Figure 2. The underlying genetic diversity of the adapted populations is readily observed as phenotypic diversity, when plated on tetrazolium arabinose plates.

When arabinose is provided as the carbon source, the diversity of genotypes in the adapted populations is seen as a marked increase in phenotypic diversity. Colony size, morphology and the ability to use arabinose (as indicated by the darkness of the colony) varied widely in the adapted populations compared to the ancestor.