Image: Hylomantis lemur frog
Roberto Brenes
This frog species, Hylomantis lemur, was a reasonably widespread species, originally present at five study sites.
By
updated 9/29/2009 3:04:19 PM ET 2009-09-29T19:04:19

Like neighborhood coffee shops and independent movie theaters around the United States, unusual varieties of frogs are rapidly disappearing from rainforests in Central America.

A fungal infection seems to be hitting those rare species of frogs harder than common ones, found a new study, leading to local extinctions and a homogenized version of nature where everything is more similar than it used to be. The result is both a less interesting world aesthetically and a less resilient one biologically.

The decline in diversity could end up harming larger ecosystems since frogs are an important part of the food web — other creatures eat them and their eggs. It could also impact the tourist industry since the amphibians' variety of shapes and colors has been a tourist draw to Central America.

Finally, a decline in species could even limit medical possibilities since scientists have found potential cancer therapies in amphibian skin.

"Everyone knew that amphibian declines were really bad," said ecologist Kevin Smith, of Washington University in St. Louis. "But it looks like it's worse than we actually thought."

Smith and colleagues looked for patterns of extinction in frogs from eight rainforest sites around Costa Rica and Panama. The researchers compiled several years worth of data from previous studies, in which scientists had painstakingly surveyed frog diversity both before and after the arrival of a fungus called Batrachochytrium dendrobatidis (Bd).

Bd has swept through amphibians around the world in the last decade, often decimating populations. In Central America, Smith said, infections can wipe out half of the species at a given site. Evidence has been growing, however, that some species are more vulnerable to the fungus than others, and Smith wondered which ones were most at risk.

Image: Hemiphractus fasciatus frog
Roberto Brenes
Hemiphractus fasciatus, which carries its eggs on its back, was originally found at three of the study sites and disappeared from all three.
His results, published in the journal Ecology Letters, showed that in Central America at least, the fungus seems to target the rarest of species, which often exist only in one or two sites across the region. It's not yet clear why rare frogs are succumbing most frequently to the Bd fungus. But as they disappear, so often do the roles they fill in the ecosystem.

"If you knock out a very rare species from the only place it exists, of course that's going to be an extinction," Smith said. "In terms of conservation, that's the opposite of what we want."

The new findings add another disheartening dimension to the biodiversity crisis, said Tom Rooney, an ecologist at Wright State University in Dayton, Ohio. The loss of variety, he said, makes it increasingly hard for the species that are left behind to deal with further environmental change.

On a more positive note, documenting which species are most vulnerable to infections and other threats might help scientists predict which creatures are most at risk now, allowing them to focus future conservation efforts on the most vulnerable ones.

"If you're thinking globally, studies like this are telling us that losing rare species is not a local phenomenon," Rooney said. "If they are disappearing locally, there's a good chance they're disappearing regionally, and local efforts can be even more important."

In the meantime, the study points out how similar the natural world is to the more cultural parts of our lives — particularly in the way that people value diversity and mourn the loss of it.

"We no longer have all the little hardware stores, little coffee shops, and little bars where everyone knows your name," Smith said. "What we see across the world is that it's decreasingly the case where you see different things in different places."

© 2012 Discovery Channel

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