Genetic complexity of adapting populations.

<p>A small number of point mutations rose to appreciable frequencies in each population with the exception of the allantoin-limited population, which contains ∼500 SNPs most of which have frequencies less than 10% (see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004041#pgen.1004041.s013" target="_blank">Table S2</a> and <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004041#pgen.1004041.s014" target="_blank">Table S3</a>). This population also contains a mutant <i>MSH2</i> gene, suggesting the existence of a low frequency mutator phenotypes <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004041#pgen.1004041-Drotschmann1" target="_blank">[73]</a>, <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004041#pgen.1004041-Barrick1" target="_blank">[74]</a>. Nitrogen concentrations were normalized between environments by adjusting the concentration of each compound according to its molecular composition.