Estimates of gene flow from rare alleles in natural populations of medflyCeratitis capitata(Diptera: Tephritidae)

Abstract

AbstractGene flow based on the spatial distribution of rare alleles at 25 gene loci was estimated in 15 populations ofCeratitis capitata(Wiedemann) from different parts of the world. Estimates ofNm, the number of migrants exchanged per generation among populations in different regions of the world, appeared to be quite similar, ranging from 3.36 in tropical Africa to 2.94 in the New World and 2.72 in Mediterranean basin populations. This suggests that gene flow among neighbouring populations of medfly is quite extensive. The genetic differentiation in American, Mediterranean and African populations was related to major climatic differences between North and South. These differences arise mainly from five loci that showed gene frequency patterns suggestive of latitudinal clines in allele frequencies. The clinal variation was such that tropical-subtropical populations were more heterozygous than temperate populations. It was concluded that gene flow, counteracting the forces of natural selection and genetic drift, determines the extent to which geographical populations ofC. capitataare differentiated.