Chemical camouflage: a key process in shaping an ant-treehopper and fig-fig wasp mutualistic network

Bo Wang,Min Lu,James M Cook,Derek W Dunn,Da-Rong Yang,Rui-Wu Wang

doi:10.1038/s41598-018-20310-7

Abstract

Different types of mutualisms may interact, co-evolve and form complex networks of interdependences, but how species interact in networks of a mutualistic community and maintain its stability remains unclear. In a mutualistic network between treehoppers-weaver ants and fig-pollinating wasps, we found that the cuticular hydrocarbons of the treehoppers are more similar to the surface chemical profiles of fig inflorescence branches (FIB) than the cuticular hydrocarbons of the fig wasps. Behavioral assays showed that the cuticular hydrocarbons from both treehoppers and FIBs reduce the propensity of weaver ants to attack treehoppers even in the absence of honeydew rewards, suggesting that chemical camouflage helps enforce the mutualism between weaver ants and treehoppers. High levels of weaver ant and treehopper abundances help maintain the dominance of pollinating fig wasps in the fig wasp community and also increase fig seed production, as a result of discriminative predation and disturbance by weaver ants of ovipositing non-pollinating fig wasps (NPFWs). Ants therefore help preserve this fig-pollinating wasp mutualism from over exploitation by NPFWs. Our results imply that in this mutualistic network chemical camouflage plays a decisive role in regulating the behavior of a key species and indirectly shaping the architecture of complex arthropod-plant interactions.

Highlights

Mutualism is a common and widespread ecological interaction[1]
The cuticular hydrocarbons of Tricentrus and the surface chemical profile of F. racemosa inflorescence branches were most similar, with the most similar profile being the cuticular chemicals of C. fusciceps
Our results show that the cuticular hydrocarbons of treehoppers on one hand attract mutualistic weaver ants, but on the other hand help protect the treehoppers from ant predation even in the absence of honeydew rewards

Summary

Introduction

Mutualism is a common and widespread ecological interaction[1]. The partner species of a single mutualism often interact with other community members to form a complex interacting network, which is regarded as the ‘architecture of biodiversity’[2,3]. When alternative food resources are limited, the ants themselves may prey upon their hemipteran partners[12], which suggests that the benefits associated with honeydew are not always enough to maintain the mutualism. Chemical signals and their perception are important in ant foraging and inter/intra specific recognition, and have been frequently reported to reduce ant aggression and contribute to mutualism stability[13,14,15]. The aggressive, predatory behavior of O. smaragdina towards some NPFWs differs from that often directed at honeydew producing hemipterans, which concurs with the classical food-for-protection ant-hemipteran model (Digital appendices 1 and 2)

Methods

Results

Conclusion