Niche-assembly vs. dispersal-assembly rules in coastal fish metacommunities: implications for management of biodiversity in brackish lagoons

1. Biodiversity is rapidly being lost in a world transformed increasingly by human activities. We need to determine urgently the factors which control the coexistence of species and thus allow local biodiversity to be maintained. 2. Coexistence between interacting species can be explained by species-sorting, mass-effect, patch dynamic and neutral perspectives on metacommunities. According to the first two paradigms, community assembly rules are based on species' ecological niches or functional roles, whereas the latter two emphasize the role of stochastic processes. 3. Here I consider whether effective strategies for managing fish biodiversity in coastal lagoons depend on the predominant paradigm. 4. The neutral perspective was not considered relevant because lagoon fishes belong to different trophic levels and have clear niche differences. 5. Where fish coexistence is ruled by species-sorting, priority must be given to the preservation or restoration of habitat, whereas heterogeneity among lagoons and population densities become critical when mass effects predominate. 6. According to the patch dynamics perspective, the key factors are individual turn-over and the fitness equivalence among species. 7. Synthesis and applications. Coastal fish metacommunities are not ruled consistently by a single theoretical paradigm. However, consideration of such extreme cases sets clear boundaries for species assembly rules. Confronting the three main views is not only a controversial topic, but also has consequences for ecosystem and biodiversity management.