title: Complexities in the genetic structure of Anopheles gambiae populations in west Africa as revealed by microsatellite DNA analysis.
abstract: Chromosomal forms of Anopheles gambiae, given the informal designations Bamako, Mopti, and Savannah, have been recognized by the presence or absence of four paracentric inversions on chromosome 2. Studies of karyotype frequencies at sites where the forms occur in sympatry have led to the suggestion that these forms represent species. We conducted a study of the genetic structure of populations of An. gambiae from two villages in Mali, west Africa. Populations at each site were composed of the Bamako and Mopti forms and the sibling species, Anopheles arabiensis. Karyotypes were determined for each individual mosquito and genotypes at 21 microsatellite loci determined. A number of the microsatellites have been physically mapped to polytene chromosomes, making it possible to select loci based on their position relative to the inversions used to define forms. We found that the chromosomal forms differ at all loci on chromosome 2, but there were few differences for loci on other chromosomes. Geographic variation was small. Gene flow appears to vary among different regions within the genome, being lowest on chromosome 2, probably due to hitchhiking with the inversions. We conclude that the majority of observed genetic divergence between chromosomal forms can be explained by forces that need not involve reproductive isolation, although reproductive isolation is not ruled out. We found low levels of gene flow between the sibling species Anopheles gambiae and Anopheles arabiensis, similar to estimates based on observed frequencies of hybrid karyotypes in natural populations.
authors.affiliation: Department of Pathology and Center for Tropical Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA. glanzaro@utmb.edu
authors.forename: G C
authors.initials: GC
authors.lastname: Lanzaro
authors.forename: Y T
authors.initials: YT
authors.lastname: Touré
authors.forename: J
authors.initials: J
authors.lastname: Carnahan
authors.forename: L
authors.initials: L
authors.lastname: Zheng
authors.forename: G
authors.initials: G
authors.lastname: Dolo
authors.forename: S
authors.initials: S
authors.lastname: Traoré
authors.forename: V
authors.initials: V
authors.lastname: Petrarca
authors.forename: K D
authors.initials: KD
authors.lastname: Vernick
authors.forename: C E
authors.initials: CE
authors.lastname: Taylor
mesh_terms: D000354:Africa, Western; D000818:Animals; D000852:Anopheles / Q000235:genetics*; D005075:Biological Evolution; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics / Q000648:ultrastructure; D019143:Evolution, Molecular; D005819:Genetic Markers; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D010802:Phylogeny
chemical_list: D005819:Genetic Markers