Leaf Chewers Research Articles

Taxonomic and Functional Structure of Phytophagous Insect Communities Associated with Grain Amaranth.

Amaranthus are worldwide attacked mainly by leaf chewers and sucker insects. Stem borers and leaf miners follow in importance, while minor herbivores are leaf rollers, folders, and rasping-sucking insects. The herbivorous community observed on Amaranthus spp. in Argentina was consistent with the information reported worldwide both in guild composition and order proportion. Amaranth plants had a higher number of phytophagous species in their native rather than in its introduced range. Occurrence of insect guilds differed in space and time. The highest density of leaf chewers was observed shortly after the emergence of plants, while higher density of borer and sucker insects coincided with reproductive stages of the crop. The sucking guild was observed mainly at panicles, while the insects within the leaf chewer group were registered in both leaves (92.6%, n = 746 adults) and inflorescences (7.4%). The borer guild was also recorded in stems and inflorescences; however, the density of larvae in stems was about four times as high as the density observed in panicles (n = 137 larvae).

Importance of Secondary Metabolites for Leaf Beetles (Coleoptera: Chrysomelidae)

Leaf beetles (Chrysomelidae) are one of the most diverse families of herbivorous insects. Many of them are important agricultural pests and cause remarkable loss of crop and money as well. Plant leaves and roots are primary food source of both larva and adults of leaf beetles. Plants produce many secondary metabolites in reaction to herbivore insects. It is a well-known phenomenon that quantity and variety of secondary metabolites in plant leaves may change in response to insect attacks. Herbivore insects have to deal with such defensive secondary chemicals and overcome either by detoxifying or storing them. Accordingly, many specialist herbivores coevolved with their host plant. Certain phenolic glycosides may reduce leaf beetle feeding. Condensed tannins are anti-herbivore defenses against leaf chewing beetles, including leaf beetles. Flavonoid compounds are feeding deterrents for many flea leaf beetles. Cinnamic acid derivatives are other known feeding deterrents for leaf beetles. Secondary metabolites quantity and nutritional quality of host plants are not only important for feeding but also for providing enemy-free space and suitable oviposition sites.

Fossil evidence of insect folivory in the eastern Himalayan Neogene Siwalik forests

Fossil leaves from the Siwalik sedimentary rocks of Arunachal Pradesh, eastern Himalaya, evidence a variety of plant-insect interactions that operated during the evolution of monsoon-influenced forests from middle Miocene to lower Pleistocene times. Five principal categories of damage are identified in this study namely leaf mining, hole feeding, skeletonizing, galling and marginal or non-marginal feeding. These traces indicate that insects interacted with the plants for various purposes, including feeding, egg laying and sheltering. Furthermore, these morphotraces tend to suggest similarities in insect interactions with leaves of extant plant species such as Millettia cineria, Canarium bengalense, Glochidion gamblei, Callicarpa arborea, Chonemorpha macrophylla, Actinodaphne angustifolia and others. On the basis of comparison with extant taxa, possible leaf chewers could have belonged to the insect orders Orthoptera, Coleoptera, Lepidoptera and Diptera. Although the morphology of the phytophagous insects associated with the fossil leaves is unknown, present findings reveal that many modern plant-insect relationships were established by the Miocene and continue to the present, shaping both the present day flora and fauna. The study shows an increasing tendency towards folivory (expressed in terms of percentage of leaf damage; 35% in lower Siwalik, 39% in middle Siwalik and 45% in upper Siwalik). This increase in insect activity is unconnected to measurable climate change but was due to biotic change, where there was a competition between insects and plants and insects appear increasingly successful.

Insect leaf-chewing damage tracks herbivore richness in modern and ancient forests.

The fossil record demonstrates that past climate changes and extinctions significantly affected the diversity of insect leaf-feeding damage, implying that the richness of damage types reflects that of the unsampled damage makers, and that the two are correlated through time. However, this relationship has not been quantified for living leaf-chewing insects, whose richness and mouthpart convergence have obscured their value for understanding past and present herbivore diversity. We hypothesized that the correlation of leaf-chewing damage types (DTs) and damage maker richness is directly observable in living forests. Using canopy access cranes at two lowland tropical rainforest sites in Panamá to survey 24 host-plant species, we found significant correlations between the numbers of leaf chewing insect species collected and the numbers of DTs observed to be made by the same species in feeding experiments, strongly supporting our hypothesis. Damage type richness was largely driven by insect species that make multiple DTs. Also, the rank-order abundances of DTs recorded at the Panamá sites and across a set of latest Cretaceous to middle Eocene fossil floras were highly correlated, indicating remarkable consistency of feeding-mode distributions through time. Most fossil and modern host-plant pairs displayed high similarity indices for their leaf-chewing DTs, but informative differences and trends in fossil damage composition became apparent when endophytic damage was included. Our results greatly expand the potential of insect-mediated leaf damage for interpreting insect herbivore richness and compositional heterogeneity from fossil floras and, equally promisingly, in living forests.

Oral proliferative verrucous leucoplakia: are there particular features for such an ambiguous entity? A systematic review

Proliferative verrucous leucoplakia (PVL) is a distinct, particularly aggressive form of oral leucoplakia. Given the low prevalence of PVL, data are sparse and are mostly from case reports, case series and only a few case-control studies, meaning that the literature is able to provide only weak evidence. The present systematic literature review aims to collate the available evidence on the following issues: patient demographics, aetiology, lesion location(s), malignant potential, location and histopathological features of transformed lesions, disease-specific survival rates and treatment response. Electronic databases were searched for studies in the English language reporting original data from at least 10 patients with PVL on the target issues of the present review. The retrieved data were merged and a descriptive analysis performed. The 20 studies selected indicated that PVL does not seem to be correlated with the major risk factors for oral carcinoma (tobacco, alcohol and/or areca nut/betel leaf chewing). The disorder affects mainly adult/elderly women and has a very high malignant transformation rate, particular site distribution and particular location and histopathological features of transformed lesions. The present results may be limited by some articles being unintentionally excluded as they were not found during the electronic search, a lack of worldwide accepted diagnostic criteria for PVL, and overlapping data from multiple studies performed in a limited number of centres. Despite these potential drawbacks, the present results demonstrate that PVL does have particular features.

Changes in Clonal Poplar Leaf Chemistry Caused by Stem Galls Alter Herbivory and Leaf Litter Decomposition

Gall-inducing insects are highly specialized herbivores that modify the phenotype of their host plants. Beyond the direct manipulation of plant morphology and physiology in the immediate environment of the gall, there is also evidence of plant-mediated effects of gall-inducing insects on other species of the assemblages and ecosystem processes associated with the host plant. We analysed the impact of gall infestation by the aphid Pemphigus spirothecae on chemical leaf traits of clonal Lombardy poplars (Populus nigra var. italica) and the subsequent effects on intensity of herbivory and decomposition of leaves across five sites. We measured the herbivory of two feeding guilds: leaf-chewing insects that feed on the blade (e.g. caterpillars and sawfly larvae) and skeletonising insects that feed on the mesophyll of the leaves (e.g. larvae of beetles). Galled leaves had higher phenol (35%) and lower nitrogen and cholorophyll contents (35% respectively 37%) than non-galled leaves, and these differences were stronger in August than in June. Total herbivory intensity was 27% higher on galled than on non-galled leaves; damage by leaf chewers was on average 61% higher on gall infested leaves, whereas damage by skeletonising insects was on average 39% higher on non-galled leaves. After nine months the decomposition rate of galled leaf litter was 15% lower than that of non-galled leaf litter presumably because of the lower nitrogen content of the galled leaf litter. This indicated after-life effects of gall infestation on the decomposers. We found no evidence for galling x environment interactions.

Latitudinal trends in herbivory and performance of an invasive species, common burdock (Arctium minus)

Plants often lose natural enemies (herbivores and pathogens) while invading new geographic regions, as predicted by the Enemy Release Hypothesis. However, a similar reduction in attack might occur at a more local scale within an invader’s range as plants in marginal areas escape enemies that fail to find them or cannot maintain local populations. In this study, we test the hypothesis that isolated populations near the northern edge of an invader’s range escape the enemies present in more southern populations, using the non-native monocarpic biennial, common burdock (Arctium minus), as a model species. In southern Ontario, this plant is attacked by a wide range of insect herbivores, including generalist leaf chewers as well as leaf-mining flies (Liriomyza arctii,Calycomyza flavinotum) and an abundant lepidopteran seed predator (Metzneria lappella). Surveys over an 815 km transect from temperate southern to boreal northern Ontario indicate that damage by all of these enemies declines sharply with latitude, while plants in more northern areas are slightly larger and more fecund. Critically, seed parasitism drops from more than 85 % in the south to less than 25 % in the north. These results indicate that populations of Arctium near this species’ northern limit escape many of their usual natural enemies, potentially counteracting less favourable environmental conditions. Such escape from enemies near invaders’ range margins may accelerate further spread, including expected migration in response to climate change.

Do alien plants escape from natural enemies of congeneric residents? Yes but not from all

As predicted by the enemy release hypothesis, plants are supposedly less attacked by herbivores in their introduced range than in their native range. However, the nature of the natural enemies, in particular their degree of specificity may also affect the level of enemy escape. It is therefore expected that ectophagous invertebrate species, being generally considered as more generalists than endophagous species, are more prompt to colonise alien plants. In Swiss, Siberian and Russian Far East arboreta, we tested whether alien woody plants are less attacked by native herbivorous insects than native congeneric woody plant species. We also tested the hypothesis that leaf miners and gall makers show stronger preference for native woody plants than external leaf chewers. In all investigated regions, leaf miners and gall makers were more abundant and showed higher species richness on native woody plants than on congeneric alien plants. In contrast, external leaf chewers did not cause more damage to native plants than to alien plants, possibly because leaf chewers are, in general, less species specific than leaf miners and gall makers. These results, obtained over a very large number of plant-enemy systems, generally support the hypothesis that alien plants partly escape from phytophagous invertebrates but also show that different feeding guilds may react differently to the introduction of alien plants.

Fluctuating asymmetry of and herbivory on Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae) in pasture and secondary tropical dry forest

Plants subjected to stressful environments tend to be more asymmetric with reduced defenses and are therefore more vulnerable to herbivory. This study investigates the relationship between herbivory and fluctuating asymmetry (FA) in Poincianella pyramidalis in two contrasting habitat types in the Brazilian caatinga (shrublands). We tested the following hypotheses: that FA occurs in P. pyramidalis; that FA of P. pyramidalis leaves is greater in individuals located in pasture than in those located in secondary tropical dry forest; that herbivory by insects (leaf chewers and leaf miners) increases in parallel with increases in the level of FA; and that herbivory is more common in pasture than in secondary tropical dry forest. In each of the two environments, we sampled 20 plants and evaluated 400 leaflets. We submitted FA data to the Shapiro-Wilk test of normality, and we investigated the other variables using generalized linear models. We found that FA was present in all P. pyramidalis individuals evaluated but was greater in those located in the more degraded habitat (pasture). In addition, although herbivory was similar between the two habitats, there was positive relationship between FA and herbivory. This indicates that herbivores select plants that are more asymmetric, regardless of the type of habitat involved, which might be attributable to the mechanisms posited in the plant stress hypothesis.

Plant apparency, an overlooked driver of associational resistance to insect herbivory

Summary Herbivore regulation is one of the services provided by plant diversity in terrestrial ecosystems. It has been suggested that tree diversity decreases insect herbivory in forests, but recent studies have reported opposite patterns, indicating that tree diversity can trigger associational resistance or susceptibility. The mechanisms underlying the tree diversity–resistance relationship thus remain a matter of debate. We assessed insect herbivory on pedunculate oak saplings (Quercus robur) in a large‐scale experiment in which we manipulated tree diversity and identity by mixing oaks, birch and pine species. Tree diversity at the plot scale had no effect on damage due to leaf chewers, but abundance of leaf miners decreased with increasing tree diversity. The magnitude of this associational resistance increased with host dilution, consistent with the ‘resource concentration hypothesis’. At a smaller scale, we estimated tree apparency as the difference in total height between focal oak saplings and their nearest neighbouring trees. Levels of oak infestation with leaf miners decreased significantly with decreasing tree apparency. As the probability of having taller neighbours increased with tree diversity, notably due to the increase in the proportion of faster growing nonhost trees, such as birches and pines, tree apparency may be seen as a ‘hidden’, sampling effect of tree diversity. Synthesis. These findings suggest that greater host dilution and lower tree apparency contribute to associational resistance in young trees. They also highlight the importance of taking plant size into account as a covariate, to avoid misleading interpretations about the biodiversity–resistance relationship.

Gall volatiles defend aphids against a browsing mammal

BackgroundPlants have evolved an astonishing array of survival strategies. To defend against insects, for example, damaged plants emit volatile organic compounds that attract the herbivore’s natural enemies. So far, plant volatile responses have been studied extensively in conjunction with leaf chewing and sap sucking insects, yet little is known about the relationship between plant volatiles and gall-inducers, the most sophisticated herbivores. Here we describe a new role for volatiles as gall-insects were found to benefit from this plant defence.ResultsChemical analyses of galls triggered by the gregarious aphid Slavum wertheimae on wild pistachio trees showed that these structures contained and emitted considerably higher quantities of plant terpenes than neighbouring leaves and fruits. Behavioural assays using goats as a generalist herbivore confirmed that the accumulated terpenes acted as olfactory signals and feeding deterrents, thus enabling the gall-inducers to escape from inadvertent predation by mammals.ConclusionsIncreased emission of plant volatiles in response to insect activity is commonly looked upon as a “cry for help” by the plant to attract the insect’s natural enemies. In contrast, we show that such volatiles can serve as a first line of insect defences that extends the ‘extended phenotype’ represented by galls, beyond physical boundaries. Our data support the Enemy hypothesis insofar that high levels of gall secondary metabolites confer protection against natural enemies.

Plant evolutionary ecology: molecular genetics, global warming and invasions, and the novel approaches we are using to study adaptations

Plant evolutionary ecology: molecular genetics, global warming and invasions, and the novel approaches we are using to study adaptations

Effect of Concurrent Chemo Radiation in the Treatment of Locally Advanced Carcinoma of Tongue

This quasi experimental study was conducted to observe the effects and toxicities of concurrent chemo radiation in locally advanced tongue cancer from January 2009 to December 2009 in the Radiotherapy Department of Chittagong Medical College Hospital. A total number of forty patients were purposively selected according to inclusion criteria. Among them, 30 patients presented with lesion in anterior two third & 10 patients in posterior one third. Thirty patients were male & ten were female. All of the patients having betel nut chewing habit & 90% were smoker & tobacco leaf chewer. The mean age of patient was 56.25 years. All patients received chemotherapy on D1, D8, D15, D22, D29, D36, D43 & 66 Gy external beam radiotherapy in 200 cGY/day in six and half weeks. Pretreatment status of mean size of primary lesion of anterior two third and posterior one third of tongue cancer patients significantly decreased in last follow up. Mean size of lymph nodes significantly decreased from pretreatment to last follow up in both anterior two third and posterior one third of tongue cancer patients. Over all response of patients treated with concurrent chemo radiation only three patients of anterior two third & one patient of posterior one third showed complete response followed by seventeen patients of anterior two third & five patients of posterior one third showed partial response. Response is better in stage III than stage IV patients in both anterior two third and posterior one third of tongue cancer. The common toxicities are mucositis, skin reaction, anemia & leucopenia in both anterior two third and posterior one third of tongue cancer patients. In the treatment of locally advanced carcinoma of tongue, coneurrent chemoradiation showed better symptom improvement, manageable toxicities. So, concurrent chemoradiation may be one of the treatment modality in locally advanced carcinoma of tongue patients. Period of study and number of patients were small. So, long term follow-up and large number of patients should be included to conduct more in-depth research and more specific comments.
 JCMCTA 2012; 23(1): 36-41

EFFECT OF SESAME LEAF DIET ON DETOXIFICATION ACTIVITIES OF INSECTS WITH DIFFERENT FEEDING BEHAVIOR

Three diverse insects, a polyphagous "leaf chewer" (Atractomorpha lata), a polyphagous "sap feeder" (Myzus persicae), and a "restrictive feeder" (Plutella xylostella) responded differently when fed with eight cultivars of sesame either as whole leaf or via artificial diet. There was limited or no correlation in induction between detoxifying enzyme substrates (esterase, glutathione s-transferase [GST], and mixed function oxidase [MFO] activities) when activity toward various substrates α-naphthyl acetate, 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, and p-nitroanisole (pNA), were compared although they were generally elevated in the tissues from insects on sesame than a reference fed with radish seedlings. In A. lata, esterase activity for the cultivar 11Pusan and 45Laos were three-fold higher compared to the reference, while other cultivars, 24Nanbu-twasaki and 56S-radiatum were--two- to three-fold lower than the reference. In M. persicae, the esterase activity was as much as five-fold higher than the reference in one test cultivar. GST activities of the sesame cultivars were generally higher (≈two-fold) than the reference in all insects and at variable ratios among the cultivars. The MFO activity toward pNA in grasshoppers feeding on these sesame cultivars was either highly expressed or nonexistent. These results indicate that although the cultivars belong to the same species, they might have undergone changes in secondary phytochemicals in response to varying biogeographical distribution. Each insect species is suspected to target a specific plant chemical burden that it tries to overcome in each cultivar through enzyme activation.

Insect herbivory along environmental gradients

There is a general assumption in the literature that insect herbivory increases towards the tropics, but decreases with increasing altitude. Similar generalities have been identified along other environmental gradients, such as resource, temperature, climatic and biotic gradients. However there is growing evidence in the scientific literature that such generalities are not consistent. This could be due to a number of reasons including the lack of consistency in the way herbivory is assessed such as different methodologies used by researchers, or fundamental differences in leaf damage caused by different types of insect herbivores. Here we assess 61 publications researching insect herbivory along a range of environmental gradients (both biotic and abiotic) and review the methods that researchers have used to collected their data. We found leaf chewing from samples collected in North America dominated the field and most studies assessed herbivory on a single host plant species. Thirty three percent of the studies assessed latitudinal gradients, while 10% assessed altitudinal gradients. Insect herbivory was most commonly expressed as percentage leaf damage using point herbivory. Fewer studies measured a range of different types of herbivory (such as sap sucking, leaf mining, galling, and root feeding) as leaves aged. From our synthesis, we hope that future research into insect herbivory along environmental gradients will take into account herbivory other than just leaf chewing, such as sap sucking, which may cause more damage to plants. Future research should also assess herbivory as a rate, rather than just a single point in time as damage to a young leaf may be more costly to a plant than damage to a mature or senescing leaf. Measurements of plant traits will also assist in comparing herbivory across habitats, plant species, and within species physiological variation. The true impacts that insects have on plants via herbivory along environmental gradients are still poorly understood.

Diverting the Flux of the JA Pathway in Nicotiana attenuata Compromises the Plant's Defense Metabolism and Fitness in Nature and Glasshouse

A plant's inducible defenses against herbivores as well as certain developmental processes are known to be controlled by the jasmonic acid (JA) pathway. We have previously shown that ectopically expressing Arabidopsis thaliana JA O-methyltransferase in Nicotiana attenuata (35S-jmt) strongly reduces the herbivory-elicited jasmonate bursts by acting as metabolic sink that redirects free JA towards methylation; here we examine the consequences of this metabolic sink on N. attenuata's secondary metabolism and performance in nature. In the glasshouse, 35S-jmt plants produced fewer seed capsules due to shorter floral styles, which could be restored to wild type (WT) levels after hand-pollination, and were more susceptible to Manduca sexta larvae attack. When transplanted into the Great Basin Desert in Utah, 35S-jmt plants grew as well as WT empty vector, but were highly attacked by native herbivores of different feeding guilds: leaf chewers, miners, and single cell feeders. This greater susceptibility was strongly associated with reduced emissions of volatile organic compounds (hexenylesters, monoterpenes and sesquiterpenes) and profound alterations in the production of direct defenses (trypsin proteinase inhibitors [TPI], nicotine, diterpene glycosides [DTGs] and phenylpropanoid-polyamine conjugates) as revealed by a combination of targeted and metabolomics analyses of field collected samples. Complementation experiments with JA-Ile, whose formation is outcompeted in 35S-jmt plants by the methylation reaction, restored the local TPI activation to WT levels and partially complemented nicotine and DTG levels in elicited but not systemic leaves. These findings demonstrate that MeJA, the major JA metabolite in 35S-jmt plants, is not an active signal in defense activation and highlights the value of creating JA sinks to disrupt JA signaling, without interrupting the complete octadecanoid pathway, in order to investigate the regulation of plants' defense metabolism in nature.

Community‐wide impact of an exotic aphid on introduced tall goldenrod

1. The aphid Uroleucon nigrotuberculatum Olive, which is specialised to the tall goldenrod, Solidago altissima L., in its native range, has become a dominant species on the introduced tall goldenrod in Japan. How this exotic aphid influenced arthropod communities on the introduced tall goldenrod in aphid‐present (spring) and aphid‐absent (autumn) seasons was examined, using an aphid removal experiment.2. In spring, aphid presence increased ant abundance because aphid honeydew attracted foraging ant workers. A significant negative correlation was found between the numbers of ants and herbivorous insects other than aphids on the aphid‐exposed plants, but no significant correlation was detected on the aphid‐free plants. Thus, the aphid presence was likely to decrease the abundance of co‐occurring herbivorous insects through removal behaviour of the aphid‐tending ants. There were no significant differences in plant traits between the aphid‐exposed and aphid‐free plants.3. In autumn, the numbers of lateral shoots and leaves, and the leaf nitrogen content were increased in response to the aphid infestation in spring. Because of the improvement of plant traits by aphid feeding, the abundance of leaf chewers increased on aphid‐exposed plants. In contrast, the abundance of sap feeders decreased on the aphid‐exposed plants. In particular, the dominant scale insect among sap feeders, Parasaissetia nigra Nietner, decreased, followed by a decrease in the abundance of ants attending P. nigra. Thus, aphid feeding may have attenuated the negative impacts of the tending ants on leaf chewers.4. Aphid presence did not change herbivore species richness but changed the relative density of dominant herbivores, resulting in community‐wide effects on co‐occurring herbivores through ant‐mediated indirect effects, and on temporally separated herbivores through plant‐ and ant‐mediated indirect effects. The aphid also altered predator community composition by increasing and decreasing the relative abundance of aphid‐tending ants in the spring and autumn, respectively.

Plant‐mediated facilitation between a leaf‐feeding and a phloem‐feeding insect in a brassicaceous plant: from insect performance to gene transcription

Summary1. Plants face threats from a variety of herbivorous insects and can use induced responses to defend themselves against these attackers. Induced responses are mediated by signal transduction involving phytohormones, such as jasmonic acid (JA) and salicylic acid (SA). Cross‐talk between signal transduction pathways triggered by attackers with contrasting feeding styles allows plants to fine‐tune defences. A central question in this emerging field is to understand how responses to single attackers interfere with responses to other attackers, especially by integratively addressing molecular and ecological aspects.2. We examined the plant‐mediated interactions between the leaf‐chewing Pieris brassicae and the phloem‐sucking Brevicoryne brassicae, and their respective parasitoids Cotesia glomerata and Diaeretiella rapae, when feeding simultaneously, sequentially or in isolation on the brassicaceous ecological model plant Brassica oleracea. We analysed the underlying defence mechanisms in the plant. Levels of the phytohormones JA and SA transcriptional responses of a number of selected defence‐related genes and secondary plant compounds were quantified at different time points during the single and multiple infestations.3. The caterpillars developed faster and reached a larger body mass on plants previously attacked by aphids. Aphids initially developed faster on plants with caterpillars, although the moment of moulting to adults was independent of the presence of caterpillars. Both parasitoid species performed better under multiple‐infestation scenarios than in single‐herbivore situations.4. On plants attacked by aphids, the JA levels were tenfold lower than on undamaged plants or plants with caterpillars. Additionally, the low transcript levels of LOX and MYC, genes coding for a JA biosynthesis‐related enzyme and a transcription factor, respectively, in aphid‐infested plants, suggest that the facilitation of the caterpillar performance was mediated by interference in signal transduction. Levels of carbon and nitrogen and secondary plant compounds (glucosinolates) did not differ significantly between treatments, suggesting that these compounds did not mediate the facilitation.5. Our data show that the leaf chewer and phloem feeder asymmetrically interact not via competition as would be expected from interspecific herbivores but instead via facilitation; the phloem feeder attenuated JA‐related plant defences, thus facilitating the growth and development of the leaf chewers. In linear bitrophic systems, interactions between JA and SA signalling pathways have been proposed to allow plants to fine‐tune their defences, but if facilitation frequently occurs in interspecific interguild interactions among herbivores this may represent an important constraint for plant defences. Such a constraint might be reduced if, as in our model system, parasitoids also benefit from interactions between interguild hosts and nonhosts, but parasitoids are rarely considered in model molecular systems to assess the impact of herbivore‐induced plant defences.

Belowground rhizobia positively affect abundances of aboveground sap feeding and leaf chewing herbivores

Belowground rhizobia positively affect abundances of aboveground sap feeding and leaf chewing herbivores.

Diversity of Shrub-Dwelling Arthropods to Thinning of Young Douglas-Fir Forests in the Pacific Northwest, USA

Abstract We examined an unthinned control stand and three different thinning intensities in 40- to 60-year-old Douglas-fir forests in western Oregon to assess the effects of thinning on the abundance, species richness, and diversity of shrub-dwelling arthropods. Shrub-dwelling arthropods, collected with a bagging technique, decreased significantly as thinning intensity increased in deciduous foliage (vine maple, Acer circinatum Pursh), but arthropods showed no response to thinning on the two types of conifer foliage (Douglas-fir, Pseudotsuga menziesii [Mirb.] Franco and western hemlock, Tsuga heterophylla [Raf.] Sarg.). The species richness and diversity of shrub-dwelling arthropods showed significantly higher values on the coniferous branches than on the deciduous foliage. Functional group composition for the two foliage types revealed consistently different proportions. Deciduous branch supported a higher proportion of sapsuckers and leaf chewers, and conifer branch hosted a higher proportion of predators and detritivores. Nonmetric multidimensional scaling ordination showed a distinct difference between the species assemblages inhabiting the deciduous and conifer branches. The effects of thinning on the arthropods were complex. Seasonal effects on arthropods exceed treatment effects because the species composition in the dry season was very different from that in the wet season. The shrub-dwelling arthropod community reveals little seasonal difference on coniferous branch, but significant differences occur on deciduous branch. In this study, treatment effects were very limited, but our results indicate that as thinning increased, the response of arthropod community on deciduous branch increased more. This large-scale experiment provided an opportunity to assess responses of shrub-dwelling arthropods to levels and patterns of forest management.