Palaeoecology of Southeast Asian megafauna‐bearing sites from the Pleistocene and a review of environmental changes in the region

Abstract

Aim To reconstruct the palaeoenvironments of megafauna‐bearing sites from Pleistocene Southeast Asia, and to describe general environmental changes in the region. Location Indochina and Sundaland, including Myanmar, Laos, Vietnam, Cambodia, Thailand, the Malay Peninsula, Borneo, Sumatra and Java. Methods This study reconstructs the habitat types of 25 Pleistocene sites in Southeast Asia through a synecological (community‐based) method. This method specifically targets medium‐ and large‐bodied mammals, and ecovariables that could be directly assessed from species lists were chosen. The methods allow the reconstruction of fossil sites as closed (continuous tree cover), mixed (heterogeneous tree cover) and open (very limited to no tree cover) through discriminant functions analysis of community guild structure. Results Four Pleistocene sites can confidently be assigned to one of the three habitat types. Tam Hang (south), a Middle Pleistocene site from Laos, is classified as mixed. Ban Fa Suai, a Middle Pleistocene site from Thailand, is also classified as mixed. Trinil, a Middle Pleistocene site from Java, is classified as open. Lastly, Hang Hum II, a Late Pleistocene site from Vietnam, is classified as open. Insufficient species are present in the fossil faunas of remaining sites to allow statistically confident habitat assignment. Nevertheless, conditional habitat assignments can be achieved, and these are largely congruent with other palaeoenvironmental evidence. Main conclusions Medium‐ and large‐bodied mammals are the most frequently recovered mammals from Pleistocene sites in Southeast Asia. Previous palaeoenvironmental reconstructions of these sites have been hampered by this body size bias, as well as by limited site and faunal descriptions. However, our analysis demonstrates that reconstructions can still be achieved for megafauna‐bearing sites in the region. The reconstructions suggest that through much of the Pleistocene, Southeast Asia had significant areas of mixed habitats, and that the widespread distribution of rain forests, such as found today, was a relatively rare phenomenon.

Continuity of mammalian fauna over the last 200,000 y in the Indian subcontinent

“…As in India, mixed, interconnected habitats facilitated long-term faunal persistence (33), including regional survival through the impact of the 74 ka Toba supereruption (34). Although Southeast Asia witnessed the extinction or reduction in range of several genera (including Stegodon, Hexaprotodon, Pongo, Crocuta, Hyaena, Tapirus, and Rhinoceros) during the late Middle Pleistocene, and increased faunal turnover and redistribution during the Late Pleistocene, this shift appears to have been generally limited to coastal areas vulnerable to eustatic changes in sea level and climate change linked to glacial cycles (33,35). Here, rising sea levels fragmented the linked, mosaic habitats permanently, resulting in isolated islands-such as Java, Sumatra, and Flores-that were potentially more vulnerable to human, climatic, and ecological change.…”

Late Pleistocene mammalian assemblages of Southeast Asia: New dating, mortality profiles and evolution of the predator–prey relationships in an environmental context

“…The "lower" breccias at TH Central and, in part, TH North, produced a mammal assemblage comprising 38 species, whereas the "upper" breccias at TH South produced a second assemblage encompassing 27 species. Both were considered as belonging to the Middle Pleistocene (Arambourg and Fromaget, 1938;Beden et al, 1972), and remained until recently among the only Middle Pleistocene palaeoecological data for the north of the Indochinese province (Tougard and Montuire, 2006;Louys and Meijaard, 2010).…”

“…Indonesia) based on sedimentological, palynological, and palaeoecological data (van der Dam, 1995, 1997;van den Bergh et al, 1996;Wang et al, 1999;Tougard and Montuire, 2006;Louys and Meijaard, 2010). The Sibrambang fauna from northwest Sumatra (81-70 ka) shows that, at the end of MIS5, a diversified modern fauna was present on the western margin of the Sundaland.…”

Savannahs of Asia: antiquity, biogeography, and an uncertain future

“…C 4 grassy vegetation became established in different parts of Asia at quite different times [22][23][24]. The history of Asian savannahs is therefore best understood by considering different regions separately.…”

“…The present extent of savannah in Southeast Asia is probably far smaller than that during past glacial maxima [23,37]. Today savannah physiognomies in Southeast Asia are found in three main areas: Indochina, east Java and the Lesser Sunda Islands northeast of Australia, and the northwest Philippines (Luzon and Mindoro) and scattered parts of Wallacea [38].…”