Conservation of ant communities in cashew tree-based agroforestry systems: key roles of tree density and diversity

Under the pressure exerted by humans on forest ecosystems, agroforestry is promoted to maintain a balance between forest and agricultural ecosystems. Agroforestry systems are the center of interactions between crops and other plants and between fauna and flora. Within this faunistic diversity, ants occupy a prominent place through their protective association with some tropical plant species as natural enemies of their arthropod pests. In this study, we analyzed the effects of the diversity of trees associated with cashew trees and of cashew tree density on ant abundance/diversity in cashew agroforestry systems. The study was conducted in 12 cashew orchards in central Benin. Data on the diversity and densities of ground-dwelling and arboreal ant species were collected using hand and bait traps. The diversity of trees in the orchards and cashew tree density were also determined. Twenty ant species were collected among which the most abundant were Pheidole spp., Lepisiota sp., Paratrechina longicornis, Camponotus sericeus, Brachyponera sennaarensis, Camponotus spp., and Oecophylla longinoda. Tree diversity and cashew tree density in those orchards had significantly positive effects on the ant densities but not on ant diversity. Structural equation modeling showed that the abundance of ants increased the diversity of ants, which decreased the herbivory index. Based on the important role of ants as biological pest control agents, it is worth promoting agroforestry systems in cashew orchards to increase ant abundance, thereby improving their productivity.