Employing genetics scientists discover distinct population of big-eyed, long-fingered tarsiers
Despite some media reports, scientists have not yet discovered a new species of big-eyed, nocturnal primate—known as tarsiers—in the Philippines. Instead what they have discovered is an intriguing population that is genetically-distinct even from nearby relatives, according to a new open-access paper in PLOS ONE.
“There does seem to be a lot of confusion on this point. Our results do not really answer that question [of new species] yet,” lead author, Rafe Brown with the University of Kansas’ Biodiversity Institute, told mongabay.com.
The genetically distinct population lives on Dinagat Island and the very northeastern tip of Mindanao Island in Philippines. It may also be on nearby Siargao Island, but genetic tests of this island’s tarsiers are needed before that can be confirmed. What the new research does is throw out how scientists and conservationists have long-viewed the evolution of Philippine tarsier (Tarsius syrichta).
A tarsier on Dinagat Island, representing a just discovered evolutionary lineage. Photo by: Andrew Cunningham.
Prior to this, scientists generally accepted three subspecies of Philippine tarsier: the large island of Mindanao contained one subspecies, Tarsius syrichta carbonarius; while the islands of Samar and Leyte sported another, Tarsius syrichta syrichta; and Bohol held the third, Tarsius syrichta fraterculus. However the new genetic research found the relationships among the Philippine tarsier populations was even messier.
Looking at mitochondrial and nuclear DNA, Brown’s team uncovered three different evolutionary lineages: one lineage of tarsier makes their home on Bohol, Samar, and Leyte Islands; another has conquered the vast majority of Mindanao; while a long-cryptic branch has evolved in northeastern Mindanao and Dinagat Island. For the purposes of the paper, the scientists refer to this as the Dinagat-Caraga tarsier.
While Rafe says its too early to claim a new species of primate yet, he says it’s a real possibility with more research.
“My suspicion is that three species will eventually be recognized in the Philippines…but I am not a primate taxonomist, so I can not really say for sure,” he told mongabay.com, adding, “there are some subtle but consistent characteristics differences between the Dinagat tarsier and the other populations from surrounding islands, and there are other large mammals that only occur on Dinagat and Siargao (the neighboring island) so it would not surprise me at all if the tarsier there eventually were determined to be endemic, distinct species.”
But why does this matter?
“Basically, we can not legally protect something if we do not know that it exists,” said Brown, who notes that this distinct population is need of some emergency conservation measures given lack of protected areas, forest loss, and mining.
Deforestation across the range of the newly-recognized lineage of tarsier, including northeastern Mindanao Island and Dinagat Island. Range may extend to Siargao Island as well. Map courtesy of Global Forest Watch. Click to enlarge.
The Philippines has undergone drastic environmental changes in the past couple centuries. Around 70 percent of the islands were once covered in dense tropical rainforest. Today the forest is a shadow of that. The FAO estimates that the Philippines’ primary forest cover in 2010 was at 11 percent. But A 2008 paper estimated just six-eight percent, while Conservation International says that only seven percent of the country’s forests are intact. Any way you measure it, however, the vast bulk of remaining forest is either heavily degraded or has been converted into plantations. A massive wave of logging in the late 20 Century became so severe, that the country has initiated logging bans several times, the most recent in 2011. Yet, illegal logging, combined with mining, remains a massive problem. In fact, the problems were for a time so severe that some conservationists argued that islands-country was practically a lost cause.
Not surprisingly, this large-scale environmental destruction has pushed many Filipino species—a high percentage of which are found no-where else—towards extinction. The Philippines tarsier is one of these.
“They’re threatened with habitat loss due to development, mining and deforestation from the timber industry,” Brown said.
Despite the current logging ban, forest loss is continuing in the Philippines. According to the Global Forest Watch, the Philippines as a whole lost 622,000 hectares of forest cover from 2001-2013, an area about the size of Delaware. Total forest cover declined by 3.1 percent during this time as well.
During the same time period, Dinagat Island lost 1,357 hectares and northeastern Mindanao Island lost 3,351 hectares, comprising nearly two percent of the tarsier’s total range. Moreover, Dinagat is a mining magnet with currently nine companies operating on the island.
A Philippine tarsier.
The discovery of a distinct tarsier roaming from Dinagat to northeastern Mindanao raises a new conservation problem: as currently there are no large protected areas in this area.
“We need a protected area—such as a national park—in the ranges of each of the genetic units if our goal is to maximally preserve the genetic underpinnings of that biodiversity,” said Brown.
Still, the Dinagat-Caraga tarsier may have one lifeline: Siargao Island. Parts of Siargao Island are listed as a Protected Landscape and Seascape, potentially providing protection to the island’s tarsiers. But the researchers aren’t yet sure if they tarsiers there are from the Dinagat-Caraga line or another one.
Yet, forest destruction isn’t the only issue imperiling the country’s tarsiers: they are also imperiled by a prop trade for tourists.
“On Bohol, where [tarsiers] are a big part of the tourist economy, literally thousands of animals are taken out of the wild, essentially harassed by tourists, and die in captivity due to the stress and inability of their captors to feed them an appropriate diet of live small animals. Tarsiers must eat an enormous amount every night to fuel their high metabolism,” said Brown.
Although the world’s tarsiers—which currently number over ten—are not as well known as other unusual primates like lemurs, they are quite charismatic—and wonderfully bizarre—animals says Brown.
“[Tarsiers] move very rapidly and jump from tree trunk to tree trunk with ‘ricochet locomotion.’ They bounce from small sapling trunk to trunk, then leap down to pounce on their prey. They’re completely carnivorous. This is relatively unique among primates. The tarsier is famous for not eating any vegetable material of any kind. They eat insects, small snakes, lizards, small mammals and birds. They communicate with ultrasonic calls outside the range of human hearing. The tarsier is so cool!”
The Philippines has lost more than half a million hectares of forest since 2001, and very little intact forest remains. While logging has been banned throughout the country, illegal logging remains rampant. Courtesy of Global Forest Watch. Click to enlarge.
- Brown RM, Weghorst JA, Olson KV, Duya MRM, Barley AJ, et al. (2014) Conservation Genetics of the Philippine Tarsier: Cryptic Genetic Variation
Restructures Conservation Priorities for an Island Archipelago Primate. PLoS ONE 9(8): e104340. doi:10.1371/journal.pone.0104340
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