Tree-like structure highlighting the links between the galaxy classes from a redshift of z = 1.2 down to z = 0.4. The black line is the complete classification tree. Each vertical step in the tree corresponds to a certain epoch, linearly sampled from 4 Gyr after the Big Bang (bottom of the tree) to 9 Gyr (top of the tree). Each node represents a class, and similarity links from epoch to epoch were retrieved using KNN (Sect. 4.2). The branches that are studied in this paper as examples of spectral evolution are shown with a colour characteristics of their main branches: reds for passive galaxies (noted P*), greens for the star forming ones (SF*) and blues for the very blue spectra (VB*). The nomenclature is explained in the text.