Testing the predictability of evolution

Albert F. Bennett, acting dean of the School of Biological Sciences, has performed the first experimental test of whether trade-offs necessarily accompany environmental adaptation. The trade-off hypothesis states that when populations of organisms evolve and improve in some areas, they lose abilities elsewhere. Bennett used 24 replicate populations of the bacterium Escherichia coli that had genetically adapted to low temperature (20’C) and measured whether they lost their ability to handle high temperature (40’C), as predicted by the trade-off hypothesis. He found that two-thirds of the populations lost performance capacity at high temperature as predicted, but one-third did not, and one even improved its performance in the heat. This study was reported in the Proceedings of the National Academy of Sciences.