Experimental ecology of rocky intertidal habitats: what are we learning?

Experimental analyses of causes of patterns of distribution and abundance o f intertidal animals and plants on rocky shores have been a major activity for many years. In this review, some of the themes and topics that have eme rged from such analyses are briefly discussed to provide an up-date for pra ctitioners and ecologists working in other habitats. Conceptual issues incl ude the widespread occurrence of transphyletic use of the same resources (s pace and food), theories and experimental analyses of intermediate disturba nce in relation to numbers of species, the complex but pervasive nature of indirect interactions among species, relative importance of 'top-down' vers us 'bottom-up' control of assemblages and the importance to rocky intertida l species of 'supply-side' influences on densities and interactions. Method ological advances include experimental designs for complex and patchy, inte racting sets of species, the importance of controls in experimental manipul ations and methods for analyses of hierarchical scales of patterns and proc esses. Finally, some contributions to social issues (pollution, biodiversit y) and some scenarios for future directions are briefly considered. (C) 200 0 Elsevier Science B.V. All rights reserved.