If all ice sheets on the planet melted sea level would rise to +50 m, their height 35 Ma The region is, or was until ~10 ka, drained by some of the most productive rivers on earth: the Salween, Chao Phraya (and its antecedent the Siam), Malacca, North Sunda, East Sunda, Mekong, and Red rivers. Throughout most of the Pleistocene the region had many sizable lakes but only the Tonle Sap of Cambodia remains, the others lay on the exposed Sunda Shelf and are now submerged (Sathiamurthy and Voris 2006). There have

been changes in the paths of some of the rivers that arise on the Tibetan H 89 molecular weight plateau and flow south through Yunnan (Brookfield 1998; Attwood and Johnston 2001; Meijaard and Groves 2006; Rainboth et al. 2010). The Red river of northern Vietnam, for example, lost its upper reaches [the current Yangtze river] about 75 ka. Such changes, the results of river captures and local tectonics, have had a significant impact on the biogeography of freshwater animals. The Salween, Mekong and Yangtze rivers all flow in sutures between adjacent terranes twisted north-south by collision of the Indian and Asian plates. The Mekong (and possibly the Salween by way of today’s Ping River) once flowed south to the Gulf of Thailand through what is now the Chao Phrya river valley. They formed a mega-river called the Siam, which delivered enormous quantities of sediment from the Tibetan Plateau to the

Sunda Shelf, and carved selleck chemicals out the Gulf of Thailand before emptying into the South China Sea. The sequential capture of the upper Mekong by the Yom, Nan and Pasak rivers (all Thai tributaries of today’s Chao Phrya) are not well dated but occurred in the last 3 million years. The present-day Mekong river did not develop until the Late Pleistocene; it assumed its present course from Tibet to Vietnam only about 5,000 years ago. The Tonle Sap formed in the last 8 ka. In Southeast Asia temperature however variation is less significant in determining the growing season and the natural vegetation than rainfall and its seasonality. The region’s characteristic seasonal (monsoonal) climate developed after the

rise of the Tibetan plateau (~30 Ma) and the closure of the seaway between the Australian and Asian plates (~15 Ma) and intensified ~10 Ma (Morley 2007; Berger 2009). The frequent interruption of this seasonality by ENSOs became significant 3–5 Mya. Today the region’s climates range from perhumid near the equator to markedly seasonal in the interior of Indochina (Chuan 2005; Corlett 2009a). Annual mean rainfall varies from 1,000–2,000 mm over most of continental Southeast Asia, to 2,000–3,000 in the Thai-Malay peninsula, Sumatra and southern Borneo, and >3,000 mm in central Borneo and isolated super-wet spots elsewhere. Weck’s climatic index (which includes a measure of seasonality based on water availability and temperature) also shows this north-south variation; from 200–300 in the seasonal north to >1000 in the perhumid Fedratinib equatorial south.