Variation in ribosomal DNA intergenic spacers among populations of Anopheles albimanus in South and Central America

Variation in the length and copy number of intergenic spacers (IGS) of nuclear ribosomal DNA were examined to test for genetic differentiation among Anopheles albimanus populations. Extensive collections were made in Guatemala but populations were also sampled over a large range of its distribution in Central and South America. Discriminant analysis of IGS patterns in individual mosquitoes indicated that populations generally had unique sets of IGS length variants. The IGS patterns from populations on the Pacific side of Central America were distinct from those on the Atlantic side or from South America. Cluster analysis indicated a similar trend. The IGS diversity in Central America was 50% greater than in South America. These results suggest that barriers to gene flow exist among Atlantic and Pacific coast populations of An. albimanus. No gene flow barriers were detected among populations from Colombia, Ecuador, Peru, and Venezuela.