Atmospheric concentrations of carbon dioxide (CO2) have steadily increased from 280 ppm to 367 ppm since the industrial revolution. Carbon cycle models predict that concentrations will reach between 540 and 970 ppm by 2100. Nitrogen availability in natural ecosystems is also continuing to increase, due to agricultural run-off and industrial pollution. This research focuses on how these two environmental variables alter insect herbivory on herbaceous plants. The PIs will investigate how elevated CO2 and increased soil nitrogen affect insect herbivory on five Flaveria species in an open top chamber experiment. The genus Flaveria provides a highly suitable system with which to investigate effects of environmental change on plants and their insect herbivores because the species in this genus possess a range of physiological pathways for photosynthesis. Flaveria species are predicted to show a range of physiological responses to CO2 and nitrogen availability, which can be clearly explained based on their photosynthetic pathways. This research will determine the relationship between the responses of a plant's leaf characteristics to increased CO2 and nitrogen and the degree to which insect feeding is influenced by differences in these leaf characteristics. The leaves of plants grown at elevated CO2 levels undergo changes in their water content, in the concentrations of chemicals that defend against insect herbivory, and nitrogen content. Differences in plant chemistry may therefore alter the feeding preferences of insect species, leading to changes in the diversity and composition of natural plant habitats and communities.
