Figure 2. Maximum-likelihood tree inferred from the complete merozoite surface protein 1 gene sequences of Plasmodium knowlesi from humans (red circles) and macaques (blue circles). The tree is drawn to scale, and branch lengths are measured in number of substitutions per site by using MEGA version 5.01 (14). Bootstrap values >50% from 1,000 iterations are shown. Human isolates are from the following provinces: Narathiwat (NR280, NR234, and NR522); Yala (YL975 and YL978); Chantaburi (CT157, CT190, and CT273); and Prachuab Khirikhan (BMC151, MC128, and DQ220743). Isolates HB3, HB92, HB126, HB132, and HB149 are from macaques in Narathiwat Province. GenBank accession nos. are shown after isolate names.