Landscape affects the composition but not functionality of tropical bird communities in cacao agroforestry

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Carolina Ocampo-Ariza and Teja Tscharntke, Agroecology, University of Göttingen, Göttingen, Germany, Bea Maas, Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria, Tara Hanf-Dressler, Agroecology, Georg-August-Universität Göttingen, Göttingen, Germany, Jorge Novoa-Cova, CORBIDI, Lima, Peru, Evert Thomas, Bioversity International, Justine Vansynghel and Ingolf Steffan-Dewenter, Department of Animal Ecology and Tropical Biology, University of Würzburg, Würzburg, Germany

Background/Question/Methods
The development of wildlife-friendly management strategies for tropical agroforests has been driven by current evidence of the decline of bird diversity and functionality with increasing distance between these agroecosystems and primary forests. However, potential differences in these bird diversity patterns due to landscape factors have been overlooked so far. This may lead to mistakes on our large-scale conclusions about the value of agroecosystems for biodiversity, and the availability of ecosystem services inside of them. We studied bird communities in Peruvian cacao agroforests and adjacent forests inside two landscapes with contrasting forest types: tropical dry forests in the region of Piura and subtropical forests in Cusco. These landscapes diverge largely in their vegetation structure and composition, but share a strong climatic seasonality. Inside each landscape, we evaluated beta-diversity by calculating pair-wise dissimilarity indices, and evaluated whether they varied between landscapes and along a gradient of distance to forest. We also calculated the turnover and nestedness components of beta-diversity to distinguish whether differences between communities inside each landscape were better explained by the replacement or loss of bird species. Finally, we assessed if functional diversity and key functional traits of bird communities changed with forest distance and between landscapes.

Results/Conclusions
Our study provides the first comparison of functional and beta diversity of bird communities between cacao agroforests surrounded by contrasting tropical forest types. We found that the number of functional traits decreased around 50% with increasing distance to forest while functional evenness increased. This indicates that bird communities further from forests were more dominated by certain species. These patterns were consistent in both landscapes. In contrast, only among bird communities in subtropical forests we found higher dissimilarity due to species turnover, indicating large species replacement in this landscape. On the other hand, in dry forests beta diversity increased with distance to forest, explained by growth in nestedness (from ca. 0.05 to ca. 0.2). This indicates that distant cacao agroforests lose bird species found in forests of this landscape. These contrasts highlight the need for regionally adapted conservation strategies in cacao agroforestry. In tropical dry forest landscapes conservation should focus on improving the connection with forests to prevent species loss in cacao agroforests. On the other hand, wildlife-friendly agroforestry in subtropical forest landscapes should improve conditions for certain functional groups, such as insectivorous birds and forest specialists, to guarantee the maintenance of irreplaceable ecosystem services.