A variety of ecological and evolutionary factors contribute to the susceptibility of the tall goldenrod, Solidago altissima to its natural enemy the chrysanthemum lace bug Corythucha marmorata. These factors include genetic variation due to geographic origin, genetic variation within a population, and environmental stress such as drought. We established a common garden in Duluth, MN of tall goldenrod collected from several US and Japanese sites to analyze the effects of genotypic variation among and within sites, drought, and the interaction of genotype and drought. One experiment measured lace bug preference for genotypes within and among geographic sites, and another experiment measured lace bug preference and performance among varying drought levels and genotypes. We recorded phenotypic characteristics and collected leaves for nitrogen sampling for each plant, and counted the number of lace bug adults, nymphs, and eggs found on each plant.
We found that i) genotypic variation within geographic sites had a larger influence on lace bug preference than variation among geographic sites, and ii) the interaction of drought and genotype determined plant susceptibility to lace bug. Lace bugs showed no preference among geographic sites, however, these plants were only moderately stressed and this may have masked variation in susceptibility. Lace bugs preferred and survived better on some genotypes within geographic sites compared to others and water stress levels impacted fitness and survival of lace bugs on genotypes. Increasing drought stress improved lace bug performance on some plants and reduced it on others. These results indicate that the interaction of water stress and plant genotype influences plant susceptibility to lace bug herbivory.