Chemoecology最新文献

Social wasps build their nests using plant material and can thereby occupy different types of habitats. The organization of their colonies is generally based on complex communication systems that include chemical compounds of the cuticle that are shared with the material of their nests thus contributing to the specific chemical signature of their colony. These compounds can vary by environmental factors, in this case the nesting substrate may interfere with this composition. However, no study to date has investigated whether there is any relationship between the chemical signature of the colony and the nesting substrate of their nests. Therefore, in this study we investigated the relationship between the colonial chemical signature and the plant in which the colonies were nesting. Colonies of three species of social wasps and samples of plants where they nested were collected, then extractions of the chemical composition of adult wasps, nest material and plants were performed. The results show that the colonies of social wasps investigated here share their chemical composition with the plants where their nests were built. Our results suggest that the plant can provide the colony with more than just a place with ideal physical conditions and safety, but also compounds that compose the colonial chemical signature.

Numerous species of herbivorous insects are associated with soybeans, including the specialist velvetbean caterpillar (VBC), Anticarsia gemmatalis, and the generalist fall armyworm (FAW), Spodoptera frugiperda. Expression of plant resistance is influenced by factors intrinsic to host plants, such as leaf age and plant stage, which can differentially affect specialist and generalist insects due to varying levels of plant defense and corresponding insect adaptation. In this study, four experiments were carried out to test the hypotheses that levels of antibiosis-resistance to VBC and FAW in the resistant genotype PI 227,687 and susceptible genotype IGRA RA 626 RR are related to leaf age and plant stage of soybean. Furthermore, the concentrations of nutrients and selected flavonoids were quantified to give insights into possible chemical mechanisms underlying the resistance. As results, development of VBC and FAW were negatively affected when larvae fed leaves of the resistant genotype, older leaves from the lower part of plants, or leaves from reproductive-stage soybeans. The effects were partly different for each insect species, and the generalist FAW was more affected by higher resistance levels in the older leaves of soybean than the specialist VBC. Distribution and concentrations of nutrients and flavonoids in soybean in function of leaf age and plant stage may explain the varying levels of antibiosis-resistance to VBC and FAW. These results can benefit developments of specific protocols for screening resistant soybean genotypes and pest management strategies focused in plant parts and growth stages that insect-resistance levels are lowest.

The behavioral responses of two bed bug species, Cimex lectularius L. and C. hemipterus (F.), to conspecific or heterospecific nymphal aldehyde blends were examined using a two-choice olfactometer. Volatile cues from exuviae or a synthetic blend containing (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal, and 4-oxo-(E)-2-octenal were tested. In both species, the adults settled preferentially on the olfactometer treatment side when conspecific volatile aldehyde cues were provided. When tested with heterospecific volatile aldehyde cues, only adult C. lectularius preferentially responded to C. hemipterus volatile cues. Adult C. hemipterus was indifferent to the aldehyde blend of C. lectularius. Potential implications of the finding on bed bug biology and practical pest management are discussed.

Bark beetles of the genus Polygraphus have recently been involved in large bark beetle outbreaks in central Sweden, together with the European spruce bark beetle Ips typographus. Three species of Polygraphus can be found in this region; Polygraphus poligraphus, Polygraphus punctifrons and Polygraphus subopacus. Efficient pheromone traps would facilitate further investigations of these species and their role in bark beetle outbreaks. Pheromone compounds have previously been identified in P. poligraphus and P. punctifrons, but not in P. subopacus. Thus, we allowed males and females of P. subopacus to bore in the bark of stem sections of Norway spruce (Picea abies) in the laboratory. Volatile organic compounds from boring insects were sampled with SPME and analysed with GC–MS and several male-specific compounds were observed. The male specific compounds were 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, 3-methyl-2-butenal, grandisol, fragranol, (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, (Z)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, (E)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, geranial and γ-isogeraniol. (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, [(Z)-DMCHE], was identified from GC–MS analysis to be the major male-specific compound while the (E)-isomer, [(E)-DMCHE], was found as a minor compound. These two compounds gave positive responses in EAG analyses with antennae from males and females of P. subopacus. Thus, (Z)- and (E)-DMCHE were used in a field experiment in central Sweden but only (Z)-DMCHE was found to be attractive to males and females of P. subopacus. Consequently, (Z)-DMCHE was established to be a component of P. subopacus aggregation pheromone.

Neotropical poison frogs possess alkaloid-based antipredator defenses which they sequester from a diet of arthropods such as oribatid mites and myrmicine ants. Alkaloid sequestration is still poorly understood and although several studies have examined its uptake, most experiments directly feed alkaloids to the frogs. Here, we examined the alkaloid uptake system in the poison frog species Dendrobates auratus by feeding it an alkaloid-containing prey item, the red imported fire ant Solenopsis invicta (Formicidae, Myrmicinae). Captive bred frogs were either fed live ants or fruit flies dusted with powdered ants for 4 months. Using GC–MS, we confirm that S. invicta contain previously described piperidine alkaloids known as solenopsins; however, none of these piperidine alkaloids was detected in the skin of D. auratus, suggesting the frogs are incapable of sequestering solenopsins from S. invicta. It is possible that D. auratus are unable to sequester fire ant piperidines due to their long hydrocarbon side chains, a feature that makes them structurally different than most known alkaloids in poison frogs.

Volatilization, one of the most important mechanisms of the allelopathic effects of an exotic noxious weed Mikania micrantha, has not been adequately investigated to date. In this study, laboratory bioassays showed that the effects of volatiles from the leaves and flowers of M. micrantha on seed germination and seedling growth were negative for all four tested plants (Lactuca sativa, Chrysanthemum coronarium, Bidens pilosa, Abutilon theophrasti). Moreover, the inhibitory effect of the leaf volatiles was generally greater than that of the flower volatiles. To assess the reason for the above differences and further explore which compounds played the most crucial roles, the volatiles from the two tissues were absorbed by solid phase microextraction (SPME) and identified by gas chromatography and mass spectrometry (GC–MS). Then, 19 and 10 terpenes were determined respectively. α-Terpineol, β-ocimene, β-myrcene, α-pinene and caryophyllene had the maximum differences in content and concentration, which were selected for further bioassays with B. pilosa. The results indicated that morphological indices and SOD activity decreased with increasing concentrations of chemicals, whereas the contents of chlorophyll, soluble protein and MDA represented adverse changes. In addition, significant responses were observed in the treatments with α-terpineol at 1.0 μL·L⁻¹ and lower concentrations, while similar trends were observed in the treatments with β-ocimene, β-myrcene, α-pinene and caryophyllene at 10 μL·L⁻¹ and higher concentrations. It was concluded that terpenoids released through volatilization have an important role in the allelopathic effect of M. micrantha, and the oxygenated monoterpene α-terpineol played a crucial role in these effects.

Chemical communication is fundamental to maintain cohesion in social insect colonies, and in this communication process, cuticular hydrocarbons act as cues exchanged during interactions between nestmates. However, few studies have investigated intraspecific variation of these compounds in Neotropical swarm-founding wasps. We undertook the present investigation by performing two assessments. First, we assessed whether the cuticular chemical composition of females in Polybia sericea varies according to the degree ovarian development, relative age and different body parts. Second, we assessed whether the cuticular chemical profile of colony members and compounds found in nest materials could be used as complementary tools to assess population differences. To make these determinations, samples were collected from three different populations, and the compounds were analyzed by gas chromatography coupled with mass spectrometry. Linear alkanes were found to be the most abundant compounds in the cuticle of females and nest material. Considering the cuticular composition, it was possible to distinguish the females according to degree of ovarian development, relative age and different body parts. In addition, cuticular compounds and nest material were different in the three analyzed populations; therefore, both the cuticular chemical profile of colony members and the chemical profile of nest material can be used as complementary tools to assess population differences.

The predator-predator naïveté hypothesis suggests that non-native predators benefit from being unknown to native predators, resulting in reduced intraguild interference with native predators. This novelty advantage should depend on the ability of native predators to recognize cues of non-native predators. Here, we compared ant aggression and lady beetle reaction in four native and the invasive lady beetle species Harmonia axyridis. In addition, we tested whether lady beetle cuticular hydrocarbons (CHCs) are involved in species recognition, which might explain naïveté if the invasive species has a specific CHC profile. To this end, we conducted behavioral assays confronting two native ant species with both living lady beetles and lady beetle elytra bearing or lacking CHCs of different lady beetle species. Finally, we characterized CHC profiles of the lady beetles using GC–MS. In general, the aggression of Lasius niger was more frequent than that of Myrmica rubra and L. niger aggression was more frequent towards most native lady beetle species compared to H. axyridis. The removal of CHCs from lady beetle elytra reduced aggression of both ant species. If CHCs of respective lady beetle species were added on cue-free elytra, natural strength of L. niger aggression could be restored. CHC analyses revealed a distinct cue composition for each lady beetle species. Our experiments demonstrate that the presence of chemical cues on the surface of lady beetles contribute to the strength of ant aggression against lady beetles. Reduced aggression of L. niger towards H. axyridis and reduced avoidance behavior in H. axyridis compared to the equally voracious C. septempunctata might improve the invasive lady beetle’s access to ant-tended aphids.

The mason wasp Odynerus spinipes shows an exceptional case of intrasexual cuticular hydrocarbon (CHC) profile dimorphism. Females of this species display one of two CHC profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC–MS the CHC profile of 1042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC profile dimorphism that O. spinipes females exhibit.

Insect olfactory systems can efficiently distinguish important host signals in a complex background of odor. Notably, Conopomorpha sinensis Bradley (Lepidoptera: Gracillariidae), a host-specific pest of Litchi chinensis and Euphoria longan, causes periodic outbreaks in southern China. However, little is known about the functions of host volatiles and olfactory mechanisms through which C. sinensis senses host taxa. Consequently, the present study analyzed the Electroantennogram (EAG) responses of C. sinensis antennae to host volatile compounds and their mixtures. The results showed that volatile components were more stimulatory to female than to male C. sinensis antennae. In addition, the highest EAG responses were observed following the stimulation of female antennae by the individual volatile component β-guaiene, followed by β-caryophyllene and β-elemene. However, odorant mixtures containing β-farnesene and α-pinene significantly altered EAG responses in female antennae. This was further confirmed by behavioral responses to host volatile compounds based on the flight orientation of females and males in a wind tunnel. These findings demonstrated that the behavior of C. sinensis can be affected by single compounds or a mixture of compounds. Moreover, real-time fluorescence quantitative PCR suggested that a combination of α-pinene with β-farnesene could alter the expression of olfactory genes. Therefore, screening for odors that can effectively alter the behavior of insects provides a theoretical basis for exploring host recognition and utilizing the olfactory networks of C. sinensis for biocontrol, at the molecular level.