Three new Cascade Frog species discovered in Northeast India, one named after Kerala social worker

Guwahati: A 15-year search through the forests and fast-flowing hill streams of Northeast India has led scientists to the discovery of three new species of Cascade Frogs, including one named in memory of a Kerala social worker who was fondly known as “Ammachi”.

The discoveries, from Tripura, Nagaland and West Bengal, add to growing evidence that the Northeast still holds significant pockets of undocumented biodiversity.

The findings were published in the Bulletin of the Museum of Comparative Zoology, a scientific journal of Harvard University that has been published since 1863.

The study also reports five species of Cascade Frogs that had not previously been recorded from India, further expanding the known diversity of the group in the country.

The three new species belong to the genus Amolops, commonly known as Cascade Frogs because they are typically found around rocky waterfalls and fast-flowing forest streams. The genus has around 100 species distributed across Asia.

The research team, led by University of Delhi professor S. D. Biju, spent more than 15 years exploring mountainous areas across all seven states of Northeast India. During the study, the scientists documented more than 300 geographic populations of Cascade Frogs.

DNA analysis, combined with detailed examination of adult frogs and tadpoles, eventually established that three of the populations represented species previously unknown to science.

A frog named for ‘Ammachi’

One of the new species, Amolops ammachi, or Ammachi’s Cascade Frog, was discovered in Tripura’s Jampui Hills.

The species has been named in honour of the late Padmini Varkey, a renowned social worker and philanthropist from Kerala who was affectionately called “Ammachi”, meaning “mother” in Malayalam.

The researchers said her unconditional love and willingness to help people in need inspired the name.

The medium-sized frog, measuring about 80 mm, has a light-brown body marked with olive-green reticulations.

The second new species, Amolops sendenyu, or Sendenyu Cascade Frog, was discovered in Nagaland and is named after Sendenyu village, where it was found.

The third, Amolops bella, or Beautiful Cascade Frog, was discovered in West Bengal. It is named for its striking green body with yellowish-green or reddish-brown mosaic patterns.

A glimpse into an ancient Himalayan story

Beyond the three new species, the study provides clues to how Cascade Frogs spread and diversified across Asia.

DNA-based dating suggests that the group underwent major diversification around 32 million years ago, during the Eocene-Oligocene transition, a period of major climatic and ecological change accompanied by widespread turnover of plant and animal groups.

The researchers found evidence of multiple waves of Cascade Frog colonisation moving from east to west across Asia.

They also identified the early uplift of the Himalayas as an important factor in shaping the present-day distribution and diversity of these frogs, pointing to a complex movement of species “into and out of the Himalaya”.

“This study is a work of over 15 years to comprehensively study India’s Cascade Frogs,” said lead author Professor S. D. Biju.

He said the group had been taxonomically challenging, but the study had helped clarify several confusing aspects of its biology and would aid the identification and conservation of the species.

The findings, he added, also highlight how many Indian animal groups remain poorly studied, particularly in the northeastern states that form part of the Himalayas and Indo-Burma biodiversity hotspots.

The study, titled Systematics, molecular phylogeny, diversification, and biogeography of Cascade Frogs (Ranidae: Amolops) from India: an integrative assessment with description of three new species, was authored by S. D. Biju, Gajaba Ellepola, A. N. Dikshit, Akalabya Sarmah, Radhakrishna Upadhyaya K., Karan Bisht, Tage Tajo, James Hanken and Sonali Garg.