Kochi: Researchers from India and the US have discovered five new species of shrub frogs from the Western Ghats, one of the globally recognised biodiversity hotspots.
The frogs, belonging to the Old World tree frog family Rhacophoridae, were discovered by researchers from the University of Delhi and Kerala Forest Research Institute and the University of Minnesota as part of a long comprehensive study on the Shrub frogs (genus Raorchestes) of the Western Ghats, carried out over a period of nearly 10 years.
The new species were identified and found to be distinct based on multiple criteria, such as their external morphology, DNA, calling pattern, behaviour, and other natural history observations.
The findings are published in a scientific article titled 'An integrative approach to infer systematic relationships and define species groups in the shrub frog (genus Raorchestes), with description of five new species from the Western Ghats', India'.
The authors are Sonali Garg, Robin Suyesh, Sandeep Das, Mark A Bee, and Prof S D Biju and it is published in the current issue of the International journal PeerJ.
The study was carried out under the leadership of Delhi University Professor Biju.
The new species
Raorchestes drutaahu (common name: Fast-calling Shrub Frog). This new species is named for its unique calling pattern. The species name is derived from Sanskrit ‘druta’ (meaning fast) and ‘ahu’ (meaning call). The Fast-calling Shrub Frog was discovered from two localities: Kadalar in Idukki district and Siruvani in Palakkad district of Kerala state.
Raorchestes kakkayamensis (common name: Kakkayam Shrub Frog). This new species is named after the place of its discovery, Kakkayam. The only known locality for Kakkayam Shrub Frog lies in the vicinity of Kakkayam dam, which is likely to have impacted the historical range and population size of the species.
Raorchestes keirasabinae (common name: Keira’s Shrub Frog). This new species is a unique tree frog inhabiting the highest canopy layers. It is known to have a relatively wide distribution in Agasthyamalai and Anamalai hills in the southern Western Ghats. The species is named after a young nature lover Keira Sabin, in appreciation of the long-time support and commitment of the Andrew Sabin Family Foundation towards amphibian research and conservation around the world.
Raorchestes sanjappai (common name: Sanjappa’s Shrub Frog). This beautiful green shrub frog was discovered from the Wayanad region of northern Kerala. The species is named after Dr. M. Sanjappa, a renowned Indian Botanist and former Director of the Botanical Survey of India.
Raorchestes vellikkannan (common name: Silver-eyed Shrub Frog). The name of this new species is derived from Malayalam ‘velli’ (meaning silver) and ‘kannu’ (meaning eye), referring to its distinct silver eye colour. The Silver-eyed Shrub Frog is discovered and currently known only from Siruvani hills and the adjoining regions of the Silent Valley National Park.
According to the researchers, over 80 per cent of the globally known shrub frogs are restricted to the Western Ghats, and most species are known to have narrow geographical ranges.
For the first time, male calls for as many as 48 species of shrub frogs were studied, they said.
According to the study, the shrub frogs of the genus Raorchestes exhibit highly unique and diverse eye colour and patterns. This is the first time researchers have comprehensively examined these characters for all the known shrub frog species of the Western Ghats, along with highlighting the usefulness of eye colour and patterns in the identification of species and their closest relatives.
Biju, who is the head of Department of Environmental Studies at Delhi University, said the study was a testament to how little is known about the most threatened group of vertebrates in India.
"Shrub frogs are among the most researched groups of frogs in India, with frequent new discoveries being made over the past two decades. Yet, we are far from fully understanding their existing diversity and uniqueness."
"Our work has once again added new insights on what we thought we knew about this group of frogs, from how to identify different species and their affinities to each other, to where they live and how vulnerable they may be to various anthropogenic threats," he said.
“Three out of the five new species described are from outside Protected Areas highlight the fact that the need for conservation of biodiversity outside PA’s is also crucial” said Sandeep Das who is also part of the study.
Scientists are now tracing potential evidence for population decline of the five newly discovered species, and any threats that they may be facing within their known ranges, in order to protect them from extinction.
"Several new species are often threatened even before they are formally named and known to science. Many of these may already be extinct before they are discovered."
"It is an unfortunate fate that scientists call as the nameless extinction," said Sonali Garg, the lead author of the study.
This study and the authors were funded by University of Delhi; Department of Science and Technology, Government of India; Critical Ecosystem Partnership Fund, USA; Global Wildlife Conservation, USA; Council for Scientific and Industrial Research, Government of India; Rufford Small Grants for Nature Conservation; Animal Behaviour Society’s Developing Nations Award; EDGE Fellowship grant; and Fulbright Fellowship.