Seed dispersal is a key determinant of species distribution, although it is still unclear how it contributes to species assembly in plant communities. We linked patterns of seed dispersal to coexisting species to investigate the role of dispersal in the species assembly process. We focused on 19 species coexisting in a foredune plant community, classified as “foredune foundation species”, “semi-fixed dune species,” and “alien species”. The number of seeds dispersed by the 19 species was monitored monthly in 25 plots for 12 months. Then we compared both dispersal strategies and dispersal phenology among the species. Foredune foundation species, species of the semi-fixed dune, and alien species used the same dispersal strategies, with the exception of hemerochory, which was prevalently used by alien species. The three groups of species differentiated the dispersal season: semi-fixed dune species and alien species were early and late dispersers, respectively (spring vs. late summer), while foredune foundation species dispersed seeds in summer. Seasonal differentiation in seed dispersal may play a more important role in the species assembly process than dispersal vectors. Shifts in seasonality due to climate change may influence the timing of seed dispersal and provide species with different colonization opportunities.