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Species Number, Population Density and Body Size Relationships in Natural Communities
Tim M. Blackburn, Paul H. Harvey and Mark D. Pagel
Journal of Animal Ecology
Vol. 59, No. 1 (Feb., 1990), pp. 335-345
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/5176
Page Count: 11
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(1) Population densities reported in the literature for a large range of species drawn from different communities typically decrease with increased body size. However, representative samples from feeding guilds within natural communities of both birds and beetles indicate that the highest population densities tend to be recorded from species of intermediate size. The large population densities recorded for some intermediate-sized species, but not small or large-sized species, may be a sampling effect resulting from there being more intermediate-sized species in the communities. (2) Three statistical tests show that, within four guilds of Bornean beetles and two guilds of North American birds, even though the highest population densities are found among species of intermediate size, the average population density and the variance of population densities is broadly similar for species in different size classes. (3) A simulation study showed the shape of the three-dimensional surface formed from the relationships among number of species, population density, and body size for the null distribution within each guild. In most but not all guilds, the shape of the species-density (or species-abundance) curve is broadly similar for each of the size classes. There may be no detectable relationship between body size and population density within many animal communities. (4) Before concluding that a particular community shows a relationship between density and body size, it should be tested against an appropriate null sampling model.
Journal of Animal Ecology © 1990 British Ecological Society