Arthropod Predators Research Articles

Generalist Predators Shape Biotic Resistance along a Tropical Island Chain.

Islands offer exclusive prisms for an experimental investigation of biodiversity x ecosystem function interplay. Given that species in upper trophic layers, e.g., arthropod predators, experience a comparative disadvantage on small, isolated islands, such settings can help to clarify how predation features within biotic resistance equations. Here, we use observational and manipulative studies on a chain of nine Indonesian islands to quantify predator-mediated biotic resistance against the cassava mealybug Phenacoccus manihoti (Homoptera: Pseudococcidae) and the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae). Across island settings, a diverse set of generalist lacewing, spider and ladybeetle predators aggregates on P. manihoti infested plants, attaining max. (field-level) abundance levels of 1.0, 8.0 and 3.2 individuals per plant, respectively. Though biotic resistance-as imperfectly defined by a predator/prey ratio index-exhibits no inter-island differences, P. manihoti population regulation is primarily provided through an introduced monophagous parasitoid. Meanwhile, resident predators, such as soil-dwelling ants, inflict apparent mortality rates up to 100% for various S. frugiperda life stages, which translates into a 13- to 800-fold lower S. frugiperda survivorship on small versus large islands. While biotic resistance against S. frugiperda is ubiquitous along the island chain, its magnitude differs between island contexts, seasons and ecological realms, i.e., plant canopy vs. soil surface. Hence, under our experimental context, generalist predators determine biotic resistance and exert important levels of mortality even in biodiversity-poor settings. Given the rapid pace of biodiversity loss and alien species accumulation globally, their active conservation in farmland settings (e.g., through pesticide phasedown) is pivotal to ensuring the overall resilience of production ecosystems.

Arthropod predator community associated with soybean gall midge, Resseliella maxima (Diptera: Cecidomyiidae), in Minnesotan soybean fields.

The soybean gall midge, Resseliella maxima Gagné (Diptera: Cecidomyiidae), is a pest that injures soybeans in the Midwest United States. Little is known about the natural enemies of R. maxima or the potential for biological control. Therefore, we performed a 2-yr survey in Minnesota to examine the predator community associated with R. maxima infestations. We found that Orius insidiosus (Say) (Heteroptera: Anthocoridae) and Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) were the most common foliar- and ground-foraging predators, respectively. Some of the commonly encountered predator species were tested in laboratory predation experiments. Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and O. insidiosus represented the foliar-foraging predators tested, and H. axyridis consumed significantly more R. maxima larvae than O. insidiosus. Among the ground-foraging predators, 4 carabids were tested. Poecilus lucublandus (Say) (Coleoptera: Carabidae) and Pt. melanarius consumed significantly more R. maxima larvae than Poecilus chalcites (Say) (Coleoptera: Carabidae) and Bembidion quadrimaculatum oppositum (Say) (Coleoptera: Carabidae). We conclude that Pt. melanarius should receive further attention as a potential biological control agent of R. maxima, due to its high abundance in the soybean fields in this study, temporal overlap with the pest, and high propensity to feed on the pest.

Functional identity of dominant species in a predator community prevails over functional diversity in shaping the top‐down control of herbivores

Abstract Decline in species richness as well as changes in community evenness or functional diversity have been hypothesised to jointly affect ecosystem functioning. However, disentangling the relative effects of these changes in community structure is hard as these different aspects often covary with species richness in real‐world ecosystems. In this study, we investigated the individual and interactive effects of functional diversity and community evenness of predators on the level of control of herbivorous prey. Using a highly replicated mesocosm experiment, we crossed three levels of functional diversity of arthropod predators with two levels of community evenness while controlling for the effect of species richness. Using this experimental setting, we hypothesised that the effect size of functional diversity of predators depends on community evenness. We expected a positive effect of functional diversity of predators on top‐down control at high level of community evenness while we thought that species identity and their associated traits should drive most of the effect on top‐down control at low level of community evenness. Our results did not provide any evidence for an interaction between functional diversity and community evenness nor any beneficial effect of increased functional diversity overall on predation rates of herbivorous prey. In addition, our results revealed that species and functional identity drives most of the effects of predator community composition on top‐down control of their prey in our study system. Assemblages composed of active hunters with low handling time and no starvation ability tended to have the highest impacts on prey biomass. By indicating that top‐down control of herbivorous prey by arthropod predators is mainly driven by species and functional identity and not by functional diversity, our study provides insights into the consequences of ongoing species loss on ecosystem functioning. Future research should now explore the predictability of trophic interactions based on functional traits of predator and herbivorous prey to anticipate the consequences of changes in species composition on ecosystem functioning. Read the free Plain Language Summary for this article on the Journal blog.

Microbiome of Zoophytophagous Biological Control Agent Nesidiocoris tenuis.

Many insects are associated with endosymbionts that influence the feeding, reproduction, and distribution of their hosts. Although the small green mirid, Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), a zoophytophagous predator that feeds on plants as well as arthropods, is a globally important biological control agent, its microbiome has not been sufficiently studied. In the present study, we assessed the microbiome variation in 96 N. tenuis individuals from 14 locations throughout Japan, based on amplicon sequencing of the 16S ribosomal RNA gene. Nine major bacteria associated with N. tenuis were identified: Rickettsia, two strains of Wolbachia, Spiroplasma, Providencia, Serratia, Pseudochrobactrum, Lactococcus, and Stenotrophomonas. Additionally, a diagnostic PCR analysis for three typical insect reproductive manipulators, Rickettsia, Wolbachia, and Spiroplasma, was performed on a larger sample size (n = 360) of N. tenuis individuals; the most prevalent symbiont was Rickettsia (69.7%), followed by Wolbachia (39.2%) and Spiroplasma (6.1%). Although some symbionts were co-infected, their prevalence did not exhibit any specific tendency, such as a high frequency in specific infection combinations. The infection frequency of Rickettsia was significantly correlated with latitude and temperature, while that of Wolbachia and Spiroplasma was significantly correlated with host plants. The predominance of these bacteria and the absence of obligate symbionts suggested that the N. tenuis microbiome is typical for predatory arthropods rather than sap-feeding insects. Rickettsia and Wolbachia were vertically transmitted rather than horizontally transmitted from the prey. The functional validation of each symbiont would be warranted to develop N. tenuis as a biological control agent.

The sticky hemiparasitic plant Parentucellia viscosa catches hostplant seeds that may provision its descendants

In addition to physiological functions, sticky plant trichomes perform a variety of anti-herbivory functions, such as deterring invertebrate and mammalian herbivores, and attracting the natural predators of stuck arthropods by providing them with immobilized prey. However, since the adaptive value of sticky glands has only been studied in a small fraction of trichrome-bearing plant species, other functions of these structures may yet be discovered. Several hemiparasitic plants, which obtain nutrients by both photosynthesis and from the roots of other plants, bear dense glandular trichomes on their aboveground parts. Field observations of the alien hemiparasitic plant Parentucellia viscosa were conducted in central Japan. The plants colonized a sparsely vegetated riverbank and gradually increased in number over time. The glandular trichomes on the plants not only entrapped small insects, but also grass seeds. It is thus possible that various sticky hemiparasitic plants, including P. viscosa, may intercept and capture the dispersed seeds of other plants, ensuring that their own seeds germinate in the same vicinity as those of the dispersing hostplant seeds in the following season. In so doing, P. viscosa may provision future juvenile plants with potential hosts. This scenario may be restricted to the early colonizing phase on plantless areas of disturbed soil. The seed-intercepting function of the glandular trichomes may act in conjunction with direct and indirect anti-herbivore defenses, and lower the dispersal of seeds of wind-borne plants in the vicinity beyond the reach of this hemiparasite.

Consistent benefits of fungicide reduction on arthropod predators and predation rates in viticulture: a five-year experiment

For reliable pest suppression, benefits of habitat management for natural enemies of agricultural pests need to be consistent over time. Unfortunately, most research projects allow only for one or two years of data collection. Here, we present a five-year study on effects of fungicide reduction and altered plant architecture on arthropod abundances and natural pest control in an experimental vineyard. The vineyard rows were divided into eight groups, half of which were trained in vertical shoot position (“trellis system”) and the other half as semi-minimal pruned hedge (“minimal pruning”). Every row was divided in three sections receiving three different plant protection intensities, respectively, with fungicides certified for organic viticulture. In each year we sampled arthropods from the grapevine canopy by standardized leaf collection and beat-sheet sampling, and exposed baits of a major grapevine pest (Lobesia botrana) to assess natural pest control. Arthropods, in particular predators, benefited from reduced fungicide sprayings and in turn promoted natural pest control. In contrast, effects of minimal pruning were less strong, and restricted to the leaf mesofauna, earwigs and leafhoppers. Across the five study years with their variable weather conditions, we conclude that the advantages of reduced fungicide sprayings in fungus-resistant varieties are consistent over time.

Top-Down Effect of Arthropod Predator Chinese Mitten Crab on Freshwater Nutrient Cycling.

Aquatic litter decomposition is highly dependent on contributions and interactions at different trophic levels. The invasion of alien aquatic organisms like the channeled apple snail (Pomacea canaliculata) might lead to changes in the decomposition process through new species interactions in the invaded wetland. However, it is not clear how aquatic macroinvertebrate predators like the Chinese mitten crab (Eriocheir sinensis) will affect the nutrient cycle in freshwater ecosystems in the face of new benthic invasion. We used the litter bag method to explore the top-down effect of crabs on the freshwater nutrient cycle with the help of soil zymography (a technology previously used in terrestrial ecosystems). The results showed significant feeding effects of crabs and snails on lotus leaf litter and cotton strips. Crabs significantly inhibited the intake of lotus litter and cotton strips and the ability to transform the environment of snails by predation. Crabs promoted the decomposition of various litter substrates by affecting the microbial community structure in the sediment. These results suggest that arthropod predators increase the complexity of detrital food webs through direct and indirect interactions, and consequently have an important impact on the material cycle and stability of freshwater ecosystems. This top-down effect makes macrobenthos play a key role in the biological control and engineering construction of freshwater ecosystems.

Possible earliest evidence of insect pollination based on a new species of the Carboniferous medullosalean ‘seed’ genus Pachytesta

Here we describe Pachytesta duquesnei sp. nov., a Carboniferous medullosalean ‘seed’ (middle Pennsylvanian, Bruay Formation, slag heap of Lens-Liévin district, Pas-de-Calais department, France), attributed to a female reproductive structure of ‘seed ferns’ of the genus Alethopteris, very frequent in the same layers. The peculiar micropylar extension of the new ‘seed’, as long as half of total ‘seed’ length, is compared to the other known medullosalean/trigonocarpalean ‘seeds’, including Stephanospermum, but also to Trigonocarpus considered as ‘seed’ casts present in several localities in Western Europe. The attribution of Whittleseya elegans as male organs of an Alethopteris sp. is also discussed. The latter occurs is present in the same locality with Pachytesta duquesnei sp. nov. We discuss the possible function of the extremely elongate micropylar extension of Pachytesta duquesnei sp. nov., suggesting it is unlikely adapted to a pollination-drop mechanism, but rather could be linked to a protection mechanism against arthropod predators and/or to a highly specialized pollination mechanism either by very tiny insects entering these ‘seeds’ through this tube (with figs and fig wasps as modern analogues) or an insect with elongate mouthparts able to go inside the ‘seed’ (with tube flower and moths with extremely long proboscis), to feed and transport pollen at the same time.

Anuran juveniles avoid preying on aggressive ant species

AbstractAnts occupy huge biomass in the terrestrial ecosystem. Several ant species are highly aggressive and equipped with venomous stingers and/or formic acid. Therefore, ants are abundant but potentially unpalatable prey for some predators. So far, however, the role of ants as prey is not well understood. In this study, we focused anurans (frogs and toads) as one of the major predators of terrestrial arthropods. Using two anuran species and three ant species sharing the habitats, we asked two questions. First, we hypothesized that the anuran preference for prey is ant‐species specific, and tested whether anuran prey preference is affected by ant aggressiveness. Second, we hypothesized that the anurans may innately avoid aggressive ants. To test this hypothesis, ant‐naïve anuran juveniles (Bufo toad and Rana frog) were reared from tadpoles, and juveniles' preferences for three ant species with variable aggressiveness were tested. The exposure to different ant species showed that anuran juveniles highly avoided aggressive ants (Lasius and Brachyponera) compared to less aggressive ants (Tetramorium). Additionally, ant‐naive juvenile toads avoided the aggressive ants without prior experience. In contrast, ant‐naïve juvenile frogs attacked the most of firstly encountered ants and then learned to avoid the unpalatable ants. These findings suggest that (1) some anurans selectively avoid aggressive ant species, (2) Bufo toads have innate avoidance to some ants, while Rana frogs learn to avoid the unpalatable prey.

Predator–prey interactions in the Arctic: DNA metabarcoding reveals that nestling diet of snow buntings reflects arthropod seasonality

AbstractTundra arthropods are of considerable ecological importance as a seasonal food source for many arctic‐breeding birds. Dietary composition and food preferences are rarely known, complicating assessments of ecological interactions in a changing environment. In our field study, we investigated the nestling diet of snow buntings (Plectrophenax nivalis (L., 1758)) breeding in Svalbard. We collected fecal samples from 8‐day‐old nestlings and assessed dietary composition by DNA metabarcoding. Simultaneously, the availability of potential prey arthropods was measured by pitfall trapping. Molecular analyses of nestling feces identified 31 arthropod taxa in the diet, whose proportions changed throughout the brood‐rearing period. Changes in nestling diet matched varying abundances and emergence patterns of the tundra arthropod community. Snow buntings provisioned their offspring mainly with Diptera (true flies) based on both presence/absence and relative read abundance of diet items. At the beginning of the season in June, Chironomidae (nonbiting midges) and the scathophagid fly Scathophaga furcata (Say, 1823) dominated the diet, whereas the muscid fly Spilogona dorsata (Zetterstedt, 1845) dominated the diet later in July. When accounted for availability, muscid flies were selected positively among the most often provisioned food taxa. Our study demonstrates the ecological role of the snow bunting as a generalist arthropod predator and highlights DNA metabarcoding as a noninvasive technique for diet analyses with high taxonomical precision if sufficient DNA‐sequence libraries are available.

A novel use of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) as inoculative agent of baculoviruses.

Alphabaculoviruses are Lepidoptera-specific virulent pathogens that infect numerous pests, including the Spodoptera complex. Due to their low environmental persistence, the traditional use of Alphabaculoviruses as bioinsecticides consist in high-rate spray applications with repeated treatments. Several abiotic and biotic factors can foster its dispersion, promoting their persistence in the agroecosystem. Amongst biotic factors, predatory arthropods can disperse the viruses by excretion after preying on infected individuals. Therefore, this study focused on promoting predator's ingestion of nucleopolyhedrovirus (NPV)-treated diets, and the later exposition of the insect host to leaf surfaces contaminated with predator excreta. The virus-host-predator system studied was Spodoptera littoralis nucleopolyhedrovirus (SpliNPV), Spodoptera littoralis (Boisduval) and Nesidiocoris tenuis (Reuter). The infective potential of N. tenuis feces and the retention time of SpliNPV were assessed under laboratory conditions after feeding on treated diets (sucrose solution and Ephestia kuehniella eggs). Mortality of S. littoralis larvae was lower via N. tenuis excretion than in positive control (spray application) in the first infection cycle, together with a delay in host death. In the second infection cycle, both SpliNPV-treated diets triggered 100% mortality. Both diets allowed the transmission of SpliNPV, with a faster excretion via sucrose solution compared to E. kuehniella eggs. SpliNPV remained in N. tenuis digestive tract and was viable after excretion at least for 9 days for both diets. This study demonstrated the potential of the predator N. tenuis as inoculative agent of baculoviruses, representing a new alternative that, along with inundative applications, might contribute to improve pest management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Intersexual Differences in the Gene Expression of Phoneutria depilata (Araneae, Ctenidae) Toxins Revealed by Venom Gland Transcriptome Analyses

The wandering spider, Phoneutria depilata, is one of Colombia’s most active nocturnal arthropod predators of vertebrates and invertebrates. Its venom has been a relevant subject of study in the last two decades. However, the scarcity of transcriptomic data for the species limits our knowledge of the distinct components present in its venom for linking the mainly neurotoxic effects of the spider venom to a particular molecular target. The transcriptome of the P. depilata venom gland was analyzed to understand the effect of different diets or sex and the impact of these variables on the composition of the venom. We sequenced venom glands obtained from ten males and ten females from three diet treatments: (i) invertebrate: Tenebrio molitor, (ii) vertebrate: Hemidactylus frenatus, and (iii) mixed (T. molitor + H. frenatus). Of 17,354 assembled transcripts from all samples, 65 transcripts relating to venom production differed between males and females. Among them, 36 were classified as neurotoxins, 14 as serine endopeptidases, 11 as other proteins related to venom production, three as metalloprotease toxins, and one as a venom potentiator. There were no differences in transcripts across the analyzed diets, but when considering the effect of diets on differences between the sexes, 59 transcripts were differentially expressed. Our findings provide essential information on toxins differentially expressed that can be related to sex and the plasticity of the diet of P. depilata and thus can be used as a reference for venomics of other wandering spider species.

Seasonal Abundance and Feeding Behaviour of <i>Oxyopes birmanicus</i> Thorell on Tea Mosquito Bug <i>Helopeltis theivora</i> Water House

The Burmese lynx spider, Oxyopes birmanicus Thorell (Araneae: Oxyopidae) is one of the endemic and entomophagous predatory arthropod species in India. This present study describes the seasonal abundance, vertical distribution, and feeding behaviour of O.birmanicus on nymph (4 th /5 th instar) and the adults of the tea mosquito bug, Helopeltis theivora Waterhouse (Hemiptera: Miridae) under laboratory conditions. The seasonal abundance of the O. birmanicus spider was considerably high from June to November and low from January to April. The abundance of O. birmanicus significantly correlated with the TMB infestation percentage. In a vertical distribution study, the O. birmanicus spider largely preferred the top level of the tea bush, the observed population was shared by the top and middle levels with 76% and 24% respectively. The feeding potential of the female O. birmanicus spider was significantly higher than the male and egg-guarding female. Both, male and egg-guarding female O. birmanicus showed on-par feeding efficacy. The study found that O. birmanicus was an efficient predator against TMB and the results may be useful in developing an integrated pest management strategy for TMB.

Predatory Arthropods Associated with the Invasive Tipu Psyllid, Platycorypha nigrivirga, in Southern Spain.

Platycorypha nigrivirga Burckhardt (Hemiptera: Psyllidae) is a neotropical invasive species strictly associated with the tipu tree, Tipuana tipu (Benth.) Kuntze (Fabaceae: Papilionoideae). This psyllid has rapidly spread to several temperate areas of Spain and Portugal causing considerable problems in urban landscapes. The aim of this study was to determine the arthropod predator complex of this exotic insect and report the possibility of its biological control. Three urban green areas were surveyed in southern Spain during 2018 and 2019. Platycorypha nigrivirga populations increased during the spring months and reached a maximum level between late May and mid-June, declining greatly during the summer. A large complex of generalist predator species was found to exert a certain natural control on the pest, belonging to Anthocoridae (68.53%), Coccinellidae (18.39%), Chrysopidae (5.67%), Miridae (4.39%) and Araneae (3.02%). Anthocoris nemoralis (Fabricius) (Hemiptera: Anthocoridae) was the most abundant predatory species, followed by Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) and Scymnus laetificus Weise (Coleoptera: Coccinellidae). High levels of abundance of anthocorids coincided with the highest abundance of the pest, showing a significant relationship with the psyllid density. Anthocoris nemoralis seems to be a promising candidate to control P. nigrivirga in the urban green areas of southern Spain, but more studies are needed to define the optimum management strategies.

Predatory arthropods and cues associated with predator presence elicit strong non‐consumptive effects on bluegrass billbugs

AbstractTurfgrasses hosts a diverse community of predators that contribute to herbivore suppression. However, there is little evidence that predators directly consume a common turfgrass herbivore, the billbug (Sphenophorus sp.) (Coleoptera: Curculionidae). Given low rates of direct consumption by predators, prospects for strong non‐consumptive effects in billbugs were underappreciated. However, this assumed lack of non‐consumptive effects presupposes that herbivorous prey, like billbugs, can identify predators and the level of threat that they pose. Here, we examined this assumption and quantified the extent to which exposure to predators and predator cues altered the behavior (predator avoidance, feeding, and mating) of bluegrass billbug, Sphenophorus parvulus Gyllenhal. First, using a series of behavioral assays within microcosms, we exposed billbugs to predators – Pterostichus melanarius (Illiger) (Coleoptera: Carabidae), Harpalus sp. (Coleoptera: Carabidae), Philonthus sp. (Coleoptera: Staphylinidae), and Hogna sp. (Araneae: Lycosidae) – singly and in combination to measure the effect of contact with predators and potential synergy among predator species pairs. Indirect exposure to predators, predator odor, and non‐predatory arthropods were also used to measure effects of various predator cues on billbug behavior. In subsequent Y‐tube choice assays we determined whether billbugs discriminated between filtered air and predator odor to isolate chemical signaling as a potential mechanism for billbug predator detection. Direct exposure to predators increased billbug predator avoidance (up to 201%), and decreased billbug feeding (down to −78%), though no predation was observed. Similar behavioral changes were observed when billbugs were exposed indirectly to a predator, and to predator odor. In Y‐tube assays billbugs avoided predator odor, further suggesting billbugs use chemical cues to detect predator presence and that these may be a driver in their observed behavior. Our results show that billbugs exhibit strong non‐consumptive effects, even in the absence of strong direct consumptive effects. These results provide the foundation for further research concerning the role of chemical signaling in billbug predator detection.

Scorpions, Science and Folklore in Durango City

Scorpions are incredible venomous animals found on almost every continent. According to fossil data, these animals have been able to adapt to the different environments from the Cambrian period until today with minimal anatomical changes. Scorpions are mostly nocturnal animals, and their ability to detect and tolerate light stimuli seems to be an essential tool for their subsistence, homing and mating. Centruroides suffuses is the most predominant specie of scorpions in Durango City, Mexico. Interestingly, and despite their life-threatening venom, these predatory arthropod animals have been adopted by locals as part of the landscape and daily life, by including them as part of their folklore and their economic resources, and learning how to take advantage of their abundance. In addition, the venom of scorpions possesses potential for therapeutic uses, while the scorpions themselves represent a nutritional food resource rich in protein, which has been poorly explored so far. Therefore, they are an excellent model for exploring the interplay between light sensibilities, survival and therapeutic–medicinal uses. Here, we review some of the potential benefits of scorpions and share the ways people in Durango City, Mexico, use UV light devices to detect and avoid or catch them for business and research purposes.

Genetic diversity varies with species traits and latitude in predatory soil arthropods (Myriapoda: Chilopoda).

To investigate the drivers of intra-specific genetic diversity in centipedes, a group of ancient predatory soil arthropods. Asia, Australasia and Europe. Present. Centipedes (Class: Chilopoda). We assembled a database of 1245 mitochondrial cytochrome c oxidase subunit I sequences representing 128 centipede species from all five orders of Chilopoda. This sequence dataset was used to estimate genetic diversity for centipede species and compare its distribution with estimates from other arthropod groups. We studied the variation in centipede genetic diversity with species traits and biogeography using a beta regression framework, controlling for the effect of shared evolutionary history within a family. A wide variation in genetic diversity across centipede species (0-0.1713) falls towards the higher end of values among arthropods. Overall, 27.57% of the variation in mitochondrial COI genetic diversity in centipedes was explained by a combination of predictors related to life history and biogeography. Genetic diversity decreased with body size and latitudinal position of sampled localities, was greater in species showing maternal care and increased with geographic distance among conspecifics. Centipedes fall towards the higher end of genetic diversity among arthropods, which may be related to their long evolutionary history and low dispersal ability. In centipedes, the negative association of body size with genetic diversity may be mediated by its influence on local abundance or the influence of ecological strategy on long-term population history. Species with maternal care had higher genetic diversity, which goes against expectations and needs further scrutiny. Hemispheric differences in genetic diversity can be due to historic climatic stability and lower seasonality in the southern hemisphere. Overall, we find that despite the differences in mean genetic diversity among animals, similar processes related to life-history strategy and biogeography are associated with the variation within them.

Birds and bats enhance cacao yield despite suppressing arthropod mesopredation.

Bird- and bat-mediated biocontrol benefits the productivity of tropical commodity crops such as cacao, but the ecological interactions driving these ecosystem services remain poorly understood. Whereas birds and bats prey on herbivorous arthropods, they may also prey on arthropod mesopredators such as ants, with poorly understood consequences for pest biocontrol. We used a full-factorial experiment excluding birds, bats, and ants to assess their effects on (a) the abundance of multiple arthropod groups; (b) predation pressure on arthropods evaluated through artificial sentinel caterpillars; and (c) cacao yield over 1 year in shaded agroforestry systems of native cacao varieties in Peru. Birds and bats increased cacao yield by 118%, which translates in smallholder benefits of ca. US $959 ha-1 year-1 . Birds and bats decreased predation by ants and other arthropods, but contributed to the control of phytophagous taxa such as aphids and mealybugs. By contrast, ant presence increased the abundance of these sap-sucking insects, with negative impacts for cacao yield. Notably, high abundances of the dominant ant Nylanderia sp., known to attend sap-sucking insects, were associated with lower cacao yield along a distance gradient from the closest forest edge. According to these results, arthropod predation by birds and bats, rather than mesopredation by arthropods, was most responsible for increases in cacao yield. Moving forward, detailed research about their trophic interactions will be necessary to identify the cause of such benefits. Retaining and restoring the large benefits of birds and bats as well as minimizing disservices by other taxa in cacao agroforests can benefit from management schemes that prioritize preservation of shade trees and adjacent forests within agroforestry landscapes.

Focusing on the role of abiotic and biotic drivers on cross-taxon congruence

Diversity patterns can show congruence across taxonomic groups. Consistent diversity patterns allow the identification of indicator surrogates potentially representative of unobserved taxa or the broader biodiversity patterns. However, the effective use of biodiversity surrogates depends on underlying mechanisms driving the strength of the relationship among taxonomic groups. Here, we explored congruence patterns in community composition among taxa occupying different trophic levels, accounting for abiotic and biotic factors: vascular plants and six groups of ground-dwelling arthropods (pseudoscorpions, spiders, darkling beetles, rove beetles, ground beetles and ants) were chosen as potential indicator surrogates. We evaluated the cross-taxon relationships using Mantel test; subsequently, we investigated if these relationships could partially depend on abiotic drivers, using partial Mantel tests; then, we evaluated the partial contributions of abiotic and biotic drivers in explaining these relationships through a series of variation partitioning analyses. Our results showed that a consistent cross-taxon congruence pattern was evident across almost all group pairs: pseudoscorpions, spiders, ground beetles and vascular plants showed the largest number of significant correlations with other taxa. Environmental gradients resulted as drivers of cross-taxon congruence, shaping composition patterns. However, they were not the only ones. Biotic drivers account for part of cross-taxon congruence among vascular plants and arthropod predators (i.e., pseudoscorpions and spiders, but also ground beetles), as well as among taxa at high trophic levels. Almost all strictly predatory taxa, known as biological control agents, emerged as the best predictors of plant community composition even when the role of environmental factors was considered. Spiders/ants and spiders/ground beetles showed close relationships and congruent composition patterns, irrespective of environmental parameters. Relationships among taxa might be driven by several complex biotic interactions (e.g., non-trophic and trophic interactions, direct and indirect interactions). Bottom-up and top-down forces, consumptive and non-consumptive interactions may play a role in influencing the community composition of taxa and driving the observed relationships. Future studies should broaden knowledge about the role of these forces and interactions in determining the congruence across taxa. The multi-trophic perspective in cross-taxon studies can be promising for identifying biodiversity surrogates and their application in conservation planning.

Pesticide contamination in an intensive insect predator of honey bees

Pesticides used for plant protection can indirectly affect target and non-target organisms and are identified as a major cause of insect decline. Depending on species interactions, pesticides can be transferred into the environment from plants to preys and predators. While the transfer of pesticides is often studied through vertebrate and aquatic exposure, arthropod predators of insects may represent valuable bioindicators of environmental exposure to pesticides. A modified QuEChERS extraction coupled with HPLC-MS/MS analysis was used to address the question of the exposure to pesticides of the invasive hornet Vespa velutina, a specialist predator of honey bees. This analytical method allows the accurate quantification of nanogram/gram levels of 42 contaminants in a sample weight that can be obtained from single individuals. Pesticide residues were analyzed in female workers from 24 different hornet nests and 13 different pesticides and 1 synergist, piperonyl butoxide, were identified and quantified. In 75 % of the explored nests, we found at least one compound and in 53 % of the positive samples we could quantify residues ranging from 0.5 to 19.5 ng.g−1. In this study, hornets from nests located in sub-urban environments were the most contaminated. Pesticide residue analysis in small and easy to collect predatory insects opens new perspectives for the study of environmental contamination and the transfer of pesticides in terrestrial trophic chains.