1. The influence of common mycorrhizal fungal networks (CMNs) on their components—namely the plants and the linking fungal genet—has been studied for decades and is under constant debate. Besides new research evidence on mechanisms and functionality of CMNs, the actual ecological importance of effects mediated by CMNs on the plant and fungal components is still understudied. 2. Here, we conducted a meta-analysis focusing on arbuscular mycorrhizal (AM) fungi as linking genets and evaluated the magnitude of effects mediated by CMNs on plant and fungal parameters. 3. We found neutral or inconsistent effects for the tested plant and fungal parameters. The detected effects were small. The wide range of positive to negative CMN effects in our database indicates strong context dependence. In combination with data limitations for the different tested parameters, any attempts at general inferences must be done very carefully. 4. Given the widespread lack of significant responses, it is very difficult to derive well-supported conclusions about the meaning of the CMN for the biology of the fungi and the plants and the general ecological significance of the CMN. Thus, we call for a renewed research effort to strengthen the evidence base for effects mediated by CMNs on plant and fungal parameters. We recommend exercising caution when communicating to the public about effects mediated by CMNs formed by AM fungi.
