Climb Every Mountain?

Abstract
Evolutionary biologists have long argued that adaptation to a particular environmental niche should constrain a population9s ability to survive in other niches. In their Perspective, Elena and Sanjuán discuss new evolution experiments with populations of the bacterium Pseudomonas fluorescens ( Buckling et al.). These experiments provide evidence that as a bacterial population becomes a niche specialist, it is less able to adapt to other niches.