Example of Artificial Transfers between Species. The topology of the depicted tree was calculated from 236 gene families using the majority-rule consensus method; branch lengths were calculated from 16S rRNA. The tree should be considered as unrooted. To calculate SPR distances (Figure 2C) the tree was considered as rooted in the branch leading to (Xylella fastidiosa, Xanthomonas campestris and X. citri). The double-headed arrows indicate the in silico exchanges analyzed in Figure 3.