Abstract
Early-season herbivory can cause plants to induce resistance to subsequent
herbivores, and this ubiquitous plant defense strategy has been shown to be adaptive when
subsequent vegetative-feeding herbivores impact plant fitness. However, a growing number of
studies show that leaf herbivory can also induce defenses in plant reproductive tissues, which
may deter mutualists such as pollinators and seed dispersers, or antagonists such as florivores
and seed predators. Due to their direct interaction with plant reproductive tissues, deterrence
of these mutualists or antagonists may have large negative or positive effects on plant fitness.
Despite numerous predictions, we know little regarding the fitness consequences of leaf-toreproductive
tissue induction in nature. Here, using observations of natural populations and
manipulative field experiments, we show that leaf herbivory by the invasive Japanese beetle
(Popillia japonica) induces an accumulation of jasmonic acid and complex phenolics in
reproductive tissues of the common evening primrose (Oenothera biennis). Consequently, seed
predation by three native Lepidoptera is reduced by 77% on beetle-induced plants, while leaf
herbivory itself has little impact on lifetime reproductive output. These results show that O.
biennis benefits from being consumed by an invasive folivore, and that leaf-to-reproductive
tissue induction can be an adaptive trait. Induced plant defenses can therefore be beneficial in a broader community context than previously realized.
