A fungal disease that’s killing frogs throughout Central America is also dramatically reducing the diversity of frog species, leading to what one researcher is calling “the McDonaldisation of the frog communities.”

While it’s already well known that frogs are in trouble in spots around the globe, an analysis by US researchers indicates the situation is even worse than previously thought.

In Central America, frogs are falling prey to a microscopic fungus called Batrachochytrium dendrobatidis, which causes their skin — a vital organ through which many frogs breathe or drink — to peel or slough off. The disease is doing more than simply killing off frogs, though; it’s causing rarer species to disappear completely from some sites, leading to impoverished frog populations that increasingly resemble one another.

“We’re witnessing the McDonaldisation of the frog communities,” said Kevin G. Smith, associate director of the Tyson Research Centre at Washington University in St. Louis.

The research — based on data collected by Karen R. Lips, director of the programme in sustainable development and conservation biology at the University of Maryland and a research associate at the Smithsonian Tropical Research Institute — is published online in the October issue of Ecology Letters. Jonathan M. Chase, director of the Tyson Research Centre, is a co-author.

“We already knew that at each site we were losing roughly half the species,” Smith said. However, the analysis also revealed that regional extinctions of entire species were much higher than expected.

“Our simulations showed that random local extinctions would have resulted in 41 regional extinctions across the eight sites, but instead we observed 61 regional extinctions,” Smith said. “The regional extinctions strongly suggest these species are gone not just from the region but from the planet. It’s very difficult to document an extinction, because you have to prove a negative. But if you see that a species is gone not only from point A but also from points B, C and D that gives you a much stronger case.”

Smith called the fungus an “extinction filter.” Not an equal-opportunity killer, it preferentially removes the frogs that make each habitat unusual and interesting.

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