Genome sequencing to help prevent inbreeding among tigers
New Delhi, Feb 20 (IANS) Scientists are sequencing the genome of Ranthambore's tigers, the most isolated feline and one that, it is feared, could be wiped out due to possible inbreeding.
Scientists at the National Centre for Biological Sciences (NCBS), Bengaluru, and the Wildlife Institute of India (WII), Dehradun, are also sequencing the genome of the tigers of Sundarbans to know more about their uniqueness and how they are different from mainland tigers -- so as to ensure better conservation.
Genome is the genetic material of a species and includes genes and DNA. Its sequencing is done to determine or "decode" the complete DNA sequence in one go for a better insight into its complete biological and evolutionary history.
This has helped scientists across the world to save species like the giant panda, chimpanzees, Florida panthers or puma, and Tasmanian devil by planning more suited and personalised conservation plan.
According to Uma Ramakrishnan, Associate Professor at NCBS, the genome of several tigers from Ranthambore had been sequenced and analyses on inbreeding and its possible effects are ongoing. Inbreeding, or breeding within the family, causes lowering of genetic variation that weakens the off-spring and reduces its survival rate.
Ranthambore is the western-most wild-tiger population of the world, which earlier was Sariska. Tigers went extinct in Sariska in 2004.
The other protected site near Ranthambore, Panna in Madhya Pradesh, also saw it being stripped of tigers in 2009, thereby isolating Rajasthan's tiger reserve completely. Tigers were later reintroduced in Sariska and Panna. Though poaching was blamed as a major reason for their extinction, other possible reasons were unknown due to lack of studies, biologists said.
"We are looking for signatures of inbreeding in Ranthambore. There is no inflow of any tiger from outside the forest reserve. It is completely cut off, so breeding among related individuals will happen, and may pose threats," Ramakrishnan told IANS.
"It's the first time that a whole genome of wild tigers has been sequenced in India," she added.
According to a study published in 2017 by seven eminent wildlife scientists, including Ramakrishnan, genetic diversity in Ranthambore was found to be much lower in comparison to all three genetic clusters.
Lower genetic variation contributes to higher extinction risks. The 2017 research cautioned against a realistic possibility towards in-breeding.
Currently, there are only a handful of laboratories across the world that do genome sequencing of endangered species, including NCBS that currently holds several terra-bytes of data on tigers.
"Whole genome sequencing offers 2.5 GB of information. So it is a repository of all the information," she said.
Though the genome sequencing study is still on, the 2017 study found that the individuals at Ranthambore were closely related, almost like siblings, due to lower genetic variation.
"Further results can help us think of possible management solutions, like introducing tigers from outside for genetic variation," she says, stressing on the urgent need for conservation attention at the tiger reserve.
Ranthambore has 37 tigers, according to a 2014 population estimate. According to earlier studies conducted across nine tiger reserves in central India -- including Kanha, Bandhavgarh, Satpura, Tadoba-Andhari and Bor -- Ranthambore had the most isolated tigers.
Studies say that Ranthambore is the only tiger habitat under North-West genetic cluster -- a division of tiger-ranges based on their genetic similarity. The other two genetic cluster are the "'central cluster" that covers north, north-east and central Indian tiger ranges, and "western ghats", which cover the southern states.
Historically, tigers have lost 93 per cent of ranges worldwide. India, with about 60 to 70 per cent of wild tiger population -- estimated at around 2,226 -- plays a vital role in their conservation.
However, smaller protected areas and buffers (less than 300 sq km), rapid urbanisation, encroachment, highways passing through critical tiger zones and shrinking green-corridors used by animals to transit between forests, continue to challenge their survival.
(Kushagra Dixit can be reached at firstname.lastname@example.org )