Assuaging nutritional complexity: a geometrical approach

We have introduced a framework that enables the identification of the impor tant elements in complex nutritional systems, and the quantification of the interactions among them. These interactions include those among the multip le constituents of the ingesta, as well as between behavioural (ingestive) and physiological (post-ingestive) components of nutritional homeostasis. T he resulting descriptions provide a powerful means to generate and test hyp otheses concerning the mechanisms, ecology and evolution of nutritional sys tems. We provide an overview of the key concepts involved in our scheme, an d then introduce four examples in which the framework is used to develop an d test hypotheses. In the first example we use comparative methods based on a data set of 117 insect species to test a prediction about the relationsh ip between evolving an association with bacterial endosymbionts and the com position of the optimal diet. Second, using two species of locusts (a grass specialist and a generalist), we consider the relationship between an anim al's diet breadth and the decision rules employed when feeding on foods con taining suboptimal protein :carbohydrate values. Third, we introduce a math ematical model that predicts the dose-response properties of gustatory syst ems in the context of nutritional homeostasis. Finally, we consider the int eraction between tannic acid and macronutrient balance in the diet of locus ts.