Genetic differentation among populations of Lutzomyia longipalpis (Diptera: Psychodidae) in Central and South America

Twenty-six field populations and five laboratory strains of Lutzomyia longipalpis (Lutz & Neiva), the sand fly vector of Leishmania chagasi in the Americas, were analyzed for genetic variation at 15 enzyme loci. The goal was to describe the genetic structure of natural populations, to evaluate the notion that this taxon is composed of a number of sibling species, and to delimit the boundaries among putative species within the complex. Allele frequencies for three loci, Gpi, Aat-1, and Pgm, permitted discrimination of three discrete population groups (Colombia, Central America, and Brazil) with a probability of correctly assigning an individual to one of the groups >99%. Overall F_ST was high (0.489) and estimated N_em for all 26 populations was 0.23, indicating genetic substructuring and restricted gene flow among populations. More than 90% of the variance in allele frequencies was attributed to differences among the three regions. Levels of gene flow (N_em) among populations within species (2.41) were 8.3 times higher than between species (0.29). Cluster analysis of Nei's genetic distance coefficients grouped populations into three well-defined clades (Brazil, Central America, and Colombia). Nei's genetic distance (D) among putative species varied from 0.15 to 0.19 and was consistent with values previously published for species within the genus Lutzomyia. These results are consistent with Lu. longipalpis being a complex of at least three sibling species.