The primary goal of computational molecular biology, like molecular biology itself, is to understand the meaning of the genomic information and how this information is expressed. Molecular systematics makes phylogenetic inferences from molecular data using computacional methods. The systematics of Silene section Siphonomorpha Otth was approached from three different perspectives, the first analysing global relationships within the section, the second studying two pairs of taxa with problematic species boundaries, and the third using one of the species to study rarity at ecological and genetic level.