So far, there is no study reporting the function of IFITM10. All various vertebrate IFITM10 genes can be divided into two subgroups, one of which contains IFITM10 from terrestrial vertebrates with frog IFITM10 at the basal position, suggesting that terrestrial vertebrates and frog share a common IFITM10 ancestor. The other one contains IFITM10 from aquatic vertebrates, as well as four frog IFITM10-like genes. Significant signal of functional divergence was observed between the two subgroups (Table 2) , possibly suggesting an association with terrestrial and aquatic environments. In particular, both gene duplication and positive selection can be detected in IFITM10 or IFITM10like genes from the aquatic vertebrates ( Fig. 6D and Table 3 ), indicating that IFITM10 is associated with the adaptation to aquatic environments. There are one IFITM10 gene and four IFITM10-like genes in frog (Fig. 2C ). An episodic adaptive evolution was found on the branch leading to three frog IFITM10like genes (Fig. S6) , supporting the association of IFITM10 with terrestrial and/or aquatic environments. However, what the function of IFITM10 is and how it helps the aquatic vertebrates to adapt to aquatic environments still need to be determined. Distinct from IFITM5 and IFITM10, the IR-IFITM sub-family contains IFITM1, IFITM2, IFITM3, IFITM6, IFITM7, as well as a large number of IFITM-like genes [37, 38] . This sub-family forms a large clade in the phylogenetic tree (Fig. 3) . The IR-IFITM genes from same mammalian species, such as dog, horse, cow, elephant, guinea pig and tree shrew, cluster together and form species-specific IR-IFITM gene sub-clusters (Fig. 3) , in-dicating that gene duplication occurred after the separation of these mammalian species in a species-specific pattern. The same IFITM member from mouse and rat cluster together, indicating that the gene duplication there occurred prior to the separation of the two species in a lineage-specific pattern. The rodent IFITM1, IFITM2 and IFITM3 sub-groups cluster together (Fig. 3) , suggesting a close phylogenetic relationship and similar functions. IFITM6 and IFITM7 are specific for the rodents. The rat and mouse IFITM6 genes cluster together and further group with the guinea pig IR-IFITM gene sub-cluster. Mouse IFITM7 clusters closely with mouse IFITM1 gene and rat IFITM7 clusters closely Evolutionary Dynamics of IFITM Gene Family with rat IFITM3 gene (Fig. 3) , which might indicate IFITM7 has similar functions to IFITM1 or IFITM3.