The study clarifies a long-standing mystery about whether the different-looking cobras found across the country are actually separate species or subspecies.
The spectacled cobra, known scientifically as Naja naja, is one of India’s most clinically significant animals.
The study found that the mainland population is panmictic, meaning that individuals across the entire region are interbreeding so freely that there are no distinct genetic subgroups.
While the Sri Lankan cobras are not yet considered a distinct species, they are on a unique evolutionary path.
Before this project, only 23 genetic sequences for Naja naja were available in public databases, and many of those came from snakes in Pakistan, Nepal, or Bangladesh.
Bengaluru
Scientists at the Indian Institute of Science (IISc) have completed the most comprehensive genetic map to date of the Indian spectacled cobra, revealing that snakes living across the vast Indian mainland belong to a single, interbreeding family. The study clarifies a long-standing mystery about whether the different-looking cobras found across the country are actually separate species or subspecies. While the snakes may look different from the deserts of Rajasthan to the jungles of the Western Ghats, their DNA tells a story of remarkable connectivity.
The spectacled cobra, known scientifically as Naja naja, is one of India’s most clinically significant animals. It belongs to the "Big Four," a group of snakes responsible for the vast majority of the estimated 58,000 snakebite-related deaths in India each year. Because these cobras are found nearly everywhere in the country and show a wide variety of colours, patterns, and hood markings, scientists have spent decades debating their true evolutionary history. This new research used genetic sequencing to map the predator, tracing its origins and current genetic health.
The research team, led by Kartik Sunagar from the Centre for Ecological Sciences, sequenced nine different genetic markers, including both mitochondrial DNA, which is inherited from the mother, and nuclear DNA, which comes from both parents, from 67 individual cobras. These samples were collected from a wide range of environments across India, including the Deccan Peninsula, the Gangetic plains, and the semi-arid regions of the northwest. By comparing these sequences, the team was able to reconstruct a "time-calibrated" family tree that stretches back millions of years.
The findings confirm that the entire Naja genus actually originated in Africa. Around 10 to 14 million years ago, during an epoch known as the Miocene, the ancestors of the Indian cobra began a long-distance dispersal into Asia, likely traveling through a land bridge in the Middle East. Once they reached the Indian subcontinent, they flourished. The study found that the mainland population is panmictic, meaning that individuals across the entire region are interbreeding so freely that there are no distinct genetic subgroups. This was a surprise to many, as researchers had previously proposed up to five subspecies based solely on the snakes' physical traits, such as colour, pattern, or hood markings.
However, the story changed when the researchers looked at cobras from Sri Lanka. The data revealed that the Sri Lankan population is a genetically distinct clade, or branch, that separated from the mainland Indian cobras roughly two million years ago. This split likely happened during the Pleistocene epoch when fluctuating sea levels repeatedly connected and then isolated Sri Lanka from the tip of India. While the Sri Lankan cobras are not yet considered a distinct species, they are on a unique evolutionary path. This distinction is vital because previous smaller studies had suggested the Sri Lankan cobra was a completely separate species. Now, this new, broader data suggests they are better described as a highly distinct population within the same species for now.
Before this project, only 23 genetic sequences for Naja naja were available in public databases, and many of those came from snakes in Pakistan, Nepal, or Bangladesh. Obtaining samples in India is notoriously difficult due to the strict legal protections and permits required to handle these venomous reptiles. By filling this massive data gap, the team has provided a much clearer picture of the snake’s phylogeography, the study of how historical processes lead to the current geographic distribution of genes.
While they used nine specific genetic markers, the researchers note that they did not sequence the snakes' entire genomes, which would provide even finer detail about their evolution. They also pointed out that more sampling is needed in connectivity zones, such as the southern coast of India and the northern parts of Sri Lanka, to see if there is any remaining genetic bridge between the two groups. Additionally, while the DNA shows the snakes are one family, their venom can still vary significantly from region to region due to local diets and environments, which remains a challenge for medical professionals.
