POPULATION ABUNDANCE AND BODY-SIZE IN ANIMAL ASSEMBLAGES

Studies of the relationship between body mass and population abundance for terrestrial and aquatic animal species based on pooling data from many taxa and assemblages suggest that abundance scales with mass to the -0.75 power. Because metabolic rate scales with mass as (plus) 0.7 5, this result has been taken as evidence that all species in assembla ges use equal amounts of energy. The evidence for 'energetic equivalen ce' is, however, equivocal, because within many individual assemblages the scaling of abundance on mass differs significantly from -0.75. He re, we present a summary of patterns of size and abundance in a number of different terrestrial, freshwater and marine animal assemblages, w ith the aim of discovering whether there is any generality in size-abu ndance patterns within assemblages, and whether any generality might h old across terrestrial, freshwater and marine environments.