Example. Example of observed epistasis. A visual representation of the 30 trait/QTL pairs. The phenotype average for each genotype is given by the heights of the bars, the corresponding shape is also given, and the trait (A-E) and QTL pair (1–21) listed. Under each panel we list the cluster it falls into (1–4) and the group given by  (A, B, H, L, U).