Three new cascade frog species discovered in Northeast India; one named for Kerala's 'Ammachi'

Scientists have discovered three new species of cascade frogs — amphibians that live in fast-flowing forest streams — in Northeast India, and documented five other species in India for the first time. The findings, published in the peer-reviewed Bulletin of the Museum of Comparative Zoology, cap over 15 years of field research led by Prof. S. D. Biju of the Department of Environmental Studies, Delhi University.

The team documented more than 300 geographic populations of cascade frogs and confirmed the new species using DNA analyses along with detailed comparisons of adult frogs and tadpoles. Ammachi's Cascade Frog (Amolops ammachi), found in the Jampui Hills of Tripura, honours the late Kerala social worker and philanthropist Padmini Varkey — affectionately known as 'Ammachi', or mother — for her lifelong service to people in need. Sendenyu Cascade Frog (Amolops sendenyu) from Nagaland is named after Sendenyu village, while Beautiful Cascade Frog (Amolops bella) from West Bengal is named for its striking green body with yellowish-green or reddish-brown mosaic patterns.

The study also reports five cascade frog species never before recorded from India — the Marbled (Amolops afghanus), Nepal (Amolops nepalicus), Wangyal's (Amolops wangyali), Medog (Amolops medogensis) and Pianma (Amolops bellulus) cascade frogs — expanding the known diversity and distribution of the genus Amolops in the country. Prof. Biju said the frogs are a taxonomically challenging group whose biology the study has now clarified, aiding proper identification and conservation. Many Indian faunal groups remain poorly studied, he added, especially in the lesser explored northeastern states, part of two internationally recognised biodiversity hotspots.

Using DNA-based dating, the researchers reconstructed the frogs' evolutionary history and found they diversified extensively around 32 million years ago, during the Eocene-Oligocene transition, a period of widespread biological turnover. The study points to multiple waves of colonisation from east to west across Asia and identifies the early uplift of the Himalayas as a key factor shaping their present-day distribution and diversity.