Moving continents created new centipede species

• 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.

Common ancestor

• 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

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