Microsatellite diversity and Plasmodium vivax infection rate in southern Mexico during a 10-year period. A. Pattern of allelic variation for 7 microsatellite loci using 474 bloodspot samples collected over 10 years. Grey, mean number of alleles (Na); white, mean number of alleles ≥ 5%; black line, mean effective heterozygosity (He = [n/(n-1)]×1- ∑pi2), shows a slight but persistent decrease over the time frame (R2 = 0.3109). B. Number of malaria cases per 1,000 people during a 10 year period across the entire study area (black bars), and within villages with positive malaria cases only (white bars). API: number of cases per year per 1,000 people.