Michael Barnett, Lena Meister and Paul B. Rainey provide evidence of a selective mechanism acting on bacteria that increases their evolvability.
Abstract: Can the capacity to evolve be selected by natural selection for greater ability to evolve? Barnett et al. designed experiments in which lineages of bacteria cycled between two selective environments (see the Perspective by Kussell). In response to changing conditions, a multistep evolutionary dynamic emerged in which selection first acts to elevate transcription rates at a single regulatory gene. An increase in frameshift mutations occurs at the same locus that also allows hitchhiking of secondary, possibly adaptive mutations. This phenomenon provides an evolutionary mechanism for increasing the capacity for evolvability toward specific adaptive outcomes.’
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