Why are new species of frog being discovered so often? Because there are so many of them

Ramit Singal was on a field survey for his citizen science initiative to protect the rocky laterite lands near the coastal town of Manipal in Karnataka when he spotted a thumbnail-sized frog with a call that sounded like a cricket's. Singal hadn’t seen a frog like it before and when he consulted other researchers, it turned out that they hadn't either. After studying the frog's genetics, body structure, colouration and vocalisation, Singal and his collaborators concluded that they had discovered a new frog species in the Western Ghats.

The frog, named Microhyla laterite after its habitat and described in a paper published in PLOS ONE on March 9, is just 1.6-cm long, pale brown with black markings, and is the latest in a long line of amphibian discoveries in India. A week earlier, another team of researchers discovered a species of bush frog in the Biligiri Rangaswamy mountain range, the southeastern offshoot of the Western ghats. In January, a team of biologists led by India’s most famous frog expert, Sathyabhama Das Biju, described a species of tree frog in Arunachal Pradesh that was thought to have been extinct for more than a hundred years.

In May, Biju and his team described 14 species of dancing frogs for the first time. The tiny amphibians measuring between 13-mm and 35-mm stick their legs out in what is called foot-flagging behaviour to attract potential mates, giving the impression that they are dancing. In fact, every year for the last 15 years, researchers have been finding between eight and ten new species of frogs across India.

The turning point

Frog researchers credit Biju and a paper he wrote in 2001 with turning the tide for amphibian research in India. Biju was a plant taxonomist and used to make trips to the Western Ghats to document the flora. But a chance encounter with a Malabar gliding frog and the discovery that frogs make great subjects for photography led him down the path to finding out about amphibian life. He later started his own amphibian studies in Kerala and the Western Ghats.

In his seminal paper that was published in the journal of the Indian Society for Conservation Biology in 2001, Biju said that no serious comprehensive work had been done on amphibians in the last century. Moreover, while 104 frog species were identified from the Western Ghats, his own observations showed that here were more than 200 species in the region.

“I had spent 15 years continuously in the Western Ghats and at each and every site compared the known species with the unknown species," said Biju. "Of all the species being described today, by and other people, at least 80% were photographed in that publication.”

Biju’s claims were met with scepticism from the international community of herpetologists. And yet, his work also attracted young researchers to the issue of undiscovered amphibians of the Western Ghats.

“I was interested in amphibians since I was young,” said Aravind Madhyastha, fellow at the Ashoka Trust for Research in Ecology and the Environment in Bengaluru and part of the team that found the bush frog in the Biligiri Rangaswamy range. “But I started pursuing it seriously about a decade ago when Biju said there are so many more frogs to be discovered. We started asking questions of how many more frogs there might be, what their distribution might be.”

Since Biju’s synopsis in 2001, close to 150 new species in India have been found and described, or rediscovered after having been thought extinct. Many of the discoveries have been made by “frogman” Biju and others by biologists who were excited by his prediction.

Another reason why frog discoveries have been so frequent is the availability of technological tools previously absent from taxonomic research. “We now have molecular biology to compare genes, which was not possible 40 years ago when there were using traditional taxonomic methods based on phenotype,” said Seshadri Kadaba Shamanna, PhD candidate at the National University of Singapore, and collaborator with Singhal in the discovery of the laterite frog.

The importance of amphibians

Although Nobel Prize winner James Watson once famously compared taxonomic biology to stamp collecting, the systematic discovery and documentation of frogs is no frivolous exercise. “Documenting biodiversity is good because biodiversity is good for human society," said Seshadri. "If we lost all the species that there are around us we may not survive. To know how to protect ourselves from extinction, we need to know what species here are around us. That’s the completely utilitarian approach.”

Frog evolutions are also records of our ecological history, having been present before the undivided landmass of Pangea broke up. “Take the common toad found in Bangalore,” said Madhyastha. “The toads of that family came from outside India and diversified during the Neocene. There are other species of frogs that might be about 65 million-70 million years ago in India that diversified in South East Asia.”

Madyastha is now turning to the question of what the bush frog he found in the Biligiri Rangaswamy area indicates about the area’s ecological history. His hypothesis is that the bush frog might have evolved two million years ago when a fault in the plate of the peninsula pushed the Biligiri Rangaswamy range up and isolated the evergreen forests within its arc. The frogs within these forests, like the bush frog, could then have diversified into a different species, having been cut off from a larger population. It is a hypothesis that Madhyastha and his team are now looking to test.

Continuing process

Frogs are critical links in ecosystems that they survive in. The role of a tree-dwelling frog could be quite different from a night frog, which in turn behaves differently from other ground-dwelling species. Frogs may perform important ecosystem services like controlling insect populations. Many species are important indicators of environmental health simply because they are sensitive to changes in quality of water, air and their natural surroundings.

India's purple frog, a species endemic to the Western Ghats and one of Biju's more exciting discoveries, has survived 120 million years only to be threatened with extinction now. In addition to habitat loss, the bulbous frog also has to contend with its tadpoles being consumed as food by tribes in Kerala's Idukki district.

Biju worries that frogs in India are dying out faster than they can be found. In many parts of the Western ghats, a certain kind of frog may only be found within a 10-km radius and they are not seen in any other part of the world. It would only take two people walking continuously in the forest for five days to destroy the habitat, he said.

And so Biju's work and that of other frog seekers in India is far from done. “Approximately 9.5% of the total estimated species have been discovered and described properly. Almost 85%-90% of our flora and fauna is not known to science,” said Biju.