GENETIC DIFFERENTIATION OF ANOPHELES-GAMBIAE POPULATIONS FROM EAST AND WEST-AFRICA - COMPARISON OF MICROSATELLITE AND ALLOZYME LOCI

Genetic variation of Anopheles gambiae was analysed to assess interpop ulation divergence over a 6000 km distance using short tandem repeat ( microsatellite) loci and allozyme loci. Differentiation of populations from Kenya and Senegal measured by allele length variation at five mi crosatellite loci was compared with estimates calculated from publishe d data on six allozyme loci (Miles, 1978). The average Wright's F-ST o f microsatellite loci (0.016) was lower than that of allozymes (0.036) . Slatkin's R(ST) values for microsatellite loci were generally higher than their F-ST values, but the average R(ST) value was virtually ide ntical (0.036) to the average allozyme F-ST. These low estimates of di fferentiation correspond to an effective migration index (Nm) larger t han 3, suggesting that gene flow across the continent is only weakly r estricted. Polymorphism of microsatellite loci was significantly highe r than that of allozymes, probably because the former experience consi derably higher mutation rates. That microsatellite loci did not measur e greater interpopulation divergence than allozyme loci suggested cons traints on microsatellite evolution. Alternatively, extensive mosquito dispersal, aided by human transportation during the last century, bet ter explains the low differentiation and the similarity of estimates d erived from both types of genetic markers.