Population Structure of Anopheles gambiae in Africa

Abstract

The population structure of Anopheles gambiae in Africa was studied using 11 microsatellite loci in 16 samples from 10 countries. All loci are located outside polymorphic inversions. Heterogeneity among loci was detected and two putative outlier loci were removed from analyses aimed at capturing genome-wide patterns. Two main divisions of the gene pool were separated by high differentiation (F(ST) > 0.1). The northwestern (NW) division included populations from Senegal, Ghana, Nigeria, Cameroon, Gabon, Democratic Republic of Congo (DRC), and western Kenya. The southeastern (SE) division included populations from eastern Kenya, Tanzania, Malawi, and Zambia. Inhospitable environments for A. gambiae along the Rift Valley partly separate these divisions. Reduced genetic diversity in the SE division and results of an analysis based on private alleles support the hypothesis that a recent bottleneck, followed by colonization from the NW populations shaped this structure. In the NW division, populations possessing the M rDNA genotype appeared to form a monophyletic clade. Although genetic distance increased with geographic distance, discontinuities were suggested between certain sets of populations. The absence of heterozygotes between sympatric M and S populations in the DRC and the high differentiation in locus 678 (F(ST)>0.28) contrasted with low differentiation in all other loci (-0.02<F(ST)<0.09) and with the persistence of departures from Hardy-Weinberg expectations within each form in the DRC. Neither recent reproductive isolation alone nor selection alone can explain these results, a situation that is compatible with incipient speciation. Because it is possible that the molecular forms play different roles in malaria transmission, future studies should treat them separately.

Ecological Zones Rather Than Molecular Forms Predict Genetic Differentiation in the Malaria VectorAnopheles gambiaes.s. in Ghana

“…gambiae. To date, estimates of genetic differentiation have been low even between populations separated by many thousands of kilometers (Lehmann et al 2003;Donnelly et al 2004), unless there are major hydrographic or geographic barriers to migration (e.g., Pinto et al 2002;Lehmann et al 2003). Yet in the south of Ghana (all samples from south of Kumasi) there are no obvious extant or former geographic barriers to gene flow, with all samples from this region taken from a continuous coastal plain that does not rise .100 m above sea level.…”

“…One of these is on chromosome 2L, associated with insecticide resistance (Gentile et al 2004 and references therein). The other loci (including the rDNA) are at the proximal (centromeric) end of the X chromosome Lehmann et al 2003). However, little differentiation has been found at loci elsewhere in the genome (Gentile et al 2001;Mukabayire et al 2001;Wang et al 2001;Turner et al 2005).…”

Revisiting the role of introgression vs shared ancestral polymorphisms as key processes shaping genetic diversity in the recently separated sibling species of the Anopheles gambiae complex

“…Most locations have been described in detail previously Lehmann et al, 1997Lehmann et al, , 1998Lehmann et al, , 2003Donnelly and Townson, 2000;Pinto et al, 2002). Species identification, collection location and sample size are given in Table 1.…”

Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma infestans (Heteroptera: Reduviidae)

“…Wing geometric morphometric studies of T. infestans described a spatial structuring pattern (Schachter-Broide et al, 2004), but could not provide definitive explanations for the structuring origin. Analyses of mitochondrial DNA sequences, microsatellites and RAPDs in various species of insect disease vectors and parasites have proven effective (e.g., Monteiro et al, 1999;Borges et al, 2000;Blackston et al, 2001;Lehmann et al, 2003aLehmann et al, , 2003b.…”