Arthropod-Plant Interactions最新文献

Plant invasions threaten native biodiversity, but detailed information on patterns and mechanisms of diversity changes across multitrophic levels remains unknown. Alien plants can reduce richness of native plants, thereby negatively affecting arthropods and their multitrophic interactions. In particular, tall invasive trees may limit native understory plants and associated arthropods more than small invasive shrubs, which may support light-demanding taxa under their more open canopies. In this study, we investigated how two non-native highly invasive species (shrub Sorbaria sorbifolia and tree Amelanchier spicata) and two native species (shrub Rubus idaeus and tree Prunus padus) distributed in monodominant patches along roadsides in SW Finland affect arthropod-feeding guild biomass and food webs. Under trees, regardless of their origin, the diversity and biomass of understory plants and arthropods living in the canopy and on the ground was significantly reduced compared to shrubs, which had higher biodiversity and more significant interactions between feeding guilds and understory plants. The higher biomass of native understory plants increased the abundance of herbivores under the shrubs, and thus indirectly predators. The species richness of understory plants determined the richness of saprophagous organisms in native stands. We conclude that more open roadside shrub canopies support greater plant and arthropod biodiversity and more complex food web structures compared to shady tree stands, and that alien shrubs do not necessarily reduce arthropod biodiversity. The study opens up the possibility of predicting arthropod composition and biomass using functional attributes of understory vegetation and the origin, physiognomy and species identity of overstory dominants.

As an exotic, generalist leafroller the light brown apple moth (Epiphyas postvittana) has become established in coastal California where populations have been shown to experience strong negative density dependence from an unknown cause. This study was conducted to determine whether plant secondary metabolites could be a potential source of the density dependence. Experimental observations were focused on two of its commonly used host plants (ribwort plantain and Japanese cheesewood) to test for detrimental effects of secondary metabolites on larval performance under laboratory conditions. A plant defense induction assay was used to test for density-dependent responses of the two host plants to prior larval feeding damage, and a leaf disk assay was used to quantify the impact of increased concentrations of selected groups of chemical defenses (iridoid glycosides and polyphenols). Contrary to expectations, the results from these assays provided no evidence that E. postvittana either induced a sufficient plant response to impact larval performance, or that experimentally increased chemical defense concentrations affected larval performance. Consequently, the observed results suggest that the larvae of E. postvittana may have adaptations that inhibit induced responses in their host plants and/or that allow them to tolerate secondary defenses through detoxification and excretion. In conclusion, there is no evidence that induced plant defenses can account for the strong negative density dependence observed in the dynamics of E. postvittana populations in California and further research will be needed to identify the true cause of this density dependence.

Crataegus species (Rosaceae) or hawthorns form dense thickets and displace native vegetation out of their native range. In South Africa, Crataegus monogyna and C. mexicana are under surveillance but there is lack of information on their pollination ecology. Therefore, this study sought to investigate the pollination mechanism and potential insect pollinators of these plants. Pollinator exclusion experiments were conducted on ten plants each of C. monogyna and C. mexicana near the towns of Hogsback and Seymour respectively, in the Eastern Cape Province. Flowers of each of these species were also observed to determine the diversity and distribution of insect visitors throughout the day (i.e. morning, mid day and afternoon). The results showed that C. monogyna and C. mexicana are capable of self and cross-pollination. Fruit set from open inflorescences of C. monogyna was 40.88 ± 0.08%, significantly higher than bagged inflorences. Fruit set from open inflorescences of C. mexicana was 48.18 ± 0.03%, significantly higher than those of bagged inflorescences. Hymenopterans were the most frequent visitors on C. monogyna flowers while dipterans were the most frequent visitors on C. mexicana flowers. The distribution of insects did not vary with the time of day for each plant species. Insect pollination, therefore, plays a significant role in the fruiting of C. monogyna and C. mexicana in the Eastern Cape. The results of this study contribute to the understanding of the ecology and phenology of Crataegus species in South Africa and thus the evaluation of their invasive status.

1. Larvae of multiple click beetle species, i.e. wireworms, are important pests of agriculture worldwide, and are generally managed with insecticides. Conceivably, semiochemical-based management tactics that target male beetles and reduce the mating success of females, would reduce the formation of new larvae in the field.

2. Using two of the best studied species, Agriotes obscurus (AO) and A. lineatus (AL), we evaluated the ability of male beetles to find traps that simulate calling female beetles in field plots treated with various formulations and densities of pheromone-treated substrates. Four disorientation studies were conducted, and the response of wild and marked-released beetles inferred from frequent trap collections.

3. Beetle responses differed between male AO, female AO, and male AL. The presence of AO pheromone increased male AO movements, reduced captures in baited traps, and attracted wild AO beetles into the plots. By the final experiment, the pheromone-treated substrate effectively disoriented male AO for > 17 d. However, treatment with AL pheromone reduced male AO movements and/or repelled them from the plots. Female AO were slightly attracted to their own pheromone early in the season, but not thereafter. Treatment with AL pheromone attracted male AL into plots but did not increase their activity. Both AO and AL pheromone disrupted male AL behaviour, but less significantly than observed for male AO.

4. These results suggest pheromone-based click beetle mating disruption for wireworm management is feasible. However, further work is required to determine application rates and methods, and if this can be developed for other species.

Jasmine is a traditional and economically viable ornamental plant. Jasminum sambac, J. auriculatum and J. grandiflorum are commercially cultivated in India and Asian countries. Insect pest infestation is dynamics among different Jasminum species. The biophysical characteristics of three species of jasmine were examined in the current experiment as well as their interactions with insect pests and their natural enemies. The principal component analysis validated the assumed relationship between the biophysical traits, insect occurrence and their natural enemies. Leaf web worm (Nausinea geometralis Guenee) incidence, hymenopteran wasp population and trichomes in upper surface of jasmine plants are positively interacted with each other. Correlation of leaf web worm (r = 0.891) and wasp population (r = 0.937) with trichomes in upper surface narrated interactions with both the parameters. Blossom midge (Contarinia maculipennis Felt) was infecting only J. sambac and not on J. auriculatum and J. grandiflorum. In the reverse, a non-insect pests eriyophid mite, Aceria jasmini damages J. auriculatum plants and doesn’t affect the J. sambac and J. grandiflorum. Present study reveals there was a significant interaction among jasmine crop (first trophic level), pests (second trophic level) and natural enemies (third trophic level).

Graphical abstract

More than 140 years ago Darwin proposed that leaf-trap of carnivorous plants could produce odor to increase prey attraction; however, even now, there is limited information on the role of flower and leaf-trap volatile organic compounds (VOCs) in the attraction to pollinators and prey in carnivorous plants. Here, we recorded the floral visitors and prey of Pinguicula moranensis, a carnivorous plant with adhesive leaf-traps. In addition, the VOCs from flowers and leaf-traps were analyzed. Their role in the attraction of floral visitors and prey was experimentally tested using the skipper butterfly Thorybes dorantes and the fruit fly Drosophila melanogaster as models, respectively. In the field, flowers of P. moranensis were only visited by butterflies and most of the prey were dipterans. Six VOCs, predominantly benzenoids, were identified from floral scent samples. Twelve VOCs were identified from leaf-trap scent samples, mainly monoterpenoids and benzenoids. In experimental conditions, D. melanogaster significantly preferred the scent given off by the leaf-trap over the clean air, whereas the main floral visitor, T. dorantes significantly preferred the floral scent source over the clean air. However, D. melanogaster did not show preferences for the leaf-trap scent compared to the flower scent. These results showed that leaf-traps and flowers of P. moranensis emitted a specific composition and relative abundance of VOCs. In addition, we experimentally showed that floral VOCs attracted the main floral visitor species and leaf-traps attracted D. melanogaster, as a potential prey. The VOCs play a relevant role in attracting pollinators and prey in carnivorous plants.

Bark beetles mainly rely on detoxification enzymes to overcome the defensive oleoresin terpenes of their host. Insect Carboxylesterases (CarEs) play an important role in the detoxification of plant allelochemicals and insecticides. Nevertheless, the functions of specific CarE genes in metabolization of exogenous substances are still unclear in the Chinese white pine beetle, Dendroctonus armandi. In this study, we sequenced and characterized the full-length cDNAs of six CarE (DaEST1-DaEST6) genes from D. armandi. Spatiotemporal expression profiling showed that the expression of DaEST1, DaEST3 and DaEST4 in D. armandi was higher in the larval and adult stages, and these genes mainly expressed in fat body, Malpighian tubules and midgut. Moreover, the expression of DaEST1, DaEST3 and DaEST4 was significantly induced after treatment with four terpenoids. Importantly, disruption of DaEST3 significantly inhibited the CarE activity and reduced the tolerance of adults to host allelochemicals in D. armandi. Additionally, treatment with triphenyl phosphate to adults also reduced the tolerance after terpenoids exposure, which resulted in a significant decrease of CarE activity, leading to a significant improvement of mortality in D. armandi. These results indicate that DaEST3 plays an important role in determining the tolerance to host allelochemicals in D. armandi, which might be of great significance in developing new therapeutic methods to pest control.

Bulbophyllum is the largest orchid genus with > 2000 species. There are many daciniphilous Bulbophyllum species with unique lip mechanisms for fly pollination. Their flowers exclusively attract pest and non-pest Dacini fruit fly species via fragrant floral synomones containing at least one major male attractant. Bulbophyllum hortorum bears non-resupinate and solitary flowers. The four-year study showed that anthesis normally started at dawn; and every flower closed nightly and reopened the next morning (if pollinarium is not removed previously). The flowers attracted many raspberry ketone-responsive fruit fly species. In Malaysia, eleven Dacini species were attracted, of which six species with light-weight males (< 13 mg) were unable to open the small close-spring lip (CSL), thereby, they are not potential pollinators but mere floral visitors. The other five species had individuals sufficiently heavy to overcome the CSL’s torsional force (equivalent to a mean weight of 13 mg) to open the CSL; and also with some lighter males unable to pry open the CSL, thereby, rendering them floral visitors and not potential pollinators. The CSL moved slowly towards the column in the afternoon before the flower closed for the night. Besides selecting for an adequately heavy male fly to be a potential pollinator, the CSL has the vital role of catapulting the fly in to the column cavity, thereby, enhancing spontaneous pollinarium removal. The unique dynamic lip mechanism and the ‘stopper’ (the tip of column-foot which maintains the temporarily opened CSL in a horizontal position) may be pre-adaptations to floral resupination in B. hortorum.

Gall-inducing insects are a classic example of how insects can impact the morphology and physiology of their host plants by forming galls which act as nutrient sinks. An 8-months laboratory study was conducted to determine the impact of the galls induced by Polymorphomyia basilica oviposition and or the subsequent larval feedingon the growth and reproduction of Chromolaena odorata. Three treatment levels were used, viz. control: 0% of the shoots were exposed, low infestation: 50% of shoots were exposed, and high infestation, where 100% of the shoots were exposed for P. basilica to oviposit for 48 h each month. Results showed that P. basilica oviposition and or the subsequent feeding by larvae reduced the height and flower production of C. odorata plants but promoted lateral growth by increasing the number of shoot tips. Basal stem diameter was not affected by the presence of the galls. The presence of galls also decreased the leaf and root dry biomass on the treated plants but had no significant impact on stem biomass. The difference between the low- and high-infestation treatments was only significant for root biomass, suggesting that more galls are required for the roots to be affected. Overall, the study showed that P. basilica meets the requirements of an effective biocontrol agent against C. odorata in South Africa. Its release should complement the already released agents in reducing the fitness and productivity of C. odorata.