title: Evidence for subdivision within the M molecular form of Anopheles gambiae.
abstract: The principal vector of malaria in sub-Saharan Africa, Anopheles gambiae is subdivided into two molecular forms M and S. Additionally, several chromosomal forms, characterized by the presence of various inversion polymorphisms, have been described. The molecular forms M and S each contain several chromosomal forms, including the Savanna, Mopti and Forest forms. The M and S molecular forms are now considered to be the reproductive units within A. gambiae and it has recently been argued that a low recombination rate in the centromeric region of the X chromosome has facilitated isolation between these forms. The status of the chromosomal forms remains unclear however. Therefore, we studied genetic differentiation between Savanna S, Forest S, Forest M and Mopti M populations using microsatellites. Genetic differentiation between Savanna S and Forest S populations is very low (F(ST) = 0.0053 +/- 0.0049), even across large distances. In comparison, the Mopti M and Forest M populations show a relatively high degree of genetic differentiation (F(ST) = 0.0406 +/- 0.0054) indicating that the M molecular form may not be a single entity, but could be subdivided into at least two distinct chromosomal forms. Previously it was proposed that inversions have played a role in the origin of species within the A. gambiae complex. We argue that a possible subdivision within the M molecular form could be understood through this process, with the acquisition of inversions leading to the expansion of the M molecular form into new habitat, dividing it into two distinct chromosomal forms.
authors.affiliation: Department of Entomology & Center for Vectorborne Diseases, University of California Davis, Davis, CA 95616, USA. michel.slotman@yale.edu
authors.forename: M A
authors.initials: MA
authors.lastname: Slotman
authors.forename: F
authors.initials: F
authors.lastname: Tripet
authors.forename: A J
authors.initials: AJ
authors.lastname: Cornel
authors.forename: C R
authors.initials: CR
authors.lastname: Meneses
authors.forename: Y
authors.initials: Y
authors.lastname: Lee
authors.forename: L J
authors.initials: LJ
authors.lastname: Reimer
authors.forename: T C
authors.initials: TC
authors.lastname: Thiemann
authors.forename: E
authors.initials: E
authors.lastname: Fondjo
authors.forename: A
authors.initials: A
authors.lastname: Fofana
authors.forename: S F
authors.initials: SF
authors.lastname: Traoré
authors.forename: G C
authors.initials: GC
authors.lastname: Lanzaro
mesh_terms: D000483:Alleles; D000818:Animals; D000852:Anopheles / Q000145:classification* / Q000235:genetics*; D002163:Cameroon; D007446:Chromosome Inversion; D002875:Chromosomes / Q000235:genetics; D017753:Ecosystem; D005260:Female; D049810:Genetic Speciation; D015810:Linkage Disequilibrium; D008302:Mali; D010802:Phylogeny