Local and landscape factors: Biodiversity, ecosystem services and parasitism in coffee agroecosystems
Intensification processes in coffee agroecosystems have recently begun to be studied at local and landscape scales with different approaches and goals. The purpose of this research was to find which factors, at the local and/or landscape scale, influence biodiversity and ecosystem services delivered by ants. We measured the factors that drive the ant diversity, the predation by ants, and ant parasitism in a coffee landscape with different intensities of agricultural management in the Soconusco region of Chiapas, Mexico. Our objectives included: a) to find which factors are important for ant diversity and abundance of the wood-nesting ants b) which factors promote the predation by these ants, and c) which factors influence their parasitism. This study was conducted in seven coffee farms with different levels of management and several forest patches (study area, 52 km²). Using the ArcView package, we chose 40 experimental sites that included 30 sites in coffee plantations (13 high and 17 low shade) and 10 sites in forest. In each coffee and forest site we measured 27 variables (litter mass, shade tree, and species number) and we created a VCI (Vegetation Complexity Index) with eight structural variables (shade tree species, etc). We also conducted interviews, to determine which management techniques were being used in each farm, to create an Agrochemical Index (AI). Finally, with the Arc View package we calculated seven landscape variables, which included distance to forest, proportion of forest in 50, 200 and 500m in each experimental site. At each site, we collected all ants that were found in rotten wood, on predation trails (baits on ground) and all the pupae found in the rotten wood colonies. Data was analyzed using the R program: GLM, GLMM and Regression Trees.
We found that local factors are the most important for biodiversity of ants; however landscape factors are more critical for the ecological services they deliver. This suggests that the components of the biodiversity-ecosystem function relationship are influenced by factors at different scales. However, these effects are indirectly related, thus suggesting the importance of performing studies that compare varying levels of complexity. Our results implicate the need for further studies that model biodiversity and the maintenance of ecosystem services, particularly in complex landscapes, and where a high diversity of organisms providing services is maintained.