Community assembly of tropical Fagaceae-dominated forests in Thailand dates back at least to the Late Palaeogene

Abstract The Late Oligocene to Early Miocene flora of the Ban Pa Kha Subbasin (Li Basin, northern Thailand) provides a record montane dry tropical oak-pine forests. rich ensemble Fagaceae typical these forests might have existed in wider region Southeast Asia since Eocene times and various fossil plant assemblages represented both lowland (Fagaceae, Dipterocarpaceae) upland Pinaceae) These findings are conflict with previous interpretations vegetation development Thailand, which stressed that stratigraphically older (possibly Oligocene) spore pollen Thailand were markedly different from modern had distinct temperate character. A major change climate would caused dramatic shift conditions Mid-Miocene. Considering palaeobotanical data adjacent regions Asia, we suggest differences intermontane basins more likely represent facies lowland/upland settings. Assembly forest ecosystems, typically comprising Quercus sections Cyclobalanopsis, Ilex Quercus, Castaneoideae affinities Castanopsis Lithocarpus, extinct fagaceous genera such as Eotrigonobalanus, most probably dates back Eocene. absence oaks section Cerris assemblage Subbasin, despite this group being part vegetation, reflect late arrival (secondary radiation) chiefly Asia.