Chemoecology最新文献

Olfaction plays a major role in the host-finding behaviors of insects. However, the irregularity of insect responses to odor interactions has hindered our efforts to draw broad conclusions about how a host-finding insect uses the complex mixture of various odor plumes in natural environments. Particularly, it is still unclear so far why the use of non-host odors to control insect pests in practices have met with mixed results. To further understand the host-finding of a specific insect, we highlight the role of the real-time odor environment (ROE) that the host-finding insect is passing through. The ROE may contain various odors with different ranks and changes during the insect’s host finding. A host-finding insect may always prone to switch to the higher rank odor plumes in each ROE regardless of the distance is “short” or “long” from the odor source. For a specific herbivorous insect, only mixing degree of the given host and non-host plant odors reaches some certain level (threshold value), can the non-host odors significantly affect its ability to locate host plants. When the odor mixing degree is low, masking effects may not occur or the non-host plant odors’ “attractive” effects at long distances and “repellent” effects at short distances can even increase the pest loads. In forests, the mixing degree of different plant odors is determined by turbulence intensity which is mainly affected by plant structures. These may further advance our understanding of herbivorous insects’ host finding and have important implications for the development of pest management strategies.

Stink bugs (Pentatomidae) produce volatile chemical substances in the scent glands, with unpleasant odors that function as alarm and defense signals against natural enemies. The contents of the scent glands of the predatory Podisus nigrispinus and its prey, the phytophagous Euschistus heros were used to evaluate the behavioral interactions between these two insects. Quantitative and qualitative analyses of odor components were performed by gas chromatography (GC/FID and GC/MS) and behavioral response evaluated by video-tracking system. The chemical composition of the odor produced by P. nigrispinus and E. heros contains aldehydes and hydrocarbons. The chemical mixture has quantitative and qualitative component differences between species and sexes, with 20 compounds identified for P. nigrispinus and 17 compounds for E. heros. The compounds (E)-2-hexenal, hexenoic acid, (E)-2-decenal, tridecane, tetradecane, and pentadecane occur in both species, but with different amounts between males and females. The secretion of the scent gland of P. nigrispinus and E. heros produces repellent and irritant effects between species and between sexes of the same species, supporting the defensive function of these compounds. Chemical identification of the Pentatomidae scent gland compounds may influence in insect behavior cause side effects in other insects. Overall, these compounds can be a sustainable and novel source of insecticides with potential to agricultural pest control.

An underlying assumption of optimal foraging models is that animals are behaviorally, morphologically, and physiologically adapted to maximize their net energy intake. Here we explored whether this concept applies to web-building spiders in a multi-trophic context. If a spider were to build her web next to herbivore-fed-on plants that signal the herbivores’ enemies for help by emitting herbivore-induced plant volatiles (HIPVs), that spider may maximize web captures in the short term. However, she would also risk predation by generalist predators that “listen” to signaling plants to find both herbivore and spider prey, likely resulting in lower overall reproductive fitness for the spider. We tested the hypothesis that HIPVs trigger avoidance responses by web-building spiders. We selected seven common HIPVs and one HIPV elicitor, and in two-choice olfactometer bioassays tested their effect on four synanthropic spider species (false black widow, Steatoda grossa; common cellar spider, Pholcus phalangioides; hobo spider, Eratigena agrestis; western black widow, Latrodectus hesperus). The 8-component HIPV/HIPV elicitor blend had a weak deterrent effect on S. grossa, but the effect did not extend to P. phalangioides, E. agrestis, and L. hesperus. Our findings imply that there was insufficient selection pressure for these spiders to recognize HIPVs in a multi-trophic context, where spiders themselves could become prey if generalist predators or spider-hunting parasitoid wasps were to respond to signaling plants.

European foulbrood (EFB), caused by Melissococcus plutonius, is a globally distributed bacterial brood disease affecting Apis mellifera larvae. There is some evidence, even if under debate, that spreading of the disease within the colony is prevented by worker bees performing hygienic behaviour, including detection and removal of infected larvae. Olfactory cues (brood pheromones, signature mixtures, diagnostic substances) emitted by infected individuals may play a central role for hygienic bees to initiate the disease-specific behaviour. However, the mechanisms of cue detection and brood removal, causing hygienic behaviour in EFB affected colonies, are poorly understood. Here, coupled gas chromatography-mass spectrometry (GC–MS) was used to detect disease-specific substances, changes in cuticular hydrocarbon (CHC) profiles, and brood ester pheromones (BEPs) of honey bee larvae artificially infected with M. plutonius. Although no diagnostic substances were found in significant quantities, discriminant analysis revealed specific differences in CHC and BEP profiles of infected and healthy larvae. β-Ocimene, a volatile brood pheromone related to starvation and hygienic behaviour, was present in all larvae with highest quantities in healthy young larvae; whereas oleic acid, a non-volatile necromone, was present only in old infected larvae. Furthermore, γ-octalactone (newly discovered in A. mellifera in this study) was detectable in trace amounts only in infected larvae. We propose that the deviation from the olfactory profile of healthy brood is supposed to trigger hygienic behaviour in worker bees. To confirm the relevance of change in the chemical bouquet (CHCs, BEPs, γ-octalactone, etc.), a field colony bioassay is needed, using healthy brood and hygienic bees to determine if bouquet changes elicit hygienic behaviour.

Gonipterus weevils have been a taxonomic challenge for many years, with implications on our understanding of invasive species, host plant relationships and natural enemies. We assessed cuticular hydrocarbon (CHC) analysis as a tool for discrimination of some of the many species of Gonipterus occurring in Australia. Weevils were collected across several localities and kept under identical conditions prior to a whole-body wash for extraction of CHCs in hexane. Weevil identifications were confirmed using morphology and molecular tools. CHC extracts were analyzed by gas chromatography–mass spectrometry (GC–MS) and the relative peak areas in profiles were compared; compounds were identified according to MS fragmentation and retention indices. CHC profiles of the seven species of Gonipterus analyzed differed from each other, and from another weevil genus (Oxyops), used as an outgroup. The compounds that contributed most to species differences were alkanes, alkenes and methyl branched alkanes. Within some species, locality of collection affected CHC profiles. Our study presents CHC analysis as a promising tool for distinction of Gonipterus species.

Nickel hyperaccumulation in Blepharidium guatemalense Standl. (Rubiaceae) was found in the tropical forests of south-eastern Mexico. This study aimed to document the geographic extent of nickel hyperaccumulation in this species, to understand its process of hyperaccumulation and to explore nickel distribution within the tissues of this plant. To accomplish these objectives, a complete non-destructive elemental screening of herbarium specimens was performed with a hand-held X-ray fluorescence spectrometer. Besides, rhizosphere soils and plant tissues were collected in Mexico and analyzed for physical–chemical parameters. Finally, elemental distribution maps of nickel and other elements in plant tissues were obtained by X-ray fluorescence spectroscopy and microscopy. This study revealed that Blepharidium guatemalense is distributed throughout Chiapas, Tabasco and Campeche, reaching the maximum nickel concentration in leaves (4.3 wt%) followed by roots and seeds (2.0 wt%) and bark (1.8 wt%). Simultaneous hyperaccumulation of cobalt and nickel was found in 15% of the herbarium specimens. Blepharidium guatemalense has uncommon re-distribution mechanisms via phloem since this tissue is the highest nickel-enriched from all parts of the plant (from roots to leaves). A high total nickel (mean of 610?μg?g^?1) was found in rhizosphere soils even though no evidence of ophiolite emplacement in that area has been reported. Blepharidium guatemalense represents the first hypernickelophore (>?1 wt% Ni) to be reported as growing in soils that are neither ultramafic nor enriched by anthropogenic pollutants.

Bactrocera bryoniae is a polyphagous and economically significant fruit fly found in Indonesia, Papua New Guinea and Australia. To understand chemical-mediated sexual communication, and the potential for novel pheromone-based attractants for monitoring and mass-trapping of B. bryoniae, rectal gland exudates and emissions from sexually mature males and females were investigated. Gas chromatography–mass spectrometry showed that male rectal glands contained six compounds, of which 1,7-dioxaspiro[5,5]undecane elicited electroantennographic (EAD) and electropalpographic (EPD) responses in both sexes, ethyl 3-acetoxybutanoate elicited EPD responses in both sexes, N-(3-methylbutyl)acetamide elicited EAD response from males and 4-hydroxy-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and females and EPD responses in females. Female rectal glands contained 23 compounds with the esters ethyl laurate and ethyl myristate as major components. Amongst the female rectal gland constituents, ethyl laurate, ethyl myristate and ethyl palmitate elicited EAD responses in males and females, N-(3-methylbutyl)acetamide elicited EAD responses in males only, (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and EPD responses in females, and 2,7-dimethyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane, (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, (E,E)-2-propyl-8-methyl-1,7-dioxaspiro[5.5]undecane and ethyl caprate elicited EPD responses in females only. Y-tube bioassays indicated that male rectal gland extracts and headspace volatiles attracted females and males, while female rectal gland extracts and headspace volatiles only attracted males. The results suggest that ethyl 3-acetoxybutanoate, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male-produced sex pheromone in B. bryoniae while (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, N-(3-methylbutyl)acetamide, ethyl laurate, ethyl myristate and ethyl palmitate may be components of female-produced sex pheromone. Ethyl 3-acetoxybutanoate, N-(3-methylbutyl) acetamide, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male aggregation pheromone. These findings contribute to the understanding of pheromone communication in B. bryoniae and provide a foundation for developing pheromone-based monitoring and control methods.

The West Indian fruit fly, Anastrepha obliqua (Macquart), infests a wide diversity of tropical fruit. Previous studies suggest that A. obliqua adults are attracted to volatile compounds common in different hosts. However, to date, most studies have used ripe fruit for the identification of attractive compounds. In this study, we investigated the attraction of sexually mature A. obliqua females and males to two cultivars and three ripening stages of guava. We also identified the attractive compounds to A. obliqua by combined gas chromatography-electroantennographic detector (GC-EAD) and gas chromatography-mass spectrometry (GC–MS) and evaluated the biological activity of the identified compounds in field-cage tests. We found that individuals of both sexes of A. obliqua showed no preference to the volatiles of either of the two cultivars of guava evaluated. In contrast, flies were more attracted to ripe and half-ripe fruit than to unripe ones. GC-EAD analyses of extracts of ripe “Creole” or “Thai” cultivars identified six compounds that elicited antennal responses by A. obliqua females and males. The compounds were identified by GC–MS as ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, cis-3-hexenyl acetate, ethyl benzoate, and ethyl octanoate. Half-ripe guava emit ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, and cis-3-hexenyl acetate, while only traces of cis-3-hexenyl-acetate were found in unripe guava. Field-cage tests with synthetic standards confirmed that the compounds identified are responsible for the attraction of A. obliqua flies to ripe guava.

In social insects, chemical communication is the main communication mode among colony members, which use the blends of cuticular hydrocarbons as recognition cues to discriminate between nestmates and non-nestmates and to prevent the exploitation of their nest resources by aliens. The aim of this study was to assess the variation of nestmate recognition cues in the ant Ectatomma ruidum, a species complex with a considerably conserved morphology and one of the few ant species where intraspecific thievery, a form of cleptoparasitism, has been reported. We analyzed the cuticular hydrocarbon profiles of ants collected from a number of geographically separated populations and examined DNA sequence data to assess their species identity. We focused on one species of the complex, E. ruidum sp. 3–4, whose species delineation remains controversial. We documented that several quantitative and qualitative traits of the cuticular hydrocarbon profiles varied significantly between populations, indicating that this species harbors more cuticular chemical phenotypic diversity than expected within a single species. In particular, there was a striking divergence among populations in the proportion of methylalkanes, alkenes, alkadienes and odd-chain components, which likely play a major role in nestmate/non-nestmate discrimination, a process which might have been crucial in these cleptobiotic ants. Further investigations are needed to test the hypothesis that biotic pressures, such as the need to discriminate conspecific intruders and limit thievery, could have played an important role in promoting the evolutionary divergence between populations in this ant species complex.