Contents

23 November 1990
Vol 250, Issue 4984

About The Cover

The rocky intertidal zone of central Chile during a spring low tide showing zonation pattern and dominant sessile invertebrates (Perumytilus purpuratus and chthamaloid barnacles) and algae (Lessonia nigrescens and lithothamnioids). In this zone, communities of invertebrates are heavily modified by human predation on ecologically critical organisms, affecting dominance, population densities, and the network of species interactions. In spite of the dramatic changes produced by human intervention, the relation between body size of invertebrates and their population density remained unchanged. See page 1125. [Photograph by A. Larrea, Santiago, Chile]