The genomics of diet breadth in fall webworm (Hyphantria cunea, Erebidae)

The majority of insect herbivores are specialized to feed on one or a few host plant families, though extreme generalism persists in some herbivore species. Significant attention has been paid to the genomic basis of adaptation in specialist herbivores. In contrast, dietary generalists, especially non-pest species, are less well represented in studies of host plant adaptation, even though some generalist herbivores show geographic and intraspecific differences in diet breadth and host preference. Studying a geographically and ecologically diverse generalist provides an opportunity to probe the genomic and evolutionary basis of dietary generalism. We collected whole genome sequence data from widespread generalist Hyphantria cunea (Lepidoptera: Erebidae) populations across its North American range and from its two genetically distinct morphotypes (red-headed and black-headed, hereafter red and black) to investigate how these populations are structured and how geographic variation in diet breadth and host use might produce genomic signatures of selection. We confirm that the H. cunea reds and blacks are genetically distinct and that the Colorado red population is differentiated from the eastern red populations. We also report a hybridization zone between blacks and reds in Massachusetts, where the growing season is compressed and reds and blacks overlap temporally. We will present results about the genomic distribution of polymorphisms under selection across geographic regions that vary in diet breadth, and in hybrid populations. Understanding diet breadth and its genomic basis is critical for understanding community ecology, the diversity and specialization of insects, and management and conservation of both plants and insects.