Chemoecology最新文献

A major hypothesis for the evolution of chemical signals is that pheromones arise from non-communicative precursor compounds. However, data supporting this hypothesis are rare, primarily because the original functions of the antecedent compounds often have been lost. A notable exception, however, is the parasitoid wasp species Leptopilina heterotoma, whose compound (?)-iridomyrmecin is used as a defensive secretion, a cue for females to avoid competition with con- and hetero-specific females, and as the primary component of the females’ sex pheromone. To better understand the evolution of sex pheromones from defensive compounds, we examined the chemical ecology of L. pacifica, the sister species of L. heterotoma. Here, we show that L. pacifica also produces a defensive secretion containing a species-specific mixture of mostly iridoid compounds. However, the composition of the secretion is more complex than in L. heterotoma, and iridomyrmecin is only a minor component. Moreover, in contrast to L. heterotoma, conspecific female competitors were not avoided by female subjects, and a role of the iridoids in the female sex pheromone of L. pacifica can be excluded, as only the females’ cuticular hydrocarbons (CHCs) resulted in the elicitation of courtship by males. Although closely related, the two sister species show substantial differences in the use of the defensive secretion for communicative purposes. Variation in pheromone usage in this genus still presents a conundrum, highlighting the need for additional studies to understand the selective forces shaping the evolution of pheromone composition.

Raspberry ketone (RK) supplements provided together with sugar and yeast hydrolysate accelerate sexual maturation and increase mating success of Queensland fruit fly (‘Qfly’) males. However, the mechanisms underlying this enhanced mating ability are currently unknown. Volatiles are an important element of Qfly sexual calling and courtship and so changes in volatiles quantity or quality may be involved, and the present study investigated this possibility. Flies were fed a diet of sugar only (S) or yeast hydrolysate mixed with sugar (YH?+?S) (1:3) that contained 0% RK (control) and 5% RK (treated) for 2?days after emergence. Volatile compounds were extracted from rectal glands when flies were 6, 8, 10, 20, and 30?days old. Males fed on RK exhibited a significant increase in total volatile production in rectal glands compared to RK-unfed males (control). Males fed on RK with YH?+?S produced significantly higher amount of volatiles than males fed on RK with sugar only. Males fed on YH?+?S diet produced more volatiles in the presence of RK compared to males fed on YH?+?S diet only. Two compounds, N-(3-methylbutyl)acetamide and N-(3-methylbutyl)propanamide were dominant in endogenously produced rectal gland volatiles comprising ca. more than 90% of the total amount in both RK-fed and control males. Considering exogenous and endogenous compounds together, unaltered RK was dominant along with these two endogenous compounds in RK-fed males in rectal gland until 30?days of age in both diet groups.

Volatile organic compounds derived from microbes recruit insects to carrion, shaping community assembly and ecological succession. The importance of individual volatiles and interactions between volatiles are difficult to assess in the field because of (1) the myriad compounds from decomposing animals and (2) the likelihood that complex volatile blends are important for the final approach to carrion. On the assumption that searching carrion-frequenting beetles may use simpler cues to orient at a distance, we employed a chemically-supplemented minimal trap that uses test chemicals associated with active decay to attract from a distance and a minimal carrion bait (a small fresh mouse carcass) to induce trap entry. Traps supplemented with both methyl thiolacetate (MeSAc) and dimethyl trisulfide (DMTS) attracted greater numbers of beetles including adult silphids (Necrophila americana and Oiceoptoma noveboracense) and the histerid Euspilotus assimilis than the combined totals of DMTS-only and MeSAc-only traps, demonstrating a synergism. The attraction of larval Necrophila americana to traps left in the field for less than 24?h suggests that larvae move between carrion sources. The use of such species for forensic applications requires caution.

The transition from a perennial to an annual life cycle, as well as domestication, are expected to increase plant growth and reproduction at the same time that anti-herbivore defences are reduced. Here, we investigated the effects of the life-history transition (the perennial teosinte Zea diploperennis to the annual teosinte Z. mays ssp. mexicana) and domestication of Zea (annual teosinte to the modern maize Z. mays ssp. mays) on direct and indirect defences against the fall armyworm Spodoptera frugiperda. The direct defence of Zea was assessed by larval survival and nutritional indices based on food intake and utilisation. Indirect defence was measured in terms of the olfactory preference of the night-active predatory earwig Doru luteipes for nocturnal herbivore-induced plant volatiles (HIPVs) from the teosintes and maize. Larval growth and survival were reduced on teosintes relative to maize. Whilst larvae fed on perennial teosinte had lower food intake indices, those on annual teosinte showed lower food utilisation indices relative to maize. The earwig preferred HIPVs emitted by teosintes over those by maize, but it did not discriminate between odours of herbivore-damaged annual and perennial teosinte. The nocturnal HIPV blend from maize contained the lowest total amount of fatty acid derivatives, while it had higher total amounts of terpenes compared to teosintes. Our study shows that the teosintes are better defended than maize in terms of direct and indirect defences; however, the perennial teosinte have stronger direct defences against the fall armyworm than the annual teosinte.

The use of chemical pesticides as a main pest control strategy has been highly criticised due to environmental pollution and negative effects on natural enemies of pests. In modern farming, it is essential to implement integrated pest management approaches that seek to control insect pests without causing environmental damage, e.g. the use of companion plants. Basil and Mexican marigold are often used as companion plants to attract greenhouse whiteflies, hence reducing damage to solanaceous crops, but the mechanism and role of volatile cues in crop protection strategies are unknown. This study found that both flowering basil and marigold were preferred to tomato by the greenhouse whitefly (Trialeurodes vaporariorum) in Y-tube olfactometer bioassays. PCA revealed that some volatiles were more correlated to one stage than to another. The dominant volatile constituents of Mexican marigold are limonene, dihydrotagetone, (Z)-β-ocimene, α-pinene, (Z)-3-hexenyl acetate, and those from basil are linalool, 1,8-cineole, eugenol and β-elemene. Among these dominant compounds, 1,8-cineole and (Z)-3-hexenyl acetate elicited strong attraction in greenhouse whitefly at 0.01%, whereas (Z)-β-ocimene and linalool elicited strong repellence at 0.1% and 1% dosages. This suggested that the basil flowering stage attraction is due to 1,8-cineole. These volatiles demonstrated potential as lures or bio-repellents and could be used in a “push–pull” semiochemical approach for greenhouse whitefly management.

Apple proliferation disease is caused by the phloem-dwelling bacterium ‘Candidatus Phytoplasma mali’, inducing morphological changes in its host plant apple, such as witches’ broom formation. Furthermore, it triggers physiological alterations like emission of volatile organic compounds or phytohormone levels in the plant. In our study, we assessed phytoplasma-induced changes in the phloem by sampling phloem sap from infected and non-infected apple plants. In infected plants, the soluble sugar content increased and the composition of phloem metabolites differed significantly between non-infected and infected plants. Sugar and sugar alcohol levels increased in diseased plants, while organic and amino acid content remained constant. As ‘Ca. P. mali’ is vectored by the phloem-feeding insect Cacopsylla picta (Foerster, 1848), we assessed whether the insect–plant interaction was affected by ‘Ca. P. mali’ infection of the common host plant Malus domestica Borkh. Binary-choice oviposition bioassays between infected and non-infected apple leaves revealed C.?picta’s preference for non-infected leaves. It is assumed and discussed that the changes in vector behavior are attributable to plant-mediated effects of the phytoplasma infection.

The ability of Australian native metallophytes to tolerate extreme metal concentrations in the soil and other difficult edaphic conditions is still not well understood. Copper is an essential micronutrient for plants to survive, but at high concentrations (>?20?μg?g^?1) in plant tissues, it can cause foliar chlorosis, stunted growth, and ultimately plant death. The Roseby Corridor in Central Queensland (near Cloncurry) is host to copper metallophytes (Polycarpaea spirostylis, Bulbostylis barbata, Tephrosia virens, Eriachne mucronata) which are able to tolerate soils with total copper concentrations up to 12,700?μg?g^?1_. Even with these high levels of copper in the rhizosphere, the maximum copper in all species is relatively low when compared to Cu concentrations in the soil (leaf/stem: Bulbostylis barbata: 40.9?μg?g^?1, Eriachne mucronata: 12.3?μg?g^?1, Polycarpaea spirostylis: 10.9?μg?g^?1, Tephrosia virens: 128?μg?g^?1). Therefore, all of these species can be classified as copper Excluder-type metallophytes. Their affinity to copper makes these metallophytes useful indicators of copper surface mineralisation within the Roseby Corridor.

The Neotropical family Serritermitidae is a monophyletic group of termites including two genera, Serritermes and Glossotermes, with different way-of-life, the former being the sole obligatory inquiline among “lower” termites, while the latter is a single-site nester feeding on dry rotten red wood. Like the most advanced termite’s family, the Termitidae, the Serritermitidae is an inner group of the paraphyletic family “Rhinotermitidae”, but unlike the Termitidae, it has been poorly studied so far. In this study, we bring new insights into the chemical ecology of this key taxon. We studied the trail-following pheromone of Serritermes serrifer and we identified (10Z,13Z)-nonadeca-10,13-dien-2-one as the only component of the trail-following pheromone of this termite species, as it is the case in Glossotermes, the other genus belonging to Serritermitidae. This result makes the family Serritermitidae clearly distinct from other Rhinotermitidae, such as the termites Psammotermes and Prorhinotermes, that use (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol and/or neocembrene as trail-following pheromones.

Mating and oviposition behavior can change the gene expression levels in insect antennae, especially for pheromone-binding protein (PBP) genes. In this study, we observed the development of the ovaries in the yellow peach moth, Conogethes punctiferalis (Guenée), from its early emergence to full maturity. Sex pheromones in the sex gland reached their highest quantity and influenced the expression of the PBP2 gene in male antennae. Furthermore, the expression of PBP genes was measured after mating and oviposition. The result showed that mating resulted in an increased expression of the PBP2 gene in male antennae, while the expression of the PBP1 gene increased in female antennae, indicating that PBP genes might play different functions in different sexes. Compared with females that had not mated, the PBP1 and PBP5 genes were up-regulated in female antennae after mating or oviposition. Altogether, the PBP genes were regulated by sex pheromone release, mating or oviposition, suggesting that these genes may play some critical roles in behaviors associated with reproduction.