Effect of farm diversity on harvesting of coffee leaves by the leaf-cutting ant Atta cephalotes
1 In Mesoamerica, shade trees are often included within coffee (Coffea arabica) agroforestry systems. Shade trees potentially protect the main crop by increasing vegetational diversity and reducing insect herbivory through one or more mechanisms.
2 The effect of on-farm vegetational diversity on harvesting of coffee leaves by the leaf-cutting ant, Atta cephalotes L., was examined on 15 coffee farms varying in vegetational diversity near Turrialba, Costa Rica. The farms ranged from coffee monocultures to complex-shade coffee systems with three or more tree species present. The vegetational diversity of each farm was quantified using a leaf area index.
3 The species composition and biomass of the plant material being carried into colonies by ants was collected, identified to species, and its biomass was quantified four times during one year for at least two colonies in each of the 15 farms.
4 The proportion of plant biomass that was coffee being retrieved by A. cephalotes differed significantly among farm management types, and was highest (40%) in monocultures and lowest (< 1%) in farms with complex shade. Coffee was always harvested in a lower proportion than predicted based upon its relative abundance on the farms.
5 In dual-choice bioassays with laboratory colonies, A. cephalotes significantly preferred the leaves of the predominant shade tree species on the farms, poró (Erythrina poeppigiana) over coffee.
6 The results indicate risk of injury by A. cephalotes can be reduced in vegetationally diverse coffee agroecosystems due at least in part to a foraging preference by the ants for plants other than coffee.
Document Type: Research Article
Affiliations: 1: University of Idaho, Department of Plant, Soil and Entomological Sciences, PO Box 442339, Moscow, ID 83844-2339, U.S.A 2: Centro Agronómico Tropical de Investigación y Enseñanza (CATIE), Department of Agriculture and Agroforestry, PO Box 7170, Turrialba, Costa Rica
Publication date: 2007-02-01