Systematics, diversity & speciation of Lepidoptera

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Spruce budworm moths are major defoliators of conifer forests in North America, influencing forest structure by their regular outbreaks and causing much economic damage despite many decades of effort to manage their population numbers. Butterflies of the Old World Swallowtail species group have received much attention as well, although mainly because they are large and visually attractive to naturalists. Both groups of Lepidoptera share the fact that we still don't know how many species they contain and how to tell them apart, in spite of years of study. This may be because these species are in the process of diverging in some areas but merging in others. We would like to know why this might be happening, since this would give us insight into how speciation occurs. In other words how and why can one species can turn into two species? And can new species sometimes form from hybridization between previously distinct species? My graduate students will trace the origin and evolution of spruce budworm moths and their relatives in the genus Choristoneura in the context of their associations with the trees they feed on, the attractants they use for mating, and the continental dispersal routes that they have used to spread across the Northern Hemisphere and through Africa. They will also study the extent to which local landscape structure influences mating and gene flow between the species of swallowtail butterflies across North America. New technologies for efficiently surveying large numbers of genes in many specimens have made this an exciting time to carry out this kind of study. We can finally ask what kinds of genes, and how many, are implicated in divergences or merging of populations. Older work has suggested that the genes associated with species differences are disproportionately found on the sex chromosomes which, in the case of butterflies and moths, make up only about 3% of their total genome. If that is true, then perhaps we should be looking first at the genes on these chromosomes if we want to effectively diagnose and understand the diversity of moths, butterflies, and life around us.