The Aftermath of an Amphibian Apocalypse
On September 23, 2004, biologists in the El Copé region of Panama found a frog with a fungal infection. By the next February, this infection — known as chytridiomycosis, or chytrid fungus — would kill half of the amphibians in the region. By 2008, more than 40 percent of those species would be locally extinct.
[…] biologists in the El Copé region of Panama found a frog with a fungal infection.
The fungus behind chytridiomycosis, B. dendrobatidis, had been on scientists’ radars since 1998, when it was identified as the culprit behind the mass amphibian die-offs that had been occurring across the globe for several decades. Affected animals grow lethargic as the fungus spreads, until their skin thickens and starts to slough off. The loss of function in such a vital organ, which in amphibians is responsible for taking in water and maintaining electrolyte levels, causes cardiac arrest and death within a few weeks. As far as the scientific community is aware, it has already driven nearly 200 species extinct.
The situation in El Copé was no less severe than it had been elsewhere, with one small caveat: by the time chytridiomycosis reached Panama, its spread was being monitored. Biologists in El Copé knew that the fungus would eventually hit the region, and had spent years studying the local amphibian populations in preparation. In-depth knowledge of the healthy community was crucial to their research both during and after the outbreak.
It is because of the frogs themselves, and something the study’s authors call eco-evolutionary rescue.
A study published on October 3 in the journal Ecological Applications is the culmination of some of this work, and it offers hopeful news for the damaged ecosystem of El Copé: the remaining frog populations are stabilizing, with some species even increasing in number. It is not because chytrid fungus is gone; the pathogen is still widespread, and as virulent as it was in 2004. It is because of the frogs themselves, and something the study’s authors call eco-evolutionary rescue. Tests indicate that frogs living in El Copé now are able to tolerate infection with chytridiomycosis because the mucus secreted by their skin inhibits fungal growth, an evolutionary response by the species that were more able to resist the infection during the initial outbreak. Scientists hope that something similar is happening in other areas affected by the fungus; if so, it may be a good sign for the future of amphibians worldwide.
