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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]

The larvae of many hoverflies (Diptera: Syrphidae) are important polyphagous predators used in integrated pest management programs. Because the accurate identification of preimaginal stages by morphological characters is difficult, we have developed a multiplex PCR to identify the immature and/or adult stages of the most common syrphid species in Mediterranean vegetable crops: Episyrphus balteatus, Scaeva pyrastri, Eupeodes corollae, Meliscaeva auricollis, Sphaerophoria scripta, and Sphaerophoria rueppellii. The latter two species were amplified by the same primer pair due to the high similarity of their cytochrome oxidase subunit I sequences. Additionally, the assay included a primer pair targeting Diplazon laetatorius, a common koinobiont ichneumonid endoparasitoid of predatory syrphid larvae. The multiplex PCR assay proved to be highly specific and sensitive, and it was used to study the assemblage of hoverfly species in larval stage in two Mediterranean lettuce crops in two consecutive years. The molecular analysis revealed that Eu. corollae, Ep. balteatus, and Sph. scripta/Sph. rueppellii were the species present in the investigated fields. Species composition differed depending on sampling date and whether the larvae were collected on the plants or on the ground. The parasitoid D. laetatorius was not detected in any of the analyzed hoverfly larvae, suggesting low-parasitism pressure in the studied syrphid populations. The wide distribution of most of these syrphid species makes this multiplex PCR assay an ideal tool to deepen our knowledge on the ecology of these polyphagous hoverfly species in preimaginal stages and to improve the use of hoverflies to control insect pests. [ABSTRACT FROM AUTHOR]

Abstract: Food webs in agricultural systems are complex and trophic linkages are difficult to track using conventional methodologies. Here, we review three alternative approaches that allow empirical assessment of feeding interactions: DNA-based techniques, and stable isotope and fatty acid analyses. DNA-based methods, namely multiplex PCR and next-generation sequencing, allow identification of food types and host–parasitoid linkages, resulting in taxonomically highly resolved feeding networks. Stable isotopes and fatty acids reflect the assimilation of broader categories of resources, as metabolised into the consumers’ tissue, together with the associated energy and nutrient fluxes in the food web. We discuss the strengths of the approaches but also highlight their limitations, providing practical advice on which technique is best suited to answer specific questions in examining food web interactions in agroecosystems. Future refinements of these techniques, especially when used in combination, could herald a new era in agricultural food web ecology, enabling management and environmental impact to be placed in the mechanistic context of trophic networks. [Copyright &y& Elsevier]

DNA-based gut content analysis has become an important tool for unravelling feeding interactions in invertebrate communities under natural conditions. It usually implies killing of the consumer and extracting the DNA from its food, using either the whole animal or its dissected gut. This post-mortem approach, however, is not suitable for investigating the diet of rare or protected species and also prohibits tracking individual dietary preferences as each consumer can provide trophic information only once. Moreover, removing large numbers of consumers from a habitat for analysis might critically change population densities and affect species interactions. Here, we present DNA-based analysis of invertebrate regurgitates, a novel approach to overcome these limitations. Conducting feeding experiments where adult Poecilus cupreus (Coleoptera: Carabidae) were fed with larvae of Amphimallon solstitiale (Coleoptera: Scarabaeidae), we show that detection success in regurgitates compared to samples prepared from whole beetles was similar or significantly enhanced for small/medium and large prey DNA fragments, respectively. Prey DNA detection success remained high in regurgitates stored in ethanol for 21 months at room temperature prior to DNA extraction. We conclude that in those invertebrates where regurgitates can be obtained, examination of food DNA in regurgitates offers many advantages over conventional post-mortem gut content analysis. [ABSTRACT FROM AUTHOR]

Generalist predators such as carabid and cantharid beetles form an important component within natural enemy communities in arable land. Usually, predator-prey interactions are examined during the vegetation period, largely ignoring food web interactions occurring in the cold season. This is, however, when the larval stages of many polyphagous beetles develop whose survival critically depends on the availability of suitable prey. In this study, we examined intra- and extraguild feeding links in larval Cantharis spp. (Coleoptera: Cantharidae) and Nebria brevicollis (Coleoptera: Carabidae), both abundant cold-adapted invertebrate predators in European arable land. As these immature beetles are fluid feeders, which impedes a microscopic analysis of their gut content, multiplex polymerase chain reaction assays were developed to examine trophic linkages in the field. Collembolan DNA was detected in 49% and 54% of cantharid and carabid larvae, respectively. Earthworms were consumed by 34% of cantharid and 24% of carabid larvae. Significant differences in lumbricid and collembolan prey detection rates occurred between sampling dates in Cantharis spp. and N. brevicollis larvae, respectively, suggesting that these predators utilized different feeding strategies. In both predator taxa, however, only few individuals (0·2-1%) tested positive for DNA of intraguild prey, indicating that predator-predator trophic interactions were scarce in this community. Synthesis and applications. We present conclusive evidence that cold-adapted predatory beetle larvae are strongly linked to the detrital food chain by feeding on collembolans and earthworms. By improving the habitat conditions for detritivores in arable land by mulching, compost applications, or provision of plant cover during winter, their densities can be increased easily. Applying these measures year round will retain and sustain predatory beetles during their whole life cycle in arable land. Ultimately, we expect that these measures will enhance the ability of polyphagous beetle predators to provide their fundamental ecosystem service as regulators of agricultural pests. [ABSTRACT FROM AUTHOR]

This analysis focuses on estimation difficulties pollsters had in the primaries in 2008 in light of recent trends in improved polling accuracy in general elections. We consider the series of polls that were conducted in New Hampshire and other states holding primaries, looking at how the dynamics of the primary contest affected polling accuracy in those contests. The data come from published state-level results of public pollsters from the week preceding each primary or caucus for which polls were conducted; all told, we used 258 polls in thirty-six different Democratic events and 219 polls in twenty-six Republican events. The results show that the winner's vote share almost always exceeded the poll share while the race remained competitive, particularly early on in the nomination process. In an unusual perspective made possible by the length of the contest on the Democratic side in particular, this could be observed through most of the primaries; it was not the case in the Republican events after John McCain became the presumptive nominee. The analysis shows there are contextual factors at work that can affect the quality of the estimates that public pollsters make. Measures of momentum and viability affect the estimates differently early in the process compared to later, and there are special factors associated with the insurgent candidacy of Barack Obama that may also have affected the accuracy of the polls. We model these factors, investigate their explanatory power, and discuss the implications for pollsters in future primary sequences. [ABSTRACT FROM PUBLISHER]

1. Polyphagous predators, such as spiders and beetles, perform a fundamental ecosystem service as regulators of agricultural pests, particularly aphids. They are most effective when they colonize the crop before the pest has reached its exponential growth phase. However, this is also when predators find themselves in a state of near-starvation. 2. Predator numbers can be enhanced by applications of different types of organic matter, but the mechanism is not clearly understood. One hypothesis is that compost applied to the field may introduce a new detrital food chain to maintain predators until the pest arrives, but this may also be detrimental to effective pest control, fostering a surplus of alternative prey and causing a switch away from the pest. To elucidate these possible outcomes, we report on the use of within-field compost applications on aphids and their predators, presenting 4 years of field-scale manipulations. 3. We found both direct and indirect links between compost, aphids and predators. In years when compost-treated plots had significantly higher numbers of predators, aphids were in significantly lower numbers than in plots without compost. Conversely, when there was a lack of response by predators, aphid numbers showed similar trends in all treatments. 4. In all years, alternative prey responded strongly to compost application and did not fluctuate at the level shown by predators, suggesting that these two prey groups were decoupled. Instead, the predicted positive feedback of compost on predators numbers was either weak or absent. 5. Synthesis and applications. The effect of compost on aphids clearly requires further practical refinement if it is to provide constant pest suppression, making it difficult to provide specific management recommendations at this stage. In the short term, compost application may not always confer immediate benefits in terms of pest control alone but this must be set against other better known benefits (moisture retention, nutrients). In the long term, experiments measuring the full trophic pathway are needed to unravel the effects of organic matter type, application time and the siting of compost relative to the crop in order to optimise pest suppression potential. [ABSTRACT FROM AUTHOR]

Abstract: To understand soil food webs, empirically generated data on the trophic connections and the feeding ecology of the major below-ground animal taxa are needed. Here we used stable isotope analysis to assess the trophic ecology of wireworms, the larvae of click beetles, in Central European arable land. Wireworms are amongst the major soil macroinvertebrates and are of practical importance in arable soils. Besides feeding on crops, they are thought to feed on weeds, soil organic matter (SOM), and even animal prey, but their feeding ecology is poorly studied under natural conditions. Elaterid larvae and their putative feeding substrates—plant roots, SOM, and litter—were sampled at 17 locations in Austria, Germany, and Italy and their isotope ratios of carbon (12C/13C) and nitrogen (14N/15N) measured to determine the wireworms’ trophic level, the importance of SOM and weeds within the diet of Agriotes larvae, as well as the individual diet variation in Agriotes obscurus larvae. δ 15N signatures suggested that Agriotes larvae are predominately herbivorous, whereas the other wireworm species primarily fed on animal prey. In contrast to SOM, weeds were readily eaten by Agriotes larvae: their dietary contribution ranged between 28% and 67% in weedy maize fields. Most A. obscurus larvae fed on a mixed diet of weeds and maize, although ∼15% of the larvae fed primarily on one of the two food sources only. δ 15N signatures indicated that ∼10% of the “herbivorous”A. obscurus larvae fed primarily on animal prey, revealing high intraspecific trophic plasticity in these soil insects. Wireworm feeding behaviour is apparently complex at the individual level: the population consists of types A and B generalists, a phenomenon which needs further assessment. [Copyright &y& Elsevier]

Abstract: Carbon and nitrogen isotope ratios in consumer tissues can be used to analyse the diet and trophic level of soil animals. However, life history traits may significantly influence stable isotope patterns. We evaluated in a series of experiments how stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) at natural abundance can be used to study the diet and trophic position of long-lived macro-invertebrates, elaterid larvae, which are major below-ground herbivores. Small, but significant differences in δ 13C signatures were found between the larvaes’ anterior and posterior body segments, whereas exuvia reflected the body''s overall isotopic composition. The species-specific trophic shift (±SE) in δ 15N for Agriotes obscurus and Agriotes sputator (1.62±0.24‰ and 1.08±0.27‰, respectively) was significantly lower than “mean enrichment estimates” reported in the literature, showing the limited applicability of such generalised estimates in studies of invertebrate trophic ecology. To avoid false-positive assignments to two trophic levels due to variation in δ 15N values, a minimum sample size of three and five individuals for A. obscurus and A. sputator, respectively, was needed to reduce this risk to below α=5%. Keeping elaterid larvae for up to 128 days without food did not affect their isotopic signatures, in contrast to previous studies on starving animals. Switching wireworms to isotopically different diets induced changes in their isotopic signatures within 2 weeks. Changes, however, were significant only when the isotopic difference between diets was large. We conclude that experimental studies evaluating how specific life history traits affect stable isotope signatures in consumers have to precede any interpretation of stable isotope data gathered in the field. [Copyright &y& Elsevier]

Abstract: The use of diagnostic polymerase chain reaction (PCR) is a valuable approach to study host–parasitoid interactions. It circumvents problems inherent to rearing parasitoids from field-collected hosts or host dissection. Here, we present a PCR-based detection method for Diadegma semiclausum, Cotesia glomerata, and Cotesia rubecula, which are key-parasitoids of the three lepidopteran cabbage pests Plutella xylostella, Pieris brassicae, and Pieris rapae, respectively. Primer pairs for the three parasitoid species and Pl. xylostella were developed: they were used either separately in singleplex PCR or combined in multiplex PCR to (1) screen simultaneously for the two Cotesia species or to (2) detect the parasitoid D. semiclausum and identify its host Pl. xylostella in one PCR. The new idea to simultaneously identify parasitoid and host by molecular markers is useful when the host, in our case early-instar larvae of Pl. xylostella, is morphologically difficult to distinguish from other host species also occurring in the same habitat. Concentration–response trials revealed comparable detection sensitivity of singleplex and multiplex PCR, with detection limits ranging from 0.03 to 2.2pg of parasitoid DNA/μl PCR. Furthermore, the different developmental time of immature D. semiclausum and C. glomerata did not influence parasitoid detection success in either assay type. Based on multiplex PCR screening of field-collected caterpillars, we found in Pl. xylostella, P. brassicae, and P. rapae parasitism rates of 33.4% by D. semiclausum, 52% by C. glomerata, and 53.4% by C. rubecula, respectively. [Copyright &y& Elsevier]

Abstract: Polymerase chain reaction (PCR) can be used to detect prey within the gut contents of predators and allows specific trophic interactions to be studied among soil-dwelling invertebrates which cannot be examined by other approaches. PCR-inhibitory substances, however, are commonly found in DNA prepared from soil organisms or from biological material contaminated with soil. This can lead to false-negative results and the risk of not detecting trophic connections or of underestimating predation rates in field studies. In the present study, we developed mitochondrial DNA markers to detect Amphimallon solstitiale (Coleoptera: Scarabaeidae) in the gut contents of invertebrate predators. Larvae of A. solstitiale can cause serious damage in grasslands, field crops, and forests by feeding on roots. Adequate methodologies to study predation on these pests are lacking, and their invertebrate predator guild is, therefore, barely known. To test the new molecular markers for prey detection, larvae and eggs of A. solstitiale were fed to Poecilus versicolor larvae (Coleoptera: Carabidae), which are abundant below-ground predators in grassland ecosystems. Unfortunately, even when specific DNA extraction and purification methods were used, DNA extracts from predators were of poor quality and not amplifiable by PCR; this yielded false-negative results and a dramatically lower prey-detection rate. We overcame PCR-inhibition by applying ⩾1.28μgμl−1 bovine serum albumin to the PCR reaction mix. This enabled us to detect A. solstitiale DNA within fed carabid larvae up to 48 and 40h post-feeding for 127 and 463bp sized DNA fragments, respectively. When single A. solstitiale eggs were consumed by the carabid larvae, predation could be verified in 100% of the predators within the first 8h of digestion; some carabid larvae even tested positive 32h after feeding. Moreover, by multiplexing primers targeting both prey and predator, we were able to simultaneously screen for prey consumption and check for co-purified PCR inhibitors. Sensitivity in prey detection was not reduced compared to singleplex PCR. We recommend the multiplex approach because it considerably reduces time and costs compared to singleplex assays. We also show that multiplex PCR not only detects specific prey, but also can identify the predator itself. This allows the identification of taxa which are difficult or not identifiable based on morphological characters, such as soil-dwelling predatory beetle larvae. [Copyright &y& Elsevier]

Abstract: Generalist predators play a key role in agriculturally and environmentally sustainable systems of pest control. A detailed knowledge on their ecology, however, is needed to improve management practices to maximize their service of pest control. The present study examines the habitat use and activity patterns of larval and adult Cantharis beetles that are abundant predators in arable land. Laboratory experiments revealed that sixth instar larvae of Cantharis fusca and Cantharis livida significantly preferred high relative humidity levels of 85–90% to lower ones. This can explain their preference for meadows over fields due to the more favorable microclimatic conditions in the former habitats. Surface activity of sixth instar Cantharis larvae during autumn, winter and early spring occurred at soil temperatures above 0 °C. However, no correlation between surface activity and soil temperature, air temperature or relative humidity was found above 0 °C. Catches of sixth instar Cantharis larvae within fenced pitfall traps were higher in a meadow (Mean±S.D.; 13.8±7.63 individuals m−2) than in a field (4.60±2.89 individuals m−2). Mark-recapture density estimations for sixth instar larvae indicated mean densities of 25.9±5.63 (field) and 42.8±16.0 individuals m−2 (meadow). The same pattern was found for adult emergence rates in the field (0.17±0.39 adults m−2) and meadow (1.83±1.17 adults m−2) as well as for adult densities in the vegetation (field 4.89±3.62 adults 60 m−2; meadow 12.5±11.2 adults 60 m−2). It is concluded that especially in winter elements that provide plant cover should be incorporated in arable fields to enhance larval cantharid population densities and to attract them from their prime grassland habitats into arable sites. [Copyright &y& Elsevier]

The 2004 presidential election campaign provided a venue for a wide variety of polling, and it was not without its controversies. In the end, the final estimates of the preelection polls, the bread and butter of the polling industry, were very good at suggesting it would be a close race, with Bush the likely winner. In historical perspective, the overall performance was above average for the period since 1956. Issues raised in the media leading up to the end of the campaign and the final estimates, however, created some controversy, especially about the likely voter methodology used by different organizations. There were also some anomalies at the end of the campaign as some firms and collaborators ended up producing different estimates of the outcome depending on likely voter definitions or the mode of data collection. [ABSTRACT FROM AUTHOR]

Abstract: Non-target effects of the entomopathogenic fungus Beauveria brongniartii (Ascomycota: Clavicipitaceae) on Poecilus versicolor (Coleoptera: Carabidae), a potential antagonist of the European cockchafer Melolontha melolontha, were studied with three different B. brongniartii formulations, Melocont-Pilzgerste, Melocont-WP, and Melocont-WG. All formulations induced significantly enhanced mortality rates among third instar larvae of the target pest M. melolontha, but no negative effects on the non-target organism were observed. However, small but statistically significant differences were observed for P. versicolor when the fungus was applied: larval development time from first instar to adult stage was decreased by 6.8% (4 days) and the biomass of teneral beetles increased by 8.4% (3.7mg) compared to that of the control groups. Additionally, third instar larvae of P. versicolor were exposed to B. brongniartii-infected M. melolontha cadavers to either consume material from the mycosed carcasses or come in contact with them while searching for food. Again, no significant negative effects on P. versicolor could be observed. The results suggest that under field conditions B. brongniartii would be a negligible risk for P. versicolor. [Copyright &y& Elsevier]

White grubs (larvae of Coleoptera: Scarabaeidae) are abundant in below-ground systems and can cause considerable damage to a wide variety of crops by feeding on roots. White grub populations may be controlled by natural enemies, but the predator guild of the European species is barely known. Trophic interactions within soil food webs are difficult to study with conventional methods. Therefore, a polymerase chain reaction (PCR)-based approach was developed to investigate, for the first time, a soil insect predator-prey system. Can, however, highly sensitive detection methods identify carrion prey in predators, as has been shown for fresh prey? FreshMelolontha melolontha(L.) larvae and 1- to 9-day-old carcasses were presented toPoecilus versicolorSturm larvae. Mitochondrial cytochrome oxidase subunit I fragments of the prey, 175, 327 and 387 bp long, were detectable in 50% of the predators 32 h after feeding. Detectability decreased to 18% when a 585 bp sequence was amplified. Meal size and digestion capacity of individual predators had no influence on prey detection. Although prey consumption was negatively correlated with cadaver age, carrion prey could be detected by PCR as efficiently as fresh prey irrespective of carrion age. This is the first proof that PCR-based techniques are highly efficient and sensitive, both in fresh and carrion prey detection. Thus, if active predation has to be distinguished from scavenging, then additional approaches are needed to interpret the picture of prey choice derived by highly sensitive detection methods. [ABSTRACT FROM AUTHOR]

The arthropod predator community of an organically cultivated 0.3 ha field was sampled by pitfall trapping during 1 year and analysed for small-scale spatial distribution patterns and their seasonal variation. Due to the small size of the study site, most of the investigated species were able to colonise the whole field. Ordination analyses revealed significant differences in community composition (i) between field centre and margin in summer and (ii) between field parts adjacent to meadows or conventionally cultivated arable land in all seasons. Results changed considerably if only adult carabids or spiders were used instead of the whole predator community.During summer the following significant differences in community parameters were found: (i) total catches in the centre were nearly twice as high as near the margin, (ii) predator richness did not differ between centre and margin while significantly more species were found close to meadows and (iii) evenness and heterogeneity were significantly higher at the margin versus the centre.The arthropod predator community even of a small field site showed distinct spatial distribution patterns with seasonal changes. Selecting appropriate taxonomic groups is crucial for the outcome of such studies and should be tailored to the aim of the investigation. [Copyright &y& Elsevier]

Most of the studies of voter behavior have dealt with voter turnout, but few have looked at other aspects of voting behavior that could be linked to balloting method. A reasonable amount of information has now accumulated about the impact of the shift from polling place elections to voting by mail on turnout, rolloff, drop-off, differences in voting for partisan offices and referenda, and differences in straight-ticket voting. This article analyzes recent time series of voting data in Oregon to assess the impact of the shift in voting method on these issues. The analysis includes data at the state, county, precinct, and individual levels, including individual ballots. The results suggest new criteria for evaluating shifts from one voting method to another that may be applied to other electoral reforms, such as those that will result from the Help America Vote Act. [ABSTRACT FROM AUTHOR]

The dispersal ability, home range size and habitat preference of sixth instar larvae of the widespread cantharid species Cantharis fusca (L.) and C. livida (L.) were studied in a mark–recapture experiment in a meadow–field (winter grain) area between autumn and spring in 1999/2000. The main results and conclusions were: (i) The mean dispersal velocity of C. fusca/C. livida larvae was 1.4/1.6 m d–1 with a maximum of 3.2/2.3 m d–1. The larvae were able to disperse more than 100 m during their larval development, demonstrating that larvae and not only adults contribute to spreading. (ii) The average home range area of seven C. fusca individuals was 12.9 m2 (minimum 8 m2/maximum 19 m2). The low number of multiple recaptures and the large distances larvae can cover indicate that the real home range size was underestimated. (iii) C. fusca larvae significantly preferred the meadow area compared to the bare ground of the field. This can be explained by the meadow''s higher plant cover and humidity C. livida specimens that were released one month later and recaptured only in low numbers showed no such preference. (iv) Due to the high dispersal ability of soldier beetle larvae, immigration from meadows and grass bulks of boundary strips into the crop margins and inner field areas is possible; it can be augmented by creating constant plant cover, e.g. through winter grain or cover crops. [Copyright &y& Elsevier]

This project seeks theoretical and methodological advances in the study of political advertising effects during election campaigns. On the theoretical side, we hypothesize that racial cues embedded in standard political advertising appeals, involving taxation and government spending, boost opinion constraint by priming global political ideology. On the methodological side, we replicate a lab experiment in face-toface interviews with a probability sample of a large metropolitan area. Results suggest that subtle race cues do increase issue constraint for "racialized" issues such as welfare, affirmative action, crime policy, and the overall size of government. Constraint of opinions about issues less relevant to race, such as abortion, spending on public schools, universal health care, and raising the minimum wage, does not increase as a result of exposure to racial cues. Global ideology is powerfully primed by implicit racial cues embedded in typical political appeals. Finally, though demographic differences in the samples moderate some effects, the general pattern is highly consistent across the two research settings. Implications for strategic communication during campaigns, group centrism in American elections, and the benefits of methodological pluralism in the study of media effects are discussed. [ABSTRACT FROM AUTHOR]

This article examines issues involving the national preelection polls in the U.S. in 2000, including the subset of tracking efforts at the end of the campaign, the state-level election polls and some aggregate data models. The 2000 election campaign saw more polls and more reporting of polls than ever before. The final outcome of the election was very close, decided by .5 percent of the popular vote. Presidential candidate Al Gore won the popular vote, but George W. Bush became the forty-third president of the U.S. when he was awarded Florida's 25 electoral votes on December 12, 2000 by a U.S. Supreme Court decision. There were 18 organizations that produced a final estimate of the outcome of the election, compared to nine in 1996 and six in 1992. This set of organizations includes those producing final estimates based on data collected as early as October 24, 2000, as well as by using information from some organizations that collected data via the Internet. According to statistical methods used to assess poll accuracy in the past, most of the pollsters did an efficient job in producing their final estimates of the election outcome. One feature that distinguished the final 2000 polls was an increase in their sample sizes compared to previous years.

Many claims are being made about the advantages of conducting surveys on the Web. However, there has been little research on the effects of format or design on the levels of unit and item response or on data quality. In a study conducted at the University of Michigan, a number of experiments were added to a survey of the student population to assess the impact of design features on resulting data quality. A sample of 1,602 students was sent an e-mail invitation to participate in a Web survey on attitudes toward affirmative action. Three experiments on design approaches were added to the survey application. One experiment varied whether respondents were reminded of their progress through the instrument. In a second experiment, one version presented several related items on one screen, while the other version presented one question per screen. In a third experiment, for one series of questions a random half of the sample clicked radio buttons to indicate their answers, while the other haft entered a numeric response in a box. This article discusses the overall implementation and outcome of the survey, and it describes the results of the imbedded design experiments. [ABSTRACT FROM AUTHOR]

The article relates the concern about polling in the public's interest. Polling has become ubiquitous for a variety of reasons. Probably the most important is that the cost of data collection has declined and anyone can get into the game for a marginal investment. A second important factor was a set of business and editorial decisions by news organizations that they could produce their own data rather than accept the preprinted results from major national polling firms. By exercising independent judgments about newsworthy topics, writing their own questions, deciding on their field periods and conducting their own analyses and writing them up, these organizations satisfied a long-standing institutional desire for independent fact gathering and interpretation. Eventually, these decisions carried over to the development of the networks' exit poll operations and then to the consolidation of these efforts. The proliferation of polls presents a problem for citizens who are at one and the same time generally interested in public opinion and what their fellow citizens think and yet have almost no ability to differentiate good data from bad, useful information from useless or to understand why two polls might produce seemingly different results.

• 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]

The article discusses experimental results from a revised question wording that has successfully reduced the levels of overreport and improved the accuracy of self-reports of voting behavior in the U.S. Often survey measurement errors results in overreporting. Two different possible explanations of overreporting have been put forward. One considers overreporting the result of social desirability, in which case the respondents claim that they voted, when they clearly remember that they did not vote, for reasons of self-presentation. The other explanation is the result of memory failure, in which respondents are seen to forward telescope a remote voting experience when reporting that they voted in the most recent election. According to this study, overreporting results from a combined influence of these two reasons. A revised question wording, which encouraged respondents to scrutinize several possible contributions to response error limited combinations of these processes and question wordings based on them, is reported to have successfully reduced the levels of overreport and improved the accuracy of self-reports of voting behavior.

The article discusses the exit poll of 1989 Virginia gubernatorial election. In the contest, Democrat L. Douglas Wilder narrowly defeated his Republican opponent, J. Marshall Coleman, winning by two-tenths of one percentage point. Yet an experienced research firm, Mason-Dixon Opinion Research (MDOR), conducted an exit poll for several television stations in Virginia and Washington, DC, and estimated an easy Wilder victory by a 10-percentage-point margin. This 5-percentage-point discrepancy was outside the bounds of normal sampling error. The 1989 MDOR exit poll raised several interesting methodological questions and prompted a variety of speculations about what might have caused the error. The article points out that the number of interviews in the MDOR poll was not equally distributed across the 10 congressional districts, nor was registrants or actual voters. The results suggest that the estimates from the 1989 Virginia exit poll stemmed from the use of face-to-face interviews conducted in person than from a problematic sample of precincts by congressional district.

One interpretation for the common survey finding that the background characteristics of vote overreporters resemble those of actual voters is that misreporters usually vote. This hypothesis-that misreporters regularly voted in earlier elections-is tested with data from the 1972-74-76 Michigan Election Panel. It receives no support: the 1972 and 1974 validated turnout of the 1976 misreporters was very low. Moreover, misreporting was a fairly stable respondent characteristic: misreporting about an election in one interview was correlated with misreporting about the remaining elections in each of the other two interviews. A comparison of regressions predicting turnout using the validated reports versus the self-reports shows that the respondent errors can distort conclusions about the correlates of voting. For example, controlling for three other variables, education was related to self-reported voting but not to validated voting. Here, as well as in surveys of other socially desirable or undesirable issues, respondent self-reports may bias survey data in favor of commonsense models of the world. [ABSTRACT FROM AUTHOR]

This article reports on the annual membership meeting of the American Association for Public Opinion Research (AAPOR), held on My 19, 1989, in Lancaster, Pennsylvania. Retiring president Phil Meyer presided the meeting. President Meyer called the meeting to order. He announced that Chuck Cowan has expressed his intention to step down as Site Selection Committee chair. He introduced Karen Goldenberg, who has been selected as Associate Site Selection Committee chair by the Executive Council. Meyer reiterated the Council's interest in hearing from volunteers to serve on the committee. He then turned to various Council members for reports of their committees' activities during the past year. In reviewing budgetary matters discussed during the past year, three items were noted. A review had been undertaken of the relative costs of supplying services to foreign members: while the dues structure was not covering the full cost of all these memberships, the Council agreed to continue to provide a small net subsidy to this class of members. Second, a decision was made to invest nonworking AAPOR cash balances in conservative bond funds in order to obtain a higher rate of return than is available in checking accounts. Third, slight revisions will be made to current accounting procedures to reflect better the allocation of funds to projects that continue across multiple fiscal years, such as the allocations to cover the production and printing of the AAPOR history.

This article reports on the results of a series of experiments designed to improve response rates for telephone surveys. In three surveys telephone households were selected using both standard random digit dialing (RDD) techniques and lists of telephone numbers purchased from a commercial firm. In the RDD portions of the samples "cold contact" interviewing methods were used; in the list frame portions advance letters were mailed, and the listed household name was used in the introduction. Experiments were designed to test the effects on response rates of the advance letters and use of the listed household name as a means of establishing rapport. The advance letters increased response rates, but no difference could be attributed to the use of names. The mixture of RDD and list sampling techniques is also used to evaluate the effects of relative response rates on substantive findings. The cost consequences of these dual frame designs are assessed along a number of dimensions, and the cost and error components of these designs are discussed. [ABSTRACT FROM AUTHOR]

Different techniques for respondent selection can affect data quality. These differences can result in variations in the distribution of partisans in preelection surveys, which in turn can have an effect on the distribution of candidate preference. Persistence in trying to interview designated respondents in telephone households increased the number of Republicans in a 1984 sample, and therefore Reagan's margin over Mondale. Such differences in interviewing techniques might account for some of the variations in national preelection estimates of the outcome of the presidential election, and they suggest that caution be used in comparing marginals for party identification from different surveys employing different respondent selection techniques. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the special edition of the journal on topics including race and voting behavior in the U.S. presidential elections of 2008 and 2012, political party identification and voting behavior in the U.S., and estimating election outcomes.

The author reflects on the points of Kurt Lang in his work on the function of public opinion polls. He views on the issues which were not expressed but applicable to the discussion engendered by Lang. Also, the author examines the representativeness of the expressions of public opinion, and its representation in policy or legislation.

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]