Biodiversity may enhance productivity either because diverse communities more often contain productive species (selection effects) or because they show greater complementarity in resource use. Our understanding of how these effects influence community production comes almost entirely from studies of plants. To test whether previous results apply to higher trophic levels, we first used simulatio...

Simple ecosystems in the northern Pacific Ocean are particularly suitable to test the hypothesis. In 1970’s, communities at islands lacking sea otters were characterized by high density of sea urchins and a distinct lack of macrophytic vegetation.. In contrast, communities at islands with sea otters had relatively high kelp densities and low sea urchin biomass (Estes and Palsamino 1974). Howeve...