Fernando, Columbia University biologist Don Melnick, and a group of researchers in the United States, India, and Malaysia set out to settle the debate once and for all. The team gathered two different types of DNA samples from local elephants, and compared it to DNA taken from animals across the Asian elephant's range, including Sumatra, Peninsular Malaysia, and Indiathree likely possible sources of introduced elephants.
The analysis showed that, while Borneo's elephants bear most similarity to elephants from Malaysia, they are genetically distinct from all Asian elephants. "If Borneo elephants were introduced, they would not have had time to become genetically distinct from the source population [in just 250 years]," said Fernando.
The most probable explanation is that the animals became isolated from those on the mainland 18,000 years ago when the last land bridges disappeared under rising sea levels. However the genetic differences are great enough to hint that Borneo's elephants may have been a distinct population for as many as 30,000 years, says the report.
The results of this analysis "are very tight in my opinion," said Samuel K. Wasser, a conservation biologist at the University of Washington in Seattle. The elephants "likely came over on a land-bridge present during the glacial periods of the Pleistocene," when sea levels were lower, he said.
The elephants should now be considered a conservation priority, "representing an important extension of the Asian elephants' known range," said Wasser. The find extends the natural range of the Asian elephant by 1,300 kilometers (800 miles).
Conservation projects are now essential. "The whole population is only a couple of thousand animals," said Fernando. "There is widespread habitat loss in Borneo, and there are very few captive animals."
Finding that these elephants are unique and have been isolated for at least 18,000 years, means that elephants from other regions shouldn't be introduced, as they may not share adaptations to local conditions, observed Eggert, the Smithsonian conservation geneticist. "These animals have co-evolved with parasites and pathogens, as well as local food plants," she said. "Introducing outside animals could disrupt those adaptations."
The study's authors argue that Borneo's elephants deserve reassignment to their own sub-species, but that may have to wait for a more comprehensive analysis of the physical differences to other Asian elephants.
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