Analysis of the genetic structure of a natural population of Anastrepha fraterculus (Diptera : Tephritidae)

The South American fruit fly Anastrepha fraterculus (Wiedemann) is distribu ted from Mexico to northern and central Argentina. It is a polyphagous spec ies using diverse fruit from wild and cultivated tree or shrub species as f eeding and breeding sites. During larval stages, the environment is discont inuous, because the larvae are restricted to the fruit where their eggs wer e laid. This population structure should profoundly influence the distribut ion of genetic variation and the modes of action of adaptive mechanisms. Du ring the adult stage, in contrast, the population is not structured. In the current work we analyze the genetic structure in an Argentine population ( Yuto) among attacked fruits at 4 enzyme loci. The results differed from the expected for a random mating population in the genotypic frequency distrib ution, the effective inbreeding coefficients, and the correlation between a llelic and nonallelic valiant frequencies. The most plausible explanation i s that populations of this species may include heterogeneous groups of indi viduals having different origins as the species undergoes host shifts throu ghout the year.