Biologists Find Evolution Evidence in Kentucky Caves

At its simplest, it's the story of a beetle and a cricket. The cricket lays its eggs buried in the soil deep inside a cave. The beetle digs up the eggs and eats them.

At its most complex, it's the story of evolution in action. Different species seeking the best strategies to survive and reproduce.

Molly White, a graduate student in biological sciences, is continuing the work of her adviser, Professor Thomas Kane. He and other UC graduate students have spent years studying how animals have adapted to live inside caves.

Previous work has shown that a different species of cave crickets and cave beetles behave in a similar manner. White is trying to demonstrate that another cricket- beetle pair does the same thing.

Her work takes her to the caves in southern Kentucky, spread across the Lake Cumberland region. She relies on the good will of private landowners, the Kentucky Geological Survey, and other government agencies which control access to the cave sites.

She also requires help. Safe caving is a team effort, so she never works alone.

On a recent trip, White returned to Overlook Cave near Somerset, Kentucky to check on her experimental setups. Using a series of hoops, she's able to measure how successful the cave crickets are at producing offspring. Some hoops prevent the beetles from reaching the cricket eggs. Others have gaps, allowing the predatory beetles access to the eggs.

The crickets in Overlook Cave belong to the genus Hadenoecus. What's interesting to White, Kane, and other evolutionary biologists is the fact that two different species of cave beetles dig up and prey on their eggs Darlingtonea kentuckensis and Neaphaenops tellkampfi. It's the same behavior in two completely separate cave systems.

"These beetles are the only ones that do this," explained White. "But there is absolutely no gene flow between the species. It's a physical impossibility."

That means that each species apparently evolved the same behaviors, even though they are separated physically in different caves and living in different cave environments. Biologists have studied three different layers of Mississippian rock formations. The beetles appear to be doing the same things in all three study areas.

"It's called convergent evolution," explained White. "The species end up doing the same thing, even though they started at completely different places."

Convergent and parallel evolution are often cited as support for the role of natural selection leading to adaptation," added White's adviser Professor Thomas Kane. "Thus the beetle/cricket predator-prey interactions support Darwin's view of the significance of natural selection in evolution."

Long-term, White says "understanding an ecosystem's past and present can be helpful in protecting the ecosystem's future."

So, her overall goal is not just to understand how the cave crickets protect their eggs. She'd really like to know how humans can protect the fragile and beautiful environments in which they live.