• Fossils and advanced genetic methods to study relationships between species now tell an intriguing story about a group of tropical centipedes.
• Continental drift (the moving apart of continents) almost 100 million years ago created many species of Ethmostigmus centipedes in the world’s tropics.
• In the Indian peninsula, these centipedes first originated in the southern and central Western Ghats, and then spread across the ranges here, finds a study published in BMC Evolutionary Biology.
Diversity of species
• India is home to six, fairly large Ethmostigmus centipedes: four dwell in the Western Ghats, one in the Eastern Ghats and one in north-east India.
• Africa, south-east Asia and Australia are also home to other species of Ethmostigmus centipedes.
What explains its distribution across continents and the diversity of species in peninsular India?
• To find out, scientists Jahnavi Joshi and Gregory Edgecombe of the Natural History Museum (London, United Kingdom) turned to genetics.
• Using genetic data of 398 Ethmostigmus centipedes from published studies, they constructed a species ‘time-tree’ a network that reveals how species are related to each other and when new species emerged of nine species (across peninsular India, Africa, Australia and southeast Asia).
• They used three fossil centipedes to calibrate the DNA tree, which gave them the approximate times that the species originated in the past.
• The results suggest that a single ancestor gave rise to all Ethmostigmus centipedes in the ancient supercontinent of Gondwana (continents including Australia, Africa and peninsular India comprised this single landmass then).
• The subsequent breakup of Gondwana and the drifting away of different landmasses shaped the early evolutionary history of Ethmostigmus. And the Ethmostigmus in peninsular India are very unique, says co-author Joshi.
• They started evolving at a time when peninsular India was moving towards south Asia.
• This started around 72 million years ago, in the southern and central Western Ghats.
• The Ethmostigmus here dispersed to the Eastern Ghats (now home to E. tristis).
• From there, Ethmostigmus dispersed to the southern Western Ghats. Ethmostigmus centipedes also reached the northern Ghats from the south-central Ghats too, and later dispersed back to the central Ghats again from there.
Mains Paper 3: Environment
Prelims level: Centipede species