Historical demography and molecular taxonomic status of the malaria vector (Anopheles albimanus) in the Northern Neotropics

Anopheles albimanus is a primary malaria vector throughout the northern Neotropics, and mountain ranges are expected to restrict its dispersal and gene flow. To analyze the historical demography and molecular taxonomic status of Anopheles albimanus, we used mosquitoes from five countries and three different DNA regions, the mitochondrial cytochrome oxidase subunit I gene (COI), the single copy nuclear white gene and the ribosomal internal transcribed spacer two (ITS2). We hypothesized that An. albimanus is a single, albeit polymorphic species, that is not at demographic equilibrium, likely due to past fluctuation in its effective population size at a regional scale. All the molecular markers supported the status of a single species of An. albimanus. In addition, there was a strong geographic component in the genetic structure of An. albimanus with three population demes and an admixture zone across eastern Panama and northern Colombia. The COI gene suggests that this is because of Pleistocene geographic fragmentation, and subsequent range expansion by four divergent maternal lineages. The white gene does not support the high genetic diversity depicted by the COI, but agrees with its scenario of Pleistocene population expansion, thus supporting demographic processes as the cause of structure instead of natural selection. Results from both the white and COI genes indicate that a population contraction across Panama with subsequent expansion towards Nicaragua and Ecuador is the likely cause of the population structure in An. albimanus.