Genetic differentiation between three ecological variants ('type', mysorensis' and 'intermediate') of malaria vector Anopheles stephensi (Diptera: Culicidae)

Anopheles stephensi is the main vector of urban malaria in South Asia. Three ecological variants ('type', mysorensis' and 'intermediate') of An. stephensi have been reported on the basis of ecology and egg morphology. However, it is unclear if there is any genetic isolation between the three variants. We analyzed the three variants of An. stephensi using eight microsatellite loci and found that large and significant genetic differentiation exists between them (mean F-ST = 0.393 and mean R-ST = 0.422). Pairwise estimates of genetic differentiation between the variants were 'type' versus mysorensis' (mean F-ST = 0.411 and mean R-ST = 0.308), 'type' versus 'intermediate' (mean F-ST = 0.388 and mean R-ST = 0.518) and 'intermediate' versus mysorensis' (mean F-ST = 0.387 and mean R-ST = 0.398) and all were statistically significant (P < 0.05). The greater sensitivity of R-ST in differentiation indicated that mutations and not genetic drift had generated the differences between three variants of An. stephensi. The present study indicated large genetic differentiation and presence of non-significant low level of gene flow between the three variants ('type', mysorensis' and 'intermediate') of An. stephensi.