Scientists Thought This Frog Was One species For Nearly 200 Years. DNA Tells a Different Story.
A small brown frog from the rainforests of Borneo is forcing scientists to rethink one of biology’s most basic questions: what counts as a species? For nearly two centuries, a group of fanged frogs in Southeast Asia was classified as a single species, Limnonectes kuhlii, first recognized by science in 1838.
That classification held until a new genomic analysis, published Jan. 14 in the journal Systematic Biology, found that these frogs actually fall into six or seven genetically distinct species. The catch? They all look nearly identical.
Hidden Species Hiding In Plain Sight
“Animals that look similar but are genetically distinct are called cryptic species,” said Chan Kin Onn, a herpetologist at Michigan State University who led the research. Advances in genetic sequencing have accelerated discoveries of these hidden species, he said, and the Bornean fanged frogs are a vivid case study.
Chan and his colleagues analyzed DNA from frog specimens collected across the mountain rainforests of Malaysian Borneo. They examined more than 13,000 genes across the frogs’ genomes.
Genetic studies over the past two decades had already hinted that the frogs might represent as many as 18 different species rather than a single widespread one. The new data landed somewhere in the middle.
“It’s not just one species. But it’s not 18 species, either,” Chan said.
The ‘Gray Zone’ of Speciation
That space between one species and 18 is where the science gets complicated. The researchers detected significant interbreeding between the frog populations. “We found a ton of gene flow going on,” Chan said.
Because genetic material moves between populations, the boundaries between potential species can become blurred. Chan said some proposed cryptic species may reflect differences in scientific methods rather than clear biological divisions.
“It’s not like all of a sudden, boom. It’s more of a speciation ‘gray zone’ that can make it hard to draw the line,” Chan said. “It’s more of a continuum.”
How Species Actually Get Discovered Now
The popular image of species discovery involves an explorer stumbling across a strange creature in an untouched jungle. The reality, according to Chan, looks different. “Most people have this image of an intrepid explorer braving an isolated mountain or some other remote place, and stumbling across a creature that no one has ever seen before,” he said. “But most of the time it’s far less glamorous.”
Many new vertebrate species are identified by revisiting known populations and using improved data and technology to determine whether they are more genetically distinct than previously understood.
Chan studies amphibians and reptiles and noted that there are more than 9,000 amphibian species worldwide, with roughly 100 to 200 new species added each year. Most of those additions come from this kind of genomic reassessment, not from jungle expeditions.
The Bornean fanged frogs, named for tooth-like projections on their jaws, are small, brown and live across Southeast Asia. Nothing about their appearance suggests multiple species. Only the DNA tells a different story.
What It Means for Counting Life on Earth
Earlier estimates suggested Earth contained about 8.7 million species. Newer models that account for cryptic species indicate the total number could be anywhere from seven to 250 times higher than that estimate.
That range raises a pressing question: how many species exist that science hasn’t named yet?
A 2023 global study of roughly 8,000 amphibian species found that two out of five amphibian species are threatened with extinction, making them the most endangered group of vertebrates. If there are far more species hiding in plain sight than anyone counted, the scale of potential loss grows with them.
“There are so many species in the world that we still haven’t discovered, and that could go extinct before we can give them a name,” Chan said.
Similar genetic studies across animals, including insects, fish, birds and mammals, suggest that many species could still be undiscovered.
The Conservation Problem With Finding New Species
Identifying hidden species isn’t automatically good news for conservation. Chan cautioned that splitting species too aggressively can complicate conservation decisions. Resources for protecting wildlife are finite, and every new species designation changes how those resources get allocated.
“We cannot possibly conserve everything, so we have to triage and decide how to allocate limited resources toward what we think are the highest priorities,” Chan said. “We could be putting names on things that shouldn’t be prioritized.”
More data doesn’t always produce clearer answers. In the case of the Bornean fanged frogs, the genomic evidence revealed that interbreeding blurs the lines between populations, making clean species boundaries harder to draw.
Production of this article included the use of AI. It was reviewed and edited by a team of content specialists.
