Threats to wildlife survival, such as habitat loss and climate change, tend to strike some species harder than others, and the threat of chytrid, a deadly amphibian fungus, appears to be no different. A study published in this month's Ecology Letters finds that rarer species were more likely to disappear, leading to loss of frog biodiversity in Central America.

The study compares frog surveys taken at eight different sites in Costa Rica and Panama. Karen Lips, an associate professor of biology at the University of Maryland, College Park, along with Kevin Smith and Jonathan Chase at Washington University in St. Louis, found that the average number of frog species at the eight sites dropped from 45 to 23 after the appearance of the chytrid fungus. Rare species that were only present at one or a few of the sites were disproportionately wiped out, making up more than half of the species lost.

"All species can get infected [but] the point is that not everything completely disappears," says Lips, who conducted the frog surveys that were used in the study.

Although abundant species enjoy safety in numbers, factors other than abundance could help protect certain frogs after the deadly skin fungus hits their homes. Terrestrial species fared better than frogs living in wet habitats, where the fungus thrives. In addition, certain genes or differences in skin chemistry may allow some species to be less susceptible to chytrid, Lips says. Even with these advantages, frogs still die from chytrid, just at slower rates. Once the fungus arrives at a site, it remains in the soil and never really goes away. "I think, in time, species will continue to go extinct," she says.

View a slide show of some of the frogs hit hardest by chytrid