The multidimensional Temsirolimus in vivo scaling supports this finding in that bee communities of openland plots were highly clustered, while forested habitats covered a larger variety of species compositions. Hence, agroforestry systems

may maintain high regional species richness due to high management diversity and medium-intensity disturbance, enhancing floral abundance and spatiotemporal habitat heterogeneity. Canopy disturbances in primary forests occur frequently due to tree fall gaps, resulting in increased herbaceous vegetation density and insect richness compared to interior forest (Dirzo et al. 1992; Bruna and Ribeiro 2005; Horn et al. 2005; Wunderle et al. 2005). Anthropogenic disturbances in agroforestry systems, such as opening of the canopy (Liow et al. 2001; Winfree et al. 2007), appeared to simulate and promote the positive effect of natural tree fall on the plant, and thereby, the bee community in our study. Forested habitats offer nesting sites for many bee species (Klein et al. 2003b; Brosi et al. 2007; Brosi et al. 2008), while openland provides better food resources in the herb layer, but bees are known to often bridge different habitats providing different resources (Tscharntke et al. 2005a). Therefore, bee diversity of human-dominated habitats may often depend DAPT mw on large areas of natural habitats providing nesting resources (Steffan-Dewenter et al. 2002),

but floral resources may be similarly or even more important (Westphal et al. 2003; Jha and Vandermeer 2009). In conclusion, the different habitat types strongly differed in their relative contribution to the bee community. The land-use

systems in the studied human dominated tropical landscape strongly increased local and regional pollinator species richness through enhanced heterogeneity of the landscape. Local species richness was highest many in openland, but the high beta-diversity of agroforestry systems levelled off this difference, resulting in similar gamma-diversity. However, farmers recently tend to remove shade trees in coffee and cacao agroforestry, thereby simplifying these systems (Perfecto et al. 1996; Steffan-Dewenter et al. 2007). Such reduction of heterogeneity in tropical landscapes will further reduce overall biodiversity and associated ecological services such as pollination of wild and crop plants provided by the native bee communities. Acknowledgments We thank Andrea Holzschuh and Owen T. Lewis for valuable suggestions on the manuscript, Stephan Risch, Leverkusen (Germany) for species identification of bees and Ramadhanil Pitopang, Palu (Indonesia) for identification of herbaceous plant species. We thank the Deutsche Forschungsgemeinschaft (DFG) for financing the Collaborative Research Centre STORMA (SFB 552), LIPI for the research permit and Damayanti Buchori for collaboration.