"Gene flow among populations maintains the integrity of a species across its geographical range. To a large extent, gene flow depends on the mobility or dispersal abilities of a species, as well as on landscape features such as the presence of barriers to dispersal. For parasitic organisms, gene flow and the extent of genetic structure among populations are crucial for several key evolutionary processes, ranging from local adaptation to speciation. However, our understanding of genetic structuring in parasitic species is very limited, in particular with respect to the influence of life-cycle characteristics and transmission routes. This project addresses the application of a novel comparative molecular approach at different evolutionary, ecological and spatial scales to assess the effects of key life history variables, host and habitat characteristics on patterns of genetic structuring of parasite populations, using two species complexes of trematode parasites as model systems. The project will first investigate the processes acting on microevolutionary scales to generate variability among populations of parasites (outgoing phase), before turning to their consequences at the macroevolutionary scale and the evolution of different patterns of host use between related parasite species (return phase). The novelty of the proposed research lies in trans-disciplinary approach linking advanced ecology and molecular epidemiology concepts with population genetics and evolution. Key novel aspect of the methodology is the application of a comparative approach across multiple populations and species by contrasting a range of life history, transmission and co-existence strategies as well as genetic markers which reveal both mitochondrial and nuclear DNA variability. The successful implementation of the project will result in a substantial transfer of expertise from a world centre leading in molecular parasitology to the applicant and her team at the return European institute."