Leaf Herbivory Research Articles

Plant defence responses to volatile alert signals are population‐specific

Herbivore‐induced volatiles are widespread in plants. They can serve as alert signals that enable neighbouring leaves and plants to pre‐emptively increase defences and avoid herbivory damage. However, our understanding of the factors mediating volatile organic compound (VOC) signal interpretation by receiver plants and the degree to which multiple herbivores affect VOC signals is still limited. Here we investigated whether plant responses to damage‐induced VOC signals were population specific. As a secondary goal, we tested for interference in signal production or reception when plants were subjected to multiple types of herbivore damage. We factorially crossed the population sources of paired Phaseolus lunatus plants (same versus different population sources) with a mechanical damage treatment to one member of the pair (i.e. the VOC emitter, damaged versus control), and we measured herbivore damage to the other plant (the VOC receiver) in the field. Prior to the experiment, both emitter and receiver plants were naturally colonized by aphids, enabling us to test the hypothesis that damage from sap‐feeding herbivores interferes with VOC communication by including emitter and receiver aphid abundances as covariates in our analyses. One week after mechanical leaf damage, we removed all the emitter plants from the field and conducted fortnightly surveys of leaf herbivory. We found evidence that receiver plants responded using population‐specific ‘dialects’ where only receivers from the same source population as the damaged emitters suffered less leaf damage upon exposure to the volatile signals. We also found that the abundance of aphids on both emitter and receiver plants did not alter this volatile signalling during both production and reception despite well‐documented defence crosstalk within individual plants that are simultaneously attacked by multiple herbivores. Overall, these results show that plant communication is highly sensitive to genetic relatedness between emitter and receiver plants and that communication is resilient to herbivore co‐infestation.

Leaf Fluctuating Asymmetry and Herbivory of Tibouchina heteromalla in Restored and Natural Environments.

Fluctuating asymmetry (FA) is a parameter to measure developmental stability in plants, which can be altered by disturbances, pollution, and biotic factors such as herbivory. We evaluated the effects of environmental stress and herbivory on the FA levels in individuals of Tibouchina heteromalla (Melastomataceae) that occur in natural and undergoing restoration areas in rupestrian grasslands at Serra do Cipó, Brasil. Individuals were collected and measured in seven restored and five natural areas, totalizing 240 individuals. We found that individuals in restored areas had greater leaf area, higher levels of insect herbivory and FA compared to individuals that occurred in natural areas. In both environments, the proportion of individuals with leaf damage caused by herbivory was higher than the proportion of undamaged individuals. In addition, FA was positively correlated with herbivory and total leaf area in both restored and natural areas. These results suggest that more favorable conditions in the restored areas enhanced leaf growth, resulting in higher FA.

Root herbivory indirectly affects above‐ and below‐ground community members and directly reduces plant performance

Summary There is a widespread recognition that above‐ and below‐ground organisms are linked through their interactions with host plants that span terrestrial subsystems. In addition to direct effects on plants, soil organisms such as root herbivores can indirectly alter interactions between plants and other community members, with potentially important effects on plant growth and fitness. We manipulated root herbivory by Acalymma vittatum in Cucumis sativus to determine indirect effects on arbuscular mycorrhizal fungi, leaf herbivory, the leaf pathogen downy mildew and pollinators. We also manipulated pollen receipt by plants to determine whether root herbivory reduced plant reproduction through changes in pollinator visitation. Overall, root herbivory had strong net negative effects on plant growth and fitness, with 34% reductions in both leaf and fruit production by high root damage levels relative to control, despite reduced infection by downy mildew. High root herbivory also reduced floral visitation by 39%, apparently due to lower flower production, as flower size and scent were unaffected. Above‐ground herbivory was not affected by root herbivores. Although root herbivory reduced pollinator visits, pollen receipt manipulations had no effect on fruit set, indicating that reduced pollinator service did not affect plant reproduction. Synthesis. Root herbivory had indirect effects on a range of community members, including mutualists and antagonists both above‐ and below‐ground. Although reduced pathogen infection associated with root herbivory would be expected to benefit plants, root herbivory had an overall strong negative effect on plant growth and reproduction, indicating that direct negative effects over‐rode any potential indirect benefits.

Leaf damage effects on leaf expansion timing in Mallotus japonicus (Euphorbiaceae)

AbstractFor many plant species, biotic factors determining the timing of leaf expansion have not been elucidated sufficiently. We investigated the effects of leaf damage on the timing of leaf defoliation and on the timing of leaf expansion in Mallotus japonicus (Euphorbiaceae). The degree of leaf herbivory of M. japonicus in the field was examined in summer, with subsequent investigation of the date of leaf defoliation in autumn and that of leaf expansion the following spring. Effects of artificial leaf damage on the timing of leaf defoliation and of leaf expansion were also examined in a greenhouse. In the field, the degree of leaf herbivory sustained by M. japonicus did not affect the timing of defoliation. However, the timing of leaf expansion the next spring advanced earlier, concomitantly with the increase of leaf damage during the previous year. Fifty per cent artificial leaf damage in M. japonicus saplings in summer had no marked effect on the timing of leaf defoliation in autumn. However, the effects of leaf damage on the timing of leaf expansion were apparent the following spring: the damaged plants expanded new leaves ca. 8 days earlier than control plants did. Plants that showed earlier leaf expansion tended to have a higher shoot/root ratio. Our results demonstrate that the plants advance the timing of their leaf expansion in response to leaf damage sustained during the previous year, suggesting that the shoot/root ratio is a determining factor.

Species Introductions and Their Cascading Impacts on Biotic Interactions in desert riparian ecosystems.

Desert riparian ecosystems of North America are hotspots of biodiversity that support many sensitive species, and are in a region experiencing some of the highest rates of climatic alteration in North America. Fremont cottonwood, Populus fremontii, is a foundation tree species of this critical habitat, but it is threatened by global warming and regional drying, and by a non-native tree/shrub, Tamarix spp., all of which can disrupt the mutualism between P. fremontii and its beneficial mycorrhizal fungal communities. Specialist herbivorous leaf beetles (Diorhabda spp.) introduced for biocontrol of Tamarix are altering the relationship between this shrub and its environment. Repeated episodic feeding on Tamarix foliage by Diorhabda results in varying rates of dieback and mortality, depending on genetic variation in allocation of resources, growing conditions, and phenological synchrony between herbivore and host plant. In this article, we review the complex interaction between climatic change and species introductions and their combined impacts on P. fremontii and their associated communities. We anticipate that (1) certain genotypes of P. fremontii will respond more favorably to the presence of Tamarix and to climatic change due to varying selection pressures to cope with competition and stress; (2) the ongoing evolution of Diorhabda's life cycle timing will continue to facilitate its expansion in North America, and will over time enhance herbivore impact to Tamarix; (3) defoliation by Diorhabda will reduce the negative impact of Tamarix on P. fremontii associations with mycorrhizal fungi; and (4) spatial variability in climate and climatic change will modify the capacity for Tamarix to survive episodic defoliation by Diorhabda, thereby altering the relationship between Tamarix and P. fremontii, and its associated mycorrhizal fungal communities. Given the complex biotic/abiotic interactions outlined in this review, conservation biologists and riparian ecosystem managers should strive to identify and conserve the phenotypic traits that underpin tolerance and resistance to stressors such as climate change and species invasion. Such efforts will greatly enhance conservation restoration efficacy for protecting P. fremontii forests and their associated communities.

Relation between flower head traits and florivory in Asteraceae: a phylogenetically controlled approach.

• While much research has examined the relation between leaf traits and herbivory, very little is known about the interaction between floral traits, particularly biochemical traits, and florivory. We investigated patterns between floral traits and florivory across multiple species using phylogenetic comparative approaches to enhance our understanding of the evolution of plant-florivore interactions.• The relation between the intensity of florivory and five biochemical traits (concentrations of carbon, nitrogen, phosphorus, water, and total phenolics) and two morphological traits (diameter and number of flower heads) were investigated in wild individuals of 18 native species of Asteraceae. The phylogenetic signals in the morphological traits and intensity of florivory were also tested.• We found that species with higher nitrogen, water, and total phenolics and lower phosphorus concentrations in the flower heads and species with a large number and diameter of flower heads tended to be attacked by florivores. In addition, we found significant phylogenetic signals in florivory and morphological traits.• Our results clearly show that biochemical traits also play important roles in plant-florivore interactions, as previously shown in plant-leaf herbivore interactions. The positive relationship between florivory and total phenolics implies that phenolic compounds in flower heads may not act as a defense in the species. In addition, the observed pattern of signals in florivory might not be solely explained by the signals of the measured traits and other plant traits may also play significant roles in plant-florivore interaction in these species.

Conspecific and Heterospecific Aboveground Herbivory Both Reduce Preference by a Belowground Herbivore.

Insect herbivores damage plants both above- and belowground, and interactions in each realm can influence the other via shared hosts. While effects of leaf damage on aboveground interactions have been well-documented, studies examining leaf damage effects on belowground interactions are limited, and mechanisms for these indirect interactions are poorly understood. We examined how leaf herbivory affects preference of root-feeding larvae [Acalymma vittatum F. (Coleoptera: Chrysomelidae)] in cucumber (Cucumis sativus L.). We manipulated leaf herbivory using conspecific adult A. vittatum and heterospecific larval Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) herbivores in the greenhouse and the conspecific only in the field, allowing larvae to choose between roots of damaged and undamaged plants. We also examined whether leaf herbivory induced changes in defensive cucurbitacin C in leaves and roots. We hypothesized that induced changes in roots would deter larvae, and that effects would be stronger for damage by conspecifics than the unrelated caterpillar because the aboveground damage could be a cue to plants indicating future root damage by the same species. In both the greenhouse and field, plants with damaged leaves recruited significantly fewer larvae to their roots than undamaged plants. Effects of conspecific and heterospecific damage did not differ. Leaf damage did not induce changes in leaf or root cucurbitacin C, but did reduce root biomass. While past work has suggested that systemic induction by aboveground herbivory increases resistance in roots, our results suggest that decreased preference by belowground herbivores in this system may be because of reduced root growth.

Leaf traits and herbivory on deciduous and evergreen trees in a tropical dry forest

Deciduous and evergreen trees coexist in tropical dry forests, but exhibit distinct leaf syndromes for resource-use efficiency and defenses against herbivores. Moreover, these functional groups may have contrasting patterns of temporal variation in leaf traits and herbivory along leaf ontogeny. We tested these predictions by comparing a set of leaf traits related to water stress and defense, and herbivory levels between young and mature leaves from evergreen leaf-exchanger and deciduous species. We evaluated deciduous and evergreen trees within the same habitat type: a tropical dry forest with 90–100% of leaf deciduousness during the dry season. We sampled 10 individuals of three deciduous and three evergreen species. Evergreen plants had greater leaf thickness and concentration of phenolics and tannins. On the other hand, deciduous plants had higher leaf nitrogen content and specific leaf area. Deciduous plants lost twice as much leaf area by herbivory as evergreen plants (6.48% versus 3.20%), and leaf damage was positively related to both phenolic compounds and nitrogen content. Mature leaves from both phenological groups had higher levels of tannins and phenolic compounds, and lower levels of nitrogen and herbivory increment than young leaves. Our results suggest an adaptive convergence on leaf traits primarily related to water stress for different species within each phenological group. Some of these traits also play a role in leaf palatability, although the fitness consequences of the absolute difference in leaf damage (approximately 3%) between evergreen and deciduous species remain unclear.

Latitudinal variation in herbivory: influences of climatic drivers, herbivore identity and natural enemies

Although a number of investigations have concluded that lower latitudes are associated with increases in herbivore abundance and plant damage, the generality of this pattern is still under debate. Multiple factors may explain the lack of consistency in latitude–herbivory relationships. For instance, latitudinal variation in herbivore pressure may be shaped entirely or not by climatic variables, or vary among herbivore guilds with differing life‐history traits. Additionally, the strength of top–down effects from natural enemies on herbivores might also vary geographically and influence latitude–herbivory patterns. We carried out a field study where we investigated the effects of latitude and climate on herbivory by a seed‐eating caterpillar and leaf chewers, as well as parasitism associated to the former across 30 populations of the perennial herb Ruellia nudiflora (Acanthaceae). These populations were distributed along a 5° latitudinal gradient from northern Yucatan (Mexico) to southern Belize, representing one‐third of the species' latitudinal distribution and the entirety and one‐third of the precipitation and temperature gradient of this species' distribution (respectively). We found opposing latitudinal gradients of seed herbivory and leaf herbivory, and this difference appeared to be mediated by contrasting effects of climate on each guild. Specifically, univariate regressions showed that seed herbivory increased at higher latitudes and with colder temperatures, while leaf herbivory increased toward the equator and with wetter conditions. Multiple regressions including temperature, precipitation and latitude only found significant effects of temperature for seed herbivory and latitude for leaf herbivory. Accordingly, that latitudinal variation in seed herbivory appears to be driven predominantly by variation in temperature whereas latitudinal variation in leaf herbivory was apparently driven by other unexplored correlates of latitude. Parasitism did not exhibit variation with latitude or climatic factors. Overall, these findings underscore that the factors driving latitudinal clines in herbivory might vary even among herbivore species coexisting on the same host plant.

Using 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) to study carbon allocation in plants after herbivore attack.

BackgroundAlthough leaf herbivory-induced changes in allocation of recently assimilated carbon between the shoot and below-ground tissues have been described in several species, it is still unclear which part of the root system is affected by resource allocation changes and which signalling pathways are involved. We investigated carbon partitioning in root tissues following wounding and simulated leaf herbivory in young Nicotiana attenuata plants.ResultsUsing 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), which was incorporated into disaccharides in planta, we found that simulated herbivory reduced carbon partitioning specifically to the root tips in wild type plants. In jasmonate (JA) signalling-deficient COI1 plants, the wound-induced allocation of [18F]FDG to the roots was decreased, while more [18F]FDG was transported to young leaves, demonstrating an important role of the JA pathway in regulating the wound-induced carbon partitioning between shoots and roots.ConclusionsOur data highlight the use of [18F]FDG to study stress-induced carbon allocation responses in plants and indicate an important role of the JA pathway in regulating wound-induced shoot to root signalling.

Leaf wounding or simulated herbivory in young N. attenuata plants reduces carbon delivery to roots and root tips.

In Nicotiana attenuata seedlings, simulated herbivo ry by the specialist Manduca sexta decreases root growth and partitioning of recent photoassimilates to roots in contrast to increased partitioning reported for older plants. Root elongation rate in Nicotiana attenuata has been shown to decrease after leaf herbivory, despite reports of an increased proportion of recently mobilized photoassimilate being delivered towards the root system in many species after similar treatments. To study this apparent contradiction, we measured the distribution of recent photoassimilate within root tissues after wounding or simulated herbivory of N. attenuata leaves. We found no contradiction: herbivory reduced carbon delivery to root tips. However, the speed of phloem transport in both shoot and root, and the delivery of recently assimilated carbon to the entire root system, declined after wounding or simulated herbivory, in contrast with the often-reported increase in root partitioning. We conclude that the herbivory response in N. attenuata seedlings is to favor the shoot and not bunker carbon in the root system.

Leaf herbivory and monodominance in a Cerrado–Amazonia transitional forest, Mato Grosso, Brazil

Monodominant tropical forests occur on several continents, including the Brazilian Amazon. In this study, we tested the hypothesis that seedling escape from leaf herbivory contributes to the maintenance of the monodominant Brosimum rubescens forest. The study was undertaken both in a monodominant forest of B. rubescens and in an adjacent seasonal forest in the transitional zone between the Cerrado and the Amazonian forest biomes. Percentage of leaf area damaged and herbivory rates were evaluated on young and mature leaves of seedlings of Brosimum rubescens, Protium pilosissimum and Tetragastris altissima in the understory and in the gap between the monodominant and seasonal forests. Little evidence of any significant relationship between leaf herbivory and seedling density indicates that the monodominant species does not follow the hypothesized pattern of an intensive herbivore attack in areas of higher seedling density. The escape of Brosimum rubescens from herbivore pressure under conditions of high seedling density may be part of a set of conditions that determine the maintenance of this monodominant forest.

Spatial variation in leaf traits and herbivore community within the beech canopy between two different latitudes

To understand how the herbivore community on beech canopies varies between two different latitudes, we assessed leaf traits and herbivory by three major feeding types (chewing, mining, and galling) at different positions in the canopy using a scaffolding system along a 1,400-km latitudinal gradient between Kuromatsunai (north) and Shiiba (south) in Japan. The chemical and morphological traits of the canopy foliage differed significantly between latitudes and between canopy parts. The leaf mass per area (LMA), leaf nitrogen, and carbon/nitrogen (CN) ratio were higher at south latitude than at north latitude. The upper canopy had a greater LMA, leaf nitrogen, and CN ratio than the lower canopy at both latitudes. On the other hand, herbivory by the three major feeding types differed significantly between latitudes and between canopy parts. The miner and galler densities were higher at south latitude than at north latitude, while the chewing herbivory was lower, showing different latitudinal patterns among feeding types. Among these feeding types, only chewing herbivory was higher in the lower canopy than in the upper canopy at both latitudes. The stepwise regression models showed that LMA and CN ratio explained spatial variation in chewing herbivory. Our study demonstrates that the latitudinal and spatial variations in leaf traits can play an important role in determining the latitudinal and spatial variations in the herbivore community on beech canopies via different responses of each feeding type.

Latitudinal gradients in herbivory onOenothera biennisvary according to herbivore guild and specialization

The latitudinal herbivory‐defense hypothesis (LHDH) posits that herbivory and plant defenses increase toward lower latitudes. Recent studies provide contradictory evidence and suggest alternative explanations for biogeographic patterns in plant–herbivore interactions. Here we test the LHDH by sampling herbivory from multiple generalist and specialist insect herbivores over the entire latitudinal native range of the plant speciesOenothera biennis L. (Onagraceae). We sampled 79 populations on a 16° north‐south gradient from Ontario and Maine to Alabama and Florida. From each population, we quantified herbivory across feeding guilds by considering leaf herbivory caused by generalist insects, damage by a specialist stem‐boring beetle, and flower/seed herbivory by three Lepidoptera that specialize onOenothera. We also related environmental and population density variables to herbivory. Our results show that latitudinal patterns vary dramatically among herbivore species. While generalist leaf herbivory showed no latitudinal pattern, stem borer damage increased with decreasing latitude. By contrast, the specialist flower/seed herbivores all caused less damage at lower latitudes. Temperature explained slightly more variation in herbivory than latitude, while precipitation and population density were less important. Overall, we show that every pattern of herbivory (positive, negative and no relationship) is possible across a latitudinal gradient, and this variation depends on the insects' degree of specialization and feeding guild.

Drought stress and leaf herbivory affect root terpenoid concentrations and growth of Tanacetum vulgare.

Plant responses of both shoots and roots to combined abiotic and biotic stress have been rarely investigated. However, stresses such as drought and aboveground herbivory might lead to conflicting resource allocation patterns and pronounced shifts in shoot vs. root defenses. In the present study, the effects of water availability and leaf herbivory by caterpillars of a generalist on various shoot and root traits of the aromatic plant Tanacetum vulgare L. were investigated. This species contains terpenoids in leaves and roots, which can differ in composition among individuals, forming so-called chemotypes. To test for intraspecific variation, responses were investigated in two chemotypes, the thujone and the carvyl acetate chemotype. Furthermore, effects of differences in plant quality on the herbivores were studied. Shoot biomass significantly decreased due to drought and herbivory, whereas the root/shoot ratio increased following drought but was unaffected by herbivory. No shifts in C/N ratios were found. In contrast to our expectation, leaf terpenoid concentrations decreased only slightly due to drought, whereas root terpenoids were significantly induced by both drought and herbivory. Chemotypes showed distinct responses to drought at least in the root/shoot ratio, with a higher drought sensitivity of the carvyl acetate chemotype. The body mass of the caterpillars was unaffected by the irrigation treatment but depended on chemotype and terpenoid concentration of the plants. Thus, both qualitative and quantitative defenses strongly affect herbivore development. The present results offer new insights into the above- and belowground organ-specific responses of plants. They highlight the importance of roots in response to various environmental challenges.

Evidence for shifts to faster growth strategies in the new ranges of invasive alien plants.

SummaryUnderstanding the processes underlying the transition from introduction to naturalization and spread is an important goal of invasion ecology. Release from pests and pathogens in association with capacity for rapid growth is thought to confer an advantage for species in novel regions.We assessed leaf herbivory and leaf-level traits associated with growth strategy in the native and exotic ranges of 13 invasive plant species from 256 populations. Species were native to either the Western Cape region of South Africa, south-western Australia or south-eastern Australia and had been introduced to at least one of the other regions or to New Zealand. We tested for evidence of herbivore release and shifts in leaf traits between native and exotic ranges of the 13 species.Across all species, leaf herbivory, specific leaf area and leaf area were significantly different between native and exotic ranges while there were no significant differences across the 13 species found for leaf mass, assimilation rate, dark respiration or foliar nitrogen.Analysis at the species- and region-level showed that eight out of 13 species had reduced leaf herbivory in at least one exotic region compared to its native range.Six out of 13 species had significantly larger specific leaf area (SLA) in at least one exotic range region and five of those six species experienced reduced leaf herbivory. Increases in SLA were underpinned by increases in leaf area rather than reductions in leaf mass.No species showed differences in the direction of trait shifts from the native range between different exotic regions. This suggests that the driver of selection on these traits in the exotic range is consistent across regions and hence is most likely to be associated with factors linked with introduction to a novel environment, such as release from leaf herbivory, rather than with particular environmental conditions.Synthesis. These results provide evidence that introduction of a plant species into a novel environment commonly results in a reduction in the top-down constraint imposed by herbivores on growth, allowing plants to shift towards a faster growth strategy which may result in an increase in population size and spread and consequently to invasive success.

General hypotheses in invasion ecology

General hypotheses in invasion ecology

Insect herbivores associated with an evergreen tree Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) in a tropical dry forest

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) is a tree species found in Brazilian tropical dry forests that retain their leaves during the dry season. That being, we addressed the following question: i) How do insect diversity (sap-sucking and chewing), leaf herbivory and defensive traits (tannin and leaf sclerophylly) vary on the evergreen tree species G. marginata between seasons? The abundance of sap-sucking insects was higher in the dry season than in the rainy season. However, we did not verify any difference in the species richness and abundance of chewing insects between seasons. Leaf herbivory was higher in the rainy season, whereas leaf sclerophylly was higher in the dry season. However, herbivory was not related to sclerophylly. Insect herbivores likely decrease their folivory activity during the dry season due to life history patterns or changes in behaviour, possibly entering diapause or inactivity during this period. Therefore, G. marginata acts as a likely keystone species, serving as a moist refuge for the insect fauna during the dry season in tropical dry forest, and the presence of this evergreen species is crucial to conservation strategies of this threatened ecosystem.

Macroecological and macroevolutionary patterns of leaf herbivory across vascular plants.

The consumption of plants by animals underlies important evolutionary and ecological processes in nature. Arthropod herbivory evolved approximately 415 Ma and the ensuing coevolution between plants and herbivores is credited with generating much of the macroscopic diversity on the Earth. In contemporary ecosystems, herbivory provides the major conduit of energy from primary producers to consumers. Here, we show that when averaged across all major lineages of vascular plants, herbivores consume 5.3% of the leaf tissue produced annually by plants, whereas previous estimates are up to 3.8× higher. This result suggests that for many plant species, leaf herbivory may play a smaller role in energy and nutrient flow than currently thought. Comparative analyses of a diverse global sample of 1058 species across 2085 populations reveal that models of stabilizing selection best describe rates of leaf consumption, and that rates vary substantially within and among major plant lineages. A key determinant of this variation is plant growth form, where woody plant species experience 64% higher leaf herbivory than non-woody plants. Higher leaf herbivory in woody species supports a key prediction of the plant apparency theory. Our study provides insight into how a long history of coevolution has shaped the ecological and evolutionary relationships between plants and herbivores.

The only African wild tobacco, Nicotiana africana: alkaloid content and the effect of herbivory.

Herbivory in some Nicotiana species is known to induce alkaloid production. This study examined herbivore-induced defenses in the nornicotine-rich African tobacco N. africana, the only Nicotiana species indigenous to Africa. We tested the predictions that: 1) N. africana will have high constitutive levels of leaf, flower and nectar alkaloids; 2) leaf herbivory by the African bollworm Helicoverpa armigera will induce increased alkaloid levels in leaves, flowers and nectar; and 3) increased alkaloid concentrations in herbivore-damaged plants will negatively affect larval growth. We grew N. africana in large pots in a greenhouse and exposed flowering plants to densities of one, three and six fourth-instar larvae of H. armigera, for four days. Leaves, flowers and nectar were analyzed for nicotine, nornicotine and anabasine. The principal leaf alkaloid was nornicotine (mean: 28 µg/g dry mass) followed by anabasine (4.9 µg/g) and nicotine (0.6 µg/g). Nornicotine was found in low quantities in the flowers, but no nicotine or anabasine were recorded. The nectar contained none of the alkaloids measured. Larval growth was reduced when leaves of flowering plants were exposed to six larvae. As predicted by the optimal defense theory, herbivory had a localized effect and caused an increase in nornicotine concentrations in both undamaged top leaves of herbivore damaged plants and herbivore damaged leaves exposed to one and three larvae. The nicotine concentration increased in damaged compared to undamaged middle leaves. The nornicotine concentration was lower in damaged leaves of plants exposed to six compared to three larvae, suggesting that N. africana rather invests in new growth as opposed to protecting older leaves under severe attack. The results indicate that the nornicotine-rich N. africana will be unattractive to herbivores and more so when damaged, but that potential pollinators will be unaffected because the nectar remains alkaloid-free even after herbivory.