In an "extremely rare" discovery, scientists have found three previously unknown species of toads living in the Great Basin of Nevada. It's rare enough to find new amphibians native to the U.S. — where only three frog species have been discovered since 1985 — but new U.S. toads are especially unusual. The last one was the Wyoming toad, which was found in 1968 and is now extinct.
Unfortunately, the scientists who discovered these toads are worried a similar fate may await one of their newfound trio.
The three species were found by biologists from the University of Nevada, Reno (UNR), who named them the Dixie Valley toad (pictured above), the Railroad Valley toad and the Hot Creek toad. Their habitats don't overlap, and they've been isolated from other toad populations for more than half a million years, according to UNR biology professor and project leader Dick Tracy.
"We've found the toads in small, wet habitats surrounded by high desert completely cut off from other populations," Tracy says in a statement. "These are absolutely new, true species that have been separated from other populations for 650,000 years."
The toads were discovered as part of Tracy's 10-year survey of the Great Basin, an arid region covering about 190,000 square miles between the Sierra Nevada Range and the Rocky Mountains. His team analyzed DNA and body-shape metrics to demonstrate that each one is distinct from known species, like the closely related western toad, and from each other.
All three species have similarly small bodies — they're about 2 inches long when full grown — but also unique coloring and other physical features that help set them apart. "The Dixie Valley toad is a pretty toad, with flecks of gold on an olive background," Tracy says. "It's not like the big, common green toads you might find in other marshes around the west."
The Dixie Valley toad gets its name from Nevada's Dixie Valley Playa, where it occupies remote wetlands fed by thermal springs. The species' habitat is "very isolated and restricted in size," Tracy and his colleagues write in the journal Zootaxa, estimating that its entire geographic distribution spans less than 1,500 acres. These toads are essentially marooned on an ecological island, since their marshy oasis is surrounded by arid expanses where water is rare and widely scattered.
Having such a small habitat can make it harder to adapt when new dangers emerge, and the Dixie Valley toad faces "a staggering number of threats to its persistence," the researchers write. The most urgent is the expansion of geothermal energy, they explain, since the toads' habitat is adjacent to the site of a proposed geothermal power plant. Dixie Valley is already home to another large geothermal plant, but plans for building more have raised concerns about straining meager water supplies — specifically the fragile marshes that have sustained Dixie Valley toads for hundreds of thousands of years.
The proposed Dixie Meadows Geothermal Utilization Project is now on hold, while the U.S. Bureau of Land Management (BLM) reviews its possible impacts. The project would pump almost 46,000 acre-feet of water annually from the area's underground reservoir, according to the nonprofit Center for Biological Diversity (CBD), which has led a campaign urging the BLM to reconsider the proposal. That would alter the natural flow of groundwater, the CBD argues, and could drain the toads' habitat.
The CBD will submit a petition asking the U.S. Fish and Wildlife Service to protect Dixie Valley toads — and thus their habitat — under the Endangered Species Act, a move Tracy supports. "If this power plant goes in and the habitat is dried up, this recently discovered species could go extinct," he says. "It's a good candidate for an Endangered Species Act listing."
As for the other new species, the Railroad Valley toad inhabits Tonopah Basin in the central Nevada desert, while the Hot Creek Toad lives about 35 miles away in Hot Creek Mountain Range. All three are endemic to the Great Basin, a watery wonderland during the Pleistocene Epoch that's now one of the most arid regions in the country. And since these toads managed to stay hidden until now, their discovery suggests we still have a lot to learn about this ancient American landscape.
"Our goal has been to understand the relationships among toad populations in the Great Basin," Tracy says. "We've found that our knowledge of amphibian diversity in the western United States remains incomplete and that novel discoveries continue to occur, even in unlikely settings. This is really, really neat; an exciting thing, to find something not known to exist before."