you have to do is hatch some eggs.

Layered in the sediments of rivers and lakes are the remains of generation upon generation of tiny animals known as zooplankton. In the 1990s, W. Charles Kerfoot, a professor of biological sciences at Michigan Technological University. was among a team of scientists studying these creatures in Germany when they made a startling discovery: The zooplankton weren't all dead. Or at least their eggs weren't.

“They should have died, but they didn't,” Kerfoot said. “They revive, and we don't quite understand how it happens.”

It doesn't take much to bring them back to life, either. “We just sieve them out of the sediment and wake them up in an incubator,” he says. “Then we grow them up. We have entire populations from nearly 100 years ago.”

A whole new field, dubbed by Kerfoot resurrection ecology, has emerged from those original discoveries. Its techniques allow scientists to study organisms from the past and compare them with their modern counterparts.

More recently, Kerfoot has done just that in Portage Lake, located in Michigan’s Upper Peninsula. He revived the eggs of a small, shrimp-like animal, Daphnia retrocurva, that he had found in sediment layers going back to the 1920s.

“We were testing a fundamental theory, Van Valen's Red Queen Hypothesis,” Kerfoot explains. “It's the idea from 'Through the Looking Glass' that you must run just to remain in place.”

Less colorfully, Leigh Van Valen of the University of Chicago postulated in 1973 that in an evolutionary system, it's not enough to rest on your laurels. Predators and their prey must constantly evolve in response to each other's changes or perish in the attempt.

In the case of D. retrocurva, Kerfoot wanted to know what, if any, changes it had made over the past 80 years. This was during a time when Portage Lake had undergone major changes, and those changes had big impacts on the predator populations that had D. retrocurva on the menu.

As it turned out, D. retrocurva, like Alice, followed the Red Queen's instructions. Eggs from different sediment layers grew up into adults with significantly different characteristics. In particular, their helmets and spines, which make them prickly to eat, changed in relation to predators over the 80-year period of the study.

Such microevolutionary adjustments had been observed in Daphnia populations, but resurrection ecology now allows scientists to bring the historical record to life.

“It's like having Rip Van Winkle wake up in your lab,” Kerfoot says.

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