Meeting Abstract

78.6  Tuesday, Jan. 6  Divergence of diapause physiology in a speciating insect: do changes in diapause energetics accompany the evolution of seasonal timing in the apple maggot fly? RAGLAND, GJ*; SIM, S; FEDER, JL; HAHN, DA; University of Florida; University of Notre Dame; University of Notre Dame; University of Florida gragland@ufl.edu

The recent evolution of apple-infesting populations of Rhagoletis pomonella from an ancestral hawthorn-infesting population provides a textbook example of seasonal adaptation driving ecological speciation. Our study identifies physiological differences in diapause energetics associated with this recent evolutionary formation of two distinct host races. In general, changes in life cycle timing can change patterns of selection on particular life history stages. R. pomonella complete one generation per year, entering an overwintering pupal dormancy (diapause) shortly after larvae exit the host fruit. Apples fruit earlier in the year than hawthorns, and the apple host race emerges as adults and enters pupal diapause earlier than the hawthorn host race. Early entrance into diapause subjects the diapausing pupae of apple flies to a longer, warmer, more metabolically demanding pre-winter period, selecting for either decreased metabolism or increased nutrient storage. We show that apple pupae contain more lipid than hawthorn pupae, and we discuss preliminary results distinguishing host fruit and genetic effects on the lipid phenotype. We also present preliminary analyses of host race differences in resting metabolic rate. Finally, we discuss how our results connect to the hypothesized relationship between geographic climatic variation and sympatric speciation via host switching.