Parents don't dictate the menu: Lack of strong host-specific parental effects may help maintain dietary generalism

The environment or experiences of a parent generation can impact the fitness of the next generation, a phenomenon known as parental effects. While a high-quality diet can directly benefit an individual and a low-quality diet can reduce fitness, a parental effect occurs only when there is a transgenerational response to these stimuli that manifests in the individual's offspring. In dietary generalists, a parental effect could play an important role for offspring performance if the species experiences considerable variation in quality across host plants; positive parental effects may result from host matching between parents and offspring on high-quality host plants, whereas negative effects may result from host matching on low-quality host plants or parent-offspring host mismatching. A lack of strong parental effects across host plants may also help explain the maintenance of dietary generalism for generalist herbivores. We investigated whether parental effects occur in the generalist herbivore fall webworm (Hyphantria cunea) by testing whether offspring performance depended on the host plant on which the parental generation was reared. We found that parental effects do not play an important role for fall webworm and the weak effects that do exist depend on both the larval and parental host plant. Rather than demonstrating benefits of parent-host matching, our results demonstrate that the offspring of parents from one poor-quality host performed worse on one high-quality host than offspring from any of the other hosts. Overall, our study suggests that larval host plant identity rather than parental effects is important to the performance of this generalist herbivore. Notably, a lack of strong, consistent parental effects may help explain the maintenance of dietary generalism in an extreme generalist herbivore.