The evolutionary ecology of body size with special reference to allometry and survivorship

Of all characteristics of animals, body size most crucially relates to the overall integration of other features. Knowing only the mature mass of a species allows fairly accurate prediction of the majority of other important functional features and life history traits. These include aspects like metabolic rates, longevities, time to mature, proportional sizes of tissues like brain and fat, fecundity, gestation time, population growth rates... and a host of others spanning molecular to community levels of organization. This represents the science of allometry. Although allometry powerfully describes the integration of features associated with size, it says virtually nothing about why species evolve to particular sizes. Remarkably, besides predicting longevity, body size also predicts both extrinsic and intrinsic mortality rates. This chapter melds allometry to the two crucial dimensions governing life history evolution (allocation and risk). This yields a synthetic theory that spans both the integrative ramifications and evolution of body size. This framework yields quantitative descriptions of organismal integration and links aspects of fitness to body size to explain body size evolution. © 2007 by Nova Science Publishers, Inc. All rights reserved.