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Crossmating experiments were conducted to determine if postmating reproductive barriers are involved in the maintenance of genetic divergence among populations of Anopheles pseudopunctipennis sensu lato, a primary malaria vector of the American continent. Reciprocal crosses were conducted between colony and wild strains from Mexico, Bolivia, and Peru. Hybridization experiments revealed unidirectional male/female hybrid sterility in crosses between Mexican females and South American males. The data presented provide the first evidence that genetic differences exist among geographic strains of An. pseudopunctipennis in neotropical America. There is a consistent pattern suggesting the presence of at least two allopatric sibling species. One species occurs in central Mexico, the other in the South American Andean Cordillera.

Enzyme electrophoresis and restriction fragment length polymorphism (RFLP) analysis of Anopheles pseudopunctipennis sensu lato from nine isolated populations in neotropical America confirmed previous observations that it constitutes a species complex. Electrophoretic studies showed fixed differences at two enzyme loci, glycerol dehydrogenase (Gcd) and phosphoglucomutase (Pgm), suggesting limited or no gene flow between populations from Mexico and South America. In addition, analysis of genetic distance showed two distinctive clusters, one from Mexico and the other from South America, separated at a Nei's distance level of 0.13, a value consistent in magnitude with that of other anopheline sibling species. The RFLP analysis revealed the presence of a ribosomal DNA fragment in Mexican strains that was absent in strains from South America. Two species have been identified through these studies, one provisionally named An. pseudopunctipennis A, a species from central Mexico, and the other An. pseudopunctipennis B, for the species found in the interAndean valleys and Andean slopes in regions of Peru and Bolivia. This research provides information required to elucidate the status of the different species of the An. pseudopunctipennis complex as vectors of malaria in the Americas.

This preliminary report provides information concerning genetic variation in the vector mosquito Anopheles pseudopunctipennis sensu lato that could have malaria control implications. Because of inconsistencies in malaria transmission patterns within geographic zones inhabited by this vector, the possibility that it represents a species complex was investigated. Hybrid crossing studies, electrophoretic analysis of enzyme variation, and DNA restriction studies were carried out in mosquitoes captured in nine areas of Mexico, Bolivia, and Peru. The findings demonstrated the existence of a species complex believed to have resulted from allopatric speciation. This research points to a need for establishing the geographic distribution of the newly recognized species because of their potential influence on malaria control.

In light of inconsistencies in the pattern of malaria transmission within geographical areas inhabited by Anopheles pseudopunctipennis pseudopunctipennis, a study was carried out to investigate the possibility that this vector constitutes a species complex. Hybrid crossing studies, electrophoretic analysis of enzyme loci, and DNA restriction analysis were conducted on mosquitoes captured at nine sites in Mexico, Bolivia, and Peru. The sterility of generations resulting from cross-mating of Mexican female mosquitoes and South American male mosquitoes; the results of electrophoretic analysis, which showed differences at two loci; and a genetic distance value of 0.13 confirmed the existence of a species complex, probably produced by allopatric speciation. It is concluded that the geographic distribution of this newly discovered species complex should be defined, in view of its potential effect on malaria control.