Amphipods are key organisms in aquatic communities. They exhibit essential roles in ecosystem functioning (e.g., leaf litter degradation) or as fish food, and are among the most successful invasive invertebrates. At the same time, they are commonly used as indicator taxa for biomonitoring and ecotoxicology. While their immense significance is generally recognized, there is a large discrepancy with respect to available knowledge: there exist no checklist, distribution maps, or broad-scale estimates on genetic, functional and morphological diversity of the estimated 30 to 40 amphipod species in Switzerland. In the project Amphipod.CH we collect data on the distribution and genetic structure of all amphipod species in Switzerland, by compiling all available literature data, identifying amphipods from monitoring projects and doing extensive fieldwork ourselves. As a first goal, we want to publish a checklist, distribution maps and identification keys of all amphipod species in Switzerland. In a second step, we want to use this database, including extensive genetic data, to analyse how amphipod diversity is shaped by the network structure of rivers. We are especially interested in studying community dynamics and community assembly of native versus non-native species. Thereby, we extrapolate our findings on dendritic networks from theoretical models and laboratory microcosms to „the real world“.