Study shows how Brahmaputra rivers limit gene flow in elephant populations
Study shows how Brahmaputra rivers limit gene flow in elephant populations
Roopak Goswami, East Mojo
September 28, 2024
See link
https://www.eastmojo.com/national-news/2024/09/28/study-shows-how-brahmaputra-rivers-limit-gene-flow-in-elephant-populations/
for photo.
Guwahati: A new study uncovering insights into the genetic history of
India’s Asian elephants has revealed the existence of five genetically
distinct populations in the country—more than previously identified.
The study, published in Current Biology, was conducted by Prof. Uma
Ramakrishnan’s group at the National Centre for Biological Sciences in
collaboration with Prof. Raman Sukumar and others at the Indian Institute
of Science.
India is home to 60% of the global population of Asian elephants, found
across South and Southeast Asia. Today, elephant habitats in India are
fragmented by farmland, human settlements, commercial plantations, and
linear transport infrastructure. This fragmentation has led to severe
human-elephant conflicts. Despite their ecological and cultural importance,
studies on the population genetic structure, diversity, and demographic
history of these elephants—essential for identifying conservation
units—have been limited.
The study analysed whole genome sequences from captive and wild elephants,
offering hope for the species' future by identifying populations that need
focused conservation strategies.
Researchers identified five distinct populations across Northern, Central,
and Southern India—two in the north and three in the south. Historically,
elephants migrated southward, but genetic diversity diminished with each
migration.
Dr. Anubhab Khan, the study’s lead author and now a faculty member at the
Indian Institute of Science, Bangalore, attributes the reduced genetic
variation to a serial founder effect. This phenomenon occurs when fewer
individuals from each starting population migrate to establish new
populations, increasing the risk of inbreeding depression.
The findings align with previous research, which showed that the elephant
populations in Northwest and Northeast India, situated in the foothills of
the Himalayas, are genetically distinct from other populations. The Ganges
and Brahmaputra rivers act as barriers to gene flow in these regions.
Elephant populations in Northern India, including the Northeast, diverged
from others over 70,000 years ago. These northern populations display
higher genetic diversity and lower levels of inbreeding compared to
Southern populations, which are more inbred and exhibit reduced genetic
diversity.
Northeastern Elephant Populations
In Northeast India, the Ganges and Brahmaputra rivers further limit gene
flow, isolating elephant populations. Despite this, some connectivity
remains, especially for male elephants who can traverse these barriers more
easily. The genetic distinctiveness and evolutionary history of these
populations highlight the critical need to maintain connectivity and
prevent further habitat fragmentation for long-term survival.
The Northwest and Northeast elephant populations are considered the most
evolutionarily unique, according to the study.
In contrast, the southernmost population, located south of the Shencottah
Gap, has the lowest genetic diversity and is particularly vulnerable. With
fewer than 50 elephants remaining, Prof. Ramakrishnan warns that this
population is at high risk of extinction. The researchers suggest that
recent infrastructure developments, including railways and highways, may
have further restricted gene flow between northern and southern
populations. They advocate for cautious translocation efforts across the
gap.
The identification of these five genetically distinct populations
underscores the need for region-specific conservation strategies. The
research team is developing a genetic toolkit based on DNA extracted from
elephant feces, which will help monitor populations more accurately and
identify individual elephants in the wild.
Prof. Sukumar emphasizes that understanding the genetic history of past
elephant populations is crucial for protecting today’s threatened
populations. This research provides a vital step toward securing a safer
future for India’s elephants, offering a new conservation roadmap.