In order to survive and reproduce, flowering plants must balance the conflicting selective pressures of herbivore avoidance and pollinator attraction. Links between herbivory and reproduction are often attributed to indirect effects of leaf damage on pollination via reductions in floral allocation, or increases in chemical defenses on herbivore-damaged plants. However, the impacts of herbivory on pollinators have the potential to extend beyond initial floral visits when plant defenses impact pollinator health, foraging behavior, and reproductive success. Here, we examine important but underexplored ways in which herbivory may alter floral phenotype and thus impact pollinators. First, we outline genetic and biochemical mechanisms predicted to underlie floral changes following herbivory, as they impact the floral resources (nectar and pollen) sought by pollinators. Next, we discuss how the consumption of secondary compounds might impact pollinator fitness, including carryover effects on subsequent foraging, mating success, and transgenerational effects on offspring. We consider how pollinator health, life history, and coevolutionary history might result in context-dependent impacts of plant defensive chemistry on pollinator fitness. Finally, we call for studies that measure the impact of herbivore-induced plant defenses on the full spectrum of flower visitors, and contrast case studies on conventional pollinators (for example, generalized bees) versus insects whose larvae are herbivores on the same plants that adults pollinate (such as several butterflies and moths). By linking these consequences of herbivory to fitness effects on both herbivores and pollinators, we will better understand how coevolution between plants, herbivores, and pollinators shapes both defensive and reproductive plant traits.

Laboratory populations of D. melanogaster have been subjected to selection for survival after live spores of B. cereus were introduced as a pathogenic agent. The present study was designed to investigate correlated traits: respiration as a metabolic trait and movement as a behavioral trait. An underlying hypothesis was that the evolution of increased survival after B. cereus infection exerts a metabolic cost associated with elevated immunity and this would be detected by increased respiration rates. There was support for this hypothesis in the male response to selection, but not for selected-line females. Two phenotypic effects were also observed in the study. Females especially showed a marked increase in respiration after mating compared to the other assay stages regardless of whether respiration was measured per fly or adjusted by lean mass or dry weight. Given that mating stimulates egg production, it is feasible that elevated metabolism was needed to provision oocytes with yolk. Females also moved less than males, perhaps due to behaviors related to oviposition whereas elevated male activity might be due to behaviors associated with seeking females and courtship. Relatively low movement of females indicated that their elevated respiration after mating was not due to a change in locomotion.

Flowering plants use volatiles to attract pollinators while deterring herbivores. Vegetative and floral traits may interact to affect insect behavior. Pollinator behavior is most likely influenced by leaf traits when larval stages interact with plants in different ways than adult stages, such as when larvae are leaf herbivores but adult moths visit flowers as pollinators. Here, we determine how leaf induction and corresponding volatile differences in induced plants influence behavior in adult moths and whether these preferences align with larval performance. We manipulated vegetative induction in four Nicotiana species. Using paired induced and control plants of the same species with standardized artificial flowers, we measured foraging and oviposition choices by their ecologically and economically important herbivore/pollinator, Manduca sexta. In parallel, we measured growth rates of M. sexta larvae fed leaves from control or induced plants to determine if this was consistent with female oviposition preference. Lastly, we used plant headspace collections and gas chromatography to quantify volatile compounds from both induced and control leaves to link changes in plant chemistry with moth behavior. In the absence of floral chemical cues, vegetative defensive status influenced adult moth foraging preference from artificial flowers in one species (N. excelsior), where females nectared from induced plants more often than control plants. Plant vegetative resistance consistently influenced oviposition choice such that moths deposited more eggs on control plants than on induced plants of all four species. This oviposition preference for control plants aligned with higher larval growth rates on control leaves compared with induced leaves. Control and induced plants of each species had similar leaf volatile profiles, but induced plants had higher emission levels. Leaves of N. excelsior produced the most volatile compounds, including some inducible compounds typically associated with floral scent. We demonstrate that vegetative plant defensive volatiles play a role in host plant selection and that insects assess information from leaves differently when choosing between nectaring and oviposition locations. These results underscore the complex interactions between plants, their pollinators, and herbivores.

Premise Plant defenses are shaped by many factors, including herbivory, lifespan, and mating system. Predictions about plant defense and resistance are often based on resource allocation trade‐offs with plant growth and reproduction. Additionally, two types of plant resistance, constitutive and induced resistance, are predicted to be evolutionary alternatives or redundant strategies. Given the variety of plant trait combinations and non‐mutually exclusive predictions, examining resistance strategies in related species with different combinations of growth and reproductive traits is important to tease apart roles of plant traits and evolutionary history on plant resistance. Methods Phylogenetic comparative methods were used to examine the potentially interacting influences of life history (annual/perennial), mating system (self‐compatible/self‐incompatible), and species growth rates on constitutive resistance and inducibility (additional resistance following damage) across Physalis species (Solanaceae). Results Resistance was evolutionarily labile, and there was no correlation between constitutive resistance and inducibility. Annual species with fast growth rates displayed higher constitutive resistance, but growth rate did not affect constitutive resistance in perennials. In contrast, inducibility was negatively associated with species growth rate regardless of life history or mating system. Conclusions The different effects of plant life history and growth rate on constitutive resistance and inducibility indicate that defensive evolution is unconstrained by a trade‐off between resistance types. The interactions among plant life history, growth, and herbivore resistance show that plant defense is shaped not only by herbivore environment, but also by plant traits that reflect a plant's evolutionary history and local selective pressures.