Coordinated Evolution of Influenza A Surface Proteins
(A) Individual toy phylogenies for segments 1 (left) and 2 (right) with respective mutations. (B) Segment 1 phylogeny with segment 2 “background” mutations mapped onto it (left) and segment 2 phylogeny with segment 1 “background” mutations mapped onto it (right). a–d, leaf nodes; e–g, internal nodes; h, virtual node arising due to the reassortment event; r, root node; nodes corresponding to the two segments of the same isolate are denoted with the same letter. Each mutation is identified by a roman numeral and a unique symbol colored according to the segment in which it occurred. Mutation ii in segment 2 maps onto two branches of the segment 1 phylogeny, once as a regular mutation onto branch ra and once as a virtual mutation (denoted by parentheses) onto branch fh.