Laboratory selection for the comparative physiologist

An increasingly popular experimental approach in comparative physiology is to study the evolution of physiological traits in the laboratory, using mic robial, invertebrate and vertebrate models. Because selective conditions ar e well-defined, selected populations can be replicated and unselected contr ol populations are available for direct comparison, strong conclusions rega rding the adaptive value of an evolved response can be drawn. These studies have shown that physiological systems evolve rapidly in the laboratory, bu t not always as one would expect from comparative studies of different spec ies. Laboratory environments are often not as simple as one thinks, so that the evolution of behavioral differences or selection acting on different l ife stages can lead to unanticipated results. In some cases, unexpected res ponses to laboratory selection may suggest new insights into physiological mechanisms, which might not be available using other experimental approache s. I outline here recent results (including success stories and caveats for the unwary investigator) and potential directions for selection experiment s in comparative physiology.