Microgeographic genetic differentiation of Anopheles gambiae mosquitoes from Asembo Bay, western Kenya: a comparison with Kilifi in coastal Kenya
Kamau, L.; Lehmann, T.; Hawley, W.A.; Orago, A.S.; Collins, F.H.
American Journal of Tropical Medicine and Hygiene 58(1): 64-69
1998
ISSN/ISBN: 0002-9637 PMID: 9452294 Document Number: 488364
Microgeographic differentiation in Anopheles gambiae s.s. from 7 villages <10 km apart in Asembo Bay, Siaya District, Nyanza Province, Kenya, was estimated by analysis of variability in 7 microsatellite loci. Results from the Asembo Bay villages (collected in June 1996) were compared with specimens collected in February 1996 in Kilifi, 700 km to the east. Allele frequency distribution was very similar in all villages in Asembo Bay, but differed for the Kilifi population. Genetic differentiation among villages was low, with loci-specific F31 falling within the range of 0.0000-0.0085. These low estimates of differentiation correspond to among-village migration indices >5.66, suggesting a high level of gene flow within the Asembo population. The Nm value between Kilifi and Asembo Bay was 1.54, indicating much lower levels of gene flow. Average observed heterozygosity among the 7 villages was in all but one case less than the expected heterozygosity, most likely indicating the presence of null alleles, but possibly the presence of randomly mating units (demes) smaller than the village. It was concluded that there is likely no genetic structure 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.