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DNA metabarcoding is increasingly important for studying feeding interactions, yet it remains unresolved whether reporting read counts or occurrences is to be preferred. To address this issue for gut content samples, basic experimental data on the relationship between read numbers and initial prey DNA amounts and how both change over digestion time is needed. Using regurgitates of the carabid Pseudoophonus rufipes the digestion of Taraxacum officinale seeds was documented for 128 h post-feeding to determine how the number of (1) seed DNA copies and (2) metabarcoding reads change over digestion time, and (3) how they correlate to each other. Additionally, we tested (4) whether PCR cycle-numbers during library preparation affect this correlation. The number of copies and reads both decreased with digestion time, but variation between samples was high. Read and copy numbers correlated when using a library preparation protocol with 35 cycles (R2 = 42.0%), yet a reduction to 30 cycles might significantly improve this correlation, as indicated by additional PCR testing. Our findings show that protocol optimization is important to reduce technical distortions of read numbers in metabarcoding analysis. However, high inter-sample variation, likely due to variable digestive efficiency of individual consumers, can blur the relationship between the amount of food consumed and metabarcoding read numbers. [ABSTRACT FROM AUTHOR]

Fish are both consumers and prey, and as such part of a dynamic trophic network. Measuring how they are trophically linked, both directly and indirectly, to other species is vital to comprehend the mechanisms driving alterations in fish communities in space and time. Moreover, this knowledge also helps to understand how fish communities respond to environmental change and delivers important information for implementing management of fish stocks. DNA‐based methods have significantly widened our ability to assess trophic interactions in both marine and freshwater systems and they possess a range of advantages over other approaches in diet analysis. In this review we provide an overview of different DNA‐based methods that have been used to assess trophic interactions of fish as consumers and prey. We consider the practicalities and limitations, and emphasize critical aspects when analysing molecular derived trophic data. We exemplify how molecular techniques have been employed to unravel food web interactions involving fish as consumers and prey. In addition to the exciting opportunities DNA‐based approaches offer, we identify current challenges and future prospects for assessing fish food webs where DNA‐based approaches will play an important role. [ABSTRACT FROM AUTHOR]

A growing body of work has examined the psychological underpinnings of conspiracy theory endorsement, arguing that the propensity to believe in conspiracy theories and political rumors is a function of underlying predispositions and motivated reasoning. We show, like others, that rumor endorsement can also be a function of individuals' group attitudes. In particular, among white Americans, birther beliefs are uniquely associated with racial animus. We merge this finding with other work which shows that rumors are more strongly endorsed by the individuals most motivated and capable of integrating them among their pre-existing attitudes and beliefs. We find, therefore, that it is white Republicans who are both racially conservative and highly knowledgeable who possess the most skepticism about Obama's birthplace. [ABSTRACT FROM AUTHOR]

The article introduces a series of papers published within the issue, including one on the use of metabarcoding of gut contents to establish the diet of the brown shrimp, Crangon crangon, another on the prey of the wolf spider and a paper on associations between birds and feather mites determined by DNA metabarcoding.

Species are embedded in complex networks of ecological interactions and assessing these networks provides a powerful approach to understand what the consequences of these interactions are for ecosystem functioning and services. This is mandatory to develop and evaluate strategies for the management and control of pests. Graphical representations of networks can help recognize patterns that might be overlooked otherwise. However, there is a lack of software which allows visualizing these complex interaction networks. Food Web Designer is a stand-alone, highly flexible and user friendly software tool to quantitatively visualize trophic and other types of bipartite and tripartite interaction networks. It is offered free of charge for use on Microsoft Windows platforms. Food Web Designer is easy to use without the need to learn a specific syntax due to its graphical user interface. Up to three (trophic) levels can be connected using links cascading from or pointing towards the taxa within each level to illustrate top-down and bottom-up connections. Link width/strength and abundance of taxa can be quantified, allowing generating fully quantitative networks. Network datasets can be imported, saved for later adjustment and the interaction webs can be exported as pictures for graphical display in different file formats. We show how Food Web Designer can be used to draw predator-prey and host-parasitoid food webs, demonstrating that this software is a simple and straightforward tool to graphically display interaction networks for assessing pest control or any other type of interaction in both managed and natural ecosystems from an ecological network perspective. [ABSTRACT FROM AUTHOR]

Many omnivorous arthropods act as important pest control agents in agroecosystems. Assessing their prey choices helps to better understand their biocontrol potential in different environmental settings. To this end, multi‐target approaches of molecular gut content analysis allow studying their prey choices. Yet, DNA‐based analysis of trophic interactions is challenged by the question of whether the detected food DNA was ingested primarily as direct prey, or secondarily via the gut content of a consumed animal. Experimental data are needed to understand the potential bias derived through secondary predation. Here we address this issue for a phloem‐feeding aphid consumed by omnivorous carabids. In feeding experiments, Pseudoophonus rufipes beetles were offered grain aphids Sitobion avenae as primary prey, which had fed on barley seedlings. Gut content samples of carabids collected after 0, 3, 9, 12, 24, 32 or 64 h of digestion time and whole‐body aphids were screened for the presence of aphid and plant DNA. Samples positive for plant DNA were subsequently tested with Poaceae‐specific primers. None of the 7.8% gut content samples that tested positive for general plant DNA amplified with the Poaceae primers. Moreover, none of the whole‐body extracted aphids tested positive for plant DNA, neither with general nor with family‐specific primers. We, therefore, conclude that the plant DNA detections in our experiment can be ascribed to remnants of plant material in the guts of the field‐collected carabids. Our findings demonstrate that these phloem‐feeding aphids are an unlikely cause of false trophic link assignment because no secondarily consumed plant DNA, derived either from aphid gut content or host‐plant environmental DNA on aphid bodies, could be detected in carabid gut content samples. [ABSTRACT FROM AUTHOR]

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), have had a centuries-long role as major soil insect pests worldwide. With insecticidal control options dwindling, research on click beetle biology and ecology is of increasing importance in the development of new control tactics. Methodological improvements have deepened our understanding of how larvae and adults spatially and temporarily utilize agricultural habitats and interact with their environment. This progress, however, rests with a few pest species, and efforts to obtain comparable knowledge on other economically important elaterids are crucial. There are still considerable gaps in our understanding of female and larval ecology; movement of elaterids within landscapes; and the impact of natural enemies, cultivation practices, and environmental change on elaterid population dynamics. This knowledge will allow generation of multifaceted control strategies, including cultural, physical, and chemical measures, tailored toward species complexes and crops across a range of appropriate spatial scales. [ABSTRACT FROM AUTHOR]

• Intraguild predation within beetle communities was analysed in cereal fields. • Organic fertilization increased non-pest prey and lowered intraguild predation. • Lower intraguild predation correlated with lower pest spread, but not density. • No effect of organic fertilization was found on pest density or consumption. • Fertilization effects may offset pest predation from lower predator interference. Intraguild predation is an extreme form of competition, that depends on resource availability, niche overlap, behaviour and diversity. However, despite modelling and mesocosm experiments, field studies are scarce, and we know nothing of its temporal dynamics within real-world food webs, particularly in the context of biological control. To address this, we added manure to cereal fields to increase decomposer prey, and analysed the diet of over 6000 predators over the entire cropping season during two consecutive years. Our results show that manure increased available prey temporarily and reduced intraguild predation. With this organic fertilization, a reduction in pest spread between tillers within fields correlated with lower intraguild predation, while pest density remained unchanged across treatments, making the net effect on biological control unclear. We hypothesize that the mechanism responsible for why lowering intraguild predation reduces pest spread are changes in predator behaviour, that allow predators to exert more pressure on pests. Conversely, the absence of an effect on pest density may be linked to other effects of fertilization, such as increased pest and plant growth counteracting any increase in predation pressure. The high temporal resolution of our data showed how dynamic IGP is throughout the season, which stresses the importance of studying food webs over time, to generate a mechanistic understanding of biological control. [ABSTRACT FROM AUTHOR]

DNA-based diet analysis of natural enemies is a valuable tool for unravelling the food choice of predators in agroecosystems. It enables the rapid identification of potential biocontrol agents of invertebrate pests. Here, we present a new multiplex PCR system for the identification of pest slug species in the diet of their natural enemies such as carabid beetles. It comprises three species-specific primers targeting the mitochondrial cytochrome c oxidase subunit I (COI) gene to detect DNA of the common garden slug, Arion distinctus (Stylommatophora: Arionidae), the Iberian slug, Arion lusitanicus (Stylommatophora: Arionidae) and the grey field slug Deroceras reticulatum (Stylommatophora: Agriolimacidae). We also include (super)family-specific primers for Arionidae and Limacoidea, which amplify parts of the 28S gene for ribosomal RNA (rRNA) in order to identify a wider range of slugs. The amplicons for Arionidae can be assigned to a total of seven Central European slug species of this family and the amplicons for Limacoidea to ten species. The multiplex assay showed high specificity against DNA extracts of field-collected slugs and co-occurring invertebrates. The assay also exhibited high sensitivity, which was confirmed by testing it with 223 dietary samples from field-collected carabids as potential natural enemies of slugs in agroecosystems. This methodology represents a new, cost-effective, highly sensitive and specific approach for the identification of common Central European slug species as well as for analysing trophic interactions to identify natural enemies for further biological control development. It can also be applied in any study where a rapid and reliable identification of slugs is needed. [ABSTRACT FROM AUTHOR]

Intensified agriculture, a driver of biodiversity loss, can diminish ecosystem functions and their stability. Biodiversity can increase functional redundancy and is expected to stabilize ecosystem functions. Few studies, however, have explored how agricultural intensity affects functional redundancy and its link with ecosystem function stability. Here, within a continental‐wide study, we assess how functional redundancy of seed predation is affected by agricultural intensity and landscape simplification. By combining carabid abundances with molecular gut content data, functional redundancy of seed predation was quantified for 65 weed genera across 60 fields in four European countries. Across weed genera, functional redundancy was reduced with high field management intensity and simplified crop rotations. Moreover, functional redundancy increased the spatial stability of weed seed predation at the field scale. We found that ecosystem functions are vulnerable to disturbances in intensively managed agroecosystems, providing empirical evidence of the importance of biodiversity for stable ecosystem functions across space. [ABSTRACT FROM AUTHOR]

The use of sensitive methods is key for the detection of target taxa from trace amounts of environmental DNA (eDNA) in a sample. In this context, digital PCR (dPCR) enables direct quantification and is commonly perceived as more sensitive than endpoint PCR. However, endpoint PCR coupled with capillary electrophoresis (celPCR) potentially embodies a viable alternative as it quantitatively measures signal strength after PCR in Relative Fluorescence Units (RFU). Provided comparable levels of sensitivity are reached, celPCR permits the development of cost-efficient multiplex reactions, enabling the simultaneous detection of several target taxa. Here, we compared the sensitivity of singleplex and multiplex celPCR to dPCR for species-specific primer pairs amplifying mitochondrial DNA (COI) of fish species occurring in European freshwaters by analyzing dilution series of tissue extracts as well as field-collected water samples. Both singleplex and multiplex celPCR and dPCR displayed comparable sensitivity with reliable positive amplifications starting at two to 10 target DNA copies per μl extract. celPCR was suitable for quantifying target DNA and direct inference of copy numbers from RFU was possible after accounting for primer effects in linear mixed-effects models and calibration via dPCR. Furthermore, multiplex celPCR and dPCR were successfully used for the detection and quantification of fish-eDNA in field-collected water samples, confirming the results of the dilution series experiment and exemplifying the high sensitivity of the two approaches. The possibility of detection and quantification via multiplex celPCR is appealing for the cost-efficient screening of high sample numbers. The present results confirm the sensitivity of this approach thus enabling its application for future eDNA-based monitoring efforts. [ABSTRACT FROM AUTHOR]

Understanding trophic interactions in agroecosystems is crucial for harnessing ecosystem services such as pest control, thus enabling a reduction in pesticide use. Carabid beetles (Coleoptera: Carabidae) have the potential to regulate not only insect pests but also weed seeds and slugs. The aim of this study was to investigate the food choice of different carabid species in the experimental setting of a cereal field with varying seed and slug prey availability during the season. In addition to varying food availability, the effects of species identity and season on carabid food choice should also be closely examined. Therefore, the gut contents of 1,120 beetles of eight carabid species were screened for the DNA of plants, aphids, springtails, earthworms and slugs via diagnostic multiplex PCR and a nested metabarcoding approach for plant species identification. Plant DNA was detected far more often (72%) than the various animal prey types (less than 12.5% each). Within the plant detections, 80 weed species were identified in the metabarcoding, with Galinsoga parviflora/quadriradiata (Galinsoga spp.—quickweeds) as the most frequently detected species. Carabid food choice was driven by their species identity and seasonality, while no effect of increased availability of seeds and slugs on their food choice was detected. While weed seeds seem to be an important food source for carabids, their availability does not directly affect the carabid diet. The importance of consumer identity and seasonality highlight the need for a diverse carabid species community for resilient pest control services. [ABSTRACT FROM AUTHOR]

This study leverages a survey experiment in the lead up to the 2016 U.S. presidential election to evaluate how partisan biases, poll results, and their methodological quality interact to shape people's assessments of polling accuracy and electoral expectations. In a nationally representative sample, we find that individuals disproportionately find polls more credible when their preferred candidate is leading. Partisan biases are mitigated when the polls themselves vary in objective indicators of quality: while more educated respondents are more likely to identify high-quality polls accurately, low education respondents' bias was reduced when they encountered polls with varying methodological quality. Finally, these moderators influence respondents' electoral expectations as well. We discuss the implications for journalistic coverage of polls, public opinion, and political polarization. [ABSTRACT FROM AUTHOR]

Journalists rely on polls as they cover public opinion. In order to provide perspectives within the news stories, journalists frequently quote pundits – expert and partisan – who evaluate the methodological quality and implications of the numbers. While partisan pundits might attack unfavorable polls as biased and even fake, experts typically provide rational assessments of methodological quality; news readers may also encounter critiques of the reliability of polls in general in op-eds. How do Americans evaluate polls when they come accompanied with such commentaries? Building on evidence that individuals perceive polls in biased ways, this study examines whether and how individuals react to pundit commentary and whether such commentary can increase or decrease partisan bias in evaluations. In a nationally representative survey experiment fielded during the 2016 U.S. presidential election, we exposed 2,078 individuals to news stories about polls that included various expert or partisan comments. Although commentaries shifted perceptions of the polls, they did little to mitigate or amplify news readers' biases. We conclude that poll commentary is not an effective tool for mitigating bias. Implications for public perceptions, corrective attempts against biased processing of statistical information in news reports, and journalistic coverage at large are discussed. [ABSTRACT FROM AUTHOR]

Functional redundancy can increase the resilience of ecosystem processes by providing insurance against species loss and the effects of abundance fluctuations. However, due to the difficulty of assessing individual species' contributions and the lack of a metric allowing for a quantification of redundancy within communities, few attempts have been made to estimate redundancy for individual ecosystem processes. We present a new method linking interaction metrics with metabolic theory that allows for a quantification of redundancy at the level of ecosystem processes. Using this approach, redundancy in the predation on aphids and other prey by natural enemies across a landscape heterogeneity gradient was estimated. Functional redundancy of predators was high in heterogeneous landscapes, low in homogeneous landscapes and scaled with predator specialisation. Our approach allows quantifying functional redundancy within communities and can be used to assess the role of functional redundancy across a wide variety of ecosystem processes and environmental factors. [ABSTRACT FROM AUTHOR]

Knowledge of trophic interaction is necessary to understand the dynamics of ecosystems and develop ecosystem‐based management. The key data to measure these interactions should come from large‐scale diet analyses with good taxonomic resolution. To that end, molecular methods that analyze prey DNA from guts and feces provide high‐resolution dietary taxonomic data. However, molecular diet analysis may also produce unreliable results if the samples are contaminated by external sources of DNA. Employing the freshwater European whitefish (Coregonus lavaretus) as a tracer for sample contamination, we studied the possible route of whitefish in beaked redfish (Sebastes mentella) guts sampled in the Barents Sea. We used whitefish‐specific COI primers for diagnostic analysis, and fish‐specific 12S and metazoa‐specific COI primers for metabarcoding analyses of intestine and stomach contents of fish samples that were either not cleaned, water cleaned, or bleach cleaned after being in contact with whitefish. Both the diagnostic and COI metabarcoding revealed clear positive effects of cleaning samples as whitefish were detected in significantly higher numbers of uncleaned samples compared to water or bleach‐cleaned samples. Stomachs were more susceptible to contamination than intestines and bleach cleaning reduced the frequency of whitefish contamination. Also, the metabarcoding approach detected significantly more reads of whitefish in the stomach than in intestine samples. The diagnostic analysis and COI metabarcoding detected contaminants in a higher and comparable number of gut samples than the 12S‐based approach. Our study underlines thus the importance of surface decontamination of aquatic samples to obtain reliable diet information from molecular data. [ABSTRACT FROM AUTHOR]

Analysis of predator–prey interactions is a core concept of animal ecology, explaining structure and dynamics of animal food webs. Measuring the functional response, i.e. the intake rate of a consumer as a function of prey density, is a powerful method to predict the strength of trophic links and assess motives of prey choice, particularly in arthropod communities. However, due to their reductionist set‐up, functional responses, which are based on laboratory feeding experiments, may not display field conditions, possibly leading to skewed results. Here, we tested the validity of functional responses of centipede predators and their prey by comparing them with empirical gut content data from field‐collected predators. Our predator–prey system included lithobiid and geophilomorph centipedes, abundant and widespread predators of forest soils and their soil‐dwelling prey. First, we calculated the body size‐dependent functional responses of centipedes using a published functional response model in which we included natural prey abundances and animal body masses. This allowed us to calculate relative proportions of specific prey taxa in the centipede diet. In a second step, we screened field‐collected centipedes for DNA of eight abundant soil‐living prey taxa and estimated their body size‐dependent proportion of feeding events. We subsequently compared empirical data for each of the eight prey taxa, on proportional feeding events with functional response‐derived data on prey proportions expected in the gut, showing that both approaches significantly correlate in five out of eight predator–prey links for lithobiid centipedes but only in one case for geophilomorph centipedes. Our findings suggest that purely allometric functional response models, which are based on predator–prey body size ratios are too simple to explain predator–prey interactions in a complex system such as soil. We therefore stress that specific prey traits, such as defence mechanisms, must be considered for accurate predictions. [ABSTRACT FROM AUTHOR]

How do citizens' motivations shape their perceptions of poll reports? Increasingly, scholars are finding that citizens engage in motivated reasoning, whereby they discredit information that differs from their preexisting attitudes. The perceived credibility of opinion polls might be prone to similar motivational processes, as individuals could discount results suggesting that they hold minority opinions. We assess whether motivated reasoning influences the credibility of poll results and whether features of the presentation of those results might moderate and potentially counteract these motivational processes. In an online survey experiment conducted with a national sample of American adults (N = 1,211), respondents were exposed to poll reports about both gun control and abortion and were asked to rate the credibility of these polls. For each report, three aspects of presentation were randomized: the direction of the poll result (majority supports/opposes), the news source reporting the poll (FoxNews/MSNBC), and the amount of methodological detail reported (none/a lot). In line with theories of motivated reasoning, respondents who held issue positions that contradicted the results of the polls found those polls less credible. Further, this decreased credibility was particularly evident among individuals with high levels of political knowledge. Source credibility cues--such as the ideological alignment of source and respondent and the presence of a message from an unexpected source--did not moderate this relationship and were unrelated to poll credibility. However, evidence suggests that methodological disclosure could moderate the motivational biases in credibility assessments. [ABSTRACT FROM AUTHOR]

The analysis of environmental DNA (eDNA) is revolutionizing the monitoring of biodiversity as it allows to assess organismic diversity at large scale and unprecedented taxonomic detail. However, eDNA consists of an extracellular and intracellular fraction, each characterized by particular properties that determine the retrievable information on when and where organisms live or have been living. Here, we review the fractions of eDNA, describe how to obtain them from environmental samples and present a four‐scenario concept that aims at enhancing spatial and temporal resolution of eDNA‐based monitoring. Importantly, we highlight how the appropriate choice of eDNA fractions precludes misinterpretation of eDNA‐based biodiversity data. Finally, future avenues of research towards eDNA fraction‐specific analyses are outlined to unravel the full potential of eDNA‐based studies targeting micro‐ and macro‐organisms. [ABSTRACT FROM AUTHOR]

Facultative scavenging by predatory carnivores is a prevalent but frequently underestimated feeding strategy. DNA‐based methods for diet analysis, however, do not allow to distinguish between scavenging and predation, thus, the significance of scavenging on population dynamics and resource partitioning is widely unknown. Here, we present a methodological innovation to differentiate between scavenging and fresh prey consumption using prey RNA as a target molecule. We hypothesized that the rapid post‐mortem breakdown of RNA in prey tissue should lead to a significantly lower detection probability of prey RNA than DNA when carrion rather than fresh prey is consumed. To test this hypothesis, ground beetles (Pseudoophonus rufipes [De Geer]) were offered either fresh or 1‐day‐old dead Drosophila melanogaster fruit flies (carrion). The detectability of prey RNA and DNA in the beetles' regurgitates was assessed with diagnostic Drosophila‐specific RT‐PCR and PCR assays at 0, 6, 12, 24 and 48 h post‐feeding. After fresh fly consumption, prey RNA and DNA were detectable equally well at all times. When carrion prey was consumed, the detection strength of prey RNA immediately after feeding was significantly lower than that of prey DNA and reached zero in most samples within 6 h of digestion. Our findings provide evidence that prey RNA allows distinguishing between the consumption of fresh and scavenged prey, thereby overcoming a long‐known weakness of molecular diet analysis. The assessment of prey RNA offers a generally applicable approach for examining the importance of scavenging in food webs to unravel its functional consequences for populations, communities, and ecosystems. [ABSTRACT FROM AUTHOR]

Piscivorous birds in aquatic ecosystems exert predation pressure on fish populations. But the site‐specific impact on fish populations, including stocked and commercially used fish species, remains disputed. One of the key questions for the management of piscivorous birds and fish is determining the origin of prey and thus which fish populations are targeted by the birds. We addressed this question by provenancing otoliths (earstones) of fish obtained from regurgitated pellets of piscivorous birds by otolith microchemistry analysis. We retrieved otoliths from regurgitated pellets of great cormorants (Phalacrocorax carbo sinensis) collected every 2 weeks for 2 years from breeding and roosting colonies at Chiemsee in Bavaria, Germany, and classified them according to family or species. We collected water samples from Chiemsee and potential surrounding foraging grounds. We measured the strontium (Sr) 87Sr/86Sr isotope ratio and Sr mass fraction of water and otoliths using (laser ablation) inductively coupled plasma‐mass spectrometry. We assigned otoliths from regurgitated pellets to habitat clusters of origin by comparing the Sr isotopic and elemental composition of otoliths and waterbodies. In 36% of cormorant pellets collected at Chiemsee, prey was assigned to waterbodies distinct from Chiemsee. Furthermore, cormorants used different foraging sites during 1 day. Microchemical provenancing of prey remains can contribute to identifying foraging sites of piscivorous birds and to what extend the birds switched among foraging sites. [ABSTRACT FROM AUTHOR]

Successful biological control of agricultural pests is dependent on a thorough understanding of the underlying trophic interactions between predators and prey. Studying trophic interactions can be challenging, particularly when generalist predators that frequently use multiple prey and interact with both pest and alternative prey are considered. In this context, diagnostic PCR proved to be a suitable approach, however at present, prey-specific PCR primers necessary for assessing such interactions across trophic levels are missing. Here we present a new set of 45 primers designed to target a wide range of invertebrate taxa common to temperate cereal crops: cereal aphids, their natural enemies such as carabid beetles, ladybeetles, lacewings, and spiders, and potential alternative prey groups (earthworms, springtails, and dipterans). These primers were combined in three 'ready to use' multiplex PCR assays for quick and cost-effective analyses of large numbers of predator samples. The assays were tested on 560 carabids collected in barley fields in Sweden. Results from this screening suggest that aphids constitute a major food source for carabids in cereal crops (overall DNA detection rate: 51 %), whereas alternative extraguild and intraguild prey appear to be less frequently preyed upon when aphids are present (11 % for springtails and 12 % for earthworms; 1 % for spiders and 4 % for carabids). In summary, the newly developed molecular assays proved reliable and effective in assessing previously cryptic predator-prey trophic interactions, specifically with focus on biological control of aphids. The diagnostic PCR assays will be applicable manifold as the targeted invertebrates are common to many agricultural systems of the temperate region. [ABSTRACT FROM AUTHOR]

Plant diversity affects species richness and abundance of taxa at higher trophic levels. However, plant diversity effects on omnivores (feeding on multiple trophic levels) and their trophic and non-trophic interactions are not yet studied because appropriate methods were lacking. A promising approach is the DNA-based analysis of gut contents using next generation sequencing (NGS) technologies. Here, we integrate NGS-based analysis into the framework of a biodiversity experiment where plant taxonomic and functional diversity were manipulated to directly assess environmental interactions involving the omnivorous ground beetle Pterostichus melanarius. Beetle regurgitates were used for NGS-based analysis with universal 18S rDNA primers for eukaryotes. We detected a wide range of taxa with the NGS approach in regurgitates, including organisms representing trophic, phoretic, parasitic, and neutral interactions with P. melanarius. Our findings suggest that the frequency of (i) trophic interactions increased with plant diversity and vegetation cover; (ii) intraguild predation increased with vegetation cover, and (iii) neutral interactions with organisms such as fungi and protists increased with vegetation cover. Experimentally manipulated plant diversity likely affects multitrophic interactions involving omnivorous consumers. Our study therefore shows that trophic and non-trophic interactions can be assessed via NGS to address fundamental questions in biodiversity research. [ABSTRACT FROM AUTHOR]

This paper attempts to measure the effect of third-party presence during the interview on sensitive questions about women's empowerment in Morocco, a country with Muslim culture and traditions. Data are from the 2003 Morocco Demographics and Health Survey, which includes only female respondents who were asked two series of questions about their participation in the decision-making process at the household level and their attitudes toward wife beating. Like previous studies, we find that the occurrence of the third-party presence during the interview is not random. It is more likely to occur among women with particular characteristics (e.g., less educated, younger, less likely to be employed, and married). We then use propensity score matching to separate the third-party effect from personal characteristics. While we find the thirdparty effect to be statistically significant for some questions, the magnitude of the effect is relatively small in all questions. [ABSTRACT FROM AUTHOR]

Soil-dwelling insect pests may cause considerable damage to crops worldwide, and their belowground lifestyle makes them hard to control. Amongst the most promising control agents for subterranean pests are soilborne entomopathogenic fungi (EPF) such as Metarhizium brunneum. Albeit EPF can be highly pathogenic to their target pest species under laboratory conditions, their efficacy in the field is often limited due to adverse environmental conditions. Here, we test for the first time if the efficacy of EPF can be improved when they are augmented with trap crops. In a field experiment, the M. brunneum strain ART2825 was combined with a trap crops mixture of six plant species and evaluated for its control effect of wireworms (Coleoptera: Elateridae). When both were combined in the main crop, potato damage was lowered on average by 42.5% and wireworm abundance by 50.8%. Single application of trap crops or EPF lowered damage/pest abundance only by 29.9%/15.89% and 34.7%/4.77%, respectively. Importantly, the strength of the synergistic pest control effect between trap crops and EPF increased disproportionately with increasing wireworm abundance. However, DNA-based gut content analysis showed that wireworms’ feeding preferences were not shifting toward the trap crops. Our findings demonstrate that combining trap crops with EPF improves the efficacy of the latter and leads to a synergistic control effect which magnifies with increasing wireworm abundance. Hence, the synergistic effect of EPF and trap crops might be a promising control strategy for soil-dwelling pests in general and significantly improve our abilities to manage soil pests environmentally friendly. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Consumer identity but not food availability affects carabid diet in cereal crops" published in the Journal of Pest Science. The correction addresses a typesetting error in Table s1 and provides the correct table and legend. The supplementary material, including a graph, is available online. The correction is authored by Yasemin Guenay-Greunke, Harald Trager, David A. Bohan, Michael Traugott, and Corinna Wallinger. Springer Nature, the publisher, remains neutral regarding jurisdictional claims and institutional affiliations. [Extracted from the article]

Potamodromous fish are considered important indicators of habitat connectivity in freshwater ecosystems, but they are globally threatened by anthropogenic impacts. Hence, non-invasive techniques are necessary for monitoring during spawning migrations. The use of environmental DNA (eDNA) potentially facilitates these efforts, albeit quantitative examinations of spawning migrations remain so far mostly uncharted. Here, we investigated spawning migrations of Danube bleak, Alburnus mento, and Vimba bream, Vimba vimba, and found a strong correlation between daily visual fish counts and downstream eDNA signals obtained from filtered water samples analysed with digital PCR and end-point PCR coupled with capillary electrophoresis. By accounting for daily discharge fluctuations, it was possible to predict eDNA signal strength from the number of migrating fish: first, the whole spawning reach was taken into account. Second, the model was validated using eDNA signals and fish counts obtained from the upper half of the examined river stretch. Consequently, fish counts and their day-to-day changes could be described via an eDNA-based time series model for the whole migration period. Our findings highlight the capability of eDNA beyond delivering simple presence/absence data towards efficient and informative monitoring of highly dynamic aquatic processes such as spawning migrations of potamodromous fish species. [ABSTRACT FROM AUTHOR]

Abundance and diversity of natural enemies increases with higher landscape complexity. However, more species can also increase negative interactions such as intraguild predation (IGP), which could be detrimental to pest control. Direct observations of these trophic interactions are still lacking. In the present study, we employed DNA-based gut content analyses of coccinellid beetles to assess IGP (direct and coincidental) and aphid consumption. Species-specific and group-specific primer pairs were used to unveil the interactions of the most abundant coccinellid species, three cereal aphids and their associated parasitoids. In order to determine whether the landscape complexity promotes these interactions, we used replicated wheat fields in two contrasting landscape contexts over the season in central Chile. With higher abundance of coccinellids, we observed greater aphid consumption in complex contexts. The consumption of parasitized aphids was mostly detected early in complex contexts, suggesting a detrimental effect on the parasitoid population. Following molecular analysis, we can state that the aphids are important feeding resources for the coccinellid assemblage and are actively foraging on this important pest. Finally, this study demonstrates that direct IGP is a common interaction in this system, independently of the landscape context during the complete season. Nevertheless, the native Eriopis chilensis was found to be the most frequently consumed intraguild prey. In contrast with expected predictions, we found little evidence that the landscape context increased negative interactions, such as IGP and IGP-C and in turn that these decrease the control of Sitobion avenae. [ABSTRACT FROM AUTHOR]

• Landscape had a lower effect on aphids and their parasitoids than fertilisation. • Fertilisation affected plants positively. • Fertilisation affected aphids and primary parasitism rate negatively. • Fertilisation had no effect on secondary parasitism rate. • H 2 ' and generality between parasitoids are affected by landscape and fertilisation. Agricultural intensification can impact agrobiodiversity in several ways such as in terms of population densities, community composition and food web interactions across all trophic levels. This effect can be investigated at two scales: field-scale and landscape scale. Here it was assessed how the impact of fertilisation (within field) and landscape complexity (within landscape) impact cereal aphid-primary parasitoid-secondary parasitoid systems in winter wheat in Germany. A newly developed molecular technique was used to quantify species-specific linkages between aphids, primary parasitoids and secondary parasitoids sampled in fertilised and unfertilised plots in either simple or complex structured landscapes. The results show a stronger effect of fertilisation than landscape complexity on the groups: fertilisation positively affected the crop plants while it negatively affected both the density of the cereal aphid Sitobion avenae and its primary parasitism rates whereas no effect on the level of secondary parasitism rates was observed. Landscape complexity had no effect on plants, aphids, as well as on primary parasitism rate. In case of secondary parasitism rate there was an effect in interaction with sampling date. Field identity accounted for the strongest effect on parasitoid community composition (10.6% of the variance) from all tested variables, while fertilisation and landscape complexity had almost no effect (1.1% and no effect). Nevertheless, a weak cascading effect of both environmental factors could be observed as the primary-secondary parasitoid network structure responded to both. However, these observed effects on food webs strongly depended on species identity, highlighting the need of species-level food web assessment. [ABSTRACT FROM AUTHOR]

The bird cherry‐oat aphid Rhopalosiphum padi is a major cereal pest with an almost cosmopolitan distribution. As one of the main groups of biocontrol agents for aphids, numerous Aphidiinae are associated with R. padi, including the genera Binodoxys and Trioxys.As a recently described species parasitizing R. padi, Trioxys sunnysidensis is recorded from Europe for the first time based on morphological and molecular data. Specimens from North America, Europe and New Zealand were used in the analysis of the cytochrome c oxidase subunit I to explore genetic variation among populations. The analysis revealed one of the highest haplotype diversities in Aphidiinae so far, with 25 haplotypes detected. The two most common haplotypes are shared across groups of populations, whereas all of the others are found either in North America or Europe.Because the genetic structure of populations is an important factor to consider when choosing a biocontrol agent, the results obtained in the present study may be helpful in guiding potential biocontrol attempts. [ABSTRACT FROM AUTHOR]

Carabid beetles are abundant in temperate agroecosystems and can play a pivotal role as biocontrol agents. While there is good knowledge regarding their effects on invertebrate pests in some systems, comparably little is known on the rate of seed feeding under field conditions. Molecular approaches are ideally suited for investigating carabid feeding interactions; to date, however, they have only been applied to animal prey. We sampled adult carabid beetles in organic cereal fields in three regions along a Central European transect. Regurgitates from populations of the three most common species, Poecilus cupreus, Pseudoophonus rufipes and Pterostichus melanarius, were screened for plant DNA, cereal aphids, collembolans and earthworms. The frequency of carabid individuals positive for plant DNA was high (> 70%) and independent of carabid species, sex, region and the time point of sampling. Detections for non-pest and pest prey were comparably lower, with 21.6% for collembolans, 18.1% for earthworms and 4.2% for aphids, respectively. Despite the prolonged detection period of plant DNA in carabid guts, as compared to animal prey, these first results suggest that weed seeds form an important part of the adult carabid diet. It would also lend support to the hypothesis that seed-feeding carabids are biocontrol agents of weeds, with effects of regulation on the weed seedbank that depend on behavioural and contextual factors including carabid species preferences for weed seed species, their life stage and tillage practices. [ABSTRACT FROM AUTHOR]

Next‐generation sequencing (NGS) is increasingly used for diet analyses; however, it may not always describe diet samples well. A reason for this is that diet samples contain mixtures of food DNA in different amounts as well as consumer DNA which can reduce the food DNA characterized. Because of this, detections will depend on the relative amount and identity of each type of DNA. For such samples, diagnostic PCR will most likely give more reliable results, as detection probability is only marginally dependent on other copresent DNA. We investigated the reliability of each method to test (a) whether predatory beetle regurgitates, supposed to be low in consumer DNA, allow to retrieve prey sequences using general barcoding primers that co‐amplify the consumer DNA, and (b) to assess the sequencing depth or replication needed for NGS and diagnostic PCR to give stable results. When consumer DNA is co‐amplified, NGS is better suited to discover the range of possible prey, than for comparing co‐occurrences of diet species between samples, as retested samples were repeatedly different in prey detections with this approach. This shows that samples were incompletely described, as prey detected by diagnostic PCR frequently were missed by NGS. As the sequencing depth needed to reliably describe the diet in such samples becomes very high, the cost‐efficiency and reliability of diagnostic PCR make diagnostic PCR better suited for testing large sample‐sets. Especially if the targeted prey taxa are thought to be of ecological importance, as diagnostic PCR gave more nested and consistent results in repeated testing of the same sample. [ABSTRACT FROM AUTHOR]

Most ecosystem functions and related services involve species interactions across trophic levels, for example, pollination and biological pest control. Despite this, our understanding of ecosystem function in multitrophic communities is poor, and research has been limited to either manipulation in small communities or statistical descriptions in larger ones.Recent advances in food web ecology may allow us to overcome the trade‐off between mechanistic insight and ecological realism. Molecular tools now simplify the detection of feeding interactions, and trait‐based approaches allow the application of dynamic food web models to real ecosystems. We performed the first test of an allometric food web model's ability to replicate temporally nonaggregated abundance data from the field and to provide mechanistic insight into the function of predation.We aimed to reproduce and explore the drivers of the population dynamics of the aphid herbivore Rhopalosiphum padi observed in ten Swedish barley fields. We used a dynamic food web model, taking observed interactions and abundances of predators and alternative prey as input data, allowing us to examine the role of predation in aphid population control. The inverse problem methods were used for simultaneous model fit optimization and model parameterization.The model captured >70% of the variation in aphid abundance in five of ten fields, supporting the model‐embodied hypothesis that body size can be an important determinant of predation in the arthropod community. We further demonstrate how in‐depth model analysis can disentangle the likely drivers of function, such as the community's abundance and trait composition. Analysing the variability in model performance revealed knowledge gaps, such as the source of episodic aphid mortality, and general method development needs that, if addressed, would further increase model success and enable stronger inference about ecosystem function.The results demonstrate that confronting dynamic food web models with abundance data from the field is a viable approach to evaluate ecological theory and to aid our understanding of function in real ecosystems. However, to realize the full potential of food web models, in ecosystem function research and beyond, trait‐based parameterization must be refined and extended to include more traits than body size. Dynamic food web models could aid our understanding of ecosystem functions driven by trophic interactions, but are rarely tested against data. The authors confront a trait‐based food web model with field data, and show that it can explain observed abundance dynamics of an arthropod herbivore and provide insight into ecosystem functioning. [ABSTRACT FROM AUTHOR]

Primary succession on bare ground surrounded by intact ecosystems is, during its first stages, characterized by predator‐dominated arthropod communities. However, little is known on what prey sustains these predators at the start of succession and which factors drive the structure of these food webs. As prey availability can be extremely patchy and episodic in pioneer stages, trophic networks might be highly variable. Moreover, the importance of allochthonous versus autochthonous food sources for these pioneer predators is mostly unknown. To answer these questions, the gut content of 1,832 arthropod predators, including four species of carabid beetles, two lycosid and several linyphiid spider species caught in early and late pioneer stages of three glacier forelands, was screened molecularly to track intraguild and extraguild trophic interactions among all major prey groups occurring in these systems. Two‐thirds of the 2,310 identified food detections were collembolans and intraguild prey, while one‐third were allochthonous flying insects. Predator identity and not successional stage or valley had by far the strongest impact on the trophic interaction patterns. Still, the variability of prey spectra increased significantly from early to late pioneer stage, as did the niche width of the predators. As such the structure of pioneer arthropod food webs in recently deglaciated Alpine habitats seems to be driven foremost by predator identity while site and early successional effects contribute to a lesser extent to food web variability. Our findings also suggest that in these pioneer sites, predatory arthropods depend less on allochthonous aeolian prey but are mainly sustained by prey of local production. [ABSTRACT FROM AUTHOR]

The nucleotide variation in the cytochrome c oxidase subunit I (COI) gene makes it ideal for assigning sequences to species. However, this variability also makes it difficult to design truly universal primers. Here, we present the forward primer "Sauron‐S878," specifically designed to facilitate library preparation for metabarcoding. This primer is modified to improve the coverage of terrestrial species compared to the primer mCOIintF, optimized for aquatic systems, which raised the in silico coverage from 74.4% to 98.3% of available NCBI sequences (perfect match in 3′ region, up to three mismatches in remaining primer). When paired with the reverse primer "jgHCO2198" (fragment length ~313 bp), these primers amplified 98.4% of 255 tested DNA extracts from various taxa, which are better than many other common COI barcoding primers. Furthermore, a single‐tube protocol was developed, wherein these primers amplify the target gene, and attach MIDs and Illumina sequencing adapters in one reaction. This eliminates the need for re‐amplification or enzymatic ligation during library preparation while keeping the flexibility to modularly combine primers and MIDs. Using the single‐tube approach, three replicates of three mock samples were sequenced on a MiSeq platform with no adverse effects compared to commercial Nextera indexing kits. From this run, 75% of all included taxa could be recovered, with no considerable bias among taxonomic groups. Despite the fact that 98.4% of the extracts were confirmed to amplify in vitro, this number was lower than expected. A reason for this discrepancy was a clear link between the relative concentration of a specific DNA type in the template and the number of returned reads for this DNA. We would argue that such a bias may be especially problematic in metabarcoding where samples usually contain trace DNA in unknown amounts. However, how this affects the completeness of metabarcoding results has yet been poorly investigated. Here, we present the forward primer "Sauron‐S878," specifically designed to facilitate library preparation for metabarcoding. This primer exhibits little bias between taxonomic groups. Furthermore, when paired with the reverse primer "jgHCO2198," these primers can be used to attach MIDs and Illumina sequencing adapters in one reaction. [ABSTRACT FROM AUTHOR]

Carabids are abundant in temperate agroecosystems and play a pivotal role as biocontrol agents for weed seed and pest regulation. While there is good knowledge regarding their effects on invertebrate pests, direct evidence for seed predation in the field is missing. Molecular approaches are ideally suited to investigate these feeding interactions; however, the effects of an omnivorous diet, which is characteristic for many carabid species, and seed identity on the detection success of seed DNA has not yet been investigated. In a series of feeding experiments, seeds of six different Central European weed species were fed to beetles of the species Pseudoophonus rufipes, to determine post‐feeding seed DNA detection rates and how these are affected by plant identity, meal size, and chemical seed composition. Moreover, we investigated the effect of a mixed diet of seeds and mealworm on prey DNA detection. Four out of six seed species were detectable for up to five days after consumption, and seed species identity significantly affected post‐feeding detection rates. Detectability was negatively influenced by protein content and seed mass, whereas oil content and meal size had a positive effect. The mixed diet led to both increased detection rates and post‐feeding detection intervals of seed DNA. This suggests that mixed feeding leads to an enhancement of food detection intervals in carabid beetles and that seed identity, their chemical composition, and meal size can affect DNA detection of consumed seeds. These aspects and potential implications of this non‐invasive approach are discussed as they can become highly relevant for interpreting field‐derived data. Carabids are abundant in temperate agroecosystems and play a pivotal role as biocontrol agents for weeds and insect pests. In a series of feeding experiments we investigated the effects of an omnivorous diet, which is characteristic for most carabids, and seed identity on the molecular detection of consumed seeds. Results indicate that meal size, seed identity, and their chemical composition can play a role and that mixed feeding leads to an enhancement of food detection intervals. [ABSTRACT FROM AUTHOR]

Abstract: The rapidly growing field of molecular diet analysis is becoming increasingly popular among ecologists, especially when investigating methodologically challenging groups, such as invertebrate generalist predators. Prey DNA detection success is known to be affected by multiple factors; however, the type of dietary sample has rarely been considered. Here, we address this knowledge gap by comparing prey DNA detection success from three types of dietary samples. In a controlled feeding experiment, using the carabid beetle Pterostichus melanarius as a model predator, we collected regurgitates, faeces and whole consumers (including their gut contents) at different time points postfeeding. All dietary samples were analysed using multiplex PCR, targeting three different length DNA fragments (128, 332 and 612 bp). Our results show that both the type of dietary sample and the size of the DNA fragment contribute to a significant part of the variation found in the detectability of prey DNA. Specifically, we observed that in both regurgitates and whole consumers, prey DNA was detectable significantly longer for all fragment sizes than for faeces. Based on these observations, we conclude that prey DNA detected from regurgitates and whole consumers DNA extracts are comparable, whereas prey DNA detected from faeces, though still sufficiently reliable for ecological studies, will not be directly comparable to the former. Therefore, regurgitates and faeces constitute a useful, nonlethal source for dietary information that could be applied to field studies in situations when invertebrate predators should not be killed. [ABSTRACT FROM AUTHOR]

Abstract: Facultative bacterial endosymbionts can protect their aphid hosts from natural enemies such as hymenopteran parasitoids. As such, they have the capability to modulate interactions between aphids, parasitoids and hyperparasitoids. However, the magnitude of these effects in natural aphid populations and their associated parasitoid communities is currently unknown. Moreover, environmental factors such as plant fertilization and landscape complexity are known to affect aphid–parasitoid interactions but it remains unclear how such environmental factors affect the interplay between aphids, parasitoids and endosymbionts. Here, we tested whether facultative endosymbionts confer protection to parasitoids in natural populations of the English grain aphid, Sitobion avenae, and if this is affected by plant fertilization and landscape complexity. Furthermore, we examined whether the effects of facultative endosymbionts can cascade up to the hyperparasitoid level and increase primary‐hyperparasitoid food web specialization. Living aphids and mummies were collected in fertilized and unfertilized plots within 13 wheat fields in Central Germany. We assessed the occurrence of primary parasitoid, hyperparasitoid and endosymbiont species in aphids and mummies using a newly established molecular approach. Facultative endosymbiont infection rates were high across fields (~80%), independent of whether aphids were parasitized or unparasitized. Aphid mummies exhibited a significantly lower share of facultative endosymbiont infection (~38%). These findings suggest that facultative endosymbionts do not affect parasitoid oviposition behaviour, but decrease parasitoid survival in the host. Facultative endosymbiont infection rates were lower in mummies collected from fertilized compared to unfertilized plants, indicating that plant fertilization boosts the facultative endosymbiont protective effect. Furthermore, we found strong evidence for species‐specific and negative cascading effects of facultative endosymbionts on primary and hyperparasitoids, respectively. Facultative endosymbionts impacted parasitoid assemblages and increased the specialization of primary‐hyperparasitoid food webs: these effects were independent from and much stronger than other environmental factors. The current findings strongly suggest that facultative endosymbionts act as a driving force in aphid–parasitoid–hyperparasitoid networks: they shape insect community composition at different trophic levels and modulate, directly and indirectly, the interactions between aphids, parasitoids and their environment. [ABSTRACT FROM AUTHOR]

Abstract: Piscivorous birds frequently display sex‐specific differences in their hunting and feeding behavior, which lead to diverging impacts on prey populations. Cormorants (Phalacrocoracidae), for example, were previously studied to examine dietary differences between the sexes and males were found to consume larger fish in coastal areas during autumn and winter. However, information on prey partitioning during breeding and generally on sex‐specific foraging in inland waters is missing. Here, we assess sex‐specific prey choice of Great Cormorants (Phalacrocorax carbo) during two subsequent breeding seasons in the Central European Alpine foreland, an area characterized by numerous stagnant and flowing waters in close proximity to each other. We developed a unique, noninvasive approach and applied it to regurgitated pellets: molecular cormorant sexing combined with molecular fish identification and fish‐length regression analysis performed on prey hard parts. Altogether, 364 pellets delivered information on both, bird sex, and consumed prey. The sexes differed significantly in their overall prey composition, even though Perca fluviatilis, Rutilus rutilus, and Coregonus spp. represented the main food source for both. Albeit prey composition did not indicate the use of different water bodies by the sexes, male diet was characterized by higher prey diversity within a pellet and the consumption of larger fish. The current findings show that female and male cormorants to some extent target the available prey spectrum at different levels. Finally, the comprehensive and noninvasive approach has great potential for application in studies of other piscivorous bird species. [ABSTRACT FROM AUTHOR]

Drosophila suzukii (Diptera: Drosophilidae) is a highly polyphagous invasive pest threatening fruit production in the Americas and Europe. The current knowledge of its host plants is mainly based on oviposition and larval development in fruits, while little is known on the diet of the adult flies. This information is important for developing effective control strategies. Here, we examine DNA-based techniques to determine food plants of D. suzukii. Adult flies were fed with raspberries (Rubus idaeus) and allowed to digest up to 72 h after feeding. Raspberry DNA was detected by diagnostic PCR for up to 48 h post-feeding with a significant negative effect of time on DNA detection success but no significant differences between male and female flies in detection probabilities. As D. suzukii walks on plants, its body surface can get contaminated with DNA. With a bleaching experiment, we succeeded to remove contaminating external plant DNA, while the DNA in the gut content stayed unaffected. Finally, field-collected flies were subjected to a next-generation sequencing approach, demonstrating that plant DNA from different host plants can be efficiently detected in both bleached and non-bleached specimens. In order to safeguard against erroneous host plant detections, we recommend bleaching flies before they are subjected to DNA extraction. The current findings encourage the use of DNA-based gut content analysis in D. suzukii to obtain a better understanding of its feeding ecology which is a prerequisite for developing successful control strategies. [ABSTRACT FROM AUTHOR]

Soil macro-invertebrates play an important role in the formation and functioning of soils, which makes them indispensable for all terrestrial ecosystems, including high alpine soils. However, in the latter, knowledge on species identity, diversity, and functionality of macro-invertebrate soil communities is scarce. Here, we address this knowledge gap by investigating the structural and functional composition of soil macro-invertebrate communities in high alpine sites of the European Alps that differ in sheep grazing intensity (low, medium, and high). Abundance data were combined with the analysis of natural variations in stable isotope ratios ( 13 C/ 12 C, 15 N/ 14 N) of food sources and soil animals, allowing insight into the trophic structure of the decomposer community. The presence of sheep significantly increased the abundance of Nematocera, but reduced the abundance of most other taxa. Diplopoda were found exclusively at the low elevation site with almost no sheep grazing, while Diptera larvae increased in numbers at higher elevation sites. Lumbricidae species were abundant at all sites except the highest site, which was intensively grazed by sheep and also used as a resting place. In contrast, trophic relations were not affected by sheep grazing intensity, four trophic groups were clearly distinguished, pointing to a relatively simple food web structure: (1) primary decomposers, (2) secondary decomposers and dung feeders, (3) root and fungal feeders, and (4) predators. We suggest that the shallow soils with high organic matter do not allow the formation of more complex food webs. [ABSTRACT FROM AUTHOR]

Abstract: The “habitat heterogeneity hypothesis” predicts positive effects of structural complexity on species coexistence. Increasing habitat heterogeneity can change the diversity (number of species, abundances) and the functional roles of communities. The latter, however, is not well understood as species and individuals may respond very differently and dynamically to a changing environment. Here, we experimentally test how habitat heterogeneity affects generalist arthropod predators, including epigaeic spiders, carabid and staphylinid beetles, under natural conditions by assessing their diversity and directly measuring their trophic interactions (which provide a proxy for their functional roles). The experiment was conducted in spring barley fields in Southern Sweden where habitat heterogeneity was manipulated by increasing within‐field plant diversity. Increased habitat heterogeneity triggered rapid changes in the feeding behaviour of generalist predators characterized by lower trophic specialization at both network (H2’, degree of interaction specialization in the entire network) and species level (d’, degree of interaction specialization at the species level). We presume that this is because spatial separation resulted in relaxed competition and allowed an increased overlap in resources used among predator species. Predators collected from heterogenous habitats also showed greater individual‐level dietary variability which might be ascribed to relaxed intraspecific competition. Our results provide conclusive evidence that habitat heterogeneity can induce rapid behavioural responses independent of changes in diversity, potentially promoting the stability of ecosystem functions. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

The vinegar fly Drosophila suzukii (Matsumura) is an invasive species that attacks ripening fruits and berries, leading to considerable losses in fruit production. So far, management mainly relies on chemical and cultural control, but additional measures such as biological control are needed. Hence, for the development of sustainable control measures of this pest it is important to identify potential natural enemies such as generalist predators that feed on D. suzukii. Here, we established a simple and cost-effective assay to specifically detect D. suzukii DNA in the guts of arthropod predators. Furthermore, we developed a general Drosophila spp. primer pair to identify predators of Drosophila species in general that might also feed on D. suzukii and to compare predation rates on D. suzukii to those of other Drosophila species. We applied the assays to field-collected predators and identified three predator taxa-earwigs, spiders and predatory bugs-that had fed on D. suzukii. The assays provide a first step towards unravelling the predator community attacking D. suzukii that should be considered as biological control agents but also as non-targets potentially affected by other measures to control this invasive pest. [ABSTRACT FROM AUTHOR]

Molecular methods allow noninvasive assessment of vertebrate predator-prey systems at high taxonomic resolution by examining dietary samples such as faeces and pellets. To facilitate the interpretation of field-derived data, feeding trials, investigating the impacts of biological, methodological and environmental factors on prey DNA detection, have been conducted. The effect of meal size, however, has not yet been explicitly considered for vertebrate consumers. Moreover, different noninvasively obtained sample types remain to be compared in such experiments. Here, we present a feeding trial on abundant piscivorous birds, Great Cormorants ( Phalacrocorax carbo), to assess meal size effects on postfeeding prey DNA detection success. Faeces and pellets were sampled twice a day after the feed of large (350-540 g), medium (190-345 g) and small (15-170 g) fish meals contributing either a large (>79%) or small (<38%) share to the daily consumption. Samples were examined for prey DNA and fish hard parts. Molecular analysis of faeces revealed that both large meal size and share had a significantly positive effect on prey DNA detection rate postfeeding. Furthermore, large meals were detectable for a significantly longer time span with a detection limit at ~76 hr and a 50% detection probability at ~32 hr postfeeding. In pellets, molecular methods reliably identified the meal consumed the previous day, which was not possible via morphological analysis or when examining individual faeces. The less reliable prey DNA detection of small meals or meal shares in faeces signifies the importance of large numbers of dietary samples to obtain reliable trophic data. [ABSTRACT FROM AUTHOR]

Molecular techniques have become an important tool to empirically assess feeding interactions. The increased usage of next-generation sequencing approaches has stressed the need of fast DNA extraction that does not compromise DNA quality. Dietary samples here pose a particular challenge, as these demand high-quality DNA extraction procedures for obtaining the minute quantities of short-fragmented food DNA. Automatic high-throughput procedures significantly decrease time and costs and allow for standardization of extracting total DNA. However, these approaches have not yet been evaluated for dietary samples. We tested the efficiency of an automatic DNA extraction platform and a traditional CTAB protocol, employing a variety of dietary samples including invertebrate whole-body extracts as well as invertebrate and vertebrate gut content samples and feces. Extraction efficacy was quantified using the proportions of successful PCR amplifications of both total and prey DNA, and cost was estimated in terms of time and material expense. For extraction of total DNA, the automated platform performed better for both invertebrate and vertebrate samples. This was also true for prey detection in vertebrate samples. For the dietary analysis in invertebrates, there is still room for improvement when using the high-throughput system for optimal DNA yields. Overall, the automated DNA extraction system turned out as a promising alternative to labor-intensive, low-throughput manual extraction methods such as CTAB. It is opening up the opportunity for an extensive use of this cost-efficient and innovative methodology at low contamination risk also in trophic ecology. [ABSTRACT FROM AUTHOR]

The focus of this study was to assess the potential of otolith microchemistry as a fishery management tool for different European freshwater fish species in an Alpine foreland with a diverse range of different water bodies but low geological variation. 87Sr/86Sr isotope ratios and Sr/Ca ratios in water samples from 26 habitat sites in a pre-alpine catchment region around lake Chiemsee, Germany, an important region for recreational and economic fisheries, were analysed. 87Sr/86Sr isotope ratios and the Sr/Ca ratios in otoliths of 246 fish out of 16 species were determined using (laser ablation) inductively coupled plasma mass spectrometry ((LA)-ICP-MS). Habitats could be differentiated into seven clusters when using the 87Sr/86Sr isotope and Sr/Ca ratios in water in combination. When using the 87Sr/86Sr isotope ratio as individual parameter, the strontium isotope groups (SIGs) based on the 87Sr/86Sr isotope ratios including the measurement uncertainties justified a three-cluster solution. The direct comparison of 87Sr/86Sr isotope ratios in water and otolith samples allowed to identify fish that a) might have migrated, b) were transferred from other water bodies or c) stocked from fish farms. Sr/Ca ratios in water and otoliths were highly correlated, although significant differences between species from the same environment were documented. Sr/Ca ratios in sagittae of Perca fluviatilis were about 64–60% of those in sagittae of Coregonus spp and of lapilli of roach Rutilus rutilus from the same habitats, respectively. Partition coefficients for water to otolith Sr/Ca ratios were calculated and differed between species. Discrimination of fish otoliths according to habitat clusters by combining 87Sr/86Sr and Sr/Ca ratios was possible with success rates of up to 100% for whitefish Coregonus spp., 90% for European perch Perca fluviatilis, 87% for cyprinids, and 89% European grayling Thymallus thymallus, and 68% for salmonids. When using the 87Sr/86Sr isotope ratios as single parameter, assignment results were generally worse, except for salmonids, where an improved accuracy of 79% could be achieved, or for cyprinids when the number of clusters was reduced from five to three. The study indicates that otolith microchemistry has great potential to serve as a fishery management tool at smaller spatial scales such as in the studied Alpine foreland when combining the 87Sr/86Sr and Sr/Ca ratios, and considering the type and spatial distribution of habitats, the species and question under investigation. • Otolith microchemistry applied in an area with limited geological variability. • Fish transferred, stocked or migrated were identified. • Sr/Ca ratios in water predict Sr/Ca ratios in otoliths. • Fish species-specific Sr discrimination from water into otoliths. • European freshwater fish species assigned to habitat clusters of origin. [ABSTRACT FROM AUTHOR]

Aphids are major pests of cereal crops and a suite of hymenopteran primary parasitoids play an important role in regulating their populations. However, hyperparasitoids may disrupt the biocontrol services provided by primary parasitoids. As such, understanding cereal aphid-primary parasitoid-hyperparasitoid interactions is vital for a reliable parasitoid-based control of cereal aphids. For this, the ability to identify the different primary and hyperparasitoid species is necessary. Unfortunately, this is often difficult due to a lack of morphologically diagnostic features. DNA sequence-based species identification of parasitoids can overcome these hurdles. However, comprehensive DNA sequence information is lacking for many of these groups, particularly for hyperparasitoids. Here we evaluate three genes [cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S) and 18S ribosomal RNA (18S)] for their suitability to identify 24 species of primary parasitoids and 16 species of hyperparasitoids associated with European cereal aphids. To identify aphelinid primary parasitoid species and hyperparasitoids, we found 16S to be more suitable compared to COI sequences. In contrast, the Aphidiinae are best identified using COI due to better species-level resolution and a more comprehensive DNA sequence database compared to 16S. The 18S gene was better suited for group-specific identification of parasitoids, but did not provide resolution at the species level. Our results provide a DNA sequence database for cereal aphid primary parasitoids and their associated hyperparasitoids in Central Europe, which will allow further improvement of our understanding of cereal aphid-primary parasitoid-hyperparasitoid interactions in relation to aphid biological control. [ABSTRACT FROM AUTHOR]

In trophic studies on piscivorous birds, it is vital to know which kind of dietary sample provides the information of interest and how the prey can be identified reliably and efficiently. Often, noninvasively obtained dietary samples such as regurgitated pellets, feces, and regurgitated fish samples are the preferred source of information. Fish prey has usually been identified via morphological analysis of undigested hard parts, but molecular approaches are being increasingly used for this purpose. What remains unknown, however, is which dietary sample type is best suited for molecular diet analysis and how the molecular results compare to those obtained by morphological analysis. Pellets, feces, and regurgitated fish samples of Great Cormorants ( Phalacrocorax carbo sinensis) were examined for prey using both morphological hard part analysis and molecular prey identification. The sample types and methods were compared regarding number of species detected (overall and per sample) as well as the prey species composition and its variability among individual samples. Via molecular analysis, significantly higher numbers of prey species were detected in pellets, feces, and fish samples. Of the three sample types, pellets contained the most comprehensive trophic information and could be obtained with the lowest sampling effort. Contrastingly, dietary information obtained from feces was least informative and most variable. For all sample types, the molecular approach outperformed morphological hard part identification regarding the detectable prey spectrum and prey species composition. We recommend the use of pellets in combination with molecular prey identification to study the diet of piscivorous birds. [ABSTRACT FROM AUTHOR]