Insect Interactions Research Articles

Mathematical model for plant-insect interaction with dynamic response to PAD4-BIK1 interaction and effect of BIK1 inhibition

Plant-insect interaction system is a widely studied model of the ecosystem. Numerical understanding of this counter system has developed from initial analogy based approach with a predator-prey model to its recent mathematical interpretation including plant immunity concept. In current work, we propose an extension to this model, including molecular interactions behind the plant defense system and its effect on ecological behaviour. Inspired from biomolecular interaction given by Louis and Shah in 2014, we propose here a mathematical model to depict molecular dependence and control of plant insect interaction system. Insect infestation mediated Botrytis Induced Kinase-1 (BIK1) induction resulted in inhibition of Phyto Alexin Deficient-4 (PAD4) protein. Lowered PAD4 triggers the plant defense mechanism, leading to degraded plant immune potential and thereby reducing the plant quality. We mathematically adapt these interactions to show their influence on plant-insect interaction system and hypothesize the significance of BIK1 inhibition leading to the improved plant quality. We implemented the plethora of computational modeling and all atom MD simulations to explain the Plant-Insect-PAD4-BIK1 interaction network and identify potential molecular mechanisms of plant improvement by BIK1 inhibition.

Fire mediated herbivory and plant defense of a neotropical shrub

Changes in morphological and physiological features of plants after fire events can modify their attractiveness to herbivorous insects. Our goal was to assess the effects of fire on plant–insect interactions and the development of induced defenses in the shrub Bauhinia brevipes (Fabaceae). We hypothesized that resprouting plants of B. brevipes after a fire occurrence would be more susceptible to herbivory by leaf-chewing and the gall-maker Schizomyia macrocapillata Maia (Diptera: Cecidomyiidae) than non-resprouting plants. We analyzed leaf area, leaf damage caused by chewing insect herbivores and attacks by the gall-midge S. macrocapillata, hypersensitivity response, chlorophyll content and silicon content after a fire event. Resprouting plants presented greater leaf area; higher chlorophyll concentration; hypersensitivity response and greater leaf silicon content. Although these plants experienced a greater number of attacks by S. macrocapillata the greater investment in growth and photosynthetic capacity, and possible leaf nitrogen content, can be determining attractiveness to a range of herbivores specifically galling insects. Leaf silicon content can be related with the lower damage by chewing insects, even with the greater vigor of resprouting plants. Thus, our results are contrary to some previous studies that report increases in leaf herbivory by chewer insects after fire events. Increases in hypersensitive response and silicon content seem to alter herbivorous insect preference and performance after fire occurrence.

Choice of Tethering Material Influences the Magnitude and Significance of Treatment Effects in Whitefly Electrical Penetration Graph Recordings

The electrical penetration graphing or electropenetrography (EPG) technique is essential for understanding interactions of hemipteran insects with their host plants. Typically, 10–12.5 μm diameter gold wire is used as the tethering material in EPG studies. This wire was originally chosen based on suitability for aphids, but application of the EPG technique to other insects necessitates testing of alternative tethering materials that permit natural foraging and probing behavior. Whiteflies are one group for which EPG studies are increasing, with most researchers using 10 or 12.5 μm diameter gold wire even though these insects are smaller than aphids and very different in mobility. However, 2.5 μm diameter Wollaston process platinum wire has been used for a subset of EPG studies and seems to permit more natural movement and feeding behaviors. Here, we compared EPG variables derived from recordings of the sweet potato whitefly (Bemisia tabaci) tethered with 12.5 μm diameter gold wire or 2.5 μm diameter platinum wire. On a suitable host, gold-tethered whiteflies had reduced phloem phases, which are indicative of host plant acceptance, compared to platinum-tethered whiteflies. When we included a treatment known to reduce plant quality (methyl jasmonate application), platinum-tethered whiteflies exhibited expected reductions in EPG variables related to host acceptance, while gold-tethered whiteflies either had no response, or the opposite response. Our results indicate that tethering material strongly influences the outcome of EPG experiments, with important consequences for evaluations of host plant resistance, putative instances of plant virus manipulation, and feeding variables associated with virus transmission.

Consequences of multiple flower-insect interactions for subsequent plant-insect interactions and plant reproduction.

Plants often interact simultaneously with multiple antagonists and mutualists that can alter plant traits at the phenotypic or genetic level, subsequent plant-insect interactions, and reproduction. Although many studies have examined the effects of single floral antagonisms on subsequent pollination and plant reproduction, we know very little about the combined, potentially non-additive effects of multiple flower-insect interactions. We simulated increased florivory, nectar robbing, and pollination on field-grown Impatiens capensis, which allowed us to determine interactive effects on five subsequent plant-insect interactions and 16 plant traits, including traits related to plant growth, floral attractiveness, floral defenses, and plant reproduction. All three manipulative treatments had significant non-additive effects on the behavior of subsequent floral visitors, indicating that the effect of floral visitors generally depended on the presence or behavior of others. Pollination increased visitation by both pollinators and nectar larcenists (robbers and thieves), while florivory reduced pollinator and larcenist visits. Surprisingly, supplemental pollination also increased leaf herbivory. Florivores often responded to manipulations in opposite ways than did nectar larcenists and pollinators, suggesting different mechanisms influencing visitors that consume nectar compared to floral tissue. While our treatments did not affect any floral trait measured, they non-additively impacted plant reproduction, with florivory having a larger overall impact than either nectar robbing or pollination. These results emphasize the importance of understanding the context in which flower-insect interactions occur because the composition of the interacting community can have large and non-additive impacts on subsequent insect behavior and plant reproduction.

Adult oviposition preferences and larval performance of rice leaf folder, Cnaphalocrocis medinalis on rice and non-rice graminaceous plants

The rice leaf folder, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae), occurs throughout southeast and northeast Asia, and has a broad host range including graminaceous crops and weeds. Unraveling the relationship between adult oviposition preference and offspring performance is central to understanding the evolution of plant–insect interactions. In the present study, we examined oviposition behavior and larval performance of the C. medinalis on rice plants and non-rice graminaceous plants. Using choice oviposition experiments, female C. medinalis moths preferred rice volatiles, and laid significantly more eggs on the leaves of rice plants than non-rice graminaceous plants. Larval performance, as assayed by host plant selection rate, and host suitability, were evaluated by using multi-choice experiments and life-table analysis, respectively. Larval host selection experiments showed that the younger C. medinalis larvae (1st and 2nd instar) exhibited a stronger ability to identify rice hosts compared to non-rice graminaceous plants than older larvae (3rd to 5th instar). The results of life-table studies showed that C. medinalis developed and grew faster on rice plants than on non-rice graminaceous plants. In particular, the graminaceous crop, sugarcane Saccharum officinarum, and graminaceous weeds Miscanthus sinensis and Setaria viridis, prevented the development and ovipositing of C. medinalis. Our results showed the strong preference that C. medinalis adults had to oviposit and larvae had to develop on rice and this was highly consistent within the population tested. This indicated that oviposition preference of female C. medinalis moths might play an important role in larval host identification between rice plants and non-rice graminaceous plants.

Associational susceptibility of a native shrub induced by context‐dependent attraction of an invasive herbivore

AbstractIndirect interactions among native and invasive species are notoriously difficult to predict. Here, we apply theory from trait‐mediated indirect effects and plant–insect interactions to explain the outcomes of multiple invader interactions. The present study investigates the roles of herbivore preference and plant ontogeny in mediating associational effects among a southern California native shrub, Atriplex canescens, an invasive annual forb, Brassica tournefortii, and an invasive stink bug, Bagrada hilaris. Ba. hilaris have been observed to form dense aggregations on A. canescens in late spring following senescence of Br. tournefortii, with subsequent increased mortality of A. canescens. A manipulative experiment found Ba. hilaris recruited to A. canescens in approximately 70 times greater numbers when neighbored by Br. tournefortii than when alone. Ba. hilaris nymph production, while minimized experimentally, occurred only on Br. tournefortii, suggesting A. canescens is not of sufficient quality for Ba. hilaris reproduction. In greenhouse preference trials, Ba. hilaris exhibited an overall preference for Br. tournefortii over A. canescens; however, the magnitude of preference depended on ontogenetic stage of Br. tournefortii. Overall, our results suggest significant potential for associational susceptibility mediated by a combination of Ba. hilaris preference for reproductive Br. tournefortii, substantial aggregation of Ba. hilaris onto Br. tournefortii, and a marked decline in Ba. hilaris preference for Br. tournefortii with advancing ontogeny—triggering spillover onto neighboring plants. Our results demonstrate an important role for multiple invaders and phenologically driven trait changes in mediating associational susceptibility.

Insect Entrapment by Plants in Kodaikanal Wildlife Sanctuary, India

The present study focused on plant–insect interactions between arthropod insects and herbs at shola forest floor such as Desmodium uncinatum (Jacq.) DC.—Fabaceae and Cerastium indicum (L.) Wight & Arn.—Caryophyllaceae. The morphological characters such as ciliate, puberulous and villous nature of plants will lead a greater role to adopt the climatic conditions. Findings of the present study revealed the trichomes of some plants are menace to pollinating agents.

Intraspecific variation in herbivore‐induced plant volatiles influences the spatial range of plant–parasitoid interactions

Chemical information influences the behaviour of many animals, thus affecting species interactions. Many animals forage for resources that are heterogeneously distributed in space and time, and have evolved foraging behaviour that utilizes information related to these resources. Herbivore‐induced plant volatiles (HIPVs), emitted by plants upon herbivore attack, provide information on herbivory to various animal species, including parasitoids. Little is known about the spatial scale at which plants attract parasitoids via HIPVs under field conditions and how intraspecific variation in HIPV emission affects this spatial scale. Here, we investigated the spatial scale of parasitoid attraction to two cabbage accessions that differ in relative preference of the parasitoid Cotesia glomerata when plants were damaged by Pieris brassicae caterpillars. Parasitoids were released in a field experiment with plants at distances of up to 60 m from the release site using intervals between plants of 10 or 20 m to assess parasitism rates over time and distance. Additionally, we observed host‐location behaviour of parasitoids in detail in a semi‐field tent experiment with plant spacing up to 8 m. Plant accession strongly affected successful host location in field set‐ups with 10 or 20 m intervals between plants. In the semi‐field set‐up, plant finding success by parasitoids decreased with increasing plant spacing, differed between plant accessions, and was higher for host‐infested plants than for uninfested plants. We demonstrate that parasitoids can be attracted to herbivore‐infested plants over large distances (10 m or 20 m) in the field, and that stronger plant attractiveness via HIPVs increases this distance (up to at least 20 m). Our study indicates that variation in plant traits can affect attraction distance, movement patterns of parasitoids, and ultimately spatial patterns of plant–insect interactions. It is therefore important to consider plant‐trait variation in HIPVs when studying animal foraging behaviour and multi‐trophic interactions in a spatial context.

Co‐option of microbial associates by insects and their impact on plant–folivore interactions

Plants possess a suite of traits that make them challenging to consume by insect herbivores. Plant tissues are recalcitrant, have low levels of protein, and may be well defended by chemicals. Insects use diverse strategies for overcoming these barriers, including co-opting metabolic activities from microbial associates. In this review, we discuss the co-option of bacteria and fungi in the herbivore gut. We particularly focus upon chewing, folivorous insects (Coleoptera and Lepidoptera) and discuss the impacts of microbial co-option on herbivore performance and plant responses. We suggest that there are two components to microbial co-option: fixed and plastic relationships. Fixed relationships are involved in integral dietary functions and can be performed by microbial enzymes co-opted into the genome or by stably transferred associates. In contrast, the majority of gut symbionts appear to be looser and perform more facultative, context-dependent functions. This more plastic, variable co-option of bacteria likely produces a greater number of insect phenotypes, which interact differently with plant hosts. By altering plant detection of herbivory or mediating insect interactions with plant defensive compounds, microbes can effectively improve herbivore performance in real time within and between generations.

Plant–insect associations from the upper Miocene of Lincang, Yunnan, China

Fossil leaves from the Bangmai Formation of Lincang, Yunnan Province, southwest China, presented a variety of plant–insect interactions in the late Miocene. Six principal functional feeding types (36 DTs) in leaves of more than 13 families were identified, i.e., hole feeding, leaf mining, surface feeding, skeletonization, galling and marginal feeding. These diverse damage traces demonstrated that at least six orders of insects interacted with plants for various purposes, e.g., feeding and sheltering. Furthermore, the frequency of herbivory (21%) and the less occurrence of galling functional feeding types (20%) suggested that the climate in Lincang was humid and subtropical in the late Miocene. Our findings also suggested that the plant–insect associations similar to those observed today have been established since the late Miocene, shaping both the present flora and fauna.

Climate and leaf traits, not latitude, explain variation in plant–herbivore interactions across a species' range

Abstract Spatial variation in abiotic and biotic factors creates local contexts that influence the intensity of plant–herbivore interactions. Some previous studies have accounted for the complexity of these interactions with latitudinal clines, while the absence of such clines in many other systems suggests other, often unknown, local community factors may instead explain the variation in herbivory across populations. We investigated plant–herbivore interactions across the entire range of a long‐lived tree (Quercus garryana), evaluating the relative importance of climate, latitude, population size, and insect feeding guilds in determining leaf phenotype and the extent and variation in insect herbivory. In this ecosystem, rain shadows create a nonlinear relationship between climate and latitude, allowing us to disentangle the effects of environmental factors. By performing similar analyses on trees grown in a common garden, we were able to assess the relative importance of environmental factors to leaf defence traits and herbivory. Total herbivory varied significantly among populations, and was best explained by variation in spring precipitation, leaf traits, and tree population size, but not latitude. The relative importance of each of these factors changed over the growing season and with insect feeding guild. Conversely, damage in the common garden did not vary among trees from different origins when grown in a constant environment, leading us to believe variation in damage in natural populations is more likely the result of the local environments. Leaf traits (trichome density and specific leaf area) varied significantly among populations, but neither showed an effect of latitude. Variation in both traits was best explained by tree size, and seasonal temperatures or precipitation. We found no variation in insect diversity among field populations, but abundance varied with mean summer precipitation and population size. Synthesis. Seasonal precipitation consistently explained the geographical variation in the extent of herbivory to Q. garryana, while latitude and winter temperatures, factors that are commonly associated with latitudinal gradients in the intensity of species interactions, did not. Our findings highlight the importance of local climates and functional traits in shaping biotic interactions and intraspecific variation in plant–insect interactions across large spatial scales.

Maintaining Biological Cultures and Measuring Gene Expression in Aphis nerii: A Non-model System for Plant-insect Interactions.

Aphids are excellent experimental models for a variety of biological questions ranging from the evolution of symbioses and the development of polyphenisms to questions surrounding insect's interactions with their host plants. Genomic resources are available for several aphid species, and with advances in the next-generation sequencing, transcriptomic studies are being extended to non-model organisms that lack genomes. Furthermore, aphid cultures can be collected from the field and reared in the laboratory for the use in organismal and molecular experiments to bridge the gap between ecological and genetic studies. Last, many aphids can be maintained in the laboratory on their preferred host plants in perpetual, parthenogenic life cycles allowing for comparisons of asexually reproducing genotypes. Aphis nerii, the milkweed-oleander aphid, provides one such model to study insect interactions with toxic plants using both organismal and molecular experiments. Methods for the generation and maintenance of the plant and aphid cultures in the greenhouse and laboratory, DNA and RNA extractions, microsatellite analysis, de novo transcriptome assembly and annotation, transcriptome differential expression analysis, and qPCR verification of differentially expressed genes are outlined and discussed here.

Effect of habitat structure on reproduction and prey capture of a rare carnivorous plant, Pinguicula lutea

Habitat degradation is one of the greatest threats to biodiversity worldwide and the main contributor to the decline of many carnivorous plant species. For carnivorous plants in the southeastern United States, including many Pinguicula species (butterwort, Lentibulariaceae), degradation via altered fire regime has been implicated in their decline. Despite this decline, limited empirical research has been conducted examining the influence of habitat structural changes (through natural succession or human management) on reproduction and prey capture by carnivorous plants. The objectives of our study were to compare reproduction and prey capture for Pinguicula lutea (yellow butterwort) in habitats with different vegetation structures in the Florida Panhandle, where differences were largely due to management history. Pinguicula lutea is a self-compatible carnivorous plant that inhabits fire-dependent longleaf pine savannas of the southeastern United States and is threatened in the state of Florida. In 2014 and 2015, 13 sites were identified occupying three different habitat structures: maintained (intermittently mowed), grassy (dominated by Aristida stricta var. beyrichiana), and woody (encroachment by Hypericum and Ilex). Reproductive output was determined by assessing fruit set and ovule fertilization rate at each site. Additionally, prey availability and prey capture were assessed at each habitat site. In general, there were no differences in either measure of reproduction across habitat structure types. There were differences in prey abundance of Collembola, Diptera, and total arthropods both in terms of availability and capture. Total arthropod availability and prey capture were lowest in grassy sites compared to maintained habitat sites and woody habitat sites. Microclimatic conditions associated with each habitat structure and leaf morphology or physiology could explain the observed arthropod abundance and prey capture patterns. This study is the first ecological assessment of plant–insect interactions for Pinguicula species of the southeastern US and highlights the importance of habitat quality and management for this understudied group of carnivorous plants.

The molecular genetic basis of herbivory between butterflies and their host plants

Interactions between herbivorous insects and their host plants are a central component of terrestrial food webs and a critical topic in agriculture, where a substantial fraction of potential crop yield is lost annually to pests. Important insights into plant–insect interactions have come from research on specific plant defences and insect detoxification mechanisms. Yet, much remains unknown about the molecular mechanisms that mediate plant–insect interactions. Here we use multiple genome-wide approaches to map the molecular basis of herbivory from both plant and insect perspectives, focusing on butterflies and their larval host plants. Parallel genome-wide association studies in the cabbage white butterfly, Pieris rapae, and its host plant, Arabidopsis thaliana, pinpointed a small number of butterfly and plant genes that influenced herbivory. These genes, along with much of the genome, were regulated in a dynamic way over the time course of the feeding interaction. Comparative analyses, including diverse butterfly/plant systems, showed a variety of genome-wide responses to herbivory, as well as a core set of highly conserved genes in butterflies as well as their host plants. These results greatly expand our understanding of the genomic causes and evolutionary consequences of ecological interactions across two of nature’s most diverse taxa, butterflies and flowering plants.

Population dynamics and overwintering of a biological control beetle, Agasicles hygrophila, on a nontarget plant Alternanthera sessilis, along a latitudinal gradient

Assessing the impact of temperature changes on insect population and overwintering on nontarget hosts is important for prediction of nontarget effects in weed biological control. Agasicles hygrophila is a beetle used for biological control of the invasive plant alligator weed, Alternanthera philoxeroides, with nontarget damage to a native plant, Alternanthera sessilis. In this study, we monitored plant growth and phenology along with beetle population and overwintering on these two hosts along a latitudinal gradient from subtropical to temperate climates (Guilin, Wuhan and Kaifeng) in China. We found only annual A. sessilis seedlings in temperate Kaifeng, but both annual seedlings and perennial ramets of A. sessilis were found in Guilin and Wuhan. However, in winter, living A. sessilis plants were found in only subtropical Guilin. Beetles at the Guilin site could successfully maintain their populations and overwinter on A. sessilis. Although the beetle could sustain its populations on A. sessilis at the other two higher-latitude sites during the growing season, it failed to overwinter on either species, indicating that the temperatures in different climate zones may directly and/or indirectly affect the development of insect biological control agents and their population sizes on nontarget hosts. Therefore, it is important to consider the shifting plant–insect interactions induced by climate when assessing potential nontarget effects of species introduced as biological control agents.

Discovery of peptide probes to modulate oxytocin-type receptors of insects

The oxytocin/vasopressin signalling system is conserved across the animal kingdom. In insects, the role of oxytocin-type (inotocin) neuropeptides has only been studied in locusts, beetles and ants, but their physiology continues to be poorly understood. One reason for this knowledge deficit is the lack of available research tools to complement functional genomics efforts. Consequently, ligands to probe insect inotocin receptors are essential. In this study, we sought to identify novel agonists and antagonists of the inotocin receptor from the representative model species Tribolium castaneum and Lasius niger. Drawing upon known ligands of the human receptors, we examined the pharmacology of the plant-derived cyclotide kalata B7 and the synthetic oxytocin analogue atosiban. Kalata B7 is a weak partial agonist of both inotocin receptors. This is the first reported direct interaction of cyclotides with an insect receptor, an observation that may explain their presumed role in herbivore defence. Furthermore, we discovered atosiban is an antagonist of the Tribolium receptor, which may provide a useful probe to investigate the functionality of inotocin signalling in beetles and related insect species. Our findings will enable further examination of insect inotocin receptor pharmacology and physiology, and may trigger studies to comprehend the interaction of plant cyclotides and insects.

Plant-insect interactions patterns in three European paleoforests of the late-Neogene-early-Quaternary.

Plants and insects are constantly interacting in complex ways through forest communities since hundreds of millions of years. Those interactions are often related to variations in the climate. Climate change, due to human activities, may have disturbed these relationships in modern ecosystems. Fossil leaf assemblages are thus good opportunities to survey responses of plant–insect interactions to climate variations over the time. The goal of this study is to discuss the possible causes of the differences of plant–insect interactions’ patterns in European paleoforests from the Neogene–Quaternary transition. This was accomplished through three fossil leaf assemblages: Willershausen, Berga (both from the late Neogene of Germany) and Bernasso (from the early Quaternary of France). In Willershausen it has been measured that half of the leaves presented insect interactions, 35% of the fossil leaves were impacted by insects in Bernasso and only 25% in Berga. The largest proportion of these interactions in Bernasso were categorized as specialist (mainly due to galling) while in Willershausen and Berga those ones were significantly more generalist. Contrary to previous studies, this study did not support the hypothesis that the mean annual precipitation and temperature were the main factors that impacted the different plant–insect interactions’ patterns. However, for the first time, our results tend to support that the hydric seasonality and the mean temperature of the coolest months could be potential factors influencing fossil plant–insect interactions.

Evaluation of Headspace Solid-Phase Microextraction Gas Chromatography–Mass Spectrometry for the Characterization of Volatile Organic Compounds from Melon (Cucumis melo L.) Flowers

The secondary metabolism of plants plays a key role in plant–insect interactions. Among the various classes of metabolites produced, volatile organic compounds (VOCs) play important echophysiological roles, including the attraction of pollinators. This work aimed to develop a method to extract VOCs using headspace (HS) and solid-phase microextraction (SPME), which can be applied in future studies to contribute to the understanding of the role of VOCs in the pollination process. Therefore, a HS–SPME method combined with gas chromatography–mass spectrometry (GC–MS) was developed for the extraction and characterization of VOCs of melon flowers (Cucumis melo L.). The extraction was carried out with the fibers PDMS, DVB/CAR/PDMS and CAR/PDMS for the times 15, 30, and 45 min. Fifty compounds belonging to the following chemical classes were identified: terpenes, hydrocarbons, esters, ethers, ketones, aldehydes, and alcohols. CAR/PDMS fiber extracted the largest amount of compounds, and was more efficient for the extraction of volatile compounds with lower molecular weight, low boiling point and ideal for analytes in low concentration. Therefore, the evaluated method proved to be a promising tool for the analysis of VOCs of melon flowers, to be applied in new studies of the relationships between chemical composition and the processes of attraction of pollinators.

What doesn’t kill you makes you stronger: The burdens and benefits of toxin sequestration in a milkweed aphid

Abstract Specialized insect herbivores commonly co‐opt plant defences for protection against predators, but the costs, benefits and mechanisms of sequestration are poorly understood. We quantified sequestration of toxic cardenolides by the specialist aphid Aphis nerii when reared on four closely related milkweed (Asclepias) species with >20‐fold variation in cardenolide content, and in the presence or absence of generalist ladybug predators. Increasing concentrations of apolar plant cardenolides increased sequestered amounts in aphids. High concentrations in plants impaired aphid population growth, but also reduced the top‐down effects of predators. An in vitro enzymatic assay of total cardenolides in aphid bodies using the cardenolides’ target (animal Na+/K+‐ATPase) revealed that the subset of sequestered cardenolides is disproportionally more toxic than cardenolides in leaves. All aphids accumulated two cardenolides not present in their host plant, even on plants with very low foliar cardenolide concentrations. Sequestration of potent cardenolides by A. nerii thus involves passive, concentration‐dependent uptake from the host plant, as well as a presumably more active mechanism of modification and up‐concentration of plant cardenolides. The concentration of toxins in the host plant thus not only determines the negative impacts on growth and performance of an aphid, but also the ease and efficiency by which toxins are sequestered for the aphid’s defence, making the costs and benefits of plant toxins highly context‐dependent for both the plant and the herbivore. Therefore, variation in plant toxins is of central importance for co‐evolutionary plant–insect interactions, particularly in environments with variable predator pressure. A plain language summary is available for this article.

Modern approaches to study plant–insect interactions in chemical ecology

Phytochemical variation among plant species is one of the most fascinating and perplexing features of the natural world and has implications for both human health and the functioning of ecosystems. A key area of research on phytochemical variation has focused on insects that feed on plants and the enormous diversity of plant-derived compounds that reduce or deter damage by insects. Empirical studies on the ecology and evolution of these chemically mediated plant–insect interactions have been guided by a long history of theoretical development. However, until recently, such theory was substantially limited by inadequate data, a situation that is rapidly changing as ecologists partner with chemists utilizing the latest technological advances. In this Review, we aim to facilitate the union of ecological theory with modern chemistry by discussing important theoretical frameworks for studying chemical ecology and outlining the steps by which hypotheses on insect–phytochemical interactions can be advanced using current methodologies and statistical approaches. We highlight unique approaches to isolation, synthesis, spectroscopy, metabolomics and genomics relevant to chemical ecology and describe future areas for research that will bring an unprecedented understanding of phytochemical variation.