Central India’s land-use patterns, roads fragmenting gaur & sambar populations, threatening genetic diversity

Umred Karhandla Wildlife Sanctuary, though centrally located, was most genetically differentiated
Gaurs were most impacted by land-use and land-cover changes, roads with high traffic and dense linear infrastructure intrusion.
Gaurs were most impacted by land-use and land-cover changes, roads with high traffic and dense linear infrastructure intrusion.Photo for representation: iStock

Land use patterns and roads in the central Indian landscape were disrupting genetic connectivity of two large herbivores — Gaur and Sambar, according to a first-of-its-kind study of large herbivores at a landscape scale in India. 

The findings of the study done by the National Centre for Biological Sciences (NCBS) indicated high genetic differentiation, suggesting that the animals were present in small populations with little to no gene flow.

Central India, like other areas of conservation concern, faced threats from growing linear infrastructure such as highways, railway lines and changes in land use patterns, expanding road network, mining activities and other development projects. 

Such infrastructure hinder animal movement, creating fragmented populations confined within small habitat patches disconnected from each other. 

To investigate genetic connectivity, a team of researchers from NCBS collected 1,144 gaur and 756 sambar faecal samples from tiger reserves and wildlife sanctuaries in Madhya Pradesh and Maharashtra. These included Kanha Tiger Reserve, Pench Tiger Reserve, Nagzira-Nawagaon Tiger Reserve, Bor Tiger Reserve, Tadoba-Andhari Tiger Reserve, Umred Karhandla Wildlife Sanctuary and the wildlife corridor between Kanha and Pench Tiger Reserve.

Following a genetic species identity, 921 samples were identified as gaur, while 504 samples were determined to be of sambar. 

The team investigated whether the species comprised a single contiguous population across the landscape or were fragmented into distinct groups, using next-generation sequencing (NGS) and combination of population and landscape genetic tools. 

Published in Molecular Ecology on July 3, 2024, the study was the first to examine the genetic connectivity of large herbivores at a landscape scale in India. 

It analysed the genetic diversity of gaur and sambar, which was crucial for any species to adapt to sudden environmental changes, diseases, climate shifts and other stressors. 

The findings revealed that gaur was most impacted by land-use and land-cover changes, roads with high traffic and dense linear infrastructure intrusion. These fragmented gaur populations also showed low levels of genetic diversity. 

Sambar, besides land use-land cover and high-traffic roads, was also impacted by human presence. Though sambar populations did not show much differentiation, low levels of genetic diversity were concerning. Researchers speculated that this could be attributed to the large population size of sambar. However, with more data, genetic differentiation may become evident.

Gaur and sambar rank among the top prey species for large carnivores like tigers.

Gaur is the largest wild cattle species and one of the few mega-herbivore species that inhabit the Indian subcontinent. Although the species was once found throughout the forested areas of India, its current distribution is restricted to fragmented habitat pockets, primarily in the Western Ghats, the central Indian highlands and northeast India.

Sambar can be found from the foothills of the Himalayas in the north to the Western Ghats in the south and the Peninsular and north-eastern regions.

Sambar exhibits a wide range but its population is very patchy, especially in central India.

Both species face threats like habitat fragmentation, habitat loss, illegal poaching, and other anthropogenic impacts responsible for population decline and local extirpation.

Umred Karhandla Wildlife Sanctuary, with a small population was most genetically differentiated, despite being centrally located among the other protected areas in the landscape. 

Habitat loss and fragmentation have been major drivers of species extinction across the globe. Maintaining movement among habitat patches usually results in mating and genetic exchange, and the loss of which can increase the probability of species extinction. 

Herbivores are crucial for maintaining ecosystem functioning, yet most species remain understudied.
Abhinav Tyagi, lead author of the study

While the connectivity of carnivores like tigers and leopards has been investigated, little is known about how herbivores respond to habitat modification and fragmentation, he added.

“This study underscores that different species have varying needs for connectivity and traversing the landscape,” the scientist noted. 

Uma Ramakrishnan, senior author and professor at NCBS, pointed out that the conservation requires demographic recovery but also sustained connectivity or gene flow between populations. 

“We hope that studies like this will help spur evidence-based approaches to maintaining connectivity for multiple endangered species in priority landscapes like central India,” said Ramakrishnan. 

Conservation action to ensure multi-species connectivity will be critical to sustained conservation and recovery in the face of ongoing development, she added. 

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