Summary of positively selected genes. (A) Distribution of positively selected genes in the phylogenetic cladogram. The numbers above and under the branches denote the number of positively selected genes and branch lengths, respectively. Thick lines and bold numbers denote the occurrences of host shift events. Internal branches are labeled from I1 to I5 with arrows. (B) Positively selected genes related to plant pathogenicity. Putative functions were based on the gene annotations of X. citri pv. citri. Genes under positive selection are filled in black at the corresponding branch, which is denoted with taxon name (terminal branch) or codes I1–I5 (internal branch). Host-shift branches were labeled in grey.