The impact of plant genetic variation and water stress on plant-herbivore  interactions          

Abstract

Plant genotype, drought stress, and their interaction are among the factors contributing to the susceptibility of the tall goldenrod, Solidago altissima, to herbivory by the chrysanthemum lace bug, Corythucha marmorata. The plant’s concentration of nitrogen, a critical and often limiting nutrient, differs with plant genotype and drought, but few studies have investigated the impact of the interaction of genotype and drought on herbivory and plant nitrogen. We established a common garden in Duluth, MN, of tall goldenrod collected from a local Minnesota site to analyze the effects of goldenrod genotype and drought on leaf nitrogen and lace bug preference and performance. Lace bugs had oviposition, nymph, and adult preferences among host plant genotypes, drought treatments, and among genotype and drought combinations. Nymph and adult survival and adult weight varied significantly due to plant genotype, drought treatment, the interaction of plant and drought treatment, and the interaction of treatment with lace bug density. Oviposition preference and offspring performance were significantly positively related. Leaf nitrogen increased with the increasing severity of the drought treatment in the absence of lace bugs. However, in the presence of lace bugs, there was no difference in nitrogen among drought treatments. We hypothesize that lace bugs feed on plants until nitrogen concentration reduces to a lower threshold and then move between plants until they have equalized the nitrogen concentration among all plants.