Mizoram yields two new-to-science frog species, one hiding in plain sight

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Ingerana aizawl has a distinctly bumpy, wrinkled back, a clearly visible domed eardrum and small toe pads, differed by up to 6.6% from its nearest relatives. | Photo Credit: Special Arrangement

Mizoram has yielded two new-to-science species of frogs, one of which was hiding in plain sight on a university campus for more than two decades.

The two species, Duttaphrynus phawngpui, a toad, and Ingerana aizawl, have been named after Mizoram’s highest mountain peak and its State capital, Aizawl, respectively.

Jayaditya Purkayastha, Hmar Tlawmte Lalremdanga, Malsawm Dawngliana, and Mara Dausa Hlychho authored two studies published in the scientific journals Taprobanica and Zootaxa.

Holiness Warjri, A.A. Thasun Amarasinghe, Amit K. Bal, Vanlal Hruaia and Mathipi Vabeiryureilai contributed to the study on Duttaphrynus phawngpui. Manmath Bharali, Malsawmtluanga, Rupankar Bhattacherjee, Arup Kumar Hazarika and Nilutpal Das are the other authors of the study on Ingerana aizawl.

The researchers found the toad at elevations above 2,000 metres within Phawngpui National Park, named after Phawngpui or Blue Mountain. Medium-sized, up to 56 mm in body length, it has yellowish-brown to earthy-brown skin covered in irregular dark blotches.

It also sports a distinctive pale stripe running down its back and crossbars on its legs. Unlike many of its relatives, including Duttaphrynus stuarti, Duttaphrynus chandai and Duttaphrynus dhara, it lacks a clearly visible eardrum and most of the bony ridges typically found on the skull.

The researchers combined three lines of evidence to confirm it was a new species rather than a variant of an existing one. All three, DNA analysis of a mitochondrial gene, detailed body measurements analysed statistically, and old-fashioned visual comparison with museum specimens of its closest relatives, pointed to a genetically distinct species.

The newly recorded species has reinforced the theory that isolated mountain peaks act like “sky islands”, trapping populations that evolve independently over time. So far, the toad is known from a single mountaintop location, a worry for conservationists in the context of climate change.

Such species are especially vulnerable to habitat loss in warmer conditions, as they have nowhere higher to retreat to.

The find also highlights how much amphibian diversity may still be eluding science in the poorly surveyed uplands of Mizoram and the wider Indo-Burma region, one of the world’s most biodiverse yet threatened areas.

For more than two decades, scientists assumed a short, stocky, 22-26 mm long, frog often spotted on the Mizoram University campus was the Ingerana borealis, a widespread species.

However, recent taxonomic reassessment questioned its identity, prompting researchers to take a fresh look at the “campus frog” using genetic sequencing alongside measurements of body shape, size, skin texture and mating calls.

The frog, with a distinctly bumpy, wrinkled back, a clearly visible domed eardrum and small toe pads, differed by up to 6.6% from its nearest relatives. It was named Ingerana aizawl.

Among other characteristics, the Aizawl frog was found to live along small forest streams and call at night, with each call consisting of a rhythmic series of 12 short notes. Frogs of this species were found to mate during the monsoon, each pair clasped together, although no eggs have yet been found in the wild or produced by captive pairs.

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