Reproductive biology of the narrow endemic Anchusa littorea Moris (Boraginaceae), an endangered coastal Mediterranean plant

Phenological and reproductive patterns are fundamental life-history components in the life cycle of plants. In this study, we analyzed phenological and reproductive data at the plant and population levels of the narrow endemic Anchusa littorea Moris, an endangered annual plant species growing in a few small patches at the Is Arenas dune system (SW Sardinia, Italy). Individuals from the main 2 patches were evaluated during a 4-year study period: plants were monitored on a monthly basis in each reproductive phenophase. To assess phenological variability within and among populations, an approach based on the Shannon–Wiener diversity index and the Morisita–Horn similarity index was applied. The seed output and the soil seed bank were also investigated in order to analyze the reproductive capacity of this plant species. Anchusa littorea showed a long flowering season and a high flowering synchrony between patches, which contrasted with a low within-patch synchrony. The seed production per plant was low and the species did not create a soil seed bank. Population size was characterized by considerable annual fluctuations: a significant migration occurred for A. littorea plants inside the dune system over the years. These results demonstrate the importance of the phenological pattern on the knowledge of the reproductive ecology of endangered coastal plant species and will contribute to orient management and conservation efforts.