In the wilds of New York City--or as wild as you can get that close to skyscrapers--scientists have found a new leopard frog species.
For years, biologists mistook it for a more widespread variety of leopard frog.
While biologists regularly discover new species in remote rainforests, finding this one in ponds and marshes--sometimes within view of the Statue of Liberty--is a big surprise, said scientists from the University of California, Los Angeles; Rutgers University; the University of California, Davis and the University of Alabama.
"For a new species to go unrecognized in this area is amazing," said UCLA biologist Brad Shaffer, formerly at UC Davis.
Shaffer's research is funded by the National Science Foundation's (NSF) Division of Environmental Biology.
In recently published results in the journal Molecular Phylogenetics and Evolution, Shaffer and other scientists used DNA data to compare the new frog to all other leopard frog species in the region.
"Many amphibians are secretive and very hard to find, but these frogs are pretty obvious animals," said Shaffer.
"This shows that even in the largest city in the U.S., there are still new and important species waiting to be discovered."
The researchers determined the frog is an entirely new species. The unnamed frog joins a crowd of more than a dozen distinct leopard frog species.
The newly identified wetland species likely once lived on Manhattan. It's now only known from a few nearby locations: Yankee Stadium in the Bronx is the center of its current range.
Lead paper author Cathy Newman, now of Louisiana State University, was working with Leslie Rissler, a biologist at the University of Alabama, on an unrelated study of the southern leopard frog species when she first contacted scientist Jeremy Feinberg at Rutgers University in New Jersey.
Feinberg asked if she could help him investigate some "unusual frogs" whose weird-sounding calls were different from those of other leopard frogs.
"There are northern and southern leopard frogs in that general area, so I was expecting to find one of those that for some reason had atypical behaviors or that were hybrids of both," Newman said.
"I was really surprised and excited once I started getting data back strongly suggesting it was a new species. It's fascinating in such a heavily urbanized area."
Feinberg suspected that the leopard-frog look-alike with the peculiar croak was a new creature hiding in plain sight.
Instead of the "long snore" or "rapid chuckle" he heard from other leopard frogs, this frog had a short, repetitive croak.
As far back as the late 1800s, scientists have speculated about these "odd" frogs.
"When I first heard these frogs calling, it was so different, I knew something was very off," Feinberg said.
"It's what we call a cryptic species: one species hidden within another because we can't tell them apart on sight. Thanks to molecular genetics, people are picking out species that would otherwise be ignored."
The results were clear-cut: the DNA was distinct, no matter how much the frogs looked alike.
"If I had one of these three leopard frogs in my hand, unless I knew what area it was from, I wouldn't know which one I was holding because they all look so similar," Newman said. "But our results showed that this lineage is very clearly genetically distinct."
Mitochondrial DNA represents only a fraction of the amphibian's total DNA, so Newman knew she needed to do broader nuclear DNA tests to see the whole picture and confirm the frog as a new species. She performed the work at UC Davis.
Habitat destruction, disease, invasive species, pesticides and parasites have all taken a heavy toll on frogs and other amphibians worldwide, said Rissler, currently on leave from the University of Alabama and a program director in NSF's Division of Environmental Biology.
Amphibians, she said, are great indicators of problems in our environment--problems that could potentially impact our health.
"They are a good model to examine environmental threats or degradation because part of their life history is spent in the water and part on land," Rissler said. "They're subject to all the problems that happen to these environments."
The findings show that even in densely-populated, well-studied areas, there are still new discoveries to be made, said Shaffer. And that the newly identified frogs appear to have a startlingly limited range.
"One of the real mantras of conservation biology is that you cannot protect what you don't recognize," Shaffer said. "If you don't know that two species are different, you can't know whether either needs protection."
The newly identified frogs have so far been found in scattered populations in northern New Jersey, southeastern mainland New York and on Staten Island.
Although they may extend into parts of Connecticut and northeastern Pennsylvania, evidence suggests they were once common on Long Island and other nearby regions.
They went extinct there in just the last few decades. "This raises conservation concerns that must be addressed," said ecologist Joanna Burger of Rutgers University.
"These frogs were probably once more widely distributed," Rissler said. "They are still able to hang on. They're still here, and that's amazing."
Until scientists settle on a name for the frog, they refer to it as "Rana sp. nov.," meaning "new frog species."