Primate Biogeography and Ecology on the Sunda Shelf Islands: A Paleontological and Zooarchaeological Perspective

Abstract

Sundaland, with its complicated history of island formation and landbridge connections with mainland Southeast Asia, has figured prominently in studies of primate biogeography. The non-human primates on Sundaland are taxonomically diverse (comprising 27 species), and they exhibit relatively high levels of provinciality and endemism. By combining archaeological and paleontological evidence, with data from molecular, paleoclimatological and paleoecological studies, it is possible to reconstruct the major zoogeographic events that took place in the formation of the present-day catarrhine primate community on the Sunda Shelf islands. It can be inferred that by the Late Pliocene the main islands of the Sunda Shelf had a primate fauna that included Pongo pygmaeus (Sumatra, Java and Borneo), Hylobates spp. of the lar-group (Sumatra, Mentawai Islands, Borneo, and Java), Macaca nemestrina (Sumatra, Mentawai Islands, Borneo, and Java), the common ancestor of the Trachypithecus auratus/cristatus clade (Java and Sumatra), and Presbytis spp. (Sumatra, Mentawai Islands, Borneo, Sumatra, and Java). Most of these taxa probably arrived during the Pretiglian cold phase, starting at ~2.8 Ma, when sea levels fell by more than 100 m. It is also likely that Nasalis larvatus (Borneo) and Simias concolor (Mentawai Islands) were already present as endemic taxa in the Late Pliocene, and that their last common ancestor had arrived in the Sunda islands by the early Pliocene. Soon after this initial period of colonization, Hylobates and Presbytis underwent rapid speciation as a consequence of vicariance and relictual survivorship, giving rise to P. thomasi on Sumatra, H. klossii and P. potenziani on the Mentawai Islands, H. albibarbis, H. muelleri, P. hosei, P. frontata, and P. rubicunda on Borneo, and H. moloch and P. comata on Java. During the Late Pliocene and Early Pleistocene, probably associated with a cold climate maximum at ∼1.8 Ma, Presbytis melalophos and P. femoralis, along with Macaca fascicularis, colonized Sumatra, the Natuna Islands and Borneo from the Malay Peninsula. At about the same time, the orang-utan populations on Sumatra, Java and Borneo began to differentiate from each other. Hylobates lar, H. agilis and H. syndactylus extended their range from the Malay Pensinsula into Sumatra (and Java), probably during the Middle to Late Pleistocene, coincident with the arrival of Trachypithecus cristatus on mainland Southeast Asia. Meanwhile, Pongo pygmaeus, Hylobates syndactylus and Macaca nemestrina were extirpated on Java, probably as a consequence of a combination of ecological changes and the impact of early hominin incursions.