Meeting Abstract
Divergent adaptation to seasonality, novel habitats, and niches can drive evolution of reproductive isolation between populations through the process of ecological speciation. Divergence in seasonal life history timing may be a particularly potent driver of ecological speciation for insects. In seasonal habitats, the timing of resource availability is a critical dimension of niche space for many specialist insects. Moreover, insect systems of mating often have a strong temporal component, resulting in a pleiotropic link between ecological divergence and reproductive isolation. Here we investigate the gene regulatory basis of seasonal life history divergence in a model system for ecological speciation, Rhagoletis pomonella, the apple maggot fly. The two host races in the classic R. pomonella system show strong differences in their adult eclosion phenology corresponding to phenological differences of their two host plants, downy hawthorn and domestic apple. This shift in life history timing is governed by the timing of pupal diapause termination, with apple flies terminating diapause sooner after the cessation of winter. Here we show differential gene expression between the host races upstream of known differences in diapause development. We report the results of an RNAseq study aimed at comparing the neuro-endocrine transcriptome of the two host races during diapause development, and we identify gene regulatory networks expressed in the earliest stages of diapause termination. Our results shed light on how insect life history timing evolves in nature and move us closer to being able to draw concrete connections between ecologically divergent phenotypes and patterns of genomic differentiation during seasonal adaptation.
