Mammals of south‐east Asian islands and their Late Pleistocene environments

Abstract

Aim The environments that existed in south-east Asian islands during the last glacial are poorly known, limiting our understanding of mammalian biogeography in the region. The objective of this research is to investigate the ecological characteristics of mammal faunas on small islands, and to see whether the habitat requirements of the species in those faunas can be used to deduct the vegetation types that existed on islands before becoming isolated by rising sea levels.Location The maps presented here cover the small islands of tropical south-east Asia, including the Burmese, Thai and Cambodian islands in the north, the islands off the coast of west Sumatra in the west, the islands around Java in the south, and the islands off the east coast of Borneo in the east, including the Philippine islands of Palawan and those in the Sulu Archipelago. MethodsThe presence records of mammal species on 215 small islands in the region were compiled, and the habitat requirements for each of these species was assessed (species that had probably been introduced by humans were excluded from the analysis). For each island location (longitude and latitude), maximum altitude of the island, total area, depth to nearest land, distance to nearest island, and distance to nearest mainland were assessed. Geographical and statistical analyses were used to investigate patterns of mammalian habitat requirements. ResultsThe geographical analysis showed that forest-dependent species, i.e. species that are only found in primary forest (lowland and mountainous), appear to be concentrated on islands off west Sumatra, in the Lingga and Riau Archipelagos, around Palawan, and around Bunguran Island; they are absent mostly from the islands of the Java Sea, those off the east coast of eastern Borneo, from most islands in the Sunda Strait, several islands in the northern South China Sea, and from all islands off the west coast of the Malay/ Thai Peninsula and in the Gulf of Thailand. Species that generally occur outside primary forest, that is those in secondary forest, gardens, plantations and open areas mostly occurred on islands where the forest-dependent species were absent. The statistical analysis showed that latitude and size of islands were important factors that determined the absence and presence of forest-dependent species on small islands. Main conclusionsThe data suggest that during the last glacial there were several areas in the Sundaic region that remained forest covered: west of Sumatra, north-west of Borneo, the Malacca Straits and around Palawan. Other areas may have been covered by more open vegetation types like tree savanna, or open deciduous forest: on and to the east of the Malay/Thai Peninsula, the Java Sea area, including the Sunda Strait, and eastern Borneo.

Biogeography and conservation in Southeast Asia: how 2.7 million years of repeated environmental fluctuations affect today’s patterns and the future of the remaining refugial-phase biodiversity

“…Dated records are important as scientists attempt to document range shifts; e.g. tapir, Sumatran rhinoceros and orangutans were more widely distributed until recently (Meijaard 2003;Tougard and Montuire 2006;Earl of Cranbrook 2009). Some of the impediments to developing regional public databases for conservation managers are discussed by Srikwan et al (2006) and Webb et al (2010).…”

“…Several workers have argued that during cooler glacial conditions rainforest retreated to the hills of peninsula Malaysia, western Sumatra, the Mentawi Islands, and the center of Borneo, and that during hypothermal periods the rainforest was replaced by savanna woodland or grassland on the emerged Sunda plains and elsewhere (Heaney 1991;Morley 2000Morley , 2007. The extent to which a continuous or broken savanna corridor covered parts of the Sunda Shelf from Indochina to Borneo is controversial as the evidence is mixed and often sitespecific (Kershaw et al 2001(Kershaw et al , 2007Meijaard 2003;Bird et al 2005;Meijaard and Groves 2006;Wang et al 2009). Recently, Cannon et al (2009) have modeling of the changes in distribution of major forest types during the last full 120,000-year glacial cycle and found they actually expanded rather than contracted in their ranges during each hypothermal phase.…”

Forest contraction in north equatorial Southeast Asia during the Last Glacial Period

“…In addition, model results for the region greatly vary, with some indicating that a broad continuous lowland tropical rainforest was maintained and others suggesting savanna over major portions of Sundaland during the LGM (6,7). Surprisingly, there are no records from peninsular Malaysia and, in places where LGM sediments with suitable proxies are recovered, they may be compromised by biases such as riparian gallery forest vegetation and wind-blown tree pollen dominating riverine and offshore deposits (6,8,11,12), or lowland swamp regions being biased toward indicating wetter conditions (13). Hence, even the general distribution of LGM vegetation is disputed.…”

Soils on exposed Sunda Shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia

“…Despite this long history of land connections, there exists a marked biogeographic boundary between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland (3,5,6). These differences have been explained by a hypothesized north-south-oriented savanna corridor through the center of Sundaland that blocked dispersal of wet forest species (7)(8)(9)(10)(11)(12)(13). Although there is strong evidence for drier conditions within the region during the last glacial period (10,(12)(13)(14)(15), the presence of a continuous north-south savanna corridor through the center of Sundaland remains controversial, and most coupled vegetationclimate reconstructions contradict this possibility (4,(16)(17)(18)(19)(20).…”