Disease wiping out amphibians before they can be identified

Michael McCarthy The Independent 19 Jul 10;

The frog-killing disease which is sweeping parts of the world is now wiping out amphibian species before they have even been described, new research has shown.

Dramatic declines in amphibian populations in the Americas and Australia have been known since the late 1980s, exemplified by the disappearance of the famous golden toad of the cloud forests of Costa Rica, which has not been seen since 1989. At first the declines were a mystery, but 10 years ago it was realised that many of the disappearing frog, toad and salamander populations were being killed off by a fungal disease called chytridiomycosis. It was thought that global warming might be helping the disease to establish itself.

Now a before-and-after monitoring programme established in Costa Rica's neighbouring state of Panama has shown just how devastating the fungal affliction is when it sweeps through amphibian communities.

American scientists working at Panama's Omar Torrijos National Park in El Copé did a detailed survey of all the frogs present between 1998 and 2003, before chytridiomycosis arrived, and identified 63 species. The disease then swept through the area, and when a repeat survey was done between 2006 and 2008, no fewer than 25 species had disappeared, according to a study published today in the Proceedings of the National Academy of Science.

But there was more bad news, as researchers used a more precise technique known as DNA barcoding to establish that among the frogs which had previously been catalogued, there were more species than they thought – in fact there were an extra 11 unnamed or "candidate" species. And of these 11, another five had been wiped out by the fungus, giving a total of 30 species lost, before they had even been properly described by science.

"It's sadly ironic that we are discovering new species nearly as fast as we are losing them," said Andrew Crawford, formerly of the Smithsonian Tropical Research Institute and now at the University of the Andes in Colombia. "Our DNA barcode data reveal new species even at this relatively well-studied site, yet the field sampling shows that many of these species new to science are already gone here."

Professor Karen Lips of the University of Maryland, who did the original survey of the frogs on the site, said that the areas where the disease had passed through were "like graveyards". She said: "There's a void to be filled and we don't know what will happen next."

Biologists are increasingly alarmed at the numbers of species disappearing. It is thought that more than 120 may have become extinct since 1980 and the Global Amphibian Assessment lists more than 400 as critically endangered. "If a disease were wiping out species of mammals at this rate, people would be freaking out," the Smithsonian Institute's Beth King said yesterday. "Just imagine if it was whales and rabbits."

It is now thought that between a third and half of the world's 6,000 amphibian species could be wiped out in the coming decades by the disease's chytrid fungus, which kills by attacking the skin of frogs, through which they breathe. Warmer temperatures likely to have been caused by climate change appear to make its effects worse.

Before and After: Deadly Fungus Wipes Out Amphibians
Andrea Thompson LiveScience.com Yahoo News 19 Jul 10;

A deadly fungus has been wiping out the world's amphibian populations, but just how many species are being lost to the disease onslaught wasn't fully known. A new study that documented a Panamanian amphibian community before and after the fungus swept through shows the significant impact on species diversity.

Dramatic declines in amphibian numbers have been reported for more than 40 years now from four continents; the culprit behind the collapse is a fungus called Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis in amphibians. The rapid spread of the disease - about 19 miles (30 kilometers) per year in the Central American highlands - has led to species extinctions and extirpations (the local extinction of a species).

Scientists had studied areas devastated by the disease after it swept through and conducted dramatic rescues of frogs in areas that had yet to be hit, but no systematic before-and-after snapshots of a particular area had been taken to document what amphibian species were present before the arrival of the fungus and what species survived the wave of disease.

In the 1980s, after the disappearance of Costa Rica's golden frogs, herpetologist Karen Lips, an associate professor at the University of Maryland in College Park, set up a monitoring program at as-yet untouched sites in neighboring Panama's Omar Torrijos National Park in El Cope.

Before-and-after shots

Lips and her colleagues conducted seven years' worth of surveys before the arrival of the fungus in El Cope in 2004, as well as surveys after the disease had wiped out many frogs.

The pre-decline surveys identified 63 species of amphibians within just a 1.5-square-mile (4-square-kilometer) area. After 2004, 25 of those species had disappeared from the site. As of 2008, none had reappeared.

An additional nine species saw an 85 percent to 99 percent decline in their abundance.

To augment the surveys and identify any so-called "cryptic species" - those that look very similar to a recognized species but are in fact a separate species, meaning they don't reproduce with the known species - scientists used a genetic technique called DNA barcoding.

This technique finds DNA sequences unique to a given species. With it, scientists estimated that another 11 unnamed species had been present at the site, five of which were wiped out by the arrival of the fungus.

"It's sadly ironic that we are discovering new species nearly as fast as we are losing them," said study team member Andrew Crawford, a former postdoctoral fellow at the Smithsonian Tropical Research Institute in Panama and a member of the Círculo Herpetológico de Panamá, now at the University of the Andes in Colombia.

"Our DNA barcode data reveal new species even at this relatively well-studied site, yet the field sampling shows that many of these species new to science are already gone here," he added.

Crawford, Lips and other researchers recently published a detailed description of two previously unknown species of frogs in Panama, which are threatened by the fungus.

Huge loss

Because El Cope is one of the better-studied sites and so many species that were lost had been undescribed, it is likely that the loss of undescribed species in other areas is far greater, the researchers noted.

The loss of so many frog species, known and unknown, not only threatens the rich biodiversity of a given area and the functioning of the local ecosystem, but it also destroys the genetic data that helps scientists learn how species have adapted to change and evolved in the past.

The researchers compared this loss to the great fire that destroyed the famous ancient library of Alexandria and the priceless, one-of-a-kind texts it held.

Their findings are detailed in the July 19 edition of the journal Proceedings of the National Academy of Sciences.