Relationship Between Cnidarian Morphological Attributes and the Structure of the Associated Amphipoda Assemblage in South Atlantic Reefs

Three-dimensional species, such as some cnidarians, act as habitat formers, providing physical structures and biological activities that favor epibiosis and result in increased local diversity. In general, basibiont (=substrate organism) complexity influences the diversity of epibionts, but little is known about the role of its morphological attributes in shaping the associated community. Thus, we evaluated the role of 10 morphological attributes of cnidarian basibionts in the taxonomic and trophic structure of the associated Amphipoda community on tropical reefs. The results show that the morphological attributes of basibionts played an important role in structuring the associated amphipod community, but their effects varied among the taxonomic and functional components of the assemblage. Abundance and species composition were influenced by the type of basibiont, but without significant differences in other diversity descriptors, indicating a pattern of species turnover. On the other hand, trophic structure showed more consistent differences among basibionts and was better explained by morphological attributes, especially those related to size and complexity, suggesting that habitat architecture acts more strongly as a functional filter than a taxonomic one. Thus, the coexistence of multiple basibionts may increase regional amphipod diversity by expanding the availability of niches.