Frog disease wiping out undiscovered species

Fungal disease advances through Central America
July 2010: The first before-and-after view of an amphibian die-off has just been published by scientists working at the Smithsonian Tropical Research Institute in Panama.

DISAPPEARING: Panamanian marsupial frog is tested for the presence of a fungal pathogen Picture: Andrew Crawford

Like a wave, the fungal disease that wipes out frogs – chytridiomycosis – advances through the Central America highlands at a rate of about 30 kilometers per year. After the disappearance of Costa Rica's golden frogs in the 1980s, Karen Lips, associate professor in the biology department at the University of Maryland, quickly established a monitoring programme at untouched sites in neighboring Panama.

Of the 63 species that she identified during surveys of Panama's Omar Torrijos National Park located in El Copé from 1998 to 2004, 25 species disappeared from the site in the subsequent epidemic. As of 2008, none of these species had reappeared. Were there additional species in the park - ‘cryptic' diversity not previously known to science? To find out, scientists used a genetic technique called DNA barcoding to quickly estimate that another 11 unnamed species were also present, five of which had also been wiped out.

We are discovering new species nearly as fast as we are losing them
‘It's sadly ironic that we are discovering new species nearly as fast as we are losing them,' said Andrew Crawford, former postdoctoral fellow at STRI and 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.'

An epidemic that wipes out a whole group of organisms destroys a huge amount of accumulated information about how life has coped with change in the past. Species surveys are like counting the number of different titles in the library, whereas a genetic survey is like counting the number of different words.

A third of frogs' evolutionary history has been wiped out
‘When you lose the words, you lose the potential to make new books,' said Lips. ‘It's like the extinction of the dinosaurs. The areas where the disease has passed through are like graveyards; there's a void to be filled and we don't know what will happen as a result.'

STRI director Eldredge Berminham said: ‘This is the first time that we've used genetic barcodes - DNA sequences unique to a given species - to characterise an entire amphibian community. STRI has also done barcoding on this scale for tropical trees on in our forest dynamics-monitoring plot in Panama. The before-and-after approach we took with the frogs tells us exactly what was lost to this deadly disease - 33 per cent of their evolutionary history.'