Population structure of Rhagoletis pomonella, the apple maggot fly

Abstract

Rhagoletis pomonella, the apple maggot fly, is the best-known member of the R. pomonella species complex. Rhagoletis pomonella has attracted interest because of its economic importance and because it has been a central focus of debate over sympatric speciation via host race formation. Based on electrophoretic data for 17 allozyme loci, the population structure of the ancestral hawthorn race of R. pomonella is characterized by: (i) strong geographical differentiation across eastern North America (FST = 0.148), (ii) pronounced latitudinal clines in allele frequencies at three loci, Aat-2, Dia-2 and Had, and (iii) very strong linkage disequilibrium involving two of these loci, Dia-2 and Aat-2, which are closely linked. The 10-fold greater level of population differentiation in R. pomonella compared with its close relative R. mendax may be related to its greater flexibility in life history timing.