A frog species known since 1838 may actually be several different species, according to a new genetic study of Southeast Asia’s “fanged frogs.”
When people hear about the discovery of a new species, they often picture something straight out of an adventure story, according to Chan Kin Onn of Michigan State University.
“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,” Chan said.
That kind of discovery still happens occasionally. But Chan noted that the reality is usually much less dramatic. “But most of the time it’s far less glamorous,” he added.
In many cases, scientists identify new vertebrate species by taking a closer look at animals that are already known to science. With better tools and new types of data, researchers can reveal differences that were previously overlooked.
The Strange Case of Borneo’s Fanged Frogs
Chan is a herpetologist, a scientist who studies amphibians and reptiles such as frogs, turtles, lizards, and snakes. There are more than 9,000 amphibian species known worldwide, and researchers add roughly 100 to 200 new ones each year, he said.
One example involves a group of small brown frogs from Southeast Asia known as Bornean fanged frogs. Their name comes from the tooth like projections along their jaws. One member of this group, Limnonectes kuhlii, has been recognized by scientists since 1838. However, genetic research over the past two decades has suggested that what appears to be one species could actually represent as many as 18.
“Animals that look similar but are genetically distinct are called cryptic species,” said Chan, who is also Curator of Vertebrate Collections and a core faculty member in MSU’s Ecology, Evolution and Behavior program.
Modern advances in DNA sequencing have made it much easier to uncover these hidden species. As Chan put it, “a ton of cryptic species are being discovered left and right.”
DNA Analysis Reveals a More Complicated Picture
To determine whether these frogs had been greatly underestimated, Chan and his colleagues analyzed DNA from specimens collected throughout the mountainous rainforests of Malaysian Borneo. The team examined more than 13,000 genes across the frogs’ genomes.
Their findings, published in the journal Systematic Biology, showed that the frogs form several distinct genetic groupings. However, the results did not support the idea that there are as many as 18 species. Instead, the researchers concluded that about six or seven of those groups qualify as separate species.
“It’s not just one species. But it’s not 18 species, either,” Chan said.
Why Accurate Species Counts Matter
This debate over how many species exist is not simply a technical discussion. It has real implications for conservation.
Frogs and other amphibians are facing serious challenges worldwide. A 2023 study examining around 8,000 amphibian species found that two out of five are threatened with extinction. That makes amphibians the most endangered group of vertebrates on Earth.
Chan, who helped author that study, said identifying species is critical for protecting 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.
However, he also pointed out that dividing species too aggressively can create its own problems.
“But there’s a flip side to that coin too,” he added.
If a single species is split into several smaller ones, each newly defined species may appear to have a much smaller geographic range. That can make their conservation status seem worse than it actually is.
“We cannot possibly conserve everything, so we have to triage and decide how to allocate limited resources towards what we think are the highest priorities,” Chan said. “We could be putting names on things that shouldn’t be prioritized.”
Blurry Boundaries Between Species
The research team also discovered frequent interbreeding among these frogs.
“We found a ton of gene flow going on,” Chan said.
When genes move back and forth between populations, it becomes harder to draw clear lines between species. Chan explained that some of the increasing number of proposed cryptic species might reflect how scientists interpret genetic data rather than clear biological boundaries.
The Bornean fanged frogs highlight how the formation of species is often gradual.
“It’s not like all of a sudden, boom. It’s more of a continuum,” Chan said.
Hidden Species Across the Animal Kingdom
Fanged frogs are not the only example of animals whose diversity may have been underestimated.
Over the past two decades, genetic research on organisms ranging from insects and fish to birds and mammals has suggested that many species could be hiding in plain sight.
Scientists once estimated that Earth is home to about 8.7 million species. More recent models that account for cryptic species suggest the true number could be far higher, possibly ranging from 7 to 250 times that figure.
So where does the real total fall?
“This study shows that there’s a speciation ‘gray zone’ that can make it hard to draw the line,” Chan said.
Reference: “A Genomic Perspective on Cryptic Species Reveals Complex Evolutionary Dynamics in the Gray Zone of the Speciation Continuum” by Kin Onn Chan, Dario N Neokleous, Shahrul Anuar, Rafe M Brown, Carl R Hutter, Indraneil Das and Stefan T Hertwig, 14 January 2026, Systematic Biology.
DOI: 10.1093/sysbio/syag001
This research was supported by grants from the U.S. National Science Foundation (GRFP 1540502, 1451148, 0907996 and 1654388).
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