What does the DNA say about the future of the rhino in India?

Subject: Environment

Introduction-

The one-horned rhino (Rhinoceros unicornis) now numbers around 4,034 individuals found only in the grasslands of India and Nepal, Due to significant human-induced pressures like hunting, encroachment and habitat degradation, the species had severely declined during the 1900s.
However, the efforts of the governments of India and Nepal and other stakeholders, along with the enforcement of conservation laws have helped the rhino population recover.

Evolution of Rhinos in India–

The study also revealed that the most recent ancestor of the species entered Indiaapproximately one million years ago through northeast India, followed by their inland movement along the Siwalik range through the Siva-Malayan route and finally concluded around the Holocene climate period (approx. 19,000-5,000 years ago).
The rhino population then established itself in Nepal as well as the northwestern parts of India.
It gradually got restricted to the grassland regions along the Ganga, Indus and Brahmaputra flood plains as well as in the terai grasslands in the foothills of the Himalayas.

Successful translocation but Skewed distribution–

The one-horned rhino was once distributed widely in the Brahmaputra-Ganges-Indus plains, and also extended further up to the Himalayan foothills, but currently, it is found only in 11 locations across India and Nepal over a cumulative area of about 4000 sq. km.
This indicates translocation is a successful and relatively safe conservation tool for rhino population restoration.
Out of the total global one-horned rhino population, about 65% is confined to Kaziranga National Park in India and 17% to Chitwan national park in Nepal.
The National Rhino Conservation Strategy adopted by India in 2019 aims to increase the rhino distribution by 5% by 2030.
From the success achieved to date, it can be advocated that translocation can play a pivotal role for this species.
In such a case, understanding the genetic status of the current rhino populations in both countries will be crucial for the long-term survival of the species.

DNA study of Indian Rhinos–

The DNA of the rhino population in India is being studied under the RhoDIS (Rhino DNA Index System) India program implemented by the Ministry of Environment, Forest and Climate Change along with the Wildlife Institute of India,WWF India and the states bearing rhinos in India.
The findings showed that the population of the Indian rhinos has three “evolutionary significant units” corresponding to the populations of Assam, West Bengal and Uttar Pradesh.
This conclusion is based on whole mitochondrial genome data analysis.

Genetic variation is key to long-term health and survival–

In the study on rhino evolution, we also looked into the genetic variation within each of the three genetically significant units and found that except for the Assam population which has high mitochondrial diversity, the population in the other two states (West Bengal and Uttar Pradesh) are genetically poor.
Building on this, we also analysed the genetic structure of the two reintroduced populations in India – theDudhwa population reintroduced during the 1984-85 period and the Manas population which was translocated under the Indian Rhino Vision 2020 program beginning in
The genetic makeup of the Dudhwa rhinos was quite poor due to the fact that the main breeding females in the Dudhwa population were sourced from Chitwan National Park in Nepal and the dominant male for a long time was an individual from Pobitora Wildlife Sanctuary of Assam.
Since mitochondrial DNA is only maternally inherited, the observed skewed genetic signature in Dudhwa can be attributed to the founder population composition.
This can be taken as learning for planning future translocations to set up new rhino populations, especially in the context of the greater one-horned rhino.

Concern remains–

The present rhino populations are all scattered and isolated with little opportunity for genetic exchange across the populations as there is no habitat connectivity in most cases. This could be detrimental since rhinos are not known to be long-ranging, unlike elephants or tigers that cover long distances to move across habitats.