Neogene and Quaternary history of vegetation, climate and plant diversity in Amazonia

The neotropical Amazonian and Andean plant diversity developed mainly during the Tertiary. In Amazonia, Miocene #oral diversity seems considerably higher than today. During the Neogene, tropical taxa entered newly created montane area, and montane taxa entered the tropical lowlands. The general decrease of temperature during the upper Neogene and especially during the Quaternary glacial periods may have caused considerable extinctions in the lowlands. Representation of pollen of apparently principally montane taxa (Podocarpus, Hedyosmum) in Miocene, Pliocene, and Quaternary sediments of Amazonia and surroundings, is still di$cult to interpret in terms of temperature decrease at low elevation. Changes in precipitation may have profound impact on the composition of vegetation communities; Ilex and Melastomataceae increase signi"cantly in many glacial pollen records. Increase of Weinmannia in Amazonian pollen records seems the best indicator of downward migration of montane vegetation belts. A temperature lowering at sea-level of 4.5 $13C during the Last Glacial Maximum (LGM) seems reasonable; it may have caused a downslope migration of some 700 m of the lower montane vegetation belt; lower montane arboreal species may have been able to grow in higher elevation areas (’500 m) of Amazonia, increasing background pollen values of montane taxa in the area. Di!erence between a cool and wet Middle Pleniglacial (60}28 ka BP), and a cold and dry Upper Pleniglacial (28}14 ka BP; thus including the LGM) is evident in Andean and Amazonian records; statements about environmental conditions of the ice-age Amazon should be speci"ed chronologically. The Middle Pleniglacial is a time of accumulation of #uvial sediments. The Upper Pleniglacial i