Many plant-eating insects (herbivores) chemically defend themselves using toxins obtained (sequestered) from plants. However, such defenses can be too much of a good thing if they impose a cost, such as reduced growth rate or fewer offspring. This study examines the evolution of sequestration, using the pipevine swallowtail butterfly as a model system. Pipevine swallowtails are unpalatable because their caterpillars sequester toxic alkaloids (aristolochic acids) from their pipevine host plants. Breeding experiments will assess genetic variation for sequestration. Natural selection should temper the amount sequestered to maximize defensive benefits and minimize costs. Field and laboratory experiments will address these costs / benefits through diet chemistry manipulation and selective breeding for sequestration ability. The ability to sequester from the chemical cocktail present in particular pipevine species could facilitate differentiation of butterfly populations. Laboratory crossbreeding of butterfly populations using different pipevine species will assess the extent of local adaptation.
This study will enhance our understanding of how plant chemistry directs herbivore evolution. This research will provide training in experimentation and analytical chemistry for undergraduate and graduate students, and will involve hands-on scientific experience for middle and high school science educators. Finally, this project will serve as a vehicle for public education about ecological interactions and evolution
