MICROGEOGRAPHIC GENETIC DIFFERENTIATION OF ANOPHELES-GAMBIAE MOSQUITOS FROM ASEMBO BAY, WESTERN KENYA - A COMPARISON WITH KILIFI IN COASTALKENYA

Microgeographic differentiation in Anopheles gambiae from seven villag es less than 10 km apart in Asembo Bay, western Kenya was estimated by analysis of variability in seven microsatellite loci. Results from th e Asembo Bay villages were compared with specimens collected in Kilifi , coastal Kenya, 700 km to the east. Allele frequency distribution was very similar in all villages in Asembo Bay, but differed for the Kili fi population. Genetic differentiation among villages was low with loc i-specific F-st falling within the range of 0.0000-0.0085. These low e stimates of differentiation correspond to among-village migration indi ces greater than 5.66, suggesting a high level of gene flow within the Asembo population. The N-m value between Kilifi and Asembo Bay was 1. 54, indicating much lower levels of gene flow. Average observed hetero zygosity among the seven villages was in all but one case less than th e expected heterozygosity, most Likely indicating the presence of null alleles, but possibly the presence of randomly mating units (demes) s maller than the village. We conclude that there is likely no genetic s tructure at the level of the village in Asembo Bay but that gene flow is restricted between western and coastal Kenya, probably by the high elevation rift.