Phylogeography of Kloss’s Gibbon (Hylobates Klossii) Populations and Implications for Conservation Planning in the Mentawai Islands

Abstract

The Kloss’s gibbon (Hylobates klossii) has long been recognized as distinct among the members of the genusHylobates due to its small size and completely black pelage with no markings. Unlike most other gibbon species, the male and female do not duet; instead, neighboring males chorus before dawn, while the females sing after dawn. The only other gibbon to share these behavioral characteristics is the closely related Javan silvery gibbon (H. moloch) (Takacs et al. 2005; Geissmann and Nijman 2006; Whittaker et al. 2007). The Kloss’s gibbon is endemic to the Mentawai Islands, located off the west coast of Sumatra in Indonesia, and is endangered as a result of continuing deforestation and hunting (Whittaker 2006). Since the 1970s, researchers have advocated increasing protection of this unusual species (McNeely 1978; World Wildlife Fund 1980; Tenaza 1988; Fuentes 1996/1997; Kobold et al. 2003; Paciulli 2004; Whittaker 2005a, 2006), but conservation planning has suffered from a lack of knowledge about intraspecific variation throughout the Mentawais. There are four endemic primates in theMentawai Islands, which have a total landmass of less than 7,000 km. The four Mentawai Islands are not connected to neighboring Sumatra: during the Tertiary period, the force of the subduction of the Indian plate under the Sunda plate pushed up this chain of islands from the ocean floor. The Mentawais have long been isolated from mainland Sundaland by the 1,500-m deep Mentawai Basin, except for brief periods when sea levels were at their lowest, the last occurring between one million and 500,000 years ago (Batchelor 1979; Karig et al. 1980; Moore et al. 1980; Whitten et al. 2000). This long history of isolation likely accounts for the islands’ high level of endemism: 65% of non-volant mammals in the Mentawai Islands are endemic at the genus or species level (World Wildlife Fund 1980).