Pest suppression by ant biodiversity is modified by pest biodiversity

Abstract

Agroecosystems are often complex ecosystems with diverse food webs. Changes in food web complexity may have important context-dependent consequences for pest control strategies. The success of predator introductions to suppress pests may depend on the diversity of pests. For crops with diverse pest assemblages, it is hypothesized that diverse predator communities are needed to suppress diverse pest assemblages below damaging levels. In this study, we compare the ability of ant predator monocultures and polycultures to suppress single- and diverse- (three species) pest assemblages in a coffee foodweb. We use a factorial experiment that compared treatments of predator and pest diversity to understand the impact of pest diversity on multiple predator effects. We show that predator polycultures enhanced pest risk relative to predator monocultures significantly more in the diverse-pest treatment relative to in the single-pest treatments for two of three pest species. Further, we show that pest diversity significantly reduced pest risk in all predator treatments except for the predator polyculture treatment. These results suggest that pest diversity may reduce the efficiency of single predator species at suppressing pest damage, but do not limit multiple predator species. This in turn leads to stronger effects of predator diversity with greater pest diversity. These results highlight the need to consider foodweb complexity, such as pest diversity, when designing and implementing biology control programs.

The ecosystem services provided by social insects: traits, management tools and knowledge gaps

“…Finally, it has been shown that several ESs provided by social insects are enhanced by higher biodiversity. For example, the biological control service provided by ants depends on the number of species both of pests and ant predators (Philpott, Pardee & Gonthier, 2012; Wielgoss et al ., 2014; Gonthier, Kuesel & Perfecto, 2015). While species richness does not necessarily affect the diversity of ESs performed by social insects, it can increase ES magnitude, stability, and resilience to future disturbances (Houadria et al ., 2016; Arnan, Molowny‐Horas & Blüthgen, 2019).…”

“…While species richness does not necessarily affect the diversity of ESs performed by social insects, it can increase ES magnitude, stability, and resilience to future disturbances (Houadria et al ., 2016; Arnan, Molowny‐Horas & Blüthgen, 2019). In an artificial predator community with three ant species, pest suppression was higher than in a community with only one predator ant species; additionally, pest diversity reduced the efficiency of a single predator species at suppressing pest damage but did not limit multiple‐predator communities (Gonthier, Kuesel & Perfecto, 2015). Ants reduced damage caused by coffee pests in landscapes with high forest cover within a 2 km radius, where biodiversity is higher (Aristizábal & Metzger, 2019).…”