Researchers at the University of Kansas have described a new species of fanged frog discovered in the Philippines that is almost indistinguishable from a species on a nearby island except for its unique mating appeal and key differences in its genome.
The team led by KU has just published its results in the peer-reviewed journal Ichthyology and herpetology.
“This is what we call a cryptic species because it hid in plain sight from biologists, for so many, many years,” said lead author Mark Herr, doctoral student at the Biodiversity Institute of the KU and the Museum of Natural History and the Department of Ecology. & Evolutionary biology. “Scientists for the past 100 years thought these frogs were the exact same species as the frogs on another island in the Philippines because they couldn’t physically distinguish them. We’ve done a bunch of tests – and they do indeed look identical to the naked eye – however, they’re genetically isolated. We also found differences in their mating calls. They sound quite different. So it was to use the acoustics to determine that the species was different, as well as the new genetic information. “
Genetic samples of the new frog, scientifically known as Limnonectes beloncioi (or commonly as Mindoro Fanged Frog), were collected years ago by KU scientists working in the field on the island. from Mindoro in the central Philippines, but have only recently been analyzed. Due to its almost identical physical similarity to a Palawan Island fanged frog, called Acanth’s Fanged Frog, it was assumed to be the same species.
“You can look at two different things, but to the human eye without careful investigation they can look the same,” Herr said. “So, we took a bunch of measurements of hundreds of these frogs – how long their numbers were precisely, what was the width of the tip of their toe, the length of a specific segment of their leg, the diameter of their eye – en in order to statistically compare populations, even though we think they look the same. We performed statistical analyzes on body shape and size, including a principal component analysis that uses all measurements at once to compare the morphology of the frog in a multivariate space. After all of this, just like scientists before us, we couldn’t find anything to differentiate frogs based on their body shape and size. “
However, since the fanged frogs inhabit islands separated by miles and miles of ocean, researchers doubted they were the same species, in part because they had different calls. They decided to analyze the frog genome and determined that Mindoro’s fanged frog qualifies as its own distinct species.
“We did genetic analyzes of these frogs using some specific genetic markers, and we used a molecular clock model just to get a very basic estimate of how long we thought these frogs may have been separated from each other. from others, ”Herr said. “We found out that they were related to each other, they are close relatives to each other, but we found that they had been apart for two to six million years – it’s a very long time for these frogs. And it’s very interesting that they still look so much alike but sound different. “
The KU graduate student specializes in studying the many species of fanged frogs across Southeast Asia, where he has done extensive fieldwork. He said the frogs’ fangs are likely used in combat to access major mating sites and to protect themselves from predators. Mindoro’s fanged frog, a stream frog, is sometimes hunted by people for food.
But the characteristic call of the frog, different from that of Acanth’s Fanged Frog, proved difficult for researchers to record.
“They’re really suspicious of us when we’re out there with our sound recorders trying to get recordings of these frogs – that’s a really tough aspect, and we were lucky in this project that we had people for many years that had gone out there and had recorded these two frogs in Palawan and Mindoro. So we had recordings from both islands, and it’s quite rare with this group of fanged frogs because people eat. They call the night, but the second a flashlight or a human voice wanders into the equation that they’re just going to take off – because they know they can be killed by people. “
Herr’s description of the Mindoro fanged frog continues a long tradition of KU field research on the herpetological biodiversity of the Philippines and Southeast Asia, according to his educational advisor Rafe Brown, a professor of ecology and evolutionary biology and curator in charge of the Herpetology Division. of the Biodiversity Institute and the Natural History Museum.
“Mark’s discovery reinforces a lesson we’ve learned time and time again over the years – things we thought we knew, combined with new information, emerge to teach us something completely unexpected,” Brown said. “A century ago, Professor Edward Taylor of KU identified the population of Mindoro Island as the Acanth’s fanged frog, the same species he named a few years earlier from the Palawan Island – an arrangement that made very little sense. Zoom in to a hundred years, and we see with new technology, genetic information and bioacoustic data that the populations of the two islands are in fact very well differentiated, as one would expect. But not morphologically; their physical characteristics have not diverged. This is a case in which the formation of species has not been accompanied by morphological differentiation – this is called “cryptic speciation”. “