Schematic representation of the distribution of different CDK subfamilies in eukaryotic organisms. The results of phylogenetic analyses of CDK family proteins in different organisms are summarized. A black dot indicates the presence of clear homologs of CDK subfamilies or clades (see text for further explanations). Phylogenetic relationships of these organisms are based on recent reports [43, 61, 62] and the results of the Origins of Multicellularity project . Detailed information regarding this figure, including CDK protein accession numbers, is given in Additional file 6: Table S1.