One of the main challenges the conservation biology faces is the preservation of biodiversity. This is, the set of variations of life forms that inhabit the Earth. Its cataloging is a huge task with advances that unfortunately lag behind in regards to the current loss of biodiversity. Normally we understand biodiversity as the set of species, but we could also speak about the diversity of the genetic pool found in them, the different populations that compose the species. In this conference I want to summarize some of the main advances that have taken place in conservation ecology and biology after incorporating genetic techniques coming from other scientific fields like molecular biology. I will review in particular four case studies: 1) the applications in conservation of the evolutionary story of biological groups (phylogenies); 2) the complexity of the genetic structure between and within different species (the trees of the Iberian Peninsula); 3) the analysis of the complex long-distance dispersion processes in patched environments, and 4) the diagnose of the situation of highly endangered species (Iberian lynx, bearded vulture, imperial eagle).