Anthropogenic habitat degradation can facilitate the formation of novel mutualisms between ants and sap-sucking insects in the order Hemiptera. The detrimental effects of these mutualisms such as hemipteran infestation and decreased native insect diversity are well known in agricultural systems but remain relatively unexplored in disturbed areas undergoing succession. I investigated a mutualism between a native but disturbance-adapted ant and a scale insect previously unknown to the country in 15-year-old restored forests in southern Costa Rica. Specifically, I used a 3-month long ant-exclusion experiment to investigate whether ants provide protection to scale insects leading to increased scale abundance and decreased scale mortality. I also examined whether such effects are mediated by the amount of remnant forest cover in the landscape.
Results/Conclusions
Treatments that excluded ants had significantly fewer scale insects than treatments with ants allowed. Scale mortality due to fungal/parasitoid attack was also significantly higher in ant-excluded vs. ant-allowed treatments but only at sites with high surrounding landscape forest cover. Together, these results suggest that disturbance-induced ant-hemipteran mutualisms can facilitate hemipteran infestation in early-successional forests and effectively disrupt biological control of hemipterans. Further, my experiment underscores the importance of remnant tropical forests as sources of biological control in anthropogenically-disturbed landscapes.