Study reveals five genetically-distinct population of wild elephants in India
Study reveals five genetically-distinct population of wild elephants in
India
G.S. Mudur, Times of India
October 1, 2024
India has five genetically distinct populations of wild elephants with
worryingly low genetic diversity in the south, scientists have said,
reconstructing for the first time the population history of Indian
elephants over the past 100,000 years.
Their study of elephant genomes has revealed two populations in the north
and three in the south with high genetic diversity and low inbreeding in
the northern populations and the lowest genetic diversity and high
inbreeding in the southernmost population.
High levels of inbreeding may lead to the accumulation of potentially
harmful genetic mutations and a slow decline in populations, researchers at
the National Centre for Biological Sciences (NCBS) and the Indian Institute
of Science (IISc) in Bangalore who conducted the study have said.
“We wanted to understand the number of genetically distinct elephant
populations, their history and potential challenges they face,” said Uma
Ramakrishnan, a study team member at the NCBS engaged in research on the
evolutionary history of mammals in the subcontinent.
Conservation scientists estimate India is home to 60 per cent of the
population of Asian elephants. Their current populations in India are
fragmented, surrounded by farmland, commercial plantations, human
settlements and transport infrastructure such as highways and railway lines.
But the impact of population fragmentation on genetic diversity of
elephants has been unclear because, scientists say, elephants have annual
home ranges stretching across hundreds of square kilometres. This could, in
principle, compensate for fragmentation and loss of genetic diversity.
The study by Ramakrishnan and her colleagues has now suggested that natural
geographic barriers — the Ganga and the Brahmaputra in the north and
mountain passes in the Western Ghats in the south — have likely contributed
to the five distinct populations.
Their analysis has indicated that the northern elephant populations
genetically diverged from the southern populations between 70,000 and
100,000 years ago, while the three southern populations diverged from each
other between 20,000 and 30,000 years ago. Their study’s findings have just
been published in the journal Current Biology.
With each migration from the north to south, the genetic diversity
declined. Anubhab Khan, the study’s lead author now at the IISc, said this
reduced genetic diversity points to what biologists call a founder effect.
“Only a few individuals migrate to establish new populations,” Khan said.
As these populations become smaller, the risk of inbreeding increases and
potentially harmful genetic variations are more likely to be inherited by
the offspring due to breeding among related individuals.
The southernmost population, south of the Shencottah gap, a major mountain
pass in the Western Ghats near Palghat region in Kerala, has the lowest
genetic diversity and is the most vulnerable to the accumulation of
potentially harmful mutations.
“With around 50 elephants, this population has a relatively high chance of
extinction and needs to be prioritised for conservation efforts,”
Ramakrishnan said.
The study’s other co-authors are Maitreya Sil, Tarsh Thekaekara, and Ishani
Sinha at the NCBS, Rupsy Khurana and Raman Sukumar at IISc, and Kritika
Garg at Ashoka University, Sonipat, Haryana.