XVI International Botanical Congess

Melastomataceae species distributions were studied at local (5 m to 1 km), landscape (1 km to 100 km) and regional (over 100 km) scale in western Amazonian unflooded lowlands. Species distributions were affected by drainage-related topographical differences at the local scale, and by soil texture and nutrinet levels at landscape and regional scales. Most strongly the edaphic factors affected species distributions at the landscape scale showing the importance of beta-diversity in explaining regional diversity. There is considerable species turn-over from one region to another which is only partly attributable to edaphic differences. This suggests that climatic and/or historical factors play an important role in understanding the overall Amazonian plant species richness.