The intact ORFs of the inferred sequences were aligned with the type-I interferons from humans and from the domestic pig, Sus scrofa (which is substantially more closely related to bats than is the human), and as an outgroup, the IFNB and IFNA gene sequences from the duckbill platypus (Ornithorhynchus anatinus). The phylogenetic tree relating these genes was inferred using maximum likelihood (Figure 3).
Figure 3 Phylogenetic tree of the type-I interferons in Pteropus vampyrus (Pva), Myotis lucifigus (Mlu), Sus scrofa (Ssc), Homo sapiens (Hsa), and Ornithorhynchus anatinus (Oan). The tree was thinned for clarity by omitting one member of any pair of sequences differing by fewer than 3 amino acids. The branch length is proportional to the evolutionary distance.