Black poplar (Populus nigra L.) is among the tree species having the largest natural distribution in Europe, from West Great Britain to West Asia, and from the foot of the Ural Mountains to the North of Africa. Thus, this species is potentially subjected to a wide variation of climatic conditions. Previous studies on variability of traits in this species showed structure and different distribution patterns depending on the trait, demonstrating potential local adaptation. In the last decade, we have developed molecular tools to study the factors shaping the diversity of the species. Today, these tools allow us to detect patterns of selection along the genome, to identify polymorphism involved in adaptative traits, to model demographic history of the species, and to evaluate how gene flow impact structure of populations. These molecular tools and results constitute the toolbox for breeding and conservation programs of black poplar.