Resurrection Ecology Chases the Red Queen Hypothesis

"Well, in our country," said Alice, still panting a little, "You'd generally get to somewhere else--if you ran very fast for a long time as we've been doing."

"A slow sort of country!" said the Queen. "Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that."

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You don't have to go back to the Jurassic to see evolution in action. W. Charles Kerfoot, a biological sciences professor at Michigan Technological University, has tracked changes that have occurred since Lewis Carroll began writing "Alice in Wonderland."

And unlike paleontologists, Kerfoot doesn't have to make inferences from the fossil record. He just hatches 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, Kerfoot 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, termed by Kerfoot resurrection ecology, is emerging from those original discoveries. Its techniques allow scientists to study organisms from the past and compare them with their modern counterparts.

As reported recently in the journal Limnology and Oceanography, Kerfoot has been doing just that in Michigan's Portage Lake, reviving eggs from a small, shrimp-like animal, Daphnia retrocurva, from various 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 'Alice in Wonderland' 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 upheavals due to mining, dredging and eutrophication, 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 to the letter. Eggs from different sediment layers grew up into adults with significantly different characteristics. In particular, their helmets and spines, which make them less appetizing, changed in relation to predators over the 80-year period of the study.

Such microevolutionary adjustments had been observed in Daphnia populations as their predator populations changed, but resurrection ecology now allows scientists to bring the historical record alive.

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