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- Published 25.08.14
Major geological events of the past often leave their mark in the biological world. Researchers studying geckos in eastern and northern India have discovered that the rising of the Himalayas, which began some 50 million years ago, has greatly influenced the diversification of geckos in India and other Himalayan countries.
The study — the first of its kind in independent India — has also resulted in the discovery of 16 new species of lizards. The team, consisting of researchers from the Indian Institute of Science (IISc) in Bangalore and Vilanova University in the US, has been studying the diversity of wild geckos belonging to the genus Cyrtodactylus, commonly known as bent-toed geckos.
“Only five species of this group were known to exist across north-eastern India and the Himalayas earlier but our study has revealed there are at least 16 additional species. That’s a three-fold increase in their diversity in this region,” says Ishan Agarwal, a doctoral student of K. Praveen Karanth, a researcher at IISc’s Centre for Ecological Sciences.
Geckos are one of the most diverse families of lizards, with over 80 species known from India, contributing more than one-third of India’s lizard diversity.
“Cyrtodactylus are the most diverse genus of geckos globally, with close to 200 species known from the Western Himalayas through Southeast Asia up to Australia and Papua New Guinea,” says Agarwal. House geckos in India are members of the genus Hemidactylus, and are widely distributed and have adapted to live with humans (commensal).
The bigger picture that emerges from the study is that the initial diversifications in three of the most species rich gecko groups (Cyrtodactylus, naked-toed geckos, and Hemidactylus) were roughly coincident with the India-Asia collision and the beginning of Himalayan uplift, says Aaron Bauer, a world-renowned lizard expert and a co-author of the study, which appeared in the journal Molecular Phylogenetics and Evolution last week.
“Each group responded differently in an evolutionary sense, with Hemidactylus ultimately speciating widely in peninsular India and Cyrtodactylus beginning a long series of lineage divergences that ultimately led it to hyper-species richness in tropical southeast Asia,” Bauer told KnowHow.
The scientists, who analysed DNA of 41 geckos from localities across the Himalayas, Burma, northern-eastern states and Andaman and Nicobar Islands, found that most of these species diverged after the Himalayan uplift intensified some 23 million years ago. The formation of the Himalayas commenced when the Indian tectonic plate started colliding with the Asian plate some 50 million years ago. The youngest mountain range in the world is still a work in progress as the two plates continue to push against each other.
“As the Himalayas began to rise, rivers and streams restricted the movement of the lizards, confining them to smaller geographical territories. This led to the emergence of new gecko species,” says Karanth, who specialises in studying subtle genetic variations within and among different species.
The scientists are yet to name the newly-discovered species. “There is a possibility that there are many more such species present in the region while many others may have already become extinct,” says Karanth.
Karanth says he was always fascinated by lizards. “When people move from one place to another, common house geckos often travel as part of the shipment. They not only survive in these unfamiliar places but often outsmart local varieties. I have been always intrigued by this survival instinct of geckos,” says Karanth.
Agarwal, who joined Karanth as a PhD student five years after a master’s in wildlife science from Wildlife Institute of India, Dehradun, travelled around the Indian Himalayas painstakingly collecting samples over three years as part of his doctoral work. “Gecko species diversity in the Himalayan region is vastly underestimated,” says Agarwal.
“This is a prominent work on Indian geckos since independence. Most of our understanding of Indian geckos is based on historical studies, mostly done prior to independence,” says Varad B. Giri, a senior scientist with Bombay Natural History Society.
“This is for the first time in the history of Indian herpetology (study of reptiles) that a team of researchers have explored the diversity of lizards in India using modern tools like DNA, visiting the places where these lizards are found and tracking them for a long period of time. The end result is really amazing as we came to know about the intriguing diversity of lizards, which was not known to science till now, or wrongly identified in historical literature,” says Giri, who is known for his work on lizards in the Western Ghats.
Both Giri and Karanth rue the fact that taxonomy — the science of naming, describing and classifying biological organisms on the basis of their shared characteristics — is a dying field in India. “Not many biologists in India find taxonomy an exciting field,” says Karanth.
“Unfortunately, taxonomy is a science which itself is endangered in India. But what is significant about this work is that it has given equal importance to classical taxonomy and DNA phylogeny (the study of evolution of species using molecular sequencing data),” quips Giri.
According to Agarwal, gecko species belonging to the Cyrtodactylus genus in the Himalayas and the northeast are largely confined to rocky habitats in forest areas. The lack of suitable habitats in the Garo-Rajmahal Gap — the alluvial lowland that separates Indian plateau from Shillong plateau — and Indo-Gangetic floodplains prevented these species from dispersing to other parts of India.