CONTRIBUTIONS OF HOST USE AND GEOGRAPHIC DISTANCE TO PHENOTYPIC AND GENOMIC VARIATION IN COMMERCIALLY RELEVANT FRUIT-INFESTING FLIES

Understanding the intricate relationships between crops and their insect pests is essential to successful agricultural systems. Since insects form tight associations with their host plants, these relationships can drive differentiation between species that are adapted to different hosts. But, geographic distance also generates variation between populations which could contribute to speciation. It remains a challenge to disentangle the relative strengths of host use and geographic distance to population differentiation and whether these mechanisms play a similar role in divergence between species. I will leverage multiple populations and species of a host-specialist insect to evaluate the relative contributions of these mechanisms in (1) a suite of morphological, behavioral, and phenological mating traits and (2) population genomics. I will compare several species in the Rhagoletis genus that vary in their adaptation to host plants and distribution across the United States. By capitalizing on this relative difference between species in the importance of host use or geographic distance, I will be able to assess the extent of variation explained by each mechanism between species (species comparison) and within species (population comparison). This project will generate a robust understanding of variation within and between populations that can inform pest management strategies of host-specialist insects.