RAPID EVOLUTION IN RESPONSE TO HIGH-TEMPERATURE SELECTION

TEMPERATURE is an important environmental factor affecting all organisms1,2, and there is ample evidence from comparative physiology that species1,3 and even conspecific populations4,5 can adapt genetically to different temperature regimes. But the effect of these adaptations on fitness and the rapidity of their evolution is unknown, as is the extent to which they depend on pre-existing genetic variation rather than new mutations. We have begun a study of the evolutionary adaptation of Escherichia coli to different temperature regimes, taking advantage of the large population sizes and short generation times in experiments on this bacterial species6-10. We report significant improvement in temperature-specific fitness of lines maintained at 42 °C for 200 generations (about one month). These changes in fitness are due to selection on de novo mutations and show that some biological systems can evolve rapidly in response to changes in environmental factors such as temperature. © 1990 Nature Publishing Group.