Effect of Phenology on Allele Frequency Divergence in Apple Maggot Fly Populations

Abstract

Recent electrophoretic studies have documented host-associated genetic differences in the apple maggot fly, Rhagoletis pomonella, from sympatric hawthorn and apple trees (Feder et al., 1988; McPheron et al., 1988) These demonstrations of the apparent widespread existence of host races have rekindled interest in possible mechanisms responsible for the lack of free interbreeding between fly populations on different hosts. Prokopy et al. (1988) evaluated host selection by flies from the two hosts and, although their findings demonstrate very complex behavioral patterns, found significant differences between the host races in acceptability of apple as a host. Smith (1988a and Smith McPheron, and Berlocher, unpublished) demonstrated that flies from apple and hawthorn have genetically-determined differences in time required for eclosion following diapause. Further, this time difference is correlated with the availability of suitable host fruits for oviposition.