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Indian scientists discover four new species of smallest known frogs from the Western Ghats

Times of India (22/02/2017)


NEW DELHI: Another big discovery from the "Frogman of India", as professor SD Biju from Delhi University (DU) and his team discovered four new miniature species, now listed among the smallest known frogs in the world.

The scientists were surprised by the relative abundance of these new miniature species. In all Biju's team have discovered seven new frog species belonging to the genus Nyctibatrachus, commonly known as Night Frogs. This find is a result of five years of extensive explorations in the Western Ghats global biodiversity hotspot in India. Four out of seven of the new species are miniature-sized frogs (12.2-15.4 mm), which can comfortably sit on a coin or a thumbnail. These are among the smallest known frogs in the world.

 

 

Unlike other frogs in the genus that are predominantly stream dwelling, the new miniature frogs were found under damp forest leaf litter or marsh vegetation.

"In fact, the miniature species are locally abundant and fairly common but they have probably been overlooked because of their extremely small size, secretive habitats and insect-like calls," said Sonali Garg, who undertook this study as part of her PhD research at DU.

In the lab, the newly sampled frogs were confirmed as new species by using an integrated taxonomic approach that included DNA studies, detailed morphological comparisons and bioacoustics. Evidence from these multiple sources confirmed that the diversity of Night frogs is higher than previously known and particularly remarkably for the miniaturized forms. Previously, the Night Frog genus comprised of 28 recognized species of which only three were miniature-sized (<18mm) Now the total number of known Nyctibatrachus species has increased to 35, of which 20% are diminutive in size. This frog genus is endemic to the Western Ghats of India and represents an ancient group of frogs that diversified on the Indian landmass approximately 70-80 million years ago.

The discovery of several new species of ancient origin can provide useful insights into the evolution of endemic frog lineages in the Western Ghats, which is a leading amphibian hotspot. The past decade has witnessed an exponential increase in the number of new amphibian species described from this region. Of the total new species of amphibians (1581) described globally between the years 2006-2015, the highest number were from the Brazilian Atlantic Forest (approximately 182) followed by the Western Ghats-Sri Lanka biodiversity hotspot (approximately 159), with 103 species described alone from the Western Ghats region.

When asked about the evolutionary significance of this finding and as to why these frogs have evolved to be so small when most other Night frogs are relatively large-sized, professor David Wake, evolutionary biologist, University of California, Berkeley said: "I was quite surprised by this paper because I think of Nyctibatrachid frogs as relatively large organisms that live in rapidly flowing streams. Among the new species are four true miniatures, between 10 and 15 mm body length, among the smallest of frogs. These seem to be common locally and they probably were overlooked because of their small size. They occur more terrestrially, in leaf litter. I work on miniaturized salamanders, which also are turning out to have previously unrecognized diversity. A general phenomenon among amphibians is that we have overlooked or not recognized the diversity of tiny forms, maybe just thinking of them as juveniles of other species. Because they are so small they are often seen as similar, but we just have to magnify them to see their distinctive traits. Many miniaturized species of other families in India and Sri Lanka have direct terrestrial development, with no tadpole stage. I infer from this report that there are tadpoles but they are not described. This makes them different from radiations of miniaturized frogs in other parts of the world. I infer tadpoles because the authors report pigmented ova, whereas direct developing forms usually have unpigmented ova."

However, the future of many of the new species may be bleak. All the newly described species are currently known only from single localities in the southern Western Ghats, and some lie outside protected areas. Researchers found the Radcliffe's Night frog and the Kadalar Night Frog inside private or state-owned plantation areas facing threats such as habitat disturbance, modification and fragmentation. The Athirappilly Night Frog was found in close vicinity to the Athirappilly waterfalls and the Sabarimala Night Frog near the Sabarimala pilgrimage centre, both of which are disturbed by anthropogenic activities.

"Over 32%, that is one-third of the Western Ghats frogs are already threatened with extinction. Out of the seven new species, five are facing considerable anthropogenic threats and require immediate conservation prioritization," said Biju, who led the new study and has also formally described over 80 new species of amphibians from India.

Many of these new species are facing anthropogenic threats. When asked what conservation measures should be taken to protect these species, Dr Ariadne Angulo, Chair of the International Union for Conservation of Nature (IUCN) Amphibian Specialist Group said: "The first immediate priority for these newly described species after being formally recognized as such would be to assess their global extinction risk. The IUCN Red List of Threatened Species (http://www.iucnredlist.org/) documents not only species' extinction risk, but also supporting documentation relating to the species' geographic range, population, ecology, threats and conservation. Because several of the species have been identified as being range-restricted and impacted by threats, it is very important to conduct these assessments to have a better understanding of the level of extinction risk for each species. Once the extinction risk is assessed and we can better understand the realities of each species, this would allow for the tailoring of both research and conservation actions accordingly."