The Amazon River harbors the largest biodiversity of freshwater fish in the world. What is the origin of this abundance of species? Researchers at the University of Geneva (UNIGE), Switzerland, have integrated a range of potential factors into a single statistical model to study the genesis of genetic diversity within a typical species, the Amazonian sardine. Published in the journal PLOS ONE, their study describes the contribution of each factor and the synergies at work. This approach, which can easily be used for any species, could be integrated into the study of the impact of various planned projects, such as the creation of new dams on the Amazon, as well as any human large-scale alteration in various ecosystems.