Meeting Abstract
Much of the research on ecological speciation has focused on identifying traits underlying reproductive isolation and examining the resulting patterns of differentiation in the genome. However, drawing concrete connections between ecologically divergent phenotypes and genomic variation has proven difficult, particularly in the case of complex, polygenic traits. Closing the gap between ecological data and the genomic data may be accomplished by a physiologically-informed framework to identify the intermediate phenotypes involved in the manifestation of the trait under selection. Here we report results from a study aimed at examining the physiological basis for divergent life history timing in Rhagoletis flies. The two host races in the classic Rhagoletis pomonella system show strong differences in their adult eclosion phenology corresponding to phenological differences of their two host plants, downy hawthorn and domestic apple. In this study, we compared the post-winter metabolic trajectories of hawthorn and apple pupae to determine whether the allochronic isolation between the races is driven by the regulation of diapause termination or post-diapause development rates. We found that apple flies typically terminate diapause within the first few weeks of warm temperatures, while hawthorn flies stay in a state of metabolic suppression long into spring. Furthermore, timing of adult eclosion within each population was strongly correlated with the timing of diapause termination, with no evidence for differences in post-diapause rates of pharate adult development. Our results show that the precise stage of developmental divergence between the two races occurs shortly after the cessation of winter, allowing for finely focused studies comparing the transcriptomic, proteomic, and metabolomics profiles of the two races during this critical phase.
