Chemoecology最新文献

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.

In flammability assessment, the terpene effect is usually studied using their total or subgroup content, missing, therefore, the information that could be provided by the molecules themselves. In this study, the specific role of terpenes on leaf flammability was sought comparing different levels of terpene identification—total, subgroup (i.e. mono-, sesqui-, and diterpene), and single compound—as well as their interactions with fuel moisture content (FMC) in four species common in Mediterranean Wildland–Urban Interfaces (Pinus halepensis, Cupressocyparis leylandii, Hesperocyparis arizonica, Cupressus sempervirens). Pinus halepensis was the most flammable species (low FMC and higher sesquiterpene content but low terpene diversity) while Cupressocyparis leylandii presented the highest terpene diversity and total terpene content (higher mono- and diterpene content). Flammability was differently affected according to the terpene identification level used in the models. The effects ranged from non-significant for most species studied, using subgroup or total terpene content, to mostly significant, using single compound content. Regarding the former, the lack of significant results could be due to opposite effects of different single compounds within a terpene subgroup. For the latter, terpene molecules driving flammability and their effects (positive or negative) differed among species. A cumulative effect with FMC was also highlighted in some cases but terpenes mostly remained the main flammability drivers regardless of the species. Using the refined terpene level in modelling allowed a better understanding of the compounds’ role on flammability, which is useful in the identification of plant traits linked to flammability.

Plants that naturally accumulate aluminium (Al) may also inadvertently accumulate rare earth elements (REEs) due to the similar chemical properties of Al and REE trivalent ions, and vice versa. In this study, an Al hyperaccumulator plant species, Melastoma malabathricum, and a species known to have a propensity to hyperaccumulate REEs (in addition to Al), Dicranopteris linearis, were evaluated for potential REE accumulation in a one-year pot dosing trial in Sabah, Malaysia. To test whether the Malaysian accessions of D. linearis and M. malabathricum hyperaccumulate REEs (and Al), both species were grown in pots containing soil treated with solutions containing yttrium (Y), lanthanum (La), neodymium (Nd), and a mixture of these three REEs. The results showed that both M. malabathricum and D. linearis accumulated > 1000 µg g⁻¹ Al in their leaves as expected. The shoots of M. malabathricum contained lower REEs than the roots (50 µg g⁻¹ compared to 905 µg g⁻¹). In D. linearis, the mean foliar REE concentrations ranged from 145 to 315 µg g⁻¹, which is below the hyperaccumulation threshold set for REEs (> 1000 µg g⁻¹ REEs). This study revealed that the Malaysian accessions of both M. malabathricum and D. linearis are Al hyperaccumulators, but their REE hyperaccumulation status requires further testing.

Two components of the Synanthedon bicingulata sex pheromone, (E,Z)-3,13-octadecadienyl acetate (E3,Z13-18:OAc) and (Z,Z)-3,13-octadecadienyl acetate (Z3,Z13-18:OAc), were synthesized to investigate the effect of pheromone blends, trap type and trap color on the capture of S. bicingulata males. The optimal sex pheromone ratio for E3,Z13-18:OAc and Z3,Z13-18:OAc was approximately 4.3:5.7 based on the purity of the two pheromone components in all test areas. A significant difference was observed in the number of S. bicingulata adult males caught in bucket and delta traps. The mean numbers of males caught in bucket and delta traps were 13.2 ± 2.2 and 7.6 ± 2.0, respectively. Trap color affected the number of adult males caught in bucket traps. More adult males were attracted to a yellow bucket trap than to green, white, blue, black and red traps. An analysis of the relationship between trap capture and trap surface-color values (L*a*b*) revealed a positive relationship between trap capture and b* value.

Endophytic fungi have the potential to enhance plant resistance to various stresses and promote the ecological adaptation of the hosts. To evaluate the effects of the riparian endophytes on rice seedlings to flooding tolerance, here we screened out two fungi from the plant Myricaria laxiflora growing in the Yangtze River zone. Through morphological characteristics and rDNA ITS (internal transcriber region) sequence, the two strains were, respectively, identified as Aspergillus fumigatus and Chaetomium globosum. Metabolites derived from both fungi were capable of increasing tolerance of rice to flooding. Systematic separation and purification coupled to bioassays revealed that two natural antioxidants, Z-N-4-hydroxystyryl formamide (NFA) and chaetoglobosin A (CheA), were effective for alleviating flooding stress. Both NFA and CheA can reverse the decline trend of oxidative parameters caused by long-term flooding, such as malondialdehyde, superoxide dismutase, ethanol dehydrogenase, and NADPH oxidase. Gene expression analyses of NADPH oxidase families indicated that OsRbohB could be involved in conferring flooding tolerance mediated by the two natural antioxidants. These findings contribute to understanding the role of the natural antioxidants in riparian endophytic fungi and providing a basis for improvement of flooding tolerance of rice and other crop plants.

Free-ranging giant pandas (Ailuropoda melanoleuca) in China recently were reported to rub and roll in horse manure, a behavior that was observed frequently at low ambient temperatures. Two sesquiterpenes, β-caryophyllene (BCP) and caryophyllene oxide (BCPO), that are abundant in fresh horse manure elicited rolling in captive giant pandas. Mice and rats treated with BCP/BCPO exhibited enhanced cold tolerance in behavioral assays, and BCP/BCPO inhibited cold-activated ion channels of mammals expressed in human kidney cells; these laboratory results were cited in support of the contention that giant pandas tolerate low ambient temperatures by applying horse manure to their integument. The demonstrated biocidal activities of BCP and BCPO against insects and ticks, and the reported elicitation of anointing in giant pandas with materials other than horse manure, including substances or constituents thereof known to act as arthropod biocides, are consistent with an anti-consumer function of anointing by giant pandas. Anointing with the scents of heterospecifics as a defense against nuisance arthropods constitutes a viable hypothesis for the rubbing and rolling behaviors of giant pandas and other ursids.