Rapid screening of invertebrate predators for multiple prey DNA targets

Exploring the use of metabarcoding to reveal eukaryotic associations with mononchids nematodes

Nematodes play a vital ecological role in soil and marine ecosystems, but there is limited information about their dietary diversity and feeding habits. Due to methodological challenges, the available information is based on inference rather than confirmed observations. The lack of correct dietary requirements also hampers rearing experiments. To achieve insight into the prey of mononchid nematodes, this study employed high-throughput Illumina paired-end sequencing using universal eukaryotic species 18S primers on 10 pooled mononchid nematode species, namely Mylonchulus brachyuris, M. brevicaudatus, Mylonchulus sp., Clarkus parvus, Prionchulus sp. M. hawaiiensis, M. sigmaturellus, M. vulvapapillatus, Anatonchus sp. and Miconchus sp. The results indicate that mononchids are associated with a remarkable diversity of eukaryotes, including fungi, algae, and protists. While the metabarcoding approach, first introduced here for mononchids, proved to be a simple and rapid method, it has several limitations and crucial methodological challenges that should be addressed in future studies. Ultimately, such methods should be able to evaluate the dietary complexity of nematodes and provide a valuable avenue for unraveling the dietary requirements of previously unculturable nematodes. This can contribute to the methodology of understanding their feeding habits and contributions to ecosystem dynamics.

DNA High-Throughput Sequencing for Arthropod Gut Content Analysis to Evaluate Effectiveness and Safety of Biological Control Agents

The search for effective biological control agents without harmful non-target effects has been constrained by the use of impractical (field direct observation) or imprecise (cage experiments) methods. While advances in the DNA sequencing methods, more specifically the development of high-throughput sequencing (HTS), have been quickly incorporated in biodiversity surveys, they have been slow to be adopted to determine arthropod prey range, predation rate and food web structure, and critical information to evaluate the effectiveness and safety of a biological control agent candidate. The lack of knowledge on how HTS methods could be applied by ecological entomologists constitutes part of the problem, although the lack of expertise and the high cost of the analysis also are important limiting factors. In this review, we describe how the latest HTS methods of metabarcoding and Lazaro, a method to identify prey by mapping unassembled shotgun reads, can serve biological control research, showing both their power and limitations. We explain how they work to determine prey range and also how their data can be used to estimate predation rates and subsequently be translated into food webs of natural enemy and prey populations helping to elucidate their role in the community. We present a brief history of prey detection through molecular gut content analysis and also the attempts to develop a more precise formula to estimate predation rates, a problem that still remains. We focused on arthropods in agricultural ecosystems, but most of what is covered here can be applied to natural systems and non-arthropod biological control candidates as well.

DNA metabarcoding of gut contents reveals key habitat and seasonal drivers of trophic networks involving generalist predators in agricultural landscapes

BACKGROUND

Understanding the networks of trophic interactions into which generalist predators are embedded is key to assessing their ecological role of in trophic networks and the biological control services they provide. The advent of affordable DNA metabarcoding approaches greatly facilitates quantitative understanding of trophic networks and their response to environmental drivers. Here, we examine how key environmental gradients interact to shape predation by Lycosidae in highly dynamic vegetable growing systems in China.

RESULTS

For the sampled Lycosidae, crop identity, pesticide use and seasons shape the abundance of prey detected in spider guts. For the taxonomic richness of prey, local- and landscape-scale factors gradients were more influential. Multivariate ordinations confirm that these crop-abundant spiders dynamically adjust their diet to reflect environmental constraints and seasonal availability to prey.

CONCLUSION

Plasticity in diet composition is likely to account for the persistence of spiders in relatively ephemeral brassica crops. Our findings provide further insights into the optimization of habitat management for predator-based biological control practices. © 2022 Society of Chemical Industry.

Connectivity dynamics in Irish mudflats between microorganisms including Vibrio spp., common cockles Cerastoderma edule, and shorebirds

Shellfish, including the key species the common cockle Cerastoderma edule, living and feeding in waters contaminated by infectious agents can accumulate them within their tissues. It is unknown if microbial pathogens and microparasites can subsequently be transmitted via concomitant predation to their consumers, including shorebirds. The objective of this study was to assess if pathogens associated with C. edule could be detected seasonally in the faeces of shorebirds that feed on C. edule and in the physical environment (sediment) in which C. edule reside, along the Irish and Celtic Seas. Two potentially pathogenic global groups, Vibrio and Haplosporidia, were detected in C. edule. Although Haplosporidia were not detected in the bird faeces nor in the sediment, identical strains of Vibrio splendidus were detected in C. edule and bird faecal samples at sites where the oystercatcher Haematopus ostralegus and other waders were observed to be feeding on cockles. Vibrio spp. prevalence was seasonal and increased in C. edule and bird faecal samples during the warmer months, possibly due to higher seawater temperatures that promote the replication of this bacteria. The sediment samples showed an overall higher prevalence of Vibrio spp. than the bird faecal and C. edule samples, and its detection remained consistently high through the sites and throughout the seasons, which further supports the role of the sediment as a Vibrio reservoir. Our findings shed light on the fact that not all pathogen groups are transmitted from prey to predator via feeding but bacteria such as V. splendidus can be. As most of the wading birds observed in this study are migratory, the results also indicate the potential for this bacterium to be dispersed over greater geographic distances, which will have consequences for areas where it may be introduced.

Multiple species-specific molecular markers using nanofluidic array as a tool to detect prey DNA from carnivore scats

Large carnivore feeding ecology plays a crucial role for management and conservation for predators and their prey. One of the keys to this kind of research is to identify the species composition in the predator diet, for example, prey determination from scat content. DNA-based methods applied to detect prey in predators' scats are viable alternatives to traditional macroscopic approaches, showing an increased reliability and higher prey detection rate. Here, we developed a molecular method for prey species identification in wolf (Canis lupus) scats using multiple species-specific marker loci on the cytochrome b gene for 18 target species. The final panel consisted of 80 assays, with a minimum of four markers per target species, and that amplified specifically when using a high-throughput Nanofluidic array technology (Fluidigm Inc.). As a practical example, we applied the method to identify target prey species DNA in 80 wolf scats collected in Sweden. Depending on the number of amplifying markers required to obtain a positive species call in a scat, the success in determining at least one prey species from the scats ranged from 44% to 92%. Although we highlight the need to evaluate the optimal number of markers for sensitive target species detection, the developed method is a fast and cost-efficient tool for prey identification in wolf scats and it also has the potential to be further developed and applied to other areas and large carnivores as well.

Molecular gut content analysis indicates the inter- and intra-guild predation patterns of spiders in conventionally managed vegetable fields

Inter- and intra-guild interactions are important in the coexistence of predators and their prey, especially in highly disturbed vegetable cropping systems with sporadic food resources. Assessing the dietary range of a predator taxon characterized by diverse foraging behavior using conventional approaches, such as visual observation and conventional molecular approaches for prey detection, has serious logistical problems. In this study, we assessed the prey compositions and compare the dietary spectrum of a functionally diverge group of predators-spiders-to characterize their trophic interactions and assess biological control potential in Brassica vegetable fields. We used high-throughput sequencing (HTS) and biotic interaction networks to precisely annotate the predation spectrum and highlight the predator-predator and predator-prey interactions. The prey taxa in the gut of all spider families were mainly enriched with insects (including dipterans, coleopterans, orthopterans, hemipterans, and lepidopterans) with lower proportions of arachnids (such as Araneae) along with a wide range of other prey factions. Despite the generalist foraging behavior of spiders, the community structure analysis and interaction networks highlighted the overrepresentation of particular prey taxa in the gut of each spider family, as well as showing the extent of interfamily predation by spiders. Identifying the diverse trophic niche proportions underpins the importance of spiders as predators of pests in highly disturbed agroecosystems. More specifically, combining HTS with advanced ecological community analysis reveals the preferences and biological control potential of particular spider taxa (such as Salticidae against lepidopterans and Pisauridae against dipterans), and so provides a valuable evidence base for targeted conservation biological control efforts in complex trophic networks.

A Literature Review of Biological and Bio-Rational Control Strategies for Slugs: Current Research and Future Prospects

Simple Summary

Terrestrial molluscs (slugs and snails) pose a major threat to agriculture, causing severe yield losses in a wide range of crops worldwide. The limited number of chemical molluscicides on the market, along with their negative impact on nontarget organisms and the environment, make mollusc control a real concern for growers and farmers. Therefore, the exploration of alternative, effective and eco-friendly control measures has become a dire need. This study focuses on slugs, as opposed to snails, and reviews the literature on three natural enemies of slugs, namely nematodes, carabid beetles and marsh flies, along with various natural products with slug control potential (for example, essential oils), and this study contributes to providing a comprehensive understanding of how slugs can be better controlled by using nonchemical measures. In doing so, this study also draws attention to the limitations of current research and discusses some important future research avenues in order to develop effective nonchemical slug control measures.

Abstract

Terrestrial gastropod molluscs (slugs and snails) (Mollusca: Gastropoda) cause significant crop damage around the world. There is no formal approach for differentiating between slugs and snails; however, an organism is usually considered a slug when there is no external shell, or when the shell is small in comparison to the body, and a snail when there is a large external shell. Although snails are an important pest of many crops, this review focuses on slug pests and their nonchemical control measures. A recent study by the UK Agriculture and Horticulture Development Board concluded that the failure to control slugs could cost the UK agriculture industry over GBP 100 million annually, with similar figures reported around the world. Whilst slugs are mostly controlled using chemical molluscicide products, some actives have come under scrutiny due to their detrimental environmental effects and impact on nontarget organisms. This has resulted in the ban of actives such as methiocarb in the UK and EU, and, more recently, the ban of metaldehyde in the UK. Therefore, there is an urgent need to find alternative and effective nontoxic solutions in the interest of global food security. In this paper, we have integrated extant literature on the three main biological control agents of slugs, namely nematodes, carabid beetles and sciomyzid flies, and various promising bio-rational slug control strategies. The review also highlights current research gaps and indicates some relevant potential future directions towards developing environmentally benign slug control solutions.

Fish as predators and prey: DNA-based assessment of their role in food webs

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.

Assessment of the Biological Control Potential of Common Carabid Beetle Species for Autumn- and Winter-Active Pests (Gastropoda, Lepidoptera, Diptera: Tipulidae) in Annual Ryegrass in Western Oregon

Simple Summary

Many studies have shown that ground beetles feed on different agricultural pests, but little is known about their species communities from US cropping systems. We assessed the biological control potential of the most common carabid beetle species in Oregon annual ryegrass grown for seed by investigating spatial and temporal overlap of the most common species with those of the most damaging autumn- and winter-active pests (slugs, caterpillars and cranefly larvae) and determined the number of field-collected specimens that had fed on the respective pests using molecular gut content analysis. Only the non-native Nebria brevicollis was abundant during pest emergence and tested positive for all three pest groups. While the other common carabid beetle species—Agonum muelleri, Calosoma cancellatum and Poecilus laetulus—were also found to have consumed pests, they were active only during spring and summer, when crop damage by pests is less critical. We also show that disk tilling did not affect any of the four common carabid beetle species and that only N. brevicollis was significantly associated with a vegetated field margin. This study contributes to expanding our knowledge on conservation biological control in a system where chemical pesticides are still the mainstay of control against invertebrate pests.

Abstract

While carabid beetles have been shown to feed on a variety of crop pests, little is known about their species assemblages in US annual ryegrass crops, where invertebrate pests, particularly slugs, lepidopteran larvae and craneflies, incur major financial costs. This study assesses the biological control potential of carabid beetles for autumn- and winter-active pests in annual ryegrass grown for seed by: (a) investigating the spatial and temporal overlap of carabids with key pests; and (b) molecular gut content analysis using qPCR. Introduced Nebria brevicollis was the only common carabid that was active during pest emergence in autumn, with 18.6% and 8.3% of N. brevicollis collected between September and October testing positive for lepidopteran and cranefly DNA, respectively, but only 1.7% testing positive for slug DNA. While pest DNA was also detected in the guts of the other common carabid species—Agonum muelleri, Calosoma cancellatum and Poecilus laetulus—these were active only during spring and summer, when crop damage by pests is less critical. None of the four carabid species was affected by disk tilling and only N. brevicollis was significantly associated with a vegetated field margin. However, as its impact on native ecosystems is unknown, we do not recommend managing for this species.

Fatty acid metabolism in an oribatid mite: de novo biosynthesis and the effect of starvation

The fatty acid (FA) composition of lipids in animals is influenced by factors such as species, life stage, availability and type of food, as well as the ability to synthesize certain FAs de novo. We investigated the effect of starvation on the neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of the oribatid mite Archegozetes longisetosus Aoki. Furthermore, we performed stable-isotope labeled precursors feeding experiments under axenic conditions to delineate de novo FA synthesis by profiling ¹³C and deuterium incorporation via single-ion monitoring. Starvation of mites resulted in a decline in the total amount of NLFAs and significantly changed the fatty acid patterns, indicating that NLFAs were metabolized selectively. Biochemical tracer experiments confirmed that oribatid mites, like other animals, can produce stearic (18:0) and oleic acid (18:1ω9) de novo. Mass spectrometric data also revealed that they appear to synthesize linoleic acid [18:2ω6,9 = (9Z,12Z)-octadeca-9,12-dienoic acid]-an ability restricted only to a few arthropod taxa, including astigmatid mites. The physiological and biosynthesis processes revealed here are crucial to understand the potential biomarker function of fatty acids-especially 18:2ω6,9-in oribatid mites and their applicability in soil animal food web studies.

Insights into aphid prey consumption by ladybirds: Optimising field sampling methods and primer design for high throughput sequencing

Elucidating the diets of insect predators is important in basic and applied ecology, such as for improving the effectiveness of conservation biological control measures to promote natural enemies of crop pests. Here, we investigated the aphid diet of two common aphid predators in Central European agroecosystems, the native Coccinella septempunctata (Linnaeus) and the invasive Harmonia axyridis (Pallas; Coleoptera: Coccinellidae) by means of high throughput sequencing (HTS). For acquiring insights into diets of mobile flying insects at landscape scale minimizing trapping bias is important, which imposes methodological challenges for HTS. We therefore assessed the suitability of three field sampling methods (sticky traps, pan traps and hand-collection) as well as new aphid primers for identifying aphid prey consumption by coccinellids through HTS. The new aphid primers facilitate identification to species level in 75% of the European aphid genera investigated. Aphid primer specificity was high in silico and in vitro but low in environmental samples with the methods used, although this could be improved in future studies. For insect trapping we conclude that sticky traps are a suitable method in terms of minimizing sampling bias, contamination risk and trapping success, but compromise on DNA-recovery rate. The aphid diets of both field-captured ladybird species were dominated by Microlophium carnosum, the common nettle aphid. Another common prey was Sitobion avenae (cereal aphid), which got more often detected in C. septempunctata compared to H. axyridis. Around one third of the recovered aphid taxa were common crop pests. We conclude that sampling methodologies need constant revision but that our improved aphid primers offer currently one of the best solutions for broad screenings of coccinellid predation on aphids.

When to use next generation sequencing or diagnostic PCR in diet analyses

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.

The effect of plant identity and mixed feeding on the detection of seed DNA in regurgitates of carabid beetles

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.

Comparing three types of dietary samples for prey DNA decay in an insect generalist predator

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.

Laboratory Protocol for Genetic Gut Content Analyses of Aquatic Macroinvertebrates Using Group-specific rDNA Primers

Analyzing food webs is essential for a better understanding of ecosystems. For example, food web interactions can undergo severe changes caused by the invasion of non-indigenous species. However, an exact identification of field predator-prey interactions is difficult in many cases. These analyses are often based on a visual evaluation of gut content or the analysis of stable isotope ratios (δ¹⁵N and δ¹³C). Such methods require comprehensive knowledge about, respectively, morphologic diversity or isotopic signature from individual prey organisms, leading to obstacles in the exact identification of prey organisms. Visual gut content analyses especially underestimate soft bodied prey organisms, because maceration, ingestion and digestion of prey organisms make identification of specific species difficult. Hence, polymerase chain reaction (PCR) based strategies, for example the use of group-specific primer sets, provide a powerful tool for the investigation of food web interactions. Here, we describe detailed protocols to investigate the gut contents of macroinvertebrate consumers from the field using group-specific primer sets for nuclear ribosomal deoxyribonucleic acid (rDNA). DNA can be extracted either from whole specimens (in the case of small taxa) or out of gut contents of specimens collected in the field. Presence and functional efficiency of the DNA templates need to be confirmed directly from the tested individual using universal primer sets targeting the respective subunit of DNA. We also demonstrate that consumed prey can be determined further down to species level via PCR with unmodified group-specific primers combined with subsequent single strand conformation polymorphism (SSCP) analyses using polyacrylamide gels. Furthermore, we show that the use of different fluorescent dyes as labels enables parallel screening for DNA fragments of different prey groups from multiple gut content samples via automated fragment analysis.

Long-term resource addition to a detrital food web yields a pattern of responses more complex than pervasive bottom-up control

Background

Theory predicts strong bottom-up control in detritus-based food webs, yet field experiments with detritus-based terrestrial systems have uncovered contradictory evidence regarding the strength and pervasiveness of bottom-up control processes. Two factors likely leading to contradictory results are experiment duration, which influences exposure to temporal variation in abiotic factors such as rainfall and affects the likelihood of detecting approach to a new equilibrium; and openness of the experimental units to immigration and emigration. To investigate the contribution of these two factors, we conducted a long-term experiment with open and fenced plots in the forest that was the site of an earlier, short-term experiment (3.5 months) with open plots (Chen & Wise, 1999) that produced evidence of strong bottom-up control for 14 taxonomic groupings of primary consumers of fungi and detritus (microbi-detritivores) and their predators.

Methods

We added artificial high-quality detritus to ten 2 × 2-m forest-floor plots at bi-weekly intervals from April through September in three consecutive years (Supplemented treatment). Ten comparable Ambient plots were controls. Half of the Supplemented and Ambient plots were enclosed by metal fencing.

Results

Arthropod community structure (based upon 18 response variables) diverged over time between Supplemented and Ambient treatments, with no effect of Fencing on the multivariate response pattern. Fencing possibly influenced only ca. 30% of the subsequent univariate analyses. Multi- and univariate analyses revealed bottom-up control during Year 1 of some, but not all, microbi-detritivores and predators. During the following two years the pattern of responses became more complex than that observed by Chen & Wise (1999). Some taxa showed consistent bottom-up control whereas others did not. Variation across years could not be explained completely by differences in rainfall because some taxa exhibited negative, not positive, responses to detrital supplementation.

Discussion

Our 3-year experiment did not confirm the conclusion of strong, pervasive bottom-up control of both microbi-detritivores and predators reported by Chen & Wise (1999). Our longer-term experiment revealed a more complex pattern of responses, a pattern much closer to the range of outcomes reported in the literature for many short-term experiments. Much of the variation in responses across studies likely reflects variation in abiotic and biotic factors and the quality of added detritus. Nevertheless, it is also possible that long-term resource enhancement can drive a community towards a new equilibrium state that differs from what would have been predicted from the initial short-term responses exhibited by primary and secondary consumers.

Predation by generalist arthropod predators on Apolygus lucorum (Hemiptera: Miridae): molecular gut-content analysis and field-cage assessment

BACKGROUND

The mirid bug Apolygus lucorum (Meyer-Dür) is a principal pest of cotton that also causes great damage to many other crops in China. A study was conducted to assess the mortality of A. lucorum from generalist arthropod predators using both molecular methods and a field-cage trial. The species-specific primer pair for the detection of A. lucorum tissues in predators was designed according to the sequences of the cytochrome oxidase subunit I (COI) gene.

RESULTS

A total of 2096 generalist predators that consisted of ladybeetles, lacewings and spiders were collected, and A. lucorum remains were detected using the designed primers. Only 1.6% of these predators contained A. lucorum DNA, with the highest positive proportion (6.1%) for Harmonia axyridis larvae. In the field-cage experiment, the daily predation rates of second-instar A. lucorum nymphs by H. axyridis adults and larvae were 4.7 and 5.2% respectively.

CONCLUSIONS

The overall low positive proportion of generalist predators with A. lucorum DNA detected using the molecular method, combined with the low predation rate in the field-cage experiment, indicated that the primary generalist predators likely had a limited role in the suppression of A. lucorum in the field. © 2016 Society of Chemical Industry.

Analysis of digestion of rice planthopper by Pardosa pseudoannulata based on CO-I gene

In order to systematically study the predatory behavior and digestion regularity of spiders, real-time fluorescence quantification PCR technique was used to detect the number of CO-I genes in Pardosa pseudoannulata after it preyed on rice planthoppers in different temperatures within different periods. At 28 °C, 0, 1, 2, 4, 8, 16, and 24 h after P. pseudoannulata preyed on rich planthopper, DNA was extracted from cephalothorax and abdomen of P. pseudoannulata. Routine PCR and real-time fluorescence PCR techniques were employed for CO-I gene amplification. The results show that: The prey liquid was temporarily stored in the sucking stomach of the spider head within 2 h after prey, and gradually transferred to the midgut of the abdomen with the prolongation of time. After 4 h, CO-I gene residues of rice planthopper in the cephalothorax gradually decreased. The CO-I gene of rice planthopper was basically transferred to the abdomen after 16 h. During 0–1 h, food contained in abdominal midgut and other digestive organs was very small, CO-I gene detection was not obvious. Over time, food entered into the midgut from the sucking stomach for digestion. During 2–4 h, CO-I gene amount increased, at 2–4 h, detected CO-I gene residue reached the peak; but rapidly declined after 8, 16, and 24 h, even it is still detectable. The results at different temperatures reveal that: As the temperature increased from 26 °C to 32 °C, CO-I gene residues of rich planthopper in cephalothorax and abdomen of P. pseudoannulata gradually decreased, which indicated that the digestion rate increased with the increase of temperature with some range. However, when the temperature continued to increase to 34 °C, the digestion rate decreased.

Uncovering Trophic Interactions in Arthropod Predators through DNA Shotgun-Sequencing of Gut Contents

Characterizing trophic networks is fundamental to many questions in ecology, but this typically requires painstaking efforts, especially to identify the diet of small generalist predators. Several attempts have been devoted to develop suitable molecular tools to determine predatory trophic interactions through gut content analysis, and the challenge has been to achieve simultaneously high taxonomic breadth and resolution. General and practical methods are still needed, preferably independent of PCR amplification of barcodes, to recover a broader range of interactions. Here we applied shotgun-sequencing of the DNA from arthropod predator gut contents, extracted from four common coccinellid and dermapteran predators co-occurring in an agroecosystem in Brazil. By matching unassembled reads against six DNA reference databases obtained from public databases and newly assembled mitogenomes, and filtering for high overlap length and identity, we identified prey and other foreign DNA in the predator guts. Good taxonomic breadth and resolution was achieved (93% of prey identified to species or genus), but with low recovery of matching reads. Two to nine trophic interactions were found for these predators, some of which were only inferred by the presence of parasitoids and components of the microbiome known to be associated with aphid prey. Intraguild predation was also found, including among closely related ladybird species. Uncertainty arises from the lack of comprehensive reference databases and reliance on low numbers of matching reads accentuating the risk of false positives. We discuss caveats and some future prospects that could improve the use of direct DNA shotgun-sequencing to characterize arthropod trophic networks.

Quantitative analysis of diet structure by real-time PCR, reveals different feeding patterns by two dominant grasshopper species

Studies on grasshopper diets have historically employed a range of methodologies, each with certain advantages and disadvantages. For example, some methodologies are qualitative instead of quantitative. Others require long experimental periods or examine population-level effects, only. In this study, we used real-time PCR to examine diets of individual grasshoppers. The method has the advantage of being both fast and quantitative. Using two grasshopper species, Oedaleus asiaticus and Dasyhippus barbipes, we designed ITS primer sequences for their three main host plants, Stipa krylovii, Leymus chinensis and Cleistogenes squarrosa and used real-time PCR method to test diet structure both qualitatively and quantitatively. The lowest detection efficiency of the three grass species was ~80% with a strong correlation between actual and PCR-measured food intake. We found that Oedaleus asiaticus maintained an unchanged diet structure across grasslands with different grass communities. By comparison, Dasyhippus barbipes changed its diet structure. These results revealed why O. asiaticus distribution is mainly confined to Stipa-dominated grassland, and D. barbipes is more widely distributed across Inner Mongolia. Overall, real-time PCR was shown to be a useful tool for investigating grasshopper diets, which in turn offers some insight into grasshopper distributions and improved pest management.

Presence of Native Prey Does Not Divert Predation on Exotic Pests by Harmonia axyridis in Its Indigenous Range

In China, two invasive pests, Bemisia tabaci MEAM1 (Gennadius) and Frankliniella occidentalis (Pergande), often co-occur with the native pest, Aphis gossypii (Glover), on plants of Malvaceae and Cucurbitaceae. All three are preyed on by the native ladybird, Harmonia axyridis (Pallas); however, the native predator might be expected to prefer native prey to the exotic ones due to a shared evolutionary past. In order to clarify whether the presence of native prey affected the consumption of these two invasive species by the native predator, field-cage experiments were conducted. A duplex qPCR was used to simultaneously detect both non-native pests within the gut of the predator. H. axyridis readily accepted both invasive prey species, but preferred B. tabaci. With all three prey species available, H. axyridis consumption of B. tabaci was 39.3±2.2% greater than consumption of F. occidentalis. The presence of A. gossypii reduced (by 59.9% on B. tabaci, and by 60.6% on F. occidentalis), but did not stop predation on the two exotic prey when all three were present. The consumption of B. tabaci was similar whether it was alone or together with A. gossypii. However, the presence of aphids reduced predation on the invasive thrips. Thus, some invasive prey may be incorporated into the prey range of a native generalist predator even in the presence of preferred native prey.

Detection of seed DNA in regurgitates of granivorous carabid beetles

Granivory can play a pivotal role in influencing regeneration, colonization as well as abundance and distribution of plants. Due to their high abundance, nutrient content and longevity, seeds are an important food source for many animals. Among insects, carabid beetles consume substantial numbers of seeds and are thought to be responsible for a significant amount of seed loss. However, the processes that govern which seeds are eaten and are therefore prevented from entering the seedbank are poorly understood. Here, we assess if DNA-based diet analysis allows tracking the consumption of seeds by carabids. Adult individuals of Harpalus rufipes were fed with seeds of Taraxacum officinale and Lolium perenne allowing them to digest for up to 3 days. Regurgitates were tested for the DNA of ingested seeds at eight different time points post-feeding using general and species-specific plant primers. The detection of seed DNA decreased with digestion time for both seed species, albeit in a species-specific manner. Significant differences in overall DNA detection rates were found with the general plant primers but not with the species-specific primers. This can have implications for the interpretation of trophic data derived from next-generation sequencing, which is based on the application of general primers. Our findings demonstrate that seed predation by carabids can be tracked, molecularly, on a species-specific level, providing a new way to unravel the mechanisms underlying in-field diet choice in granivores.

Evidence of Amblyseius largoensis and Euseius alatus as biological control agent of Aceria guerreronis

Amblyseius largoensis (Muma) (Acari: Phytoseiidae) and Euseius alatus De Leon (Acari: Phytoseiidae) are predatory mites that are mostly found on leaves and on the exposed fruit surface of coconut plants. Their morphology hampers the access to the microhabitat occupied by Aceria guerreronis Keifer (Acari: Eriophyidae), the most important pest of coconut fruits throughout the world. However, it was suggested that they can prey on A. guerreronis under natural conditions when this pest leaves its refuge to disperse. Since the trophic interactions between A. largoensis or E. alatus and A. guerreronis are unknown, we compare the frequencies of occurrence of A. largoensis and E. alatus under the bracts of coconut fruits and on coconut leaflets. In addition, because phytoseiids feed by liquid ingestion, we used molecular analysis to confirm the potential role of A. largoensis or E. alatus as predators of A. guerreronis and to assess how fast the A. guerreronis DNA fragment is degradated in the A. largoensis digestive tract. Our study demonstrated that E. alatus was only present on coconut leaflets whereas A. largoensis was found mostly on leaflets and, to a much lesser extent, under the bracts of coconuts. Species-specific ITS primers designed for A. guerreronis were shown to have a high degree of specificity for A. guerreronis DNA and did not produce any PCR product from DNA templates of the other insects and mites associated with the coconut agroecosystem. Based on molecular analysis, we confirmed that the predatory mites, A. largoensis and E. alatus, had preyed on the coconut mite in the field. Overall the predatory mites collected in the field exhibited low levels of predation (26.7% of A. largoensis and 8.9% of E. alatus tested positive for A. guerreronis DNA). The fragment of A. guerreronis DNA remained intact for a very short time (no more than 6 h after feeding) in the digestive tract of A. largoensis.

Diagnostic PCR assays to unravel food web interactions in cereal crops with focus on biological control of aphids

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.

Molecular prey identification in Central European piscivores

Diet analysis is an important aspect when investigating the ecology of fish‐eating animals and essential for assessing their functional role in food webs across aquatic and terrestrial ecosystems. The identification of fish remains in dietary samples, however, can be time‐consuming and unsatisfying using conventional morphological analysis of prey remains. Here, we present a two‐step multiplex PCR system, comprised of six assays, allowing for rapid, sensitive and specific detection of fish DNA in dietary samples. This approach encompasses 78 fish and lamprey species native to Central European freshwaters and enables the identification of 31 species, six genera, two families, two orders and two fish family clusters. All targeted taxa were successfully amplified from 25 template molecules, and each assay was specific when tested against a wide range of invertebrates and vertebrates inhabiting aquatic environments. The applicability of the multiplex PCR system was evaluated in a feeding trial, wherein it outperformed morphological prey analysis regarding species‐specific prey identification in faeces of Eurasian otters. Additionally, a wide spectrum of fish species was detected in field‐collected faecal samples and regurgitated pellets of Common Kingfishers and Great Cormorants, demonstrating the broad applicability of the approach. In conclusion, this multiplex PCR system provides an efficient, easy to use and cost‐effective tool for assessing the trophic ecology of piscivores in Central Europe. Furthermore, the multiplex PCRs and the primers described therein will be applicable wherever DNA of the targeted fish species needs to be detected at high sensitivity and specificity.

Molecular analysis of faecal samples from birds to identify potential crop pests and useful biocontrol agents in natural areas

Wild habitats adjoining farmland are potentially valuable sources of natural enemies, but also of pests. Here we tested the utility of birds as 'sampling devices', to identify the diversity of prey available to predators and particularly to screen for pests and natural enemies using natural ecosystems as refugia. Here we used PCR to amplify prey DNA from three sympatric songbirds foraging on small invertebrates in Phragmites reedbed ecosystems, namely the Reed Warbler (Acrocephalus scirpaceus), Sedge Warbler (Acrocephalus schoenobaenus) and Cetti's Warbler (Cettia cetti). A recently described general invertebrate primer pair was used for the first time to analyse diets. Amplicons were cloned and sequenced, then identified by reference to the Barcoding of Life Database and to our own sequences obtained from fresh invertebrates. Forty-five distinct prey DNA sequences were obtained from 11 faecal samples, of which 39 could be identified to species or genus. Targeting three warbler species ensured that species-specific differences in prey choice broadened the range of prey taken. Amongst the prey found in reedbeds were major pests (including the tomato moth Lacanobia oleracea) as well as many potentially valuable natural enemies including aphidophagous hoverflies and braconid wasps. Given the mobility of birds, this approach provides a practical way of sampling a whole habitat at once, providing growers with information on possible invasion by locally resident pests and the colonization potential of natural enemies from local natural habitats.

Knowing your enemies: Integrating molecular and ecological methods to assess the impact of arthropod predators on crop pests

The importance of natural enemies as the foundation of integrated pest management (IPM) is widely accepted, but few studies conduct the manipulative field experiments necessary to directly quantify their impact on pest populations in this context. This is particularly true for predators. Studying arthropod predator-prey interactions is inherently difficult: prey items are often completely consumed, individual predator-prey interactions are ephemeral (rendering their detection difficult) and the typically fluid or soft-bodied meals cannot be easily identified visually within predator guts. Serological techniques have long been used in arthropod predator gut-contents analysis, and current enzyme linked immunosorbent assays (ELISA) are highly specific and sensitive. Recently, polymerase chain reaction (PCR) methods for gut-contents analysis have developed rapidly and they now dominate the diagnostic methods used for gut-contents analysis in field-based research. This work has identified trophic linkages within food webs, determined predator diet breadth and preference, demonstrated the importance of cannibalism and intraguild predation within and between certain taxa, and confirmed the benefits (predator persistence) and potential disadvantages (reduced feeding on pest species) of the availability of alternative nonpest prey. Despite considerable efforts to calibrate gut-contents assays, these methods remain qualitative. Available techniques for predator gut-contents analysis can provide rapid, accurate, cost-effective identification of predation events. As such, they perfectly compliment the ecological methods developed to directly assess predator impacts on prey populations but which are imperfect at identifying the key predators. These diagnostic methods for gut-contents analysis are underexploited in agricultural research and they are almost never applied in unison with the critical field experiments to measure predator impact. This paper stresses the need for a combined approach and suggests a framework that would make this possible, so that appropriate natural enemies can be targeted in conservation biological control.

Group-specific multiplex PCR detection systems for the identification of flying insect prey

The applicability of species-specific primers to study feeding interactions is restricted to those ecosystems where the targeted prey species occur. Therefore, group-specific primer pairs, targeting higher taxonomic levels, are often desired to investigate interactions in a range of habitats that do not share the same species but the same groups of prey. Such primers are also valuable to study the diet of generalist predators when next generation sequencing approaches cannot be applied beneficially. Moreover, due to the large range of prey consumed by generalists, it is impossible to investigate the breadth of their diet with species-specific primers, even if multiplexing them. However, only few group-specific primers are available to date and important groups of prey such as flying insects have rarely been targeted. Our aim was to fill this gap and develop group-specific primers suitable to detect and identify the DNA of common taxa of flying insects. The primers were combined in two multiplex PCR systems, which allow a time- and cost-effective screening of samples for DNA of the dipteran subsection Calyptratae (including Anthomyiidae, Calliphoridae, Muscidae), other common dipteran families (Phoridae, Syrphidae, Bibionidae, Chironomidae, Sciaridae, Tipulidae), three orders of flying insects (Hymenoptera, Lepidoptera, Plecoptera) and coniferous aphids within the genus Cinara. The two PCR assays were highly specific and sensitive and their suitability to detect prey was confirmed by testing field-collected dietary samples from arthropods and vertebrates. The PCR assays presented here allow targeting prey at higher taxonomic levels such as family or order and therefore improve our ability to assess (trophic) interactions with flying insects in terrestrial and aquatic habitats.

Cover cropping alters the diet of arthropods in a banana plantation: a metabarcoding approach

Plant diversification using cover crops may promote natural regulation of agricultural pests by supporting alternative prey that enable the increase of arthropod predator densities. However, the changes in the specific composition of predator diet induced by cover cropping are poorly understood. Here, we hypothesized that the cover crop can significantly alter the diet of predators in agroecosystems. The cover crop Brachiaria decumbens is increasingly used in banana plantations to control weeds and improve physical soil properties. In this paper, we used a DNA metabarcoding approach for the molecular analysis of the gut contents of predators (based on mini-COI) to identify 1) the DNA sequences of their prey, 2) the predators of Cosmopolites sordidus (a major pest of banana crops), and 3) the difference in the specific composition of predator diets between a bare soil plot (BSP) and a cover cropped plot (CCP) in a banana plantation. The earwig Euborellia caraibea, the carpenter ant Camponotus sexguttatus, and the fire ant Solenopsis geminata were found to contain C. sordidus DNA at frequencies ranging from 1 to 7%. While the frequencies of predators positive for C. sordidus DNA did not significantly differ between BSP and CCP, the frequency at which E. caraibea was positive for Diptera was 26% in BSP and 80% in CCP; the frequency at which C. sexguttatus was positive for Jalysus spinosus was 14% in BSP and 0% in CCP; and the frequency at which S. geminata was positive for Polytus mellerborgi was 21% in BSP and 3% in CCP. E. caraibea, C. sexguttatus and S. geminata were identified as possible biological agents for the regulation of C. sordidus. The detection of the diet changes of these predators when a cover crop is planted indicates the possible negative effects on pest regulation if predators switch to forage on alternative prey.

Intraguild predation in pioneer predator communities of alpine glacier forelands

Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes.

Spatiotemporal analysis of predation by carabid beetles (Carabidae) on nematode infected and uninfected slugs in the field

The dynamics of predation on parasites within prey has received relatively little attention despite the profound effects this is likely to have on both prey and parasite numbers and hence on biological control programmes where parasites are employed. The nematode Phasmarhabditis hermaphrodita is a commercially available biological agent against slugs. Predation on these slugs may, at the same time, result in intraguild predation on slug-parasitic nematodes. This study describes, for the first time, predation by carabid beetles on slugs and their nematode parasites on both spatial and temporal scales, using PCR-based methods. The highest nematode infection levels were found in the slugs Deroceras reticulatum and Arion silvaticus. Numbers of infected slugs decreased over time and no infected slugs were found four months after nematode application. The density of the most abundant slug, the invasive Arion vulgaris, was positively related to the activity-density of the carabid beetle, Carabus nemoralis. Predation on slugs was density and size related, with highest predation levels also on A. vulgaris. Predation on A. vulgaris decreased significantly in summer when these slugs were larger than one gram. Predation by C. nemoralis on slugs was opportunistic, without any preferences for specific species. Intraguild predation on the nematodes was low, suggesting that carabid beetles such as C. nemoralis probably do not have a significant impact on the success of biological control using P. hermaphrodita.

Molecular and microscopic analysis of the gut contents of abundant rove beetle species (Coleoptera, Staphylinidae) in the boreal balsam fir forest of Quebec, Canada

Experimental research on beetle responses to removal of logging residues following clearcut harvesting in the boreal balsam fir forest of Quebec revealed several abundant rove beetle (Staphylinidae) species potentially important for long-term monitoring. To understand the trophic affiliations of these species in forest ecosystems, it was necessary to analyze their gut contents. We used microscopic and molecular (DNA) methods to identify the gut contents of the following rove beetles: Atheta capsularis Klimaszewski, Atheta klagesi Bernhauer, Oxypoda grandipennis (Casey), Bryophacis smetanai Campbell, Ischnosoma longicorne (Mäklin), Mycetoporus montanus Luze, Tachinus frigidus Erichson, Tachinus fumipennis (Say), Tachinus quebecensis Robert, and Pseudopsis subulata Herman. We found no apparent arthropod fragments within the guts; however, a number of fungi were identified by DNA sequences, including filamentous fungi and budding yeasts [Ascomycota: Candida derodonti Suh & Blackwell (accession number FJ623605), Candida mesenterica (Geiger) Diddens & Lodder (accession number FM178362), Candida railenensis Ramirez and Gonzáles (accession number JX455763), Candida sophie-reginae Ramirez & González (accession number HQ652073), Candida sp. (accession number AY498864), Pichia delftensis Beech (accession number AY923246), Pichia membranifaciens Hansen (accession number JQ26345), Pichia misumaiensis Y. Sasaki and Tak. Yoshida ex Kurtzman 2000 (accession number U73581), Pichia sp. (accession number AM261630), Cladosporium sp. (accession number KF367501), Acremoniumpsammosporum W. Gams (accession number GU566287), Alternaria sp. (accession number GU584946), Aspergillus versicolor Bubak (accession number AJ937750), and Aspergillusamstelodami (L. Mangin) Thom and Church (accession number HQ728257)]. In addition, two species of bacteria [Bradyrhizobium japonicum (Kirchner) Jordan (accession number BA000040) and Serratia marcescens Bizio accession number CP003942] were found in the guts. These results not only provide evidence of the consumer-resource relations of these beetles but also clarify the relationship between rove beetles, woody debris and fungi. Predominance of yeast-feeding by abundant rove beetles suggests that it may play an important role in their dietary requirements.

Impact of host plant resistance on the tritrophic interactions between wheat genotypes, Schizaphis graminum (Homoptera: Aphididae), and Coccinella septempunctata (Coleoptera: Coccinellidae) using molecular methods

The objective of the current study was to evaluate the impact of wheat resistance on digestibility of Schizaphis graminum (Rondani) in the Coccinella septempunctata L. gut. Four wheat genotypes including an ancient wheat species (Einkorn) and three Iranian wheat genotypes (Azadi, Ommid, and Moghan2) were used. Einkorn was found to be a highly resistant species, while Azadi, Ommid, and Moghan2 were characterized as resistant, semiresistant, and susceptible genotypes, respectively, based on some biological parameters of S. graminum on these plants. Adult C. septempunctata starved for 24 h were fed one S. graminum reared on the selected wheat genotypes. A semiquantitative polymerase chain reaction technique using specific primers for the gene cytochrome oxidase II (COII) of S. graminum showed a significant effect of plant resistance on S. graminum DNA disappearance time. The DNA half-lives of S. graminum fed on Einkorn, Azadi, Ommid, and Moghan2 in C. septempunctata gut was 3.3, 3.6, 4.8, and 6.7 h, respectively. The findings suggest that digestibility of S. graminum fed on resistant plant genotypes is higher than those fed on susceptible plants because of the lighter weights and smaller sizes of the first. This phenomenon could result in faster ingestion of S. graminum by C. septempunctata on these resistant plants. It is also possible that some metabolites found differentially in Einkorn and Azadi genotypes may have affected S. graminum quality as a food for C. septempunctata.

Analyzing spatial patterns linked to the ecology of herbivores and their natural enemies in the soil

Modern agricultural systems can benefit from the application of concepts and models from applied ecology. When understood, multitrophic interactions among plants, pests, diseases and their natural enemies can be exploited to increase crop production and reduce undesirable environmental impacts. Although the understanding of subterranean ecology is rudimentary compared to the perspective aboveground, technologies today vastly reduce traditional obstacles to studying cryptic communities. Here we emphasize advantages to integrating as much as possible the use of these methods in order to leverage the information gained from studying communities of soil organisms. PCR-based approaches to identify and quantify species (real time qPCR and next generation sequencing) greatly expand the ability to investigate food web interactions because there is less need for wide taxonomic expertise within research programs. Improved methods to capture and measure volatiles in the soil atmosphere in situ make it possible to detect and study chemical cues that are critical to communication across trophic levels. The application of SADIE to directly assess rather than infer spatial patterns in belowground agroecosystems has improved the ability to characterize relationships between organisms in space and time. We review selected methodology and use of these tools and describe some of the ways they were integrated to study soil food webs in Florida citrus orchards with the goal of developing new biocontrol approaches.

Dietary competition between the alien Asian Musk Shrew (Suncus murinus) and a re-introduced population of Telfair's Skink (Leiolopisma telfairii)

Re-introduction of rare species to parts of their historical range is becoming increasingly important as a conservation strategy. Telfair's Skinks (Leiolopisma telfairii), once widespread on Mauritius, were until recently found only on Round Island. There it is vulnerable to stochastic events, including the introduction of alien predators that may either prey upon it or compete for food resources. Consequently, skinks have been introduced to Ile aux Aigrettes, another small Mauritian island that has been cleared of rats. However, the island has been invaded by Asian Musk Shrews (Suncus murinus), a commensal species spread by man well beyond its natural Asian range. Our aim was to use next-generation sequencing to analyse the diets of the shrews and skinks to look for niche competition. DNA was extracted from skink faeces and from the stomach contents of shrews. Application of shrew- and skink-specific primers revealed no mutual predation. The DNA was then amplified using general invertebrate primers with tags to identify individual predators, and then sequenced by 454 pyrosequencing. 119 prey MOTUs (molecular taxonomic units) were isolated, although none could be identified to species. Seeding of cladograms with known sequences allowed higher taxonomic assignments in some cases. Although most MOTUs were not shared by shrews and skinks, Pianka's niche overlap test showed significant prey overlap, suggesting potentially strong competition where food resources are limited. These results suggest that removal of the shrews from the island should remain a priority.