CSIR-CCMB scientists unravel biodiversity changes down south over millions of years

The Hindu

02-07-2025

Peninsular India, a tropical region in Southern Asia, extending from Aravalli mountains, Vindhyas, Eastern Ghats, Deccan Plateau, and a global biodiversity hotspot— Western Ghats, harbours unique and highly diverse groups of animal and plant species, many of which do not occur anywhere else in the world.
The endemic diversity of the various species could be due to varied trajectories of speciation among different life forms — some due to stability of tropical ecosystems and others by past fluctuations in temperature and geo-climatic changes that occurred between 11 and 3 million years ago, said scientists at the CSIR-Centre for Cellular & Molecular Biology (CCMB) on Wednesday.
A recent study from Jahnavi Joshi's lab uncovered how species of life forms evolved and disappeared across South Asia and the wider Asian region by analysing 33 well-studied groups of animals and plants using mathematical models, said an official release.
The team traced patterns of species formation (speciation) and loss (extinction) across the region in a broad-scale analysis done for Asia for the first time. 'Each of the groups comprises closely related endemic species, and a common ancestor that existed at some point in time. Through millions of years, their descendants of the common ancestors spread across the landscape and diversified into multiple species, many of which exist today,' explained Dr. Joshi.
Researchers found a high disparity in how species are formed or lost across groups of animals and plants. They found evolutionarily related groups, such as different kinds of lizards, exhibited similar rates of forming and losing species. Half of the animal and plant groups had accumulated diversity gradually over millions of years.
'The stability of the tropical forest ecosystems in peninsular India has allowed for such steady diversification. Hence, this area has served as a refuge shielding species from severe climate changes,' she said. Yet, the stability of the ecosystem came as a surprise to the researchers due to the turbulent geo-climatic past of the landmass.
'Peninsular India was once part of the Gondwanaland supercontinent with land masses like Africa and Australia. It broke away around 100 million years ago, drifted northward, and eventually collided with Asia, forming the Himalayas. Despite drastic geo-climatic shifts from this movement, the biodiversity in this region has changed rather steadily. This highlights the fascinating resilience of its forest habitats,' said Pragyadeep Roy, the first author of the study.
The remaining half of the groups experienced fluctuating rates of new species forming and losing over time. 'The global temperatures have been very dynamic across several million years, and our analyses suggest that earth's temperature strongly influences how species are formed in many groups,' explained Mr. Roy.
The study found that some groups experienced abrupt changes in the rates of forming new species within the time range of 11 to three million years ago. 'The period was marked by high aridification and monsoon seasonality with a major expansion of grasses, leading to the shrinkage of evergreen forests to the Western Ghats and mountaintops of Eastern Ghats. These events certainly inflicted changes in the ranges and habitats of organisms, disrupting their earlier evolutionary trends,' explained the researchers.
These insights into how past climate and habitat stability influenced biodiversity can help in devising effective conservation strategies, especially in light of today's anthropogenic activities and climate change. The study was published in Ecology Letters, said the release.