Phylogenetic trees of the chemokine CC subfamily constructed using the amino acid sequences of chicken, human, and mouse chemokines. The numbers on the branches are bootstrap values (percentage that the simulation supports the original interpretation). Human, mouse, and chicken are abbreviated as h, m, and c, respectively. The scale bar reflects the horizontal distance at which amino acid sequences differ by 20% between two sequences. A and B are the phylogenetic trees of CCLs that are not located on Chromosome 19 or located on Chromosome 19, respectively.