Extent of adaptation is not limited by unpredictability of the environment in laboratory populations of Escherichia coli.

Environmental variability is on the rise in different parts of the earth, and the survival of many species depends on how well they cope with these fluctuations. Our current understanding of how organisms adapt to unpredictably fluctuating environments is almost entirely based on studies that investigate fluctuations among different values of a single environmental stressor such as temperature or pH. How would unpredictability affect adaptation when the environment fluctuates between qualitatively very different kinds of stresses? To answer this question, we subjected laboratory populations of Escherichia coli to selection over ~ 260 generations.

Environmental fluctuations do not select for increased variation or population-based resistance in Escherichia coli.

Little is known about the mechanisms that enable organisms to cope with unpredictable environments. To address this issue, we used replicate populations of Escherichia coli selected under complex, randomly changing environments. Under four novel stresses that had no known correlation with the selection environments, individual cells of the selected populations had significantly lower lag and greater yield compared to the controls.

ANIMAL COGNITION. Comment on "Number-space mapping in the newborn chick resembles humans' mental number line".

Rugani et al. (Reports, 30 January 3015, p. 534) tested 3-day-old domestic chicks using an innovative experimental setup and demonstrate the presence of the mental number line.