Effects of elevation on herbivore induced plant defense strategies in Solanum peruvianum

Induced plant responses to herbivory are essential for plant resistance. Adaptation to abiotic conditions and to different herbivore pressure can affect induced plant responses. We observed altitudinal differences in herbivory in the wild tomato plant, Solanum peruvianum. Solanum peruvianum is native to the western slopes of the Peruvian Andes and occurs over a wide elevation range (1000-3500m). Using S. peruvianum genotypes from three different elevations in the Andes, we conducted greenhouse and field experiments, to test whether adaptation to abiotic factors and herbivore pressure at different elevations influences plant traits, including induced defense responses. Leaf size decreased and leaf number increased as elevation increased. Using Manduca sexta as a model herbivore, we showed differences in herbivore-induced proteinase inhibitor and secondary metabolite levels in plants originating from different elevations. Herbivore performance was the poorest on plants from the medium elevation (2400-2500 meters) due to the highest chemical defense traits. We discuss the results of the bioassays and chemical characterization in regard to natural arthropod diversity and herbivory observed at the different elevations and the evolution of plant resistance traits.