¿Bajan de los árboles las hormigas que depredan en potreros y cafetales Colombianos?

Abstract

Isolated trees in agroecosystems promote the associated biodiversity and can provide functions such as predation. This study examined whether presence of the trees affects the presence and predation activity of ants in pastures and coffee plantations in two regions of the southwest Colombian Andes. We also explored whether in the dry season the ants descend trees toward the production system in order to predate. During the dry and rainy seasons in 2006, intensive samplings of ground foraging ants were made in 16 plots at Pescador and Dagua. Ten pitfall traps were placed in each plot for 96 h. Separately, Drosophila melanogaster adults were offered as prey, adhered to paper or tape, placed 1 and 5 m away from the tree and on the tree at a height of 1.5 m. There was a significant difference in ant richness and identity between regions, indicating the geographical barrier of the western mountain range to be an important factor. Prey were generally consumed within 24 h; nevertheless, consumption was influenced by the presence of trees as predation was higher at 1 m than 5 m from the trees. Ants concentrated their activity on the ground during the dry season. Linepithema neotropicum, a mass recruiter, actively predated in both localities. The results point to a positive influence of trees for ant fauna and predation.