Chemical camouflage and trophic cascade are important processes in maintaining a mutualistic network

Background/Question/Methods  Different types of mutualisms may interact, co-evolve and form complex networks of interdependences. What mechanisms maintaining the structure of networks of a mutualistic community remains unclear. Based on chemical analysis, behavior assay and field experiments.

Results/Conclusions 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 and weaver ants in a mutualistic network between treehoppers-weaver ants and fig-pollinating 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 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 the weaver ants-the key species in the fig trees. Weaver ants indirectly beneficial for pollinating fig wasps and fig tree, because ant predation causes cascading effects on NPFWs and fig seed production. We suggest that chemical camouflage and trophic cascade are essential mechanisms in shaping the architecture and maintaining stable of the complex mutualistic network.