Services and Disservices of Ant Communities in Tropical Cacao and Coffee Agroforestry Systems

Abstract

Tropical tree crops such as cacao and coffee are produced around the tropics in diverse, multistrata agroforests as well as monoculture plantations Box 16.1 and references therein). The smallholders cultivating these systems battle pests and diseases that differ regionally and change over time, but often take a significant part of their yield, and therefore their revenue. In these perennial systems, ants are tremendously diverse and abundant, and affect pests and diseases directly as well as indirectly. Management by farmers of particular ant species to control insect pests has a long history (Offenberg, 2015). It is not until recently that the effects of ants on yields have been quantified. The complex interactions through which ants affect the crop plants, and how their mediation by species- and community-level characteristics, are starting to be better understood. The extent of the impact ants have on yields and revenue justifies the anthropocentric framing of the outcome of these interactions in terms of ecosystem services and disservices. In this chapter we present the current state of knowledge on agroforest ant communities, economically relevant ecological interactions driven by these communities and the way landscape-scale land-use change and climate change can be expected to influence ants and ant effects on insect communities and yields. Finally, we discuss how farmers may adapt their management to support ant-mediated ecosystem services and minimize potential disservices. We refer to Del Toro et al. (2012) and Choate and Drummond (2011) for more broad reviews of the role of ants in agriculture, as providers of biological control and other ecosystem services and disservices. Taxonomically and Functionally Rich Ant Communities. Ant surveys from cacao and coffee systems from throughout the range of these crops show a very high species richness that in most cases is comparable to that found in undisturbed forests (Table 16.1). Agroforests harbor arboreal and ground-dwelling ants. This includes species that nest in the canopy and trunk of the trees (dead wood, hollow twigs, foliage, sometimes with carton/silk/dirt nesting structures), in the herb layer, in the litter layer, on open ground, in epiphytic and parasitic plants, dead wood debris and other plant residues, such as dry cacao pods on the ground or on the tree (Room, 1971; De la Mora et al., 2013; Castaño-Meneses et al., 2015).