Stable forests key to south India's unique biodiversity

HYDERABAD: A mix of stable tropical forests and ancient climate changes led to peninsular India's unique biodiversity over millions of years, according to a study by researchers at the CSIR-Centre for Cellular and Molecular Biology in Hyderabad.

By examining 33 groups of animals and plants, scientists discovered that some species slowly evolved thanks to long-term ecosystem stability, while others were shaped by drastic changes in climate and landscape between 11 and 3 million years ago.Peninsular India extends from the Aravalli mountains southwards, including the Satpuras and Vindhyas, the Eastern Ghats, the Deccan Plateau and global biodiversity hotspot of Western Ghats.

It harbours highly diverse groups of animal and plant species, many of which do not occur anywhere else in the world.The study published in Ecology Letters uncovered how species evolved and disappeared across South Asia and the wider Asian region.

By analysing the 33 well-studied groups of animals and plants using mathematical models, the team traced patterns of species formation (speciation) and loss (extinction) across the region.

"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 spread across the landscape and diversified into multiple species, many of which exist today," said CCMB scientist Dr Jahnavi Joshi.The 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. They also found that half of animal and plant groups accumulated diversity gradually over millions of years. "The stability of the tropical forest ecosystems in Peninsular India has allowed for such steady diversification. As a result, this area has served as a refuge for species from severe climate changes," said Joshi.Pragyadeep Roy, first author of the study, added: "The stability of this ecosystem is surprising given the turbulent geo-climatic past of the landmass.

Peninsular India was once part of the Gondwanaland supercontinent with land masses such as Africa and Australia. It broke away 100 million years ago, drifted northward, and collided with Asia, forming the Himalayas. Despite drastic geo-climatic shifts from this movement, the biodiversity changed steadily.

This highlights the resilience of its forest habitats.""Global temperatures have been very dynamic across millions of years, and our analysis suggests earth's temperature strongly influences how species are formed in many groups," explained Roy. The study found that some groups experienced abrupt changes in the rates of forming new species within the time range of 11 to 3 million years ago. "This period was marked by high aridification and monsoon seasonality in Peninsular India with a major expansion of grasses, leading to shrinkage of evergreen forests to the Western Ghats and mountaintops of the Eastern Ghats. These events inflicted changes in the ranges and habitats of organisms, disrupting their earlier evolutionary trends," the study said.