Analysis of genetic variability in Anopheles arabiensis and Anopheles gambiae using microsatellite loci

We analysed genetic variability in Anopheles arabiensis and Anopheles gambi ae populations using microsatellite loci to determine whether the Rift Vall ey restricts the flow of genes. Deviations from Hardy-Weinberg expectations were significant, and were most likely to be due to the high frequency of null alleles observed. An, arabiensis populations occurring between 40 and 700 km apart across the Eastern arm of the Rift Valley were not differentia ted (pair-wise F-ST range: 0.0033-0.0265, P > 0.05). Neither were An. gambi ae populations from Asembo Bay and Ghana (F-ST: 0.0063, P > 0.05) despite a geographical separation of about 5000 km, In contrast, significant differe ntiation was observed between An. gambiae populations from Asembo Bay and K ilifi (about 700 km apart; F-ST = 0.1249, P < 0.01), suggesting the presenc e of a barrier to gene flow.