EAGER: The evolution of anti-predator defenses in tortoise beetles (Coleoptera: Chrysomelidae: Cassidinae)

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The evolutionary hypothesis of 'escape and radiation' posits that when a species develops a novel defense against its enemies (predators or parasites) this results in more rapid speciation, at least until the enemy species (or new enemy species) adapt to circumvent this defense. The evolution of yet another novel defensive trait resets the cycle anew, which ultimately results in the accumulation of species over evolutionary time. It has been suggested that this evolutionary processes is ubiquitous and can be found not only in plant-herbivore interactions but also in many other ecological associations, where it may likewise foster creation of new biodiversity over evolutionary time. Despite the theoretical importance of this hypothesis, evidence is limited that novel defense traits spurs the diversification of new species. This study will test this hypothesis using a species rich group of plant-eating beetles and an innovative set of field bioassay methods. The work will address whether novel defensive traits are narrow or broad in efficiency against predators, and whether the evolution of novel defense traits is correlated with increased rates of speciation. This project and the novel data it will produce, promise to transform systematic study of plant-insect interactions. Understanding defense trait evolution can reveal important and novel information about speciation patterns in insects, which can be important for agriculture, invasive species control, and sustaining biodiversity. This project will also support the research training of three undergraduates, and data, specimens, and images will be disseminated broadly via publicly accessible resources.This project will provide an innovative study that will combine phylogenetics, chemical ecology, and bioassay performance experiments in an integrated approach that will enable the PIs to detect: (i) increased prey speciation rates due to the evolution of novel or more potent defensive traits; and (ii) whether the mechanism of diversification via novel defense acquisition is associated with broad-spectrum defenses, or with narrow, highly specific anti-predator adaptations. This study will significantly advance our understanding of the macroevolutionary processes that underlie the relationship between novel defensive trait evolution and prey diversification and will provide a suite of research tools for future investigations