Schematic representation of the distribution of different cyclin subfamilies in eukaryotic organisms. The results of phylogenetic analyses of cyclin family proteins in different organisms are summarized. A black dot indicates the presence of clear homologs of cyclin subfamily members (see text for further explanations). Phylogenetic relationships illustrated for these organisms are derived form a proteome-based phylogeny [43, 61, 62] and the results of the Origins of Multicellularity project . The names of cyclin B-like (cyclins B, A, D, E, J, F, G, I, O, CLB, and CLN); cyclin Y-like (cyclins Y and PCL), and cyclin C-like (cyclins C, H, L, K, T, and Fam58) group members are indicated by different colors. Detailed information regarding this figure, including cyclin protein accession numbers, may be found in Additional file 12: Table S2.