Evolutionary radiations of colonists on archipelagos provide valuable insight into the mechanisms and modes of speciation. Using both morphological and molecular genetic techniques this study will examine the coevolutionary history of multiple ectoparasite lineages parasitizing the endemic mockingbirds of the Galapagos. Using 3000+ samples collected by a recent EU funded project this study will compare and contrast the genetic structure of mockingbird ectoparasites at six different scales (between and within host species, islands, and parasite groups) for the parasitic lice and mites infecting mockingbirds on the 16 islands of the Galapagos. Each widespread parasite lineage forms an ecological replicate to test the relative contributions of host diversification and geography to patterns of parasite genetic differentiation and speciation. This system provides a framework to understand the correlates of parasite diversification, their mode of speciation and the evolution of host specialization. These data will make an important contribution to our understanding of how louse-vectored diseases may be spread, and help inform conservation plans due to the higher rates of genetic evolution in parasite groups, relative to their avian hosts. The region is a UNESCO World Heritage Site and Biosphere Reserve, and the host group played a now famous role in triggering Charles Darwin’s initial insights into natural selection. Key outputs include a genetic study of the parasite lineages, biogeographic and coevolutionary analyses of the host-parasite relationships, and a database of host-parasite associations, images, and related data. These will be collated on a project website using an EU funded EDIT “Scratchpad”. Interdisciplinary training in molecular and morphological systematics and biodiversity informatics will be provided by the project coordinator, coupled with a structured postdoctoral course run by the host institution to develop the applicant’s transferable skills.