Résumé
The importance of mutualistic symbioses is increasingly recognized in plant responses to herbivory as well as in plant-mediated interactions. It is well established that beneficial microbes such as mycorrhizal fungi and plant growth-promoting bacteria can play a role in plant responses to herbivory. Symbionts associated with herbivorous insects are also known to affect the way the herbivore interacts with its food plant by manipulating plantphysiology for the benefits of their herbivore hosts. However the role of insect-associated symbionts has received less attention in a multi-trophic perspective. Here, we will address the effects of symbionts associated with insects at different positions in the community structure. Using as model system a cabbage-based food-web system, we show that insect-associated symbionts induce phenotypic changes in the plant, with consequences for other insect community members. We argue that insect-associated symbionts can play an important role in plant-mediated interactions highlighting a fascinating complexity of terrestrial-ecological networks.