Gene orthology of CCL2 , -7 , -11 , -8 , and -13 of placental mammals supported by phylogeny. The evolutionary history was inferred by using the Maximum Likelihood method conducted in MEGA5 . The tree with the highest log likelihood (-4585.9908) is shown. Bootstrap values are placed next to the branches. Codon positions included were 1st + 2nd + 3rd and were limited to those encoding the mature chemokine. There were 231 positions in the final data set. Positions of leporid branches are highlighted by triangles ▴ for functional, or by ∇ for pseudogenes. Taxon names of sequences obtained in this study are extended by ‘gDNA’ when derived from genomic DNA or by ‘cDNA’ when (also) derived from cDNA. All other sequences represent a sample of mRNA sequences listed in Additional file 9. Mouse CCL12 and CCL8 are located between the CCL11 and CCL1 genes and are likely duplicates of the ortholog of murid CCL8.