Transgenerational effects of food quantity and quality on disease resistance in the western tent caterpillar, Malacosoma californicum pluviale

Increasing population density may alter food quantity or quality. Dietary stressors can interact simultaneously and produce emergent fitness effects both intragenerationally and potentially transgenerationally, including changes in pathogen resistance. Western tent caterpillar (WTC) Malacosoma californicum pluviale populations undergo regular 6-11 year cycles; epizootics of nucleopolyhedrovirus (NPV) characterize population declines and may be triggered by density-related dietary changes. I tested the transgenerational interaction of three factors likely to be influenced in rising WTC populations. I manipulated foliage quantity, quality, and the presence of phylloplane bacteria provided to the parental generation and assessed NPV resistance and immunity in their offspring. Food limitation had strong impacts on life history traits of tent caterpillars. Somewhat unexpectedly, changes in foliage quality and ingestion of phylloplane bacteria had transgenerational effects on offspring, enhancing their NPV resistance and affecting expression of background pathogens. There was no evidence for increased disease susceptibility in offspring from combined parental stressors.