The sympatric occurrence of two molecular forms of the malaria vector Anopheles gambiae Giles sensu stricto in Kanyemba, in the Zambezi Valley, Zimbabwe.

The complexity of Anopheles gambiae Giles sensu stricto, a sibling species of the A. gambiae complex, has been shown by the extent of chromosomal inversion polymorphisms and more recently, by divergence at the molecular level. Analysis by PCR of a field population of A. gambiae complex from the Zambezi Valley area of Kanyemba, northern Zimbabwe, showed the co-existence of three sibling species: A. arabiensis (90%), A. gambiae (4%), and A. quadriannulatus (6%). Molecular characterization of the A. gambiae s.s. material revealed the sympatric presence of the two molecular forms S and M within a sample of eight. This is the first record of the co-existence of these two molecular forms in southern Africa.