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.