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.