Drastic change in the population structure of P. vivax between 1997-2000 and 2007. The population structure of P. vivax in the Republic of Korea was inferred using STRUCTURE analysis and plots were drawn using DISTRUCT. (A) Plot of log probability of data [Ln P(D)] against the number of populations tested (K). (B) Plot of ΔK (the rate of change in the log probability of the data between successive K values) against the number of K. An individual parasite isolate is represented by a single vertical bar, which is partitioned into three (C) or five (D) segments. Sample numbers are shown along the horizontal axes. Each segment represents one population, and the colour of the segment represents the estimated membership fraction in the individual parasite assigned to K clusters.