Long-term change of ant community structure in cacao agroforestry landscapes in Indonesia

Abstract

Land-use change and agricultural intensification can strongly affect biodiversity in agricultural landscapes. Although many studies investigate management impacts, data on the long-term change of species communities in agroecosystems are scarce. We analysed the long-term change in diversity and composition of ant communities in cacao agroforestry systems in Central Sulawesi, Indonesia and attempted to disentangle the driving factors of this change. Ant communities were resampled in 2009 from sites for which previous surveys had been conducted either in 2001 (the rainforest-poor Palolo region) or 2003 (the rainforest-rich Kulawi region) using insecticide fogging. Ant community composition changed significantly over time in Palolo and Kulawi. The change in ant species richness differed between regions. Species richness increased in Kulawi, probably due to the increasing availability of nest sites and microhabitats as trees grow larger and older. In the Palolo region, species richness decreased, suggesting that the high local intensification and landscape-wide changes may have counteracted the effects of tree age. Changes in ant communities over time were significant, but were more difficult to explain than expected, despite clear difference in management changes within and between regions. The findings suggest that the landscape-scale differences between the two study regions play a more important role for species diversity and its composition than changes in local management. This highlights the importance of long-term studies across contrasting landscapes for better understanding the consequences land-use intensification has on tropical biodiversity.