Size Ratios and Artifacts: Hutchinson's Rule Revisited

We show that size ratios within the range predicted by Hutchinson's rule invariably result, given only that animal sizes are distributed lognormally and that the variances of these distributions are small. We argue that both these conditions are properties of a wide variety of animate and inanimate objects in nature, and therefore size ratios tell us little about the processes structuring animal communities. Our results confirm previous suggestions that Hutchinson's constant is an artifact, and we present a reasonable mechanism to suggest how such an artifact might arise.