Intragenomic heterogeneity of a ribosomal DNA spacer (ITS2) varies regionally in the neotropical malaria vector Anopheles nuneztovari (Diptera:Culicidae)

We investigated intragenomic heterogeneity of ITS2 within twenty individual Anopheles nuneztovari (subgenus Nyssorhynchus) from five geographical localities in the neotropics (three from Brazil and one each from Colombia and Venezuela) by cloning and sequencing PCR-amplified copies of this spacer. Intragenomic heterogeneity was observed in thirteen of twenty mosquitoes of both sexes from all localities. As estimated by uncorrected P, however, mean sequence divergence was greater in mosquitoes from Brazil (PR = 0.0100, BL = 0.0196, AB = 0.0182) than in those from Venezuela (SO = 0.0026) or Colombia (SI = 0.0078). Sequence divergence per genome was significantly higher in mosquitoes from Brazil than in those from SO and SI. In fact, divergence among ITS2 variants within single mosquitoes from the Brazilian localities was often as great as that between localities. Similarly, the number of variants per mosquito was significantly greater in Brazil (maximum of six variants) than in both SO and SI (maximum of two variants). These results indicate that homogenization of ITS2 has proceeded to a greater extent in SO and SI than in the localities in Brazil. The differences in intragenomic heterogeneity between both SO and SI versus the Brazilian localities probably reflect either differences in population-level processes such as gene flow and genetic drift, or the fact that these localities may represent two or more cryptic species, as suggested by other studies.