Figure 1. Summary of the four scenarios tested in this study, which differ on how the colonization of the swash zone affects taxonomic and functional diversity. A. In scenario 1, the conditions of the swash level select for a subset of the species that live in the shoaling and subtidal levels, with differences in species composition across beach levels explained by differences in species richness.B. In scenario 2, this subset of species found in the swash level is not random, but depends on the presence of specific traits.C. In scenario 3, if species respond differently to the conditions in the swash level according to their traits, differences in diversity across beach levels will be mostly explained by species functional traits, for example with a higher proportion of adhesive and burrowing species found in the swash level. D. Scenario 4, is neutral and not functional nor taxonomic diversity is affected by the conditions in the swash zone. The silhouettes in the central part represent the potential species pool; the silhouettes in each level represent their actual occurrence, with repeated silhouettes in one level representing different species within the same genus.