DiscussionSince the advent of molecular data, studies examining genetic variation within parasite species and populations have gathered little attention. Only recently, understanding how parasite species are subdivided has extended outside the medically or veterinary relevant species allowing a wide comparative approach. These new model systems provide a unique opportunity to test how general predictions borrowed from population genetics theory of free-living organisms apply to a broad range of parasite species. Furthermore, disentangling the contribution of multiple variables unique to the diversity of life histories of parasitic species may widen the knowledge and generality of the theoretical principles. In this talk I will first review and summarise the current state of the field. Then, I will present new comparative data from different parasite-host systems examining the role of several life history and environmental variables in structuring genetic diversity of parasite species. I will discuss our results and future research venues in the light of the new opportunities arising from genomic approaches.