The island has lost 95 percent of the rain forests it once had, with remaining patches covering around 750 square kilometers (290 square miles)less than 2 percent of the island. Many of the forests were cleared during the British colonial period, when the island was known as Ceylon, to make way for rubber, coffee, and tea plantations.
Pethiyagoda and his team collected over 1,000 frog specimens at 300 sites during the course of their extensive survey. When they attempted to identify the species they had collected they ran into considerable difficulty matching the animals to Sri Lanka's known frogs, said Schneider. International experts later confirmed that the researchers had turned up many previously undescribed species, said Schneider.
Subsequent work comparing the relationships among the species with the use of physical appearance, ecological similarity, frog vocalizations, and genetics helped confirm the novel nature of the animals. Pethiyagoda, and his team also compared the animals to Sri Lankan frog specimens in museums worldwide, to ensure none of the species had been previously described. Pethiyagoda, Schneider and their colleagues detail the discovery in the October 11 issue of the journal Science.
The fragmented nature of Sri lanka's rain forests, which are separated by grassland in some places, may have contributed to the large number of species, said Wilkinson. As direct-developing frogs are effectively stranded in habitats which have high humidity, the animals may have been divided into distinct breeding groups that over time diverged into separate species.
This remarkable discovery could mean that there are other vertebrate species waiting to be found across the tropics, said Schneider. "No other tropical rain-forest region, apart from Australia, is likely to have been as thoroughly surveyed as the Sri Lankan rain forests," he said. "Therefore we expect that there is substantial unknown diversity in tropical regions worldwide."
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