Drussey

Allometric Engineering

The process of experimentally breaking the tight covariance evident among component traits of a complex phenotype by altering variance of a trait relative to another, typically body size. Manipulations of this sort alter the scaling relationships either by shifting intercept, slope or both creating novel phenotypic variants. These novel variants can then be tested for differences in performance or fitness. Through careful testing, one could sequentially test each component of a trait suite to determine how each part contributes to the fitness of the entire complex phenotype. This technique allows for comparison within or among biological groups which differ in size by adjusting morphology to match one another and comparing their performances.

Application

Allometric engineering has been used to test Lack's hypothesis in the lizard Sceloporus occidentalis. In this study, two populations of the lizard differed in overall body size and also land speed. Smaller souther lizards were faster than their northern relatives, but once each group was "engineered" to fit morphology of the other, it was found that speed was inversely proportional to body size, but the southern population did exhibit higher stamina.

Methods

Current uses have involved truncation or cropping, yolk manipulation, temperature manipulation, or altering nutrition. Each method undoubtedly has its merits and problems to consider before designing an experiment.