|LE GOFF, G|
Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2005
Publication Date: 12/8/2005
Citation: Michel, A.P., Ingrasci, M.J., Schemerhorn, B.J., Kern, M., Le Goff, G., Coetzee, M., Elissa, N., Fontenille, D., Vulule, J., Lehmann, T. 2005. Rangewide population genetic structure of the african malaria vector anopheles funestus. Molecular Ecology. 14:4235-4248.
Interpretive Summary: Anopheles funestus mosquitoes are an important malaria vector in sub-Saharan Africa, second only to Anopheles gambiae. It is imperative that if we are to understand the transmission of malaria across Africa, as well as control it, we must have an understanding of the patterns and processes responsible for the distribution of variation in the mosquito vectors. To get a better understanding of A. funestus molecular structure, we sampled more than 500 specimens from 11 countries including: Mali, Burkina Faso, Nigeria, Gabon, Angola, Kenya, Uganda, Tanzania, Malawi, Mozambique and Madagascar. We used mitochondrial DNA (mtDNA) sequences from the ND5 gene, and 10 microsatellite loci distributed on all five chromosome arms to determine the levels of population subdivision across the full range of An. funestus habitat. It was shown that An. funestus appears to have three subdivisions (east, west, and central), and evidence of a recent population expansion. Mitchondrial DNA also showed more division that suggests that there was either horizontal transfer of mtDNA in Madagascar and Mozambique that is not present in other areas of Africa. This could be from a related species or historically divergent populations now freely inbreeding. The impact of this research is that it gives us a better understanding of Anopheles funestus population structure and dispersal patterns which is of primary importance in understanding and controlling malaria worldwide.
Technical Abstract: Anopheles funestus is a primary vector of malaria in Africa south of the Sahara. We assessed its rangewide population genetic structure based on samples from 11 countries, using 10 physically mapped microsatellite loci, two per autosome arm and the X (N= 548), and 834 bp of the mitochondrial ND5 gene (N= 470). On the basis of microsatellite allele frequencies, we found three subdivisions: eastern (coastal Tanzania, Malawi, Mozambique and Madagascar), western (Burkina Faso, Mali, Nigeria and western Kenya), and central (Gabon, coastal Angola). A. funestus from the southwest of Uganda had affinities to all three subdivisions. Mitochondrial DNA (mtDNA) corroborated this structure, although mtDNA gene trees showed less resolution. The eastern subdivision had significantly lower diversity, similar to the pattern found in the codistributed malaria vector Anopheles gambiae. This suggests that both species have responded to common geographic and/or climatic constraints. The western division showed signatures of population expansion encompassing Kenya west of the Rift Valley through Burkina Faso and Mali. This pattern also bears similarity to A. gambiae, and may reflect a common response to expanding human populations following the development of agriculture. Due to the presumed recent population expansion, the correlation between genetic and geographic distance was weak. Mitochondrial DNA revealed further cryptic subdivision in A. funestus, not detected in the nuclear genome. Mozambique and Madagascar samples contained two mtDNA lineages, designated clade I and clade II, that were separated by two fixed differences and an average of 2% divergence, which implies that they have evolved independently for '1 million years. Clade I was found'in all 11 locations, whereas clade II was sampled only on Madagascar and Mozambique. We suggest that the latter clade may represent mtDNA capture by'A. funestus, resulting from'historical gene flow either among previously isolated and divergent populations or with a'related species.