Chemoecology最新文献

Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior.

From intra-individual regulation of metabolism to entire ecosystem functioning, the thousands of biogenic compounds produced by organisms serve as a major component of ecological and evolutionary diversity mediating interactions across scales. Earlier work considers canonical reactions, defined as reactions specified along accepted (experimentally validated or theoretically postulated) biosynthetic pathways, as the primary form of constraint on chemical diversity. An emerging understanding of non-canonical reactions (reactions which occur independently of canonical reactions) suggests that the physical chemistry of compounds may play a larger role in constraining chemo-diversity than previously thought. We selected 24 studies of plant volatile profiles, satisfying a defined set of criteria, to assess the extent of correlation among profiles attributable to either shared biosynthetic enzymes or physiochemical properties. Across studies, regardless of treatment, 0.17 (±?0.16 SD) adjusted R² was attributed to both shared biosynthetic enzymes and physiochemical properties; however, there were no significant differences between the amount of unique variance attributed to shared enzymes (0.05?±?0.08 SD) or physiochemical properties (0.03?±?0.06 SD). The amount of unique variance explained by physiochemical properties, independent of their canonical relationships, provides a metric for evaluating the role of non-enzymatic and non-canonical reactions in constraining molecular diversity.

The interactions between Dacini male fruit flies and phytochemical male lures are unique. Lure response, fate and its effects after consumption on fruit fly mating behaviour are species- and lure-specific. Bactrocera frauenfeldi is known to respond to the phenylbutanoids raspberry ketone (RK) and cue lure (CL), anisyl acetone (AA), and zingerone (ZN), which are produced by some rainforest orchids. Here we compared the relative field responses of B. frauenfeldi males to these phenylbutanoids in two selected locations to determine the most attractive lure for this species. We also performed gas chromatographic-mass spectral analyses of male rectal pheromone glands to understand the fate of the ingested compounds. Results showed that B. frauenfeldi males were most responsive to CL, equally to RK and AA, while poorly to ZN in Cairns, a site with high population density. No significant difference was observed in Lockhart River which has a low population density of B. frauenfeldi. Chemical analyses showed that most of the ingested phenylbutanoids were sequestered into rectal glands, either unchanged or with minimal structural changes except for AA, which is converted to RK via a demethylation of the methoxy- to a hydroxy-moiety and reduced to 4-(4-methoxyphenyl)-2-butanol via the keto-moiety. This study provides both practical and ecological implications: it identified the most attractive lure, which is important for monitoring and management of B. frauenfeldi; and based on the relative responses, conversion and retention rates by B. frauenfeldi males, revealed the ecological significance of these phytochemical lures in plant-fruit fly co-evolution.

Females of two click beetle species, Cardiophorus tenebrosus and C. edwardsi (Coleoptera: Elateridae), produce methyl (3R,6E)-2,3-dihydrofarnesoate as their sex pheromone. We had serendipitously discovered that males of both species were also strongly attracted to (R)-fuscumol acetate ((E)-6,10-dimethylundeca-5,9-dien-2-yl acetate), a known longhorned beetle (Coleoptera: Cerambycidae) pheromone, due to its structural similarities to the click beetle pheromone. To further investigate the specificity of the responses of Cardiophorus males, additional analogs with different chain lengths and structural relationships compared to the natural pheromone were synthesized and tested. In field and electroantennogram bioassays, only fuscumol propionate ((E)-6,10-dimethylundeca-5,9-dien-2-yl propionate) elicited strong responses from Cardiophorus males, indicating that they were able to distinguish chain length and spatial relationships between the structural elements. In field trials, C. tenebrosus males were attracted equally to the analog and their natural pheromone, but the pheromone elicited stronger antennal responses from males. In contrast, traps baited with fuscumol propionate caught approximately 26 times as many C. edwardsi males compared to traps baited with the natural pheromone, although the analog elicited significantly smaller antennal responses from C. edwardsi males. Thus, in terms of behavioral responses, fuscumol propionate appears to be acting as a hyperactive pheromone mimic, a phenomenon which has rarely been observed in insect semiochemistry.

When burying beetles first emerge as adults, they search for well-rotted carcasses with fly maggots on which to feed. After attaining reproductive competence, they switch their search and respond to a small, fresh carcass to prepare for their brood. Because the cues used to locate a feeding versus a breeding resource both originate from carrion, the beetles must respond to subtle changes in volatiles during decomposition. We investigated cues used to locate a fresh carcass in the field by (1) a general subtractive method, applying an antibacterial or antifungal compound to reduce microbially derived volatiles, and (2) a specific additive method, placing chemical supplements near a fresh carcass. Five sulfur-containing compounds, known to result from bacterial metabolism of sulfur-containing amino acids, were studied: dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), methyl thiolacetate (MeSAc, also known as S-methyl thioacetate), and methyl thiocyanate (MeSCN). When a carcass aged for 48?h was treated with an antibacterial compound to reduce volatiles, there was a 59% decrease in beetles discovering the resource. The addition of the chemical supplement MeSAc had no effect on discovery of a fresh carcass, while DMS and DMDS had a limited ability to attract breeding beetles. The chemical that was least well known, MeSCN, increased beetle numbers by 200–800% on a fresh carcass and almost guaranteed discovery. DMTS, which is known to attract a variety of carrion insects, was the only compound to significantly reduce beetle presence at a fresh carcass. A laboratory experiment demonstrated that DMTS does not directly inhibit breeding, suggesting that DMTS deters breeding beetles while they fly.

Reliance on broad-spectrum insecticides and chemotherapeutic agents to control hematophagous insect vectors, and their related diseases is threatened by increasing insecticide and drug resistance, respectively. Thus, development of novel, alternative, complementary and effective technologies for surveillance and control of such insects is strongly encouraged. Semiochemicals are increasingly developed for monitoring and intervention of insect crop pests, but this has not been adequately addressed for hematophagous insects of medical and veterinary importance. This review provides an insight in the application of semiochemicals for control of hematophagous insects. Here, we provide specific information regarding the isolation and identification of semiochemical?compounds, optimization approaches, detection, perception and discrimination by the insect olfactory system. Navigation of insects along wind-borne odor plumes is discussed and methods of odor application in field situations are reviewed. Finally, we discuss prospects and future challenges for the application of semiochemical-based tools with emphasis on mosquitoes. The acquired knowledge can guide development of more effective components of integrated vector management, safeguard against emerging resistance of insects to existing insecticides and reduce the burden of vector-borne diseases.

Chemical communication is pivotal for social insects to ensure proper functioning of their colonies. Cuticular hydrocarbons (CHCs) are the most well-known class of compounds used to regulate different types of behavioural interaction within a social context. Queens of highly eusocial insects rely on the use of chemical communication to keep their reproductive monopoly, whereas queens of primitively eusocial insects often exert physical control to maintain reproductive dominance. However, in the past years, ample evidence has demonstrated that primitively eusocial insects also use chemical compounds to communicate. Based on this evidence, we aimed to elucidate whether CHCs carry some information regarding female hierarchical position, ovary activation and nestmate recognition in the primitively eusocial wasp Mischocyttarus parallelogrammus. Additionally, females were classified by their ovary activation. Finally, the cuticular profiles of females originating from different nests were compared to check whether CHCs convey information about their nest of origin. Our results confirmed that the chemical composition of alpha and subordinate females differed significantly in post-worker emergence nests, but that alpha and beta females surprisingly were not chemically different from each other in either of the colony phases. Furthermore, females with activated ovaries expressed a chemical profile distinct from that of females with non-activated ovaries. Lastly, we showed that CHCs might convey information about nest origin, since females hailing from different nests showed distinct chemical profiles. Based on our results, we conclude that CHCs might play a critical role in the nest-functioning of M. parallelogrammus, since they mirror social status.

Thapsigargin and related compounds are produced by Thapsia garganica L. (Apiaceae) and are thought to be a defence compound against herbivory. Thapsigargin inhibits the sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA) in both vertebrates and invertebrates. This activity is responsible for its potent toxicity, as well as the potential use to treat solid tumours. However, the ecological role and regulation of thapsigargin are not well understood, and the aim of this study was to investigate if thapsigargin biosynthesis was responsive to leaf damage. To test the response to potential leaf damage during a?herbivory, greenhouse plants were subjected to clipping to mimic the physical damage. Unclipped versus clipped plants were sampled for chemical analysis and the gene expression for the two known thapsigargin biosynthetic genes (TgTPS2 and TgCYP76AE2) was investigated. Data obtained by LC–ESI–MS/MS were used to perform molecular networking to identify chemical constituents related to thapsigargin and its biosynthesis. The results show a significant change in a plant’s chemical profile after mimicking an herbivory event. Both the chemical analysis and gene expression data show that T. garganica plants can induce the biosynthesis of this class of defence compounds at the site of an attack. Thapsigargins are clearly the dominant defence compounds in these plants, and they seem to be produced through a common biosynthetic pathway with little diversity. This likely means that T. garganica has a relatively simple response to herbivory, as opposed to many other plant species that have been shown to have complex metabolite responses to herbivory.

The pre-excavation activity of the neonate larvae of Cactoblastis cactorum (Lepidoptera: Pyralidae) is typically confined to an arena that encircles the base of their egg stick. If the caterpillars are unable to penetrate the host plant within the arena, they strike off en masse in search of a more favorable site, marking their pathway with secretions from their mandibular glands. One component of this secretion, 4-hydroxy-2-oleoylcyclohexane-1,3-dione (an acylcyclohexanedione, ACHD), has been previously shown to function as a trail pheromone. In this paper, we report the characterization, synthesis, and bioassays of a family of 3-acyl fatty acid methyl esters (which we named cactoblastins), a chemically distinct group of mandibular gland compounds that also elicit trail following behavior. The relative effectiveness in eliciting trail following of the ACHD and six, chemically distinct, synthetic cactoblastins was determined. The most bioactive of the cactoblastins was also compared to whole mandibular gland extract to assess its ability to disrupt the aggregative behavior of the neonates and to serve as a biorational alternative to pesticides for managing invasive populations of the caterpillar.

Southern pine beetle (Dendroctonus frontalis Zimmermann) and black turpentine beetle (Dendroctonus terebrans Olivier) are two sympatric bark beetle pests of the southeastern United States of America that adversely affect pine (Pinus spp.) health. Successful host tree colonization and reproduction is dependent on a chemical communication system that includes compounds produced by both the beetles and their host trees. To better understand the role of host volatiles in the ecology of these species, we (1) used coupled gas chromatography-electroantennographic detection (GC-EAD) to analyze olfactory sensitivity of D. frontalis and D. terebrans to volatile constituents of host resin, and (2) investigated olfactory stimulants for behavioral effects on both pest species and a major predator, Thanasimus dubius Fabricius (Coleoptera: Cleridae) in field trapping studies. In GC-EAD analyses of the headspace of fresh host resin, antenna of both D. frontalis and D. terebrans produced strongest responses to alpha-pinene, beta-pinene, myrcene, and 4-allylanisole. Field tests indicated that alpha-pinene, beta-pinene, and 4-allylanisole significantly enhanced attraction of D. frontalis, D. terebrans, and T. dubius to traps baited with attractive pheromone components of both bark beetle species, and myrcene diminished this response for D. frontalis. The observed attractive synergism of 4-allylanisole contrasts with previously reported repellency of this compound for D. frontalis and instead suggests this semiochemical may have multiple ecological roles for this species. Lures used for monitoring D. frontalis may be enhanced in sensitivity by adjusting the composition of their host odor components.