Central India region has highesttiger genetic variation, says study

Nagpur: Genetically connected tiger populations in Central India, Terai and North-East has high variation and future of tigers will depend on connected populations only, says a latest study by wildlife scientists and tiger researchers form leading Indian institutes.

The regions are geographically the largest connected forest units with maximum tiger genetic variation. The experts who conducted the study include Meghna Natesh, Goutham Atla, Parag Nigam, YV Jhala, Arun Zachariah, Anuradha Reddy, Udayan Borthakur and Uma Ramakrishnan.

For the first time, all tiger genetics labs, including the Wildlife Institute of India (WII), Centre for Cellular and Molecular Biology (CCMB), Hyderabad, National Centre for Biological Sciences-Tata Institute of Fundamental Research (NCBS-TIFR), Kerala Veterinary & Agricutural Sciences University, and Aranyak from across India came together to share their genetic and tissue samples.

The scientists investigated genetic variation and its partitioning in wild Indian tigers using information from across the genome. Their analyses identified Ranthambore as a possibly isolated, low genetic variation population while Central India, Terai and North-East as genetically connected tiger populations with high variation.

"Tigers are charismatic carnivores of global conservation concern. The Indian subcontinent is home to the largest number of tigers in the world, and the Indian government has invested significantly in tiger monitoring and conservation.

"Conservation goals include preservation of genetic diversity in endangered species. But this requires understanding what the genetic units of a species are, and which units have higher or lower variation and hence the study," says Jhala from WII.

Hence, the scientists used state-of-the-art, next generation sequencing to type 10,184 single nucleotide polymorphisms (SNPs) from across the genomes of 54 individuals, but the final study included 38 individual tigers.

"From these samples we studied amount of genetic variation, adaptive differences and related issues. SNP is a single base-pair difference in the DNA sequence of individual members of a species," said Natesh, one of the researchers.

Tigers in India can be divided into three genetic units. One unit coincides with Ranthambore in the north-west, the second unit comprise tigers from Terai, North-East and Central India, and third unit includes tigers from southern Indian reserves.

The results suggest that inbreeding, or mating between close relatives, could threaten the small and isolated tiger population of Ranthambore, the study states.

The findings mention that the second unit (Central India, Terai & North-East) was geographically the largest and had maximum genetic variation. The third (southern Indian) unit had intermediate genetic diversity.

Acquiring tissue samples from tigers is logistically challenging. But for the first time, the study was able to glimpse genetic variation from many parts of the entire tiger genome using SNPs. While previous studies looked at 10-12 regions in the genome, the latest study analysed data from over 10,000 regions. Despite this, not all tiger reserves could be sampled.

Yet, the results have implications for tiger conservation. The study shows that high genetic diversity is maintained across connected populations, while isolated populations become genetically depauperate. Genetic variation is the raw material for evolution and survival. The future of tigers will largely depend on connected populations.