Effects of 6-methoxybenzoxazolinone (6-MBOA) on animals: state of knowledge and open questions.

6-methoxybenzoxazolinone (6-MBOA) is a secondary plant metabolite predominantly found in monocotyledonous plants, especially Gramineae. In damaged tissue, 2-ß-D-glucopyranosyloxy-4-hydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA-Glc) is hydrolyzed to DIMBOA, which spontaneously decomposes into 6-MBOA. It is commonly detected in plants consumed by voles and livestock and can also be present in cereal-based products. Discovered in 1955, this compound is renowned for its ability to trigger animal reproduction. However, there is a lack of research on its functional and mechanistic properties, leaving much of their potential unexplored. This review aimed to comprehensively summarize the effects of 6-MBOA on animal reproduction and human health, as well as its defensive role against herbivores. Studies have shown that 6-MBOA effectively inhibits the digestion, development, growth, and reproduction of insects. 6-MBOA may act as a partial agonist of melatonin and exert a regulatory role in mammalian reproduction, resulting in either promoting or inhibiting effects. 6-MBOA has been theorized to possess anti-tumor, anti-AIDS, anti-anxiety, and weight-loss effects in humans. However, insufficient attention has been paid to its defense properties against mammalian herbivores, and the mechanisms underlying its effects on mammalian reproduction remain unclear. In addition, research on its impact on human health is still in its preliminary stages. The review emphasizes the need for further systematic and comprehensive research on 6-MBOA to fully understand its diverse functions. Elucidating the effects of 6-MBOA on animal reproduction, adaptation, and human health would advance our understanding of plant-herbivore coevolution and the influence of environmental factors on animal population dynamics. Furthermore, this knowledge could potentially promote its application in human health and animal husbandry.

Multitrophic and Multilevel Interactions Mediated by Volatile Organic Compounds.

Plants communicate with insects and other organisms through the release of volatile organic compounds (VOCs). Using Boolean operators, we retrieved 1093 articles from the Web of Science and Scopus databases, selecting 406 for detailed analysis, with approximately 50% focusing on herbivore-induced plant volatiles (HIPVs). This review examines the roles of VOCs in direct and indirect plant defense mechanisms and their influence on complex communication networks within ecosystems. Our research reveals significant functions of VOCs in four principal areas: activating insect antennae, attracting adult insects, attracting female insects, and attracting natural enemies. Terpenoids like α-pinene and ß-myrcene significantly alter pest behavior by attracting natural enemies. ß-ocimene and ß-caryophyllene are crucial in regulating aboveground and belowground interactions. We emphasize the potential applications of VOCs in agriculture for developing novel pest control strategies and enhancing crop resilience. Additionally, we identify research gaps and propose new directions, stressing the importance of comparative studies across ecosystems and long-term observational research to better understand VOCs dynamics. In conclusion, we provide insights into the multifunctionality of VOCs in natural ecosystems, their potential for future research and applications, and their role in advancing sustainable agricultural and ecological practices, contributing to a deeper understanding of their mechanisms and ecological functions.

Heat Stress and Microbial Stress Induced Defensive Phenol Accumulation in Medicinal Plant Sparganium stoloniferum.

An approach based on the heat stress and microbial stress model of the medicinal plant Sparganium stoloniferum was proposed to elucidate the regulation and mechanism of bioactive phenol accumulation. This method integrates LC-MS/MS analysis, 16S rRNA sequencing, RT-qPCR, and molecular assays to investigate the regulation of phenolic metabolite biosynthesis in S. stoloniferum rhizome (SL) under stress. Previous research has shown that the metabolites and genes involved in phenol biosynthesis correlate to the upregulation of genes involved in plant-pathogen interactions. High-temperature and the presence of Pseudomonas bacteria were observed alongside SL growth. Under conditions of heat stress or Pseudomonas bacteria stress, both the metabolites and genes involved in phenol biosynthesis were upregulated. The regulation of phenol content and phenol biosynthesis gene expression suggests that phenol-based chemical defense of SL is stimulated under stress. Furthermore, the rapid accumulation of phenolic substances relied on the consumption of amino acids. Three defensive proteins, namely Ss4CL, SsC4H, and SsF3'5'H, were identified and verified to elucidate phenol biosynthesis in SL. Overall, this study enhances our understanding of the phenol-based chemical defense of SL, indicating that bioactive phenol substances result from SL's responses to the environment and providing new insights for growing the high-phenol-content medicinal herb SL.

Toxic tasting: how capuchin monkeys avoid grasshoppers' chemical defenses.

Platyrrhines consume many species of arthropods in the order Orthoptera. Some species of orthopterans can produce chemical defenses that render them toxic or unpalatable and thus act as predator deterrents. These species include the stick grasshoppers (family Proscopiidae), which are widely distributed in the Caatinga biome in northeastern Brazil, which comprises part of the distribution of capuchin monkeys. Capuchin monkeys are omnivores and consume a wide variety of foods, including unpleasant-tasting, potentially toxic items, which they need to learn how to process. We describe the processing of stick grasshoppers (Stiphra sp.) by wild capuchin monkeys (Sapajus libidinosus) that live in Serra da Capivara National Park, Brazil, and compare how individuals of different age classes handle these potentially toxic food items. S. libidinosus predominantly avoided consuming the digestive tract, which contains toxic compounds, when feeding on stick grasshoppers. Immatures took longer than adults to process the stick grasshoppers, indicating that capuchins need to learn how to process the toxic digestive tract of these prey to avoid consuming it.

Induced resistance to herbivory and the intelligent plant.

Plant induced responses to environmental stressors are increasingly studied in a behavioral ecology context. This is particularly true for plant induced responses to herbivory that mediate direct and indirect defenses, and tolerance. These seemingly adaptive alterations of plant defense phenotypes in the context of other environmental conditions have led to the discussion of such responses as intelligent behavior. Here we consider the concept of plant intelligence and some of its predictions for chemical information transfer in plant interaction with other organisms. Within this framework, the flow, perception, integration, and storage of environmental information are considered tunable dials that allow plants to respond adaptively to attacking herbivores while integrating past experiences and environmental cues that are predictive of future conditions. The predictive value of environmental information and the costs of acting on false information are important drivers of the evolution of plant responses to herbivory. We identify integrative priming of defense responses as a mechanism that allows plants to mitigate potential costs associated with acting on false information. The priming mechanisms provide short- and long-term memory that facilitates the integration of environmental cues without imposing significant costs. Finally, we discuss the ecological and evolutionary prediction of the plant intelligence hypothesis.

High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle.

BACKGROUNDS AND AIMS: The hypothesis that plants evolve features that protect accessible pollen from consumption by flower visitors remains poorly understood. METHODS: To explore potential chemical defenses against pollen consumption, we examined the pollinator assemblage, foraging behaviour, visitation frequency and pollen transfer efficiency in Rhododendron molle, a highly toxic shrub containing Rhodojaponin III. Nutrient (protein and lipid) and toxic components in pollen and other tissues were measured. KEY RESULTS: Overall in the five populations, floral visits by butterflies and bumblebees were relatively more frequent than visits by honeybees. All foraged for nectar but not pollen. Butterflies did not differ from bumblebees in the amount of pollen removed per visit, but deposited more pollen per visit. Pollination experiments indicated that R. molle was self-compatible, but both fruit and seed production were pollen limited. Our analysis indicated that the pollen was not protein-poor and had a higher concentration of the toxic compound Rhodojaponin III than petals and leaves, which compound was undetectable in nectar. CONCLUSION: Pollen toxicity in Rhododendron flowers may discourage pollen robbers (bees) from taking the freely accessible pollen grains, while the toxin-free nectar rewards effective pollinators, promoting pollen transfer. This preliminary study supports the hypothesis that chemical defense in pollen would be likely to evolve in species without physical protection from pollinivores.

Triterpene Glycosides from the Viscera of Sea Cucumber Apostichopus japonicus with Embryotoxicity.

Sea cucumbers release chemical repellents from their guts when they are in danger from predators or a hostile environment. To investigate the chemical structure of the repellent, we collected and chemically analyzed the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China. Two undescribed triterpene glycosides (1 and 2), together with a known cladoloside A (3), were identified and elucidated as 3ß-O-{2-O-[ß-d-quinovopyranosyl]-4-O-[3-O-methyl-ß-d-glucopyranosyl-(1→3)-ß-d-glucopyranosyl]-ß-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (1), 3ß-O-{2-O-[ß-d-glucopyranosyl]-4-O-[3-O-methyl-ß-d-glucopyranosyl-(1→3)-ß-d-glucopyranosyl]-ß-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (2), 3ß-O-{2-O-[3-O-methyl-ß-d-glucopyranosyl-(1→3)-ß-d-xylopyranosyl-(1→4)-ß-d-quinovopyranosyl]-ß-d-xylopyranosyl}-holosta-9(11),25(26)-dien-16-one (3) by spectroscopic analysis, including HR-ESI-MS and NMR spectra. Compounds 1, 2, and 3 display embryonic toxicity, as indicated by their 96-hour post-fertilization lethal concentration (96 hpf-LC50) values of 0.289, 0.536, and 0.091 µM, respectively. Our study discovered a class of triterpene glycoside compounds consisting of an oligosaccharide with four sugar units and a holostane aglycone. These compounds possess embryotoxicity and may serve as chemical defense molecules in marine benthic ecosystems.

Sea Cucumber Viscera Contains Novel Non-Holostane-Type Glycoside Toxins that Possess a Putative Chemical Defense Function.

Sea cucumbers frequently expel their guts in response to predators and an aversive environment, a behavior perceived as releasing repellents involved in chemical defense mechanisms. To investigate the chemical nature of the repellent, the viscera of stressed sea cucumbers (Apostichopus japonicus) in the Yellow Sea of China were collected and chemically analyzed. Two novel non-holostane triterpene glycosides were isolated, and the chemical structures were elucidated as 3ꞵ-O-[ꞵ-D-glucopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (1) and 3ꞵ-O-[ꞵ-D-quinovopyranosyl-(1→2)-ꞵ-D-xylopyranosyl]-(20S)-hydroxylanosta-7,25-diene-18(16)-lactone (2) by spectroscopic and mass-spectrometric analyses, exemplifying a triterpene glycoside constituent of an oligosaccharide containing two sugar-units and a non-holostane aglycone. Zebrafish embryos were exposed to various doses of 1 and 2 from 4 to 96 hpf. Compound 1 exposure showed 96 h-LC50 41.5 µM and an increased zebrafish mortality rates in roughly in a dose- and time-dependent manner. Compound 2, with different sugar substitution, exhibited no mortality and moderate teratogenic toxicity with a 96 h-EC50 of 173.5 µM. Zebrafish embryos exhibited teratogenic effects, such as reduced hatchability and total body length. The study found that triterpene saponin from A. japonicus viscera had acute toxicity in zebrafish embryos, indicating a potential chemical defense role in the marine ecosystem.

Effects of leaf herbivory and autumn seasonality on plant secondary metabolites: A meta-analysis.

Plant secondary metabolites (PSMs) are produced by plants to overcome environmental challenges, both biotic and abiotic. We were interested in characterizing how autumn seasonality in temperate and subtropical climates affects overall PSM production in comparison to herbivory. Herbivory is commonly measured between spring to summer when plants have high resource availability and prioritize growth and reproduction. However, autumn seasonality also challenges plants as they cope with limited resources and prepare survival for winter. This suggests a potential gap in our understanding of how herbivory affects PSM production in autumn compared to spring/summer. Using meta-analysis, we recorded overall production of 22 different PSM subgroups from 58 published papers to calculate effect sizes from herbivory studies (absence to presence) and temperate to subtropical seasonal studies (summer to autumn), while considering other variables (e.g., plant type, increase in time since herbivory, temperature, and precipitation). We also compared production of five phenolic PSM subgroups - hydroxybenzoic acids, flavan-3-ols, flavonols, hydrolysable tannins, and condensed tannins. We wanted to detect a shared response across all PSMs and found that herbivory increased overall PSM production in herbaceous plants. Herbivory was also found to have a positive effect on individual PSM subgroups, such as flavonol production, while autumn seasonality was found to have a positive effect on flavan-3-ol and condensed tannin production. We discuss how these responses might stem from plants producing some PSMs constitutively, whereas others are induced only after herbivory, and how plants produce metabolites with higher costs only during seasons when other resources for growth and reproduction are less available, while other phenolic PSM subgroups serve more than one function for plants and such functions can be season dependent. The outcome of our meta-analysis is that autumn seasonality changes some PSM production differently from herbivory, and we see value in further investigating seasonality-herbivory interactions with plant chemical defense.

Norsesquiterpenes from the Latex of Euphorbia dentata and Their Chemical Defense Mechanisms against Helicoverpa armigera.

Euphorbia dentata (Euphorbiaceae), an invasive weed, is rarely eaten by herbivorous insects and could secrete a large amount of white latex, causing a serious threat to local natural vegetation, agricultural production and human health. In order to prevent this plant from causing more negative effects on humans, it is necessary to understand and utilize the chemical relationships between the latex of E. dentata and herbivorous insects. In this study, three new norsesquiterpenes (1-3), together with seven known analogues (4-10), were isolated and identified from the latex of E. dentata. All norsesquiterpenes (1-10) showed antifeedant and growth-inhibitory effects on H. armigera with varying levels, especially compounds 1 and 2. In addition, the action mechanisms of active compounds (1-3) were revealed by detoxifying enzyme (AchE, CarE, GST and MFO) activities and corresponding molecular docking analyses. Our findings provide a new idea for the development and utilization of the latex of E. dentata, as well as a potential application of norsesquiterpenes in botanical insecticides.

Four-Chlorophenoxyacetic Acid Treatment Induces the Defense Resistance of Rice to White-Backed Planthopper Sogatella furcifera.

Chemical elicitors can increase plant defense against herbivorous insects and pathogens. The use of synthetic chemical elicitors is likely to be an alternative to traditional pesticides for crop pest control. However, only a few synthetic chemicals are reported to protect plants by regulating signaling pathways, increasing the levels of defense metabolites and interfering with insect feeding. Here, we found that the exogenous application of a phenoxycarboxylic compound, 4-chlorophenoxyacetic acid (4-CPA), can induce chemical defenses to protect rice plants from white-backed planthoppers (WBPH, Sogatella furcifera). Four-CPA was rapidly taken up by plant roots and degraded to 4-chlorophenol (4-CP). Four-CPA treatment modulated the activity of peroxidase (POD) and directly induced the deposition of lignin-like polymers using hydrogen peroxide (H2O2) as the electron acceptor. The polymers, which are thought to prevent the planthopper's stylet from reaching the phloem, were broken down by WBPH nymphs. Meanwhile, 4-CPA increased the levels of flavonoids and phenolamines (PAs). The increased flavonoids and PAs, together with the degradation product of the polymers, avoided nymphal feeding and prolonged the nymphal period for 1 day. These results indicate that 4-CPA has the potential to be used as a chemical elicitor to protect rice from planthoppers. Moreover, these findings also open a pathway for molecule structure design of phenoxycarboxylic compounds as chemical elicitors.

Role of ABC Proteins in Secondary Metabolism and Immune (=Defensive) Response in Seaweeds.

Laurencia seaweed species synthesize a broad range of secondary metabolites, mainly terpenes (e.g., elatol), exhibiting diverse ecological roles, such as defense against fouling and herbivores. Recently, an intricate cellular machinery was described concerning terpenes biosynthetic pathways, storage inside corps en cerise (CC), and regulated exocytosis in these species. But for seaweeds in general, the proteins involved in transmembrane transport of secondary metabolites remain unknown. Assays with Rhodamine-123 and cyclosporine A (CSA) revealed the presence of ABC transporters in CC membrane of Laurencia dendroidea. In vivo incubation assays with CSA resulted in CC morphological changes, reduced intracellular elatol concentrations, and increased biofouling cover on the seaweed surface. Cultivation assays in the presence of a marine pathogenic bacteria induced the expression of ABC proteins belonging to the subfamilies ABCB, ABCD, ABCF, and ABCG. The latter subfamily is known to be associated with the transport of plant terpenes. Our results shed new light on the role of ABC proteins in key mechanisms of the defensive system in seaweeds against fouling and herbivory.

Evolutionary signatures of a trade-off in direct and indirect defenses across the wild grape genus, Vitis.

Evolutionary correlations between chemical defense and protection by mutualist bodyguards have been long predicted, but tests of these patterns remain rare. We use a phylogenetic framework to test for evolutionary correlations indicative of trade-offs or synergisms between direct defense in the form of plant secondary metabolism and indirect defense in the form of leaf domatia, across 33 species in the wild grape genus, Vitis. We also performed a bioassay with a generalist herbivore to associate our chemical phenotypes with herbivore palatability. Finally, we tested whether defensive traits correlated with the average abiotic characteristics of each species' contemporary range and whether these correlations were consistent with plant defense theory. We found a negative evolutionary correlation between domatia size and the diversity of secondary metabolites in Vitis leaf tissue across the genus, and also that leaves with a higher diversity and richness of secondary metabolites were less palatable to a generalist herbivore, consistent with a trade-off in chemical and mutualistic defense investment. Predictions from plant defense theory were not supported by associations between investment in defense phenotypes and abiotic variables. Our work demonstrates an evolutionary pattern indicative of a trade-off between indirect and direct defense strategies across the Vitis genus.

Quantitative Chemical Analysis of Defensive Secretion of Megacrania tsudai (Phasmatidae) and Effect of Actinidine on its Potential Predators.

Insects avoid predation in various ways, and some use multiple ways to avoid predation. However, the effects of comprehensive avoidance methods and the differences in avoidance methods among different life stages of insects have not been sufficiently discussed. The big head stick insect Megacrania tsudai uses background matching as its primary defense and chemical defense as its secondary defense. The aims of this study were to identify and isolate the chemical components of M. tsudai using repeatable methods, determine the amount of the main chemical compound, and reveal the effect of the main chemical compound on its predators. We established a repeatable gas chromatography-mass spectrometry (GC-MS) method to identify the chemical compounds of these secretions, and identified actinidine as the main compound. Actinidine was identified by nuclear magnetic resonance (NMR), and the amount of actinidine in each instar was calculated by constructing a calibration curve using pure actinidine. Mass ratios did not drastically change among instars. Furthermore, experiments involving dropping an aqueous solution of actinidine demonstrated removal behavior in geckos, frogs, and spiders. These results indicated that M. tsudai conducts secondary defenses using defensive secretions consisting mainly of actinidine.

Effects of sponge-to-sponge contact on the microbiomes of three spatially competing Caribbean coral reef species.

Sponges perform important ecosystem functions, host diverse microbial symbiont communities (microbiomes), and have been increasing in density on Caribbean coral reefs over the last decade. Sponges compete for space in coral reef communities through both morphological and allelopathic strategies, but no studies of microbiome impacts during these interactions have been conducted. Microbiome alterations mediate spatial competition in other coral reef invertebrates and may similarly impact competitive outcomes for sponges. In this study, we characterized the microbiomes of three common Caribbean sponges (Agelas tubulata, Iotrochota birotulata, and Xestospongia muta) observed to naturally interact spatially in Key Largo, Florida (USA). For each species, replicate samples were collected from sponges in contact with neighbors at the site of contact (contact) and distant from the site of contact (no contact), and from sponges spatially isolated from neighbors (control). Next-generation amplicon sequencing (V4 region of 16S rRNA) revealed significant differences in microbial community structure and diversity among sponge species, but no significant effects were observed within sponge species across all contact states and competitor pairings, indicating no large community shifts in response to direct contact. At a finer scale, particular symbiont taxa (operational taxonomic units at 97% sequence identity, OTUs) were shown to decrease significantly in some interaction pairings, suggesting localized effects for specific sponge competitors. Overall, these results revealed that direct contact during spatial competition does not significantly alter microbial community composition or structure of interacting sponges, suggesting that allelopathic interactions and competitive outcomes are not mediated by microbiome damage or destabilization.

Impact of Marine Chemical Ecology Research on the Discovery and Development of New Pharmaceuticals.

Diverse ecologically important metabolites, such as allelochemicals, infochemicals and volatile organic chemicals, are involved in marine organismal interactions. Chemically mediated interactions between intra- and interspecific organisms can have a significant impact on community organization, population structure and ecosystem functioning. Advances in analytical techniques, microscopy and genomics are providing insights on the chemistry and functional roles of the metabolites involved in such interactions. This review highlights the targeted translational value of several marine chemical ecology-driven research studies and their impact on the sustainable discovery of novel therapeutic agents. These chemical ecology-based approaches include activated defense, allelochemicals arising from organismal interactions, spatio-temporal variations of allelochemicals and phylogeny-based approaches. In addition, innovative analytical techniques used in the mapping of surface metabolites as well as in metabolite translocation within marine holobionts are summarized. Chemical information related to the maintenance of the marine symbioses and biosyntheses of specialized compounds can be harnessed for biomedical applications, particularly in microbial fermentation and compound production. Furthermore, the impact of climate change on the chemical ecology of marine organisms-especially on the production, functionality and perception of allelochemicals-and its implications on drug discovery efforts will be presented.

Silicon Nanodots Increase Plant Resistance against Herbivores by Simultaneously Activating Physical and Chemical Defenses.

Nanosilicon applications have been shown to increase plant defenses against both abiotic and biotic stresses. Silicon quantum nanodots (Si NDs), a form of nanosilicon, possess excellent biological and physiochemical properties (e.g., minimal size, high water solubility, stability, and biocompatibility), potentially making them more efficient in regulating plant responses to stress than other forms of silicon. However, to date, we still lack mechanistic evidence for how soil-applied Si NDs alter the regulation of plant physical and chemical defenses against insect herbivores. To address this gap, we compared the effect of fluorescent amine-functionalized Si NDs (5 nm) and the conventional fertilizer sodium silicate on maize (Zea mays L.) physical and chemical defenses against the oriental armyworm (Mythimna separata, Walker) caterpillars. We found that 50 mg/kg Si NDs and sodium silicate additions inhibited the growth of caterpillars the most (35.7% and 22.8%, respectively) as compared to other application doses (0, 10, and 150 mg/kg). Both Si NDs and silicate addition activated biosynthesis genes responsible for chemical (benzoxazinoids) and physical (lignin) defense production. Moreover, Si NDs upregulated the gene expression of antioxidant enzymes (SOD, CAT, and POD) and promoted the antioxidant metabolism (flavonoids) in maize leaves under M. separata attack. Finally, we show that, under field conditions, Si ND addition increased maize cob weight (28.7%), cob grain weight (40.8%), and 100-grain weight (26.5%) as compared to the control, and more so than the conventional silicon fertilizer. Altogether, our findings highlight the potential for Si NDs to be used as an effective and ecofriendly crop protection strategy in agroecosystems.

Defense response of Fraxinus mandshurica seedlings to Hyphantria cunea larvae under Cd stress: A contradiction between attraction and resistance.

Heavy metal pollution, as a common and serious environmental problem worldwide, has been regarded as an abiotic stimulus that can affect plant insect resistance and pest occurrence. This study evaluated the defense response of Fraxinus mandshurica seedlings to Hyphantria cunea larvae under Cd stress, with consideration given to chemical defense, physical defense, and elemental defense. Our results showed that the H. cunea larvae had a strong preference for Cd-treated F. mandshurica seedlings, but there was a significant reduction in body weight and survival rate in larvae that fed on leaves of Cd-treated seedlings. Under Cd treatment, the increase in attractant metabolites (e.g., styrene, dibutyl phthalate, and d-limonene) and the decrease in repellent metabolites (e.g., aromadendrene, heptadecane, and camphene) in leaf volatiles were responsible for the high attractant activity to H. cunea larvae. Based on leaf physicochemical properties, tissue structure, and phenolic acid content, an overall reduction in physical defense, chemical defense and their combination in F. mandshurica seedlings exposed to Cd stress was identified by Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) analysis. Elemental defense occurred in Cd-treated F. mandshurica seedlings, as evidenced by the high concentration of Cd in leaves and H. cunea larvae under Cd treatment. Taken together, these findings demonstrate that under Cd stress, elemental defense replaces the dominant role of basic defense in F. mandshurica seedlings and accounts for the enhanced ability to defend against H. cunea larvae.

Diversity and divergence: evolution of secondary metabolism in the tropical tree genus Inga.

Plants are widely recognized as chemical factories, with each species producing dozens to hundreds of unique secondary metabolites. These compounds shape the interactions between plants and their natural enemies. We explore the evolutionary patterns and processes by which plants generate chemical diversity, from evolving novel compounds to unique chemical profiles. We characterized the chemical profile of one-third of the species of tropical rainforest trees in the genus Inga (c. 100, Fabaceae) using ultraperformance liquid chromatography-mass spectrometry-based metabolomics and applied phylogenetic comparative methods to understand the mode of chemical evolution. We show: each Inga species contain structurally unrelated compounds and high levels of phytochemical diversity; closely related species have divergent chemical profiles, with individual compounds, compound classes, and chemical profiles showing little-to-no phylogenetic signal; at the evolutionary time scale, a species' chemical profile shows a signature of divergent adaptation. At the ecological time scale, sympatric species were the most divergent, implying it is also advantageous to maintain a unique chemical profile from community members; finally, we integrate these patterns with a model for how chemical diversity evolves. Taken together, these results show that phytochemical diversity and divergence are fundamental to the ecology and evolution of plants.