Organismal Performance and Darwinian Fitness: Approaches and Interpretations

Abstract

Organismal performance lies at the base of ecological and evolutionary processes, and the consequences of individual variation in performance have become a focus of physiological ecology. The study of the relations of performance to Darwinian fitness integrates the traditionally reductionist approach of physiological ecology with the perspectives of genetics and evolution. Four levels of biological organization have been included in this effort: the description of genetic variation, the analysis of biochemical and physiological consequences of that variation, the description of variation in the capacity of individuals to perform various activities, and the analysis of the effect of that variation in performance capacity on individual variation in Darwinian fitness. Mechanisms within each of those levels have been elaborated, and cause-and-effect links have been established among the levels. Two approaches to defining causal links are prominent. The gene-to-performance school begins with the observation of...