D3114: The responses of native insect herbivores to invasive shrubs

Invasive species are a threat to the health of ecosystems at a global level. Within ecosystems, invasive plant species can drive shifts in trophic structure and food webs through their direct effect on insect herbivore populations. The colonization of invasive plant species by insects has not been widely or comprehensively studied. Over time insects are expected to colonize, and evolutionarily adapt to more efficiently consume, invasive plant species. In this project I compared the diversity and abundance of caterpillars on invasive plants from within a heavily invaded region and from within a scarcely invaded region. These surveys were conducted throughout each of the two regions using beat sheets, while making a quantification of sampling effort. Additionally adult moths from each region were captured and stored in the lab, and their eggs/caterpillars were individually reared on the invasive plants. Given that native caterpillar communities in the heavily invaded region have had more exposure to the invasive plant, and more time to develop adaptations towards using it, I expect to find greater diversity and abundance of caterpillars on invasive plants in the heavily invaded region when compared to those in the scarcely invaded region, as well as higher growth rates and survival in caterpillars originating from the heavily invaded region when reared on the invasive plants. This research will help us understand how invasive plants are assimilated into natural communities, and whether the effects enemy release on invasive plant success may be mediated over time by herbivore adaptation.