Taxonomy, geographic variation and population genetics of Bornean and Sumatran orangutans

This chapter reviews the published data and discusses the taxonomy and population genetics of orangutans. The orangutan was traditionally classified as two separate subspecies, Pongo pygmaeus pygmaeus in Borneo and P. p. abelii in Sumatra. Recent molecular data have suggested a re-classification into two separate species: P. pygmaeus in Borneo and P. abelii in Sumatra. Moreover, three subspecies have been described on Borneo Island: P. p. pygmaeus in Sarawak and west Kalimantan, P. p. morio in Sabah and east Kalimantan and P. p. wurmbii in central and south Kalimantan. Despite this, little is known about the intra-subspecific variation between isolated Bornean populations and among the Sumatran populations. More data are needed, which should include a large sampling of all geographically separated populations in Borneo and Sumatra in order to provide a more complete genetic information database.