title: Long-term experimental evolution in Escherichia coli. VI. Environmental constraints on adaptation and divergence.
abstract: The effect of environment on adaptation and divergence was examined in two sets of populations of Escherichia coli selected for 1000 generations in either maltose-or glucose-limited media. Twelve replicate populations selected in maltose-limited medium improved in fitness in the selected environment, by an average of 22.5%. Statistically significant among-population genetic variation for fitness was observed during the course of the propagation, but this variation was small relative to the fitness improvement. Mean fitness in a novel nutrient environment, glucose-limited medium, improved to the same extent as in the selected environment, with no statistically significant among-population genetic variation. In contrast, 12 replicate populations previously selected for 1000 generations in glucose-limited medium showed no improvement, as a group, in fitness in maltose-limited medium and substantial genetic variation. This asymmetric pattern of correlated responses suggests that small changes in the environment can have profound effects on adaptation and divergence.
authors.affiliation: Center for Microbial Ecology, Michigan State University, East Lansing 48824-1325, USA. mtrav@ant.css.msu.edu
authors.forename: M
authors.initials: M
authors.lastname: Travisano
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000704:Analysis of Variance; D001089:Arabinose / Q000378:metabolism; D005075:Biological Evolution; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D005819:Genetic Markers; D014644:Genetic Variation; D005947:Glucose / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D012641:Selection, Genetic; D013997:Time Factors
chemical_list: D003470:Culture Media; D005819:Genetic Markers; D008320:Maltose; D001089:Arabinose; D005947:Glucose