Gene flow among populations of the malaria vector, Anopheles gambiae, in Mali, west Africa

The population structure of the Anopheles gambiae complex is unusual, with several sibling species often occupying a single area and, in one of these species, An. gambiae sensu stricto, as many as three "chromosomal forms" oc curring together. The chromosomal forms are thought to be intermediate betw een populations and species, distinguishable by patterns of chromosome gene arrangements. The extent of reproductive isolation among these forms has b een debated. To better characterize this structure we measured effective po pulation size, N-e, and migration rates, m, or their product by both direct and indirect means. Gene flow among villages within each chromosomal form was found to be large (N(e)m > 40), was intermediate between chromosomal fo rms (N(e)m approximate to 3-30), and was low between species (N(e)m approxi mate to 0.17-1.3). A recently developed means for distinguishing among cert ain of the forms using PCR indicated rates of gene flow consistent with tho se observed using the other genetic markers.