Moving continents created new centipede species continents created... · now tell an intriguing...

Fossils and advanced genet-ic methods to study rela-tionships between speciesnow tell an intriguing storyabout a group of tropicalcentipedes. Continentaldrift (the moving apart ofcontinents) almost 100 mil-lion years ago created manyspecies of Ethmostigmuscentipedes in the world'stropics. In the Indian penin-sula, these centipedes fi��rstoriginated in the southernand central Western Ghats,and then spread across theranges here, fi��nds a studypublished in BMC Evolu-tionary Biology.

Diversity of speciesIndia is home to six, fair-

ly large Ethmostigmus cen-tipedes: four dwell in theWestern Ghats, one in theEastern Ghats and one in

combe of the Natural HistoryMuseum (London, UnitedKingdom) turned to genet-ics. Using genetic data of 398Ethmostigmus centipedesfrom published studies, theyconstructed a species ‘time-tree’ — a network that revealshow species are related toeach other and when new

species emerged — of ninespecies (across peninsularIndia, Africa, Australia andsoutheast Asia). They usedthree fossil centipedes to ca-librate the DNA tree, whichgave them the approximatetimes that the species origi-nated in the past.

Common ancestorThe results suggest that a

single ancestor gave rise toall Ethmostigmus centipedesin the ancient superconti-nent of Gondwana (conti-nents including Australia,Africa and peninsular Indiacomprised this single land-mass then). The subsequentbreakup of Gondwana andthe drifting away of diff��erentlandmasses shaped the earlyevolutionary history of Eth-mostigmus. And the Ethmos-tigmus in peninsular Indiaare very unique, says co-author Joshi.

“They started evolving ata time when peninsular In-dia was moving towardssouth Asia,” she says. Thisstarted around 72 millionyears ago, in the southernand central Western Ghats.Following this, the Ethmos-tigmus here dispersed to theEastern Ghats (now home toE. tristis).

From there, Ethmostig-mus dispersed to the south-ern Western Ghats. Ethmos-tigmus centipedes alsoreached the northern Ghatsfrom the south-central Ghatstoo, and later dispersed backto the central Ghats againfrom there.

The formation of wet for-ests in these areas duringthis time could have aidedthis dispersal (for all existingpeninsular Indian Ethmos-tigmus centipedes now dwellonly in wet forests), write theauthors in the paper.

north-east India. Africa,south-east Asia and Australiaare also home to other spe-cies of Ethmostigmus centi-pedes. What explains its dis-tribution across continentsand the diversity of speciesin peninsular India?

To fi��nd out, scientists Jah-navi Joshi and Gregory Edge-

Ethmostigmus centipedes dispersed across peninsular India to form new speciesAathira Perinchery

Moving continents created new centipede species

Unique: The Ethmostigmus in peninsular India are very unique.* UMESH PAVUKANDY