|Michel, A. P.|
|Guelbeogo, W. M.|
|Willard, M. B.|
|Sagnon, N. F.|
|Besansky, N. J.|
Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2005
Publication Date: 8/20/2005
Citation: Michel, A. P., Guelbeogo, W. M., Grushko, O., Schemerhorn, B.J., Kern, M, Willard, M. B., Sagnon, N. F., Costantini, C., Besansky, N. J. 2005. Molecular differentiation between chromosomally defined incipient species of anopheles funestus. 14(4):375-387. . Insect Molecular Biology. Interpretive Summary: The purpose of this study was to determine how much genetic differentiation there is between collections of malaria carrying mosquitoes in sub-Saharan Africa. We used a combination of both microsatellite loci and direct sequencing. This study has concluded that there are three distinct divisions in the population continent wide. These population divisions roughly coincide with the Eastern, Western and Central regions of Africa. The Eastern area was not as genetically diverse as the other two regions. This suggests there are similar geographical constraints for Anopheles funestus as there have previously been seen in Anopheles gambiae. In the eastern part of Africa, the Rift Valley appears to be a barrier for Anopheles funestus as was seen in Anopheles gambiae. The western division showed a possible population expansion west of the Rift Valley and is likely due as a response to human agricultural practices. This information is vital in the understanding of the spread of resistance to insecticides, the spread of resistance to malaria parasites as well as for any future release of genetically modified mosquitoes.
Technical Abstract: Anopheles funestus is a primary vector of malaria in Africa south of the Sahara. We assessed its range-wide population genetic structure based on samples from 11 countries, using 10 physically mapped microsatellite loci, 2 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 co-distributed malaria vector A. 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 2 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 hybridization with a related species.