Experimental evolution and its role in evolutionary physiology

SYNOPSIS. Four general approaches to the study of evolutionary physiology—phy-logenetically-based comparisons, genetic analyses and manipulations, phenotypic plasticity and manipulation, and selection studies—are outlined and discussed. We provide an example of the latter, the application of laboratory selection experi-ments to the study of a general issue in environmental adaptation, differences in adaptive patterns of generalists and specialists. A clone of the bacterium Esche-richia coli that had evolved in a constant environment of 37°C was replicated into 6 populations and allowed to reproduce for 2,000 generations in a variable thermal environment alternating between 32 and 42°C. As predicted by theory, fitness and efficiency of resource use increased in this new environment, as did stress resis-tance. Contrary to predictions, however, fitness and efficiency in the constant an-cestral environment of 37°C did not decrease, nor did thermal niche breadth or phenotypic plasticity increase. Selection experiments can thus provide a valuable approach to testing hypotheses and assumptions about the evolution of functional characters