The burgeoning energy demand worldwide has led to a proliferation of hydroelectric dams, firstly in the northern hemisphere and subsequently across tropical developing countries, which have become the new hydropower frontiers. Currently, hydropower development is already one of the primary means of habitat loss and fragmentation in tropical forests, hence a key threat to biodiversity and the ecosystem services provided to the entire humanity. After damming, all low elevation areas are inundated, while previous ridgetops in undulating terrain often become islands. The objective of this Marie-Skłodowska-Curie Action is to dissect the ecological impacts of habitat insularization induced by hydroelectric dams on ecosystem functioning, by comprehensively assessing species interactions across 35 forest islands and three mainland continuous forest sites across one of the largest hydroelectric reservoirs in South America. Firstly, specific prey-predator interactions – herbivory, insectivory and seed predation – will be quantified in situ and related to patch, landscape and habitat-quality metrics. Then, species interactions across terrestrial food webs will be evaluated using theoretical approaches based on species co-occurrence and codispersion analysis. To do so, the Experienced Researcher will use data previously collected by the host research group on vertebrate, invertebrate and plant species, and apply novel framework approaches based on mutualistic and antagonistic networks, some of them developed by the collaborator group. The innovative knowledge to be produced is expected to considerably improve strategic environmental impact assessments of planned hydroelectric dams and manage existing and future hydropower development. Moreover, while collaborating with very-high profile researchers, this Action will allow the Experienced Researcher to acquire new sophisticated analytical skills on species interactions and foodweb-related processes.