Ecological genetics is the study of evolution in action in nature, by a combination of field-work and laboratory genetics. The most famous piece of ecological genetic research is H.B.D. Kettlewell's study of melanism in the peppered moth.

In this experiment, the frequency of genes encoding for wing color in the peppered moth was shown to be dependent on the prevalent color of the tree trunks. As the picture shows, when trees are pale, the lighter form of the moth is better camouflaged and consequently favored by selection.