Low genetic diversity threatens elephants' existence in India

New Delhi: India houses five genetically distinct populations of Asian elephants and at least one such population in southern India is now vulnerable due to years of “inbreeding”, biologists in Bengaluru have reported.

Two populations are in the Himalayan foothills and the remaining three are in the Western Ghats. Historically, elephants migrated from the north to the south, but with each migration, their genetic diversity declined.

The researchers from National Centre for Biological Sciences and Indian Institute of Science have now uncovered a new genetic history of Indian elephants and found their vulnerabilities, which may necessitate new conservation strategies in future.

“Its a story of how elephants colonised India. The northern elephant population diverged from all other populations about 70,000–100,000 years ago while the three southern Indian populations diverged from each other only around 20,000–30,000 years ago,” Anubhab Khan, first author of the study from NCBS told DH.

In between is the central Indian population that separated from the northern group around 50,000-80,000 years ago.

The southern clusters are located in three regions: north of the Palghat Gap, south of the Palghat Gap and south of the Shencottah Gap.

The Palghat and Shencottah gaps are two long and distinct breaks among a chain of hills between Tamil Nadu and Kerala.

"The reduced genetic variation could be the result of a serial founder effect, where fewer individuals from each starting population migrate to establish new populations,” said Khan, now a faculty member at the IISc.

“As these populations become smaller, the risk of in-breeding depression increases — a phenomenon where harmful genetic variants are more likely to be inherited due to breeding among related individuals.”

The southernmost cluster beyond the Shencottah Gap, has the lowest genetic diversity and is particularly vulnerable as fewer than 50 elephants are remaining in this category.

“The conservation needs are different for five genetically distinct groups. For the vulnerable elephants, there can be specific strategies but we need bigger studies on such critical populations for a better understanding of the risk factors and to evaluate the possible solutions,” said NCBS scientist Uma Ramakrishnan.

The researchers suspect railway lines, highways, and other transportation infrastructure may have further reduced the gene flow between northern and southern populations. "It is absolutely essential to find new elephant corridors and protect the existing ones," said Khan.

While the risk of inbreeding has earlier been reported in at least two groups of tigers in India, this is for the first time the researchers flagged such a risk among the pachyderms.

As per the 2017 population estimate, India has just around 30,000 jumbos in the wild and nearly 50 per cent of them are in the south.

The study has appeared in the journal Current Biology.