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Continental drift to thank for coral reef biodiversity

"It took 100 million years to build this extraordinarily large biodiversity, but it might take less than 100 years to destroy it," warned ecologist Loic Pellissier.

By Brooks Hays
The biodiversity found among the coral reefs of Australia, Indonesia and Southeast Asia was made possible by continental drift, researchers say. Photo by Simon Gingins/Zurich ETH
The biodiversity found among the coral reefs of Australia, Indonesia and Southeast Asia was made possible by continental drift, researchers say. Photo by Simon Gingins/Zurich ETH

ZURICH, Switzerland, May 6 (UPI) -- A new study suggests both the fragmentation and convergence of continents 100 million years ago explains the rich biodiversity found among the coral reefs of Indonesia and Southeast Asia.

Using a computer model, researchers were able to track the movement and evolution of corals and reef fish as Africa and Asia separated and India drifted northward into Asia.

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Scientists powered their model with fossil and geographical data, which helped it track the movement of shallow and warm waters over time -- the kind of habitat preferred by coral and reef fish. The model also incorporated a key evolutionary mechanism, whereby one species becomes two when a habitat is split in two.

When a reef becomes fragmented, so do the fish that live there. Over time, divided species evolve independently into two or more species.

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The model revealed various periods of intense tectonic movement and reef fragmentation. Around 140 million years ago, the supercontinent Gondwana began to break up and South America, Africa, India and Australia all started going their separate ways. The breakup was accompanied by intense reef fragmentation.

The model suggests another period of intense fragmentation occurred 50 to 60 million years ago.

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"At that time in the western part of Tethys, the prehistoric ocean between Africa and Eurasia, there was a complex seafloor structure with many disconnected reefs -- a bona fide patchwork," Fabien Leprieur, a professor at the University of Montpellier, explained in a news release.

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Finally, the model revealed that the hot spot of biodiversity enabled by Tethys' fragmentation has shifted toward Southeast Asia over the last 60 million years.

"Now, for the first time, our models provide an explanation for this movement," said Loic Pellissier, a professor of landscape ecology at ETH Zurich.

"Because of the plate tectonic processes, new habitats emerged in different locations over the course of millions of years, while others merged or disappeared," Pellissier explained. "These dynamic structures encouraged the relocation of the focal point of species diversity."

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This hot spot was further boosted by the continental drift of Australia toward the equator. Scientists have previously shown the Australasian encounter encouraged biodiversity among animals and plants.

"We've now shown that it happened with tropical marine life too," Pellissier added.

The new research -- published in the journal Nature Communications -- is also a reminder that the planet's most diverse ecosystems are also some of the most vulnerable to climate change.

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"Today's reef ecosystems have a very long history," Pellissier concluded. "It took 100 million years to build this extraordinarily large biodiversity, but it might take less than 100 years to destroy it."

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