Madagascar Cools as Hotspot for New Species Evolution

Madagascar's Satanic Leaf-tailed gecko — A satanic leaf-tailed gecko (*Uroplatus phantasticus*) perches on a branch in Ranomafana rain forest in eastern Madagascar.

(Image credit: Satanic Leaf-tailed gecko image via Shutterstock)

Madagascar, a large island in the Indian Ocean,may have only 1 percent of the world's land area, but it has an outsize 3 percent of its species. It is among the most diverse places for life on Earth.

But the process that put Madagascar on this list — the evolution of new species — may have slowed down, a new study suggests.

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These groups included Brookesia, tiny chameleons that pass as dead leaves; Cophylinae, a diverse group of frogs, some of which are little bigger than a fingernail; Phelsuma, impossibly bright geckos; and Uroplatus, commonly called leaf-tailed geckos. One of "nature's dark dreams," the latter geckos can blend into the sides of trees or mimic dead leaves, Scantlebury said. (One species is even known as the satanic leaf-tailed gecko.) [Photos: Wacky Madagascar Animals]

Here's how the detective work was done: DNA sequences in organisms accumulate mutations over time; these can be used to determine the amount of time since two species diverged from a common ancestor. Scantlebury used this approach to look at the rate of evolution of new species in each of these groups going back to the root of the family tree, which is the last common ancestor for the living members for each of the seven groups.

The current theory to explain this phenomenon says resources on a relatively young island like Madagascar once was are abundant, but as species emerge they take up progressively more of them, reducing the amount available until nothing is free to support new types of residents. By comparison, continents are much larger and more complex, so it's harder to imagine that biodiversity could hit an upper limit, Scantlebury told LiveScience.

Because Scantlebury's study focused on diverse groups of reptiles and amphibians that live in most of the island's habitats and evolved at different times, he said his findings likely reveal a general phenomenon on the island — one also seen at work in Malagasy birds known as vangas. Meanwhile, a separate study of Malagasy vertebrates (animals with backbones) found groups became more species-rich over time but did not look for an upper limit on diversity.

Wynne was a reporter at The Stamford Advocate. She has interned at Discover magazine and has freelanced for The New York Times and Scientific American's web site. She has a masters in journalism from Columbia University and a bachelor's degree in biology from the University of Utah.