Above- and below-ground assessment of carabid community responses to crop type and tillage

1. Carabid beetles are major predators in agro-ecosystems. The composition of their communities within crop environments governs the pest control services they provide. An understudied aspect is the distribution of predacious carabid larvae in the soil.
2. We used novel subterranean trapping with standard pitfall trapping, within a multi-crop rotation experiment, to assess the responses of above- and below-ground carabid communities to management practices.
3. Crop and trap type significantly affected pooled carabid abundance with an interaction of the two, the highest numbers of carabids were caught in subterranean traps in barley under sown with grass.
4. Trap type accounted for the most variance observed in carabid community composition, followed by crop.
5. Tillage responses were only apparent at the species level for three of the eight species modelled.
6. Responses to crop type varied by species. Most species had higher abundance in under-sown barley, than grass, wheat and barley. Crop differences were greater in the subterranean trap data. For predaceous larvae, standard pitfalls showed lowest abundances in under-sown barley, yet subterranean traps revealed abundances to be highest in this crop.
7. Comprehensive estimation of ecosystem services should incorporate both above- and below-ground community appraisal, to inform appropriate management.

     

Species‐level image classification with convolutional neural network enables insect identification from habitus images

1. Changes in insect biomass, abundance, and diversity are challenging to track at sufficient spatial, temporal, and taxonomic resolution. Camera traps can capture habitus images of ground‐dwelling insects. However, currently sampling involves manually detecting and identifying specimens. Here, we test whether a convolutional neural network (CNN) can classify habitus images of ground beetles to species level, and estimate how correct classification relates to body size, number of species inside genera, and species identity.
2. We created an image database of 65,841 museum specimens comprising 361 carabid beetle species from the British Isles and fine‐tuned the parameters of a pretrained CNN from a training dataset. By summing up class confidence values within genus, tribe, and subfamily and setting a confidence threshold, we trade‐off between classification accuracy, precision, and recall and taxonomic resolution.
3. The CNN classified 51.9% of 19,164 test images correctly to species level and 74.9% to genus level. Average classification recall on species level was 50.7%. Applying a threshold of 0.5 increased the average classification recall to 74.6% at the expense of taxonomic resolution. Higher top value from the output layer and larger sized species were more often classified correctly, as were images of species in genera with few species.
4. Fine‐tuning enabled us to classify images with a high mean recall for the whole test dataset to species or higher taxonomic levels, however, with high variability. This indicates that some species are more difficult to identify because of properties such as their body size or the number of related species.
5. Together, species‐level image classification of arthropods from museum collections and ecological monitoring can substantially increase the amount of occurrence data that can feasibly be collected. These tools thus provide new opportunities in understanding and predicting ecological responses to environmental change.

     

Bark beetle and woodborer responses to stand thinning and prescribed fire in northeastern US coastal and inland pitch pine barrens

1. Southern pine beetle, Dendroctonus frontalis, has expanded its range further into the northeastern United States. This expansion threatens rare and ecologically valuable interior and coastal pitch pine barrens.
2. Pitch pine barrens restoration and southern pine beetle infestation suppression often involve leaving downed dead wood that saproxylic insects can exploit.
3. Semiochemical-baited traps were used to investigate the response of bark beetles and woodborers to restoration treatments at Rocky Point State Forest and the Albany Pine Bush Preserve, examples of coastal and interior pitch pine forests, respectively.
4. A total of 29,598 saproxylic insects from 116 species of bark beetles and woodborers were captured at Rocky Point State Forest, while 23,117 individuals from 67 species were captured at Albany Pine Bush Preserve.
5. Ips spp. were abundant at both sites with 28%–47% and 42%–74% of total collections at Rocky Point State Forest and Albany Pine Bush Preserve, respectively.
6. Ips grandicollis did not respond to treatments at either site. However, Ips pini was found in higher numbers in thinned blocks in Rocky Point State Forest.

     

Biosurveillance for invasive insect pest species using an environmental DNA metabarcoding approach and a high salt trap collection fluid

1. With the increase in global trade and warming patterns, the movement, introduction, and establishment of non‐native insect species has increased. A rapid and effective early detection biosurveillance program to identify species of concern is needed to reduce future impacts and costs associated with introduced non‐native species. One of the challenges facing insect surveillance trapping methods is the sheer volume of individual specimens in the collections. Although molecular identification methods are improving, they currently have limitations (e.g., destructive processing of specimens) and a protocol addressing these limitations can support regulatory applications that need morphological evidence to corroborate molecular data.
2. The novel protocol presented here uses a metabarcoding approach to amplify environmental DNA from a saturated salt solution trap fluid, which retains trap specimens for downstream morphological identifications. The use of a saturated salt solution to preserve specimens in traps addresses issues with the high evaporation rate of ethanol in traps, and public safety concerns with other fluid preservation options with unattended traps in public settings.
3. Using a metabarcoding approach, a 407‐nucleotide segment of the cytochrome c oxidase subunit 1 (COI) animal barcode region was successfully amplified from Lindgren funnel trap collection fluids. These traps were placed in forested areas to survey for wood‐boring beetles of regulatory concern. Our results displayed successful amplification of target taxa, including the molecular identification of the Japanese Beetle Popillia japonica, a species regulated in Canada. A second species, Anisandrus maiche, recently introduced to North America, was identified in every trap. The genus Lymantria, which contains numerous species of concern to North American woodlands, was also detected. Also, there were six other species identified of interest due to their potential impacts on native and crop flora and fauna.
4. Our results show how this protocol can be used as an efficient method for the surveillance of insects using a trap with a saturated salt solution and eDNA metabarcoding to detect species of regulatory concern.

     

Bark beetles as lidar targets and prospects of photonic surveillance

Forestry is raising concern about the outbreaks of European spruce bark beetle, Ips typographus, causing extensive damage to the spruce forest and timber values. Precise monitoring of these beetles is a necessary step towards preventing outbreaks. Current commercial monitoring methods are catch-based and lack in both temporal and spatial resolution. In this work, light scattering from beetles is characterized, and the feasibility of entomological lidar as a tool for long-term monitoring of bark beetles is explored. Laboratory optical properties, wing thickness, and wingbeat frequency of bark beetles are reported, and these parameters can infer target identity in lidar data. Lidar results from a Swedish forest with controlled bark beetle release event are presented. The capability of lidar to simultaneously monitor both insects and a pheromone plume mixed with chemical smoke governing the dispersal of many insects is demonstrated. In conclusion, entomological lidar is a promising tool for monitoring bark beetles.     

Spatiotemporal dynamics of active flying Diptera predators among different farmland habitats

1. Farmland habitats comprise an arrangement of cropped, uncropped and natural vegetation among the farms. Despite the differences in these habitats' features, generalist highly mobile predators are more likely to explore them in time and space.
2. We investigated the spatiotemporal dynamics of the species of Dolichopodidae (Diptera) in organic vegetable farms because they are one of the most abundant generalist highly mobile predators in Brazilian agroecosystems.
3. We simultaneously sampled the abundance of Condylostylus Bigot and Chrysotus Loew adults (both Dolichopodidae) in the crop, fallow areas, agroforests and forest fragments within five organic farms for 2 years.
4. Predators preferred open-field habitats to agroforests and forest fragments. Probably, open-field habitats present more opportunities to prey foraging, resulting in higher population densities.
5. To the extent that abiotic conditions become more restrictive during the dry season, agroforests and forests act as breeding sites and shelter, thereby maintaining the predators' populations in the overall farmland habitat.
6. Both predatory genera occupy habitats with distinct features across time, forming a dynamic and contiguous population unit within the farm. Therefore, conservation biological control strategies in organic crops should consider the role of agroforests and forest fragments in species conservation beyond the plot level.

     

Risk assessment for non-crop hosts of pea enation mosaic virus and the aphid vector Acyrthosiphon pisum

1. Viral insect-borne plant pathogens have devastating impacts in agroecosystems. Vector-borne pathogens are often transmitted by generalist insects that move between non-crop and crop hosts. Insect vectors can have wide diet breadths, but it is often unknown which hosts serve as pathogen reservoirs and which non-crop host harbours the highest density of vectors.
2. In the Pacific Northwest USA, the pea aphid (Acyrthosiphon pisum) is a key virus vector in pulse crops. Despite pea aphid having a large number of potential non-crop plant hosts occuring in the region, no reservoir has yet been identified for the economically-costly pathogen Pea Enation Mosaic Virus (PEMV).
3. We addressed these issues by linking field surveys of an aphid vector and plant virus with statistical models to develop risk assessments for common non-crop legumes; in 2018, we completed a 65-site survey where aphids were surveyed in weedy legumes within and outside dry pea fields.
4. We quantified the abundance of pea aphids on 17 hosts, and plant tissue was tested for PEMV. Relatively high densities of A. pisum were found in habitats dominated by hairy vetch (Vicia villosa), which was the only legume other than cultivated dry pea where PEMV was detected.
5. Our results indicate that V. villosa is a key alternative host for PEMV, and that pest management practices in this region should consider the distribution and abundance of this weedy host in viral disease mitigation efforts for pulses.

     

Common facultative endosymbionts do not influence sensitivity of cereal aphids to pyrethroids

1. Cereal aphids, including the bird cherry-oat aphid, Rhopalosiphum padi, and the grain aphid, Sitobion avenae, can transmit viruses that significantly reduce crop yields. To mitigate against yield losses, insecticides are routinely used to manage aphid populations.
2. Aphids can form relationships with endosymbionts that confer fitness benefits or consequences to the aphid. Recent artificial inoculation experiments indicate that endosymbionts could increase aphid susceptibility to insecticides, but this has not been explored using aphid populations naturally infected with endosymbionts.
3. Here, we sampled aphids from an important cereal production region in Lower Saxony, Germany. We characterized the endosymbiont profile of these aphid populations and conducted pyrethroid dose–response assays to test the hypothesis that facultative endosymbionts increase aphid susceptibility to insecticides.
4. We find that the level of insecticide susceptibility is highly variable in S. avenae and we identify populations that are sensitive and tolerant to pyrethroids, including populations collected from the same field. For R. padi, we find evidence for decreased sensitivity to pyrethroids, representing the first report of reduced sensitivity to pyrethroids in R. padi sampled from Central Europe.
5. We detected high endosymbiont infection frequencies in the aphid populations. 84% of aphids carry one facultative endosymbiont and 9% of aphids carry two facultative endosymbionts. We detected associations with Regiella insecticola, Fukatsia symbiotica, and Hamiltonella defensa. However, we do not identify a link between endosymbiont infection and insecticide susceptibility, indicating that other factors may govern the development of insecticide resistance and the need for alternative management strategies.

     

Litter‐dwelling beetles (Insecta: Coleoptera) can survive in clear‐cutting during subsequent soil ploughing

1. A 2‐year study of litter dwelling beetles was conducted in different mature pine stands and clear‐cuts in Lithuania using the litter sifting method. We hypothesized that clear‐cutting and subsequent ploughing would increase species diversity and the abundance of beetles, and also would encourage the immediate appearance of early‐successional beetle species replacing late successional species in the clear‐cuts.
2. We did not confirm a hypothesis regarding increase in the number of species and abundance of beetles in clear‐cuts.
3. Our hypothesis regarding the immediate appearance of early successional species and disappearance of late‐successional species in clear‐cuts was confirmed.
4. We also revealed that subsequent soil ploughing in clear‐cuts did not accelerate this process, which was linked to the possibility of late successional species surviving in the undisturbed spaces between the strips of ploughed soil.
5. The present study shows that late‐successional forest litter‐dwelling coleopteran species of old pine forests have a better chance of survival in a ploughed clear‐cut, at least in northern Europe, than has been reported in other studies.

     

Predation and avoidance behaviour in aphid‐ladybird interactions of native and invasive ladybirds in Europe

1. While detrimental effects of invasive predators on native species are well documented, we often lack a mechanistic understanding of the invasion success. Lack of prey avoidance behaviour can lead to higher consumption rates by invasive predators compared to native predators. This competitive advantage is expected to contribute to the invasion success of non‐native predators.
2. We compared aphid consumption and cue avoidance behaviour of aphids between four native ladybird species (Coccinella septempunctata, Adalia bipunctata, Propylea quatuordecimpunctata, and Hippodamia variegata) and the invasive Asian ladybird Harmonia axyridis.
3. The invasive H. axyridis and the native C. septempunctata consumed more aphids than the three smaller native ladybird species. In line with our expectations, aphids avoided leaves bearing cues of most native ladybird species but not of the invasive H. axyridis.
4. Our results indicate that body size rather than ladybird origin determined aphid predation rates. The lack of aphid avoidance behaviour towards cues of H. axyridis indicates that they were not able to recognise the chemical cues of the invasive predator.
5. Relatively large body size and the absence of cue avoidance in aphids might benefit the invasive H. axyridis, particularly in comparison to smaller native ladybird species. The absence of avoidance behaviour in aphids might lead to even higher predation rates of H. axyridis under more natural conditions.

     

Modelling the effects of field spatial scale and natural enemy colonization behaviour on pest suppression in diversified agroecosystems

1. Diversifying agroecosystems by establishing or retaining natural vegetation in and around crop areas has long been recognized as a potentially effective means of bolstering pest control as a result of attracting more numerous and diverse natural enemies, although outcomes are inconsistent across species.
2. Little is known about the underlying mechanisms driving such differences in species responses, creating challenges for determining how best to manage landscapes for maximizing environmental services such as biological control.
3. The present study addresses gaps in our understanding of the link between noncrop vegetation in field margins and pest suppression by using a system of partial differential equations to model population‐level predator–prey interactions, as well as spatial processes, aiming to capture the dynamics of crop plants, herbivores and two generalist predators.
4. We focus on differences in how two predators (a carabid and a ladybird beetle) colonize crop fields where they forage for prey, examining differences in how they move into the fields from adjacent vegetation as a potential driver of differences in overall pest suppression.
5. The results obtained demonstrate that predator colonization behaviour and spatial scale are important factors with respect to determining the effectiveness of biological control.

     

The harmonic radar: a new method of tracing insects in the field

ABSTRACT.

• 1 A novel technique for tracing the movements of insects in the field is described.
• 2 The detection system is based on radar technology originally developed for locating avalanche victims. The key of the system is a tiny electronic diode that, glued to the insect, can reflect microwave beams emitted by portable detection equipment.
• 3 The technique has been successfully tested in a field-tracing experiment with carabid beetles. The results show that these insects are capable of dispersing surprisingly long distances in a relatively short period of time.

     

Mechanisms of species‐sorting: effect of habitat occupancy on aphids' host plant selection

相似文献   

Ten years after: Release cutting around old oaks still affects oak vitality and saproxylic beetles in a Norway spruce stand

1. It is often suggested to release oaks (Quercus robur) from competition, to ensure their survival and boost their conservational value. However, few studies have explored how long-lasting this effect is and how it affects saproxylic beetles.
2. Ten years after cutting, we investigated effects of different release cutting levels (high, medium, and no release) around 140-year-old retained oaks in a commercial forest with Norway spruce (Picea abies).
3. We evaluated oak vitality using crown and dead wood measurements. Saproxylic beetles were caught in window traps, identified to species level, and grouped according to their association with oak and/or Norway spruce.
4. Released oaks had more light, higher temperatures, greater crown growth, and less dead wood in the crown compared to the no-release control.
5. After 10 years we still found a higher abundance of oak-associated beetles and higher overall species richness of saproxylic beetles in the released oaks. Beetle species composition significantly differed between released oaks and control.
6. We suggest avoiding planting trees beneath retained oaks when regenerating conifer forests and to proceed with conservation management during subsequent thinning by removing regeneration under the oak crowns. We emphasize the benefits of monitoring the retained oaks to maintain tree vitality, habitat quality, and insolation.

     

Effects of different tree harvesting intensities on saproxylic beetle diversity in coniferous and broad-leaved mixed forest in the Changbai Mountain,Northeast, China

1. Saproxylic beetles have gained increasing attention due to their role in the decomposition of rotting wood in forests. Studying the response of saproxylic beetles to tree harvesting is important for developing harvesting strategies that consider conservation of saproxylic beetle diversity.
2. We report results from a case study in which we designed four treatment stands to test the effects of forest harvesting intensity on saproxylic beetle diversity, harvest intensities of 0% untreated control (CK), 17.2% light harvest (LT), 34.7% moderate harvest (MT) and 51.9% high harvest (HT). Flight intercept traps were used to collect specimens of saproxylic beetles in each stand at 2, 3 and 4 years post-harvest.
3. The richness and abundance of saproxylic beetles were higher in MT and HT than in CK. Twelve of the 15 indicator species were significantly associated with MT or HT, whereas only three species were significantly associated with CK.
4. We found that moderate and high intensity harvesting affected the composition and increased beetle abundance and richness of saproxylic beetles, and light intensity harvesting had no effect on the beetle community in years 2, 3 and 4 post-harvest. There was no difference in the beetle community composition between moderate and high harvest stands.

     

Preference,performance, and impact of the water-lily aphid on multiple species of duckweed

1. The role of herbivores in driving the structure of freshwater macrophyte communities remains poorly understood in comparison with terrestrial ecosystems. For instance, although duckweed (subfamily Lemnoideae) are globally distributed, can be locally highly abundant and ecologically dominant, and are of growing economic importance, their interactions with herbivores remain understudied.
2. To address how herbivores may impact duckweed species composition, we here experimentally quantify the preference and performance of a common duckweed herbivore, the water-lily aphid (Rhopalosiphum nymphaeae) on four widespread duckweed species.
3. Our two-way choice experiments reveal that aphids display a preference for Spirodela polyrhiza > Landoltia punctata = Lemna minor > > Wolffia brasiliensis. These results are rarely influenced by natal host species.
4. By evaluating the growth of aphid populations on each duckweed species, we find that preference may be adaptive in certain ecological conditions.
5. Quantifying the population growth rate of duckweed growing in the presence and absence of aphids revealed differential tolerance of herbivory across duckweed species.
6. This study shows that aphids, through preferential feeding and significant differential effects on duckweed growth, can have a significant impact on duckweed population dynamics and potentially community composition.

     

Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Theoretical habitat templets, species traits, and species richness: aquatic Coleoptera in the Upper Rhône River and its floodplain

• 1 To test predictions of the river habitat templet and the patch dynamics concept, trends in species traits and species richness of aquatic beetles were related to the spatial-temporal variability of eighteen habitat types in the alluvial floodplain of the French Upper Rhône River. One hundred and twenty species of beetles were used in this analysis.
• 2 The basic information was obtained either from the literature (for most of the species traits) or from observations made at approximately 500 sampling sites in the Brégnier-Cordon and Jons sections over the past 19 years (for habitat utilization). This information was structured by a fuzzy coding technique and examined by ordination analyses.
• 3 Analyses of the relationships among nineteen species traits revealed a clear distinction according to traits such as body form (for adults), functional feeding type and food (adults and larvae), attachment to the substrate and dissemination potential (adults and larvae), and patterns of aquatic and/or terrestrial life of adults and larvae. Species traits such as number of descendants per reproductive cycle, and number of reproductive cycles per year or per individual showed less contrast, because these traits are rather homogeneous in aquatic beetles.
• 4 Analyses of the habitat utilization by the aquatic beetles revealed a vertical gradient that separates interstitial from superficial habitats, and a transverse gradient for the superficial habitats, which extends from the main channel towards permanent oxbow lakes and temporary waters.
• 5 The significant relationship betweeen species traits and habitat utilization demonstrates that most beetle species use a particular set of habitat types with a particular set of species trait modalities.
• 6 Species traits of aquatic beetles are homogeneous but evidently very successful and are adapted to many potential conditions of spatial–temporal variability. Because of this homogeneity, observations on aquatic beetles do not support trends of traits in the framework of spatial–temporal variability predicted from the river habitat templet.
• 7 The observed species richness of aquatic beetles is low in habitat types with a low spatial–temporal variability, increases as spatial variability increases, and tends to be highest at intermediate temporal variability. This pattern matches predictions of the patch dynamics concept.

     

Bidirectional plant‐mediated interactions between rhizobacteria and shoot‐feeding herbivorous insects: a community ecology perspective

1. Plants interact with various organisms, aboveground as well as belowground. Such interactions result in changes in plant traits with consequences for members of the plant‐associated community at different trophic levels. Research thus far focussed on interactions of plants with individual species. However, studying such interactions in a community context is needed to gain a better understanding.
2. Members of the aboveground insect community induce defences that systemically influence plant interactions with herbivorous as well as carnivorous insects. Plant roots are associated with a community of plant‐growth promoting rhizobacteria (PGPR). This PGPR community modulates insect‐induced defences of plants. Thus, PGPR and insects interact indirectly via plant‐mediated interactions.
3. Such plant‐mediated interactions between belowground PGPR and aboveground insects have usually been addressed unidirectionally from belowground to aboveground. Here, we take a bidirectional approach to these cross‐compartment plant‐mediated interactions.
4. Recent studies show that upon aboveground attack by insect herbivores, plants may recruit rhizobacteria that enhance plant defence against the attackers. This rearranging of the PGPR community in the rhizosphere has consequences for members of the aboveground insect community. This review focusses on the bidirectional nature of plant‐mediated interactions between the PGPR and insect communities associated with plants, including (a) effects of beneficial rhizobacteria via modification of plant defence traits on insects and (b) effects of plant defence against insects on the PGPR community in the rhizosphere. We discuss how such knowledge can be used in the development of sustainable crop‐protection strategies.

     

Native flowering shrubs promote beneficial insects in avocado orchards

1. Flower strips can promote and conserve beneficial insects in agroecosystems. Knowing which groups are favoured and which plant traits affect visitation rates by beneficial insects is important for the design of plant strips.
2. We established 21 Native Flower Strips (NFS) in avocado orchards in Central Chile. NFS contained 7–11 plant species, with variable corolla length and flowering period, to promote beneficial insects. We assessed flight activity of ladybirds (Coccinellidae) and bees (Apiformes) in sites adjacent to and far from NFS within avocado orchards. Additionally, we evaluated flower visitation for the main flower visitor groups (Apiformes, Lepidoptera, Diptera, and Coleoptera) to the plant species in NFS according to season and corolla length.
3. We found almost six times greater flight activity of coccinellids and bees in NFS than sites far from NFS within avocado orchards. Visitation rates of pollinator groups varied according to corolla length and season. Diptera, Coleoptera, and Lepidoptera consistently visited short corolla flowers. NFS were highly visited in summer and autumn, when avocados were not in bloom.
4. NFS in orchards should be encouraged by policymakers because they support beneficial insects that could deliver ecosystem services and contribute to local biological conservation.