Interactions between plants and insects are critical components of natural ecosystems via their influence in structuring communities and their role in providing important ecosystem services. Plant-insect interactions also link belowground processes (e.g. biogeochemistry, nutrient cycling, microbial associations) with aboveground ecosystem dynamics including resistance or susceptibility to pests and pathogens. Plant secondary metabolites play a dominant role in mediating species interactions across trophic levels, but are sensitive to human-caused global change factors including increased temperature, CO2, ozone, nitrogen inputs, land-use change, and biological invasions. In turn, changes in plant chemical composition are expected to have cascading effects on above and belowground species interactions with consequences for ecosystem structure and function. Despite the amount of information that exists on factors contributing to global change, we know relatively little in terms of how these changes influence plant secondary chemistry. Even less is known regarding the subsequent effects on herbivory, pathogens, mutualisms, and consequences for ecosystem services. Thus, there is a pressing need to further our understanding of global change on plant-insect interactions with an eye towards elucidating the underlying mechanisms driving these relationships, namely via altered phytochemistry. To provide useful data for vegetation and risk assessment models, it is necessary to broaden our research scope to include more species, systems, secondary metabolites, and global change drivers. In light of this effort, the goal of this session is to bring together ecologists working in diverse systems to offer a well-rounded and contemporary perspective on the ways in which different mechanisms driving species interactions are responding to global change while simultaneously forging new directions through a dynamic exchange of ecological ideas. Speakers in this session will present original work within theoretical ecological frameworks to highlight recent advances in research investigating the chemical mediation of species interactions and ecosystem services.