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Genome Sequence Data Supports Existence of New Orangutan Species

Batang Toru orangutan

NEW YORK (GenomeWeb) – New genome sequence data has bolstered the notion that Indonesia is home to a previously unidentified orangutan species. 

Researchers from the University of Zurich, the University of Konstanz, and elsewhere considered genome sequence data for more than three-dozen orangutans, including 17 individuals newly sequenced for the study. Along with crucial morphometric and behavioral data, their genomic comparison pointed to a genetically distinct orangutan falling outside the known Sumatran (Pongo abelii) and Bornean (P. pygmaeus) species.

"We identified three very old evolutionary lineages among all orangutans, despite only having two species currently described," Maja Mattle-Greminger, a post-doctoral researcher at the University of Zurich and co-first author of the Current Biology paper describing the species, said in a statement.

As they reported in the journal today, the researchers dubbed the new orangutan species P. tapanuliensis for the South Tapanuli district where a male representative of the species was killed in a conflict with humans in 2013. Studies of that skeleton, nicknamed the Batang Toru individual, kicked off the orangutan analysis, which has implications for the conservation of all three species. The investigators estimated that there are roughly 800 Tapanuli orangutans remaining, found in a region south of the Sumatran orangutan range.

"A hydroelectric development has been proposed recently in the area of highest orangutan density, which could impact up to 8 percent of P. tapanuliensis's habitat," Mattle-Greminger and her co-authors noted. "The project might lead to further genetic impoverishment and inbreeding, as it would jeopardize chances of maintaining habitat corridors between the western and eastern range, as well as smaller nature reserves, all of which maintain small populations of P. tapanuliensis."

Starting with the skeleton of the male orangutan killed in 2013, the team did careful skull, jaw, and tooth assessments for the adult animal, comparing it with known orangutan species and other orangutans found in the North, Central, and South Tapanuli districts.

Using the Illumina HiSeq 2000, members of the team at the University of Zurich's Functional Genomics Center did paired-end genome sequencing on DNA extracted from blood samples for 17 orangutans, including individuals sampled at conservation or rehabilitation centers in Borneo or Sumatra.

With the new and available sequences from 20 Bornean or Sumatran orangutans, the researchers estimated that the P. tapanuliensis orangutans fall in a lineage that split from the lineage leading to Sumatran orangutans living north of the island's Lake Toba almost 3.4 million years ago.

"Due to the challenges involved in collecting suitable specimens for morphological and genomic analyses from critically endangered great apes, our description of P. tapanuliensis had to rely on a single skeleton and two individual genomes for our main lines of evidence," the authors wrote. "When further data become available, a more detailed picture of the morphological and genomic diversity within this species of the differences to other Pongo species might emerge, which may require further taxonomic revision."