Many factors have contributed to the richness of narrow endemics in the Mediterranean, including long-lasting human impact on pristine landscapes. The abandonment of traditional land-use practices is causing forest recovery throughout the Mediterranean mountains, by increasing reduction and fragmentation of open habitats. We investigated the population genetic structure and habitat dynamics of Plantago brutia Ten., a narrow endemic in mountain pastures of S Italy. Some plants were cultivated in the botanical garden to explore the species’ breeding system. Genetic diversity was evaluated based on inter-simple sequence repeat (ISSR) polymorphisms in 150 individuals from most of known stands. Recent dynamics in the species habitat were checked over a 14-year period. Flower phenology, stigma receptivity and experimental pollinations revealed protogyny and self-incompatibility. With the exception of very small and isolated populations, high genetic diversity was found at the species and population level. amova revealed weak differentiation among populations, and the Mantel test suggested absence of isolation-by-distance. Multivariate analysis of population and genetic data distinguished the populations based on genetic richness, size and isolation. Landscape analyses confirmed recent reduction and isolation of potentially suitable habitats. Low selfing, recent isolation and probable seed exchange may have preserved P. brutia populations from higher loss of genetic diversity. Nonetheless, data related to very small populations suggest that this species may suffer further fragmentation and isolation. To preserve most of the species’ genetic richness, future management efforts should consider the large and isolated populations recognised in our analyses.