MEPS 325:93-100 (2006)  -  doi:10.3354/meps325093

ABSTRACT: Habitat complexity plays an important role in the structuring of ecological assemblages in many terrestrial, freshwater and marine habitats. In this study, we investigated the effects of increased habitat complexity on the diversity and abundance of macrofauna colonising artificial kelp holdfasts of 3 varying levels of complexity. The artificial holdfasts were placed within a kelp bed off the coast of Plymouth for 20 d during the summer of 2004. High complexity holdfast mimics were colonised by significantly higher numbers of individuals and species, and had higher species diversity (Shannon-Wiener H’e), than either the medium or low complexity holdfasts. The relationship between habitat complexity and species diversity has often been attributed to a surface area effect, as habitats with a greater complexity generally also have a greater surface area to support a larger number of species. Therefore, we compared the observed community metrics with the values expected if indices were increasing in proportion to the surface area. We found that the number of species and individuals colonising both the medium and high complexity artificial kelp holdfasts were significantly greater than can be explained by a simple surface area relationship. Species diversity increased less rapidly than expected from the surface area relationship, largely because of a dominance effect from a few abundant species of amphipods and gastropods in the high complexity holdfasts. This study demonstrates that the relationship between habitat complexity and species diversity cannot be explained by surface area alone.

KEY WORDS: Habitat complexity · Artificial habitats · Kelp holdfasts · Macrofauna · Colonisation