Human activities and global changes are increasingly impacting biodiversity and the functioning of ecosystems. The ability of ecologists to determine how threatened communities and ecosystems will respond to these changes is crucial for conservation management and the setting of European environmental policy. Yet, our ability to determine how ecosystems may respond to such changes is limited, despite ecologists frequently being requested to provide policy makers with predictions. The aim of the project is to understand how non-random alteration of biodiversity by perturbations may affect ecosystem functioning, using invasive top-predatory fish as a non-random perturbation. Given their crucial role in food-webs and their high economical and social value, they are excellent candidates to investigate this question. The specific objectives are to use individual-based modelling to investigate some hypotheses related to biodiversity and ecosystem functioning and generate empirically testable predictions. After testing these predictions, the model will used to determine the consequences of scenarios of biological invasions. To achieve these objectives, model simulations, field investigations and experimentations in small lakes will be conducted. Data collection will be based on an innovative approach utilising state-of-the-art techniques (individual tagging, telemetry and stable isotope analyses). To maximize the opportunity for successful completion, the Fellowship will be nested within, and will receive complementary skills from the host organization, Universite Paul Sabatier (Toulouse, France). Using skills acquired during the previous Marie Curie fellowship and continuing collaboration with the previous host institution (Bournemouth University, UK), completion of the fellowship will facilitate knowledge transfer across the EU and develop the fellow into a world-class, European-based researcher while complementing European priority research areas.