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Managing biological control services through multi-trophic trait interactions: Review and guidelines for implementation at local and landscape scales
Abstract and Figures
Ecological studies are increasingly moving towards trait-based approaches, as the evidence mounts that functions, as opposed to taxonomy, drive ecosystem service delivery. Among ecosystem services, biological control has been somewhat overlooked in functional ecological studies. This is surprising given that, over recent decades, much of biological control research has been focused on identifying the multiple characteristics (traits) of species that influence trophic interactions. These traits are especially well developed for interactions between arthropods and flowers – important for biological control, as floral resources can provide natural enemies with nutritional supplements, which can dramatically increase biological control efficiency. Traits that underpin the biological control potential of a community and that drive the response of arthropods to environmental filters, from local to landscape-level conditions, are also emerging from recent empirical studies. We present an overview of the traits that have been identified to (i) drive trophic interactions, especially between plants and biological control agents through determining access to floral resources and enhancing longevity and fecundity of natural enemies, (ii) affect the biological control services provided by arthropods, and (iii) limit the response of arthropods to environmental filters, ranging from local management practices to landscape-level simplification. We use this review as a platform to outline opportunities and guidelines for future trait-based studies focused on the enhancement of biological control services.
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... CBC is inherently complex: as it involves myriad processes and functionally diverse plant, animal or microbial communities that act across spatio-temporal scales, its scientific understanding remains incomplete (Begg et al., 2017;Settele & Settle, 2018) and its functional ecology underpinnings stand weak (Perović et al., 2018). Often, experimental CBC interventions fail to direct biological control services, achieving few of their envisioned outcomes (Kleijn et al., 2019;González-Chang et al., 2020) and with their impacts critically obscured by landscape-level flows or processes (Karp et al., 2018). ...
... Though these approaches have become standard tools in fields such as pollination ecology, their usage in CBC is lagging. Yet, a delineation of the functional structure of S. frugiperda BCA communities can underpin trait-based approaches (Perović et al., 2018), weigh the relative contribution of landscape-versus field-level processes (Perez-Alvarez et al., 2021) and thereby inform CBC science and practice. ...
... Meanwhile, many confounding factors e.g., intraguild predation are not formally captured in our exercise as per Balvanera et al. (2005), but could be deduced by contrasting a taxon's computed functionality with actual recordings of biological control function or through life table analysis (Gardiner et al., 2009;Macfadyen et al., 2011;Naranjo et al., 2022). Further, it is worthwhile to closely examine the traits that drive the functional contribution of a given taxon e.g., body size, life history, dietary breadth (Sanders et al., 2015), dispersal capacities and/or adaptations to ephemeral habitats (Perović et al., 2018) or functional divergence in hunting strategy (Michalko and Pekár, 2016). In this regard, it may be valuable to closely examine the traits of Doru spp. or Orius spp., foliage-foraging ants and parasitoids such as C. insularis, C. grioti or T. remus. ...
Ecosystem functions such as biological pest control are mediated by the richness and abundance of service providers i.e., biological control agents (BCAs), relative contributions of individual taxa and community structure. This is especially relevant in the native range of agricultural herbivores, where a speciose community of co- evolved BCAs can prevent them from attaining pest status. Here, we use a powerful graphical approach to assess the functional structure of BCA communities of the fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize in the Neotropics. Drawing upon a curated database of all-time field and laboratory studies, we graphed patterns in the functional contribution, abundance and niche breadth for a respective 69, 53 and 3 taxa of resident parasitoids, predators and pathogens. Regardless of varying taxon coverage and rigor of the underlying studies, functional structure follows a saturating relationship in which the first three taxa account for 90–98% of aggregate biological control function. Abundance-functionality matrices prove critically incomplete, as more than 80% of invertebrate taxa miss empirically derived efficiency metrics while associated FAW infestation data are scarce. Despite its methodological shortfalls and data gaps, our work pinpoints Chelonus insularis, several taxa of egg parasitoids, Doru spp. and Orius spp. as taxa with outsized (average) functionality and conservation potential. This is also exemplified by the highly variable aggregate function across studies, with dispersion indices of 1.52 and 2.14 for invertebrate BCAs. Our work underlines the critical importance of functional ecology research, networked trials and standardized methodologies in advancing conservation logical control globally.
... A polyculture design approach aimed at increasing functional trait diversity (e.g. accessing different chemical forms of nutrients, or resource acquisition staggered in time and space) rather than simple increase in species number can potentially improve performance of crop polycultures (Perović et al. 2018). Yet common polyculture design approaches, for example increasing crop stand structural complexity (Gontijo et al. 2018;Jones and Sieving 2006) or provisioning abundant floral resources (Perović et al. 2018) may sometimes have negative impacts on pest control. ...
... accessing different chemical forms of nutrients, or resource acquisition staggered in time and space) rather than simple increase in species number can potentially improve performance of crop polycultures (Perović et al. 2018). Yet common polyculture design approaches, for example increasing crop stand structural complexity (Gontijo et al. 2018;Jones and Sieving 2006) or provisioning abundant floral resources (Perović et al. 2018) may sometimes have negative impacts on pest control. Therefore, early and comprehensive integration of observational data into trait-based polyculture design models is essential for model verification and refining. ...
... 60% higher hay yield in species-rich (25-41 plant species) than species-poor (6-17 species) sowings (Bullock et al. 2001). This is opposed to uni-functional system optimization which is peaked at low species diversity and is often composed of only a few polyculture components with the highest individual biomass production (reviewed in Perović et al. 2018). ...
... Finally, beyond species-level diversity and composition, it is vital to understand the functional diversity and composition of plant traits, as these critically impact plant ecosystem functioning, and can affect Frontiers in Sustainable Food Systems 03 frontiersin.org herbivores and ecosystem service providers like pollinators and natural enemies (Cornelissen et al., 2003;Pérez-Harguindeguy et al., 2013;Fountain-Jones et al., 2003;Perovič et al., 2018). Despite this, we are not aware of any studies that have quantified or examined the drivers of plant trait variation and diversity within urban gardens. ...
... Traits like higher average foliage height can maximize photosynthesis and minimize herbivory, and also protect plants from abiotic factors such as severe climatic conditions (Cornelissen et al., 2003;Pérez-Harguindeguy et al., 2013). The presence of trichomes can hinder herbivore feeding and have cascading effects on natural enemies (as cited in Perovič et al., 2018), while floral traits, like flower shape and color can strongly affect pollinator or natural enemy visitation (Rosas-Guerrero et al., 2014;Perovič et al., 2018). Further, measuring trait diversity at the community level can be particularly effective at describing the suite of traits supported in a single habitat patch and can be quantified in several ways (Funk et al., 2017). ...
... Traits like higher average foliage height can maximize photosynthesis and minimize herbivory, and also protect plants from abiotic factors such as severe climatic conditions (Cornelissen et al., 2003;Pérez-Harguindeguy et al., 2013). The presence of trichomes can hinder herbivore feeding and have cascading effects on natural enemies (as cited in Perovič et al., 2018), while floral traits, like flower shape and color can strongly affect pollinator or natural enemy visitation (Rosas-Guerrero et al., 2014;Perovič et al., 2018). Further, measuring trait diversity at the community level can be particularly effective at describing the suite of traits supported in a single habitat patch and can be quantified in several ways (Funk et al., 2017). ...
Urban ecological communities are shaped by an array of environmental and physical factors that include climate, biogeography, species interactions, dispersal, and ecological filters at the habitat and landscape scales. In addition, many social dynamics, decision-making processes, and other social characteristics, such as development, policy, government actions, as well as socioeconomic status of residents – the so-called ‘luxury’ effect – may also play strong roles in shaping which species occur within the urban context. This interaction between ecological and social drivers may impact species richness and may also influence functional traits and functional diversity, with important implications for ecosystem services provided within urban spaces. Urban agroecosystems provide food and other well-being benefits to urban residents, and are valuable green spaces in the city that provide refuges for biodiversity. Despite this fact, one of the biggest risks to gardens is insecure land tenure. While plant communities within gardens may be shaped by gardener demographics, food cultures, and ecological processes, little is known about how factors such as luxury and land tenure security may impact plant diversity, plant functional traits, and functional diversity, as well as species and trait composition. In this study, we ask how garden physical features, luxury, and land tenure security influence plant species richness, functional diversity, and species and trait composition within gardens in the California central coast. We surveyed vegetation, assessed plant traits related to growth form, plant defense, and floral characteristics, and collected information on multiple factors associated with land tenure and luxury. We found that land tenure secure gardens had higher plant and crop richness. Variables associated with garden luxury boosted ornamental plant richness, flower abundance and height, lowered crop richness, and strongly impacted plant species composition. Garden plot size negatively correlated with plant species and functional richness and relative abundance of trees. Weed species richness was not impacted by any social or physical feature examined. Thus overall, in community gardens, cultivated plants, and their traits, are strongly shaped by the socioeconomic factors of land tenure security and luxury as well as the spatial distribution and size of garden plots, with important implications for both conservation and ecosystem services provided by garden habitats within cities.
... To feed this potentially 'game-changing' knowledge forward into breeding pipelines, systematic analyses of genebank collections supported by automation approaches are needed [65], the value of pest tolerance or partial resistance needs to be fully explored [70], and the pace of scientific research on ecologically based defenses needs urgent quickening. ...
... Further, given the impracticality to detect every single interaction on Earth, predictive efforts are crucial and can draw upon co-occurrence patterns or matching traits such as seed size and granivore mandible width [22,56]. In such endeavors, comprehensive, high-quality trait datasets [70,83] and standardized data collection and compilation protocols [84] are essential. In this regard, valuable lessons can be drawn from coordinated, multi-site programs such as the International Long-Term Ecological Research Network (ILTER; https://lternet.edu/international/), the fledgling Long-Term Agroecosystem Research (LTAR; https://ltar.ars.usda.gov/) ...
... The functional approach has only recently been incorporated in animal ecology and for terrestrial arthropods , Perović et al. 2018. Although the term 'functional diversity' is widely used and accepted, we prefer to use the terms 'trait diversity' and 'trait-based approach' unless the functionality of traits has been assessed (by evaluating the relationships between traits and fitness along environmental gradients, see . ...
... L'approche fonctionnelle a été incorporée seulement récemment en écologie animale et pour les arthropodes terrestres , Perović et al. 2018. Bien que le terme « diversité fonctionnelle » soit largement utilisé et accepté, nous préférons utiliser les termes « diversité des traits » et « approche basée sur les traits » à moins que la fonctionnalité des traits ait été évaluée (en évaluant les relations entre les traits et la fitness le long de gradient environnementaux, voir . ...
Describing patterns of biological diversity and understanding their origins is one of the major challenges of modern ecology. Tropical environments in particular are the most species-rich terrestrial ecosystems and among the least well-known. Spiders are a relevant model group in ecology, because they are abundant and diverse with high ecological importance, whose study should allow a better understanding of the processes responsible for diversity patterns. We investigated the patterns of diversity and the processes responsible for spider assemblages in Neotropical forests and the Hawaiian archipelago using a set of complementary approaches (based on taxa, traits, evolutionary units). Due to the lack of knowledge on sampling and diversity of tropical spiders, we tested and compared different sampling methods and standardized protocols by focusing on different vegetation strata. We developed a morpho-species database to overcome the lack of taxonomic knowledge. We studied a set of traits (body size, leg length and hunting guilds) to test their informative character in tropical assemblages. Finally, we determined evolutionary units to study diversity by applying a multilocus (mitochondrial and nuclear) approach on a large collection of tropical spiders, for which taxonomic knowledge is incomplete and problematic. We have shown that the taxon-, traits- and evolutionary units diversity patterns of tropical spiders are influenced by the habitat, and that consequently habitat filtering is crucial in determining the assemblages of these spiders. In addition, we have shown the context-dependent and scale-dependent nature of diversity patterns in tropical spiders with variations of tropical spider assemblages at a finer scale than that of habitats. Overall, this plaid for more case studies studying tropical diversity patterns at the scale of strata, vegetation sub-structures, and micro-habitat conditions, for which we are suggesting research axe.
... Predator energy use integrates the abundance, body mass and metabolic rate of the predators and is increasingly used as a predictor of pest suppression in agricultural landscapes (Perović et al., 2018; see Supporting Information, Methods S1 for details and calculation). As predator energy use is partly confounded by predator abundance and richness, we standardized energy use in each sampling plot with null values generated with an independent swap null model for functional alpha diversity using package 'picante' in r (Kembel et al., 2010). ...
... While the positive effect of predator abundance has frequently been reported elsewhere , the impact of richness and energy use remains ambiguous (Rusch et al., 2015). Although energy use has been suggested as a useful proxy for prey consumption (Perović et al., 2018), it has also been argued that an increase in body size and energy requirement can alter predator-prey dynamics by F I G U R E 3 Mean ± 1 SE per sampling plot of (a) predator abundance, (b) predator family richness, (c) standardized effect sizes (SES) of predator energy use, (d) sentinel egg predation, (e) pest infestation and (f) coefficients of variation for sentinel egg predation and pest infestation in semi-natural reference sites (SN), organic orchards (Org) and orchards with integrated pest management (IPM). Letters indicate significant differences between management types. ...
Biological pest control, relying on naturally occurring predator–prey dynamics, is considered a key element to achieve more sustainable farming systems. However, the combined effects of local management and landscape factors on communities of natural enemies as well as the cascading effects on pest infestations are rarely addressed, especially in perennial crops.
Here, we used Piecewise Structural Equation Modelling (PSEM) to test direct and indirect effects of landscape composition, landscape configuration and local management practices on natural enemy communities, the pest control services they provide and ultimately on pest infestation and pest‐related yield damage in apple crops. To this end, we surveyed 12 organic and 12 Integrated Pest Management (IPM) orchards during three consecutive years, and we also established a semi‐natural benchmark to quantify the extent to which predator communities in the orchards were degraded.
Natural enemies had a different community composition and were more abundant in organic orchards compared with IPM orchards. This had a small and positive effect on sentinel egg predation rates in organic orchards, but overall had very little impact on actual apple pest infestation. On the contrary, apple pest infestation levels were directly and positively affected by organic management practices and by increasing semi‐natural habitat cover and landscape edge density. Compared with a semi‐natural benchmark, both agricultural management systems showed degraded predator communities, which translated into an impaired delivery of biological control services.
Synthesis and applications. Our results indicate that organic management and habitat conservation can enhance natural enemies and stimulate pest control, but also show that these factors can enhance pest infestations and can even lead to an overall increase in pest‐related crop damage. Our study thus highlights the complex interplay of ecosystem services and disservices provided by biodiversity, which should be taken into account when advising farmers, policy makers and land managers on effective and sustainable strategies to control pest species and safeguard crop production.
... For example, biological control impacts often even supersede those of plant quality (Asiimwe et al., 2013), while its relative contribution is greatly attenuated by 'full' host plant resistance (Kersch-Becker and Thaler, 2015). Habitat management through the establishment of intercrops, flower strips or hedgerows or a progressive phasedown of pesticide use might also enhance biological control agent abundance and diversity, which, in turn defines biological control outcomes (Landis et al., 2000;Perovic et al., 2018;Roudine et al., 2023). These approaches are slowly but surely being integrated in management toolkits for high-profile diseases such as citrus greening (Patt et al., 2020;Irvin et al., 2024;Cortez-Madrigal, 2024). ...
Diseases caused by vector-borne plant pathogens cause adverse impacts on yield resilience, food security, and farmer livelihoods, which are bound to aggravate under global change. Biological control is routinely discounted as a mitigation strategy for plant diseases, partially due to scarce and inconclusive empirical support. Here, using curated field survey data for 58 persistently or semi-persistently transmitted pathogens, we employ a multi-method approach to assess the role of resident (i.e., naturally occurring) biological control agents in these pathosystems. Our meta-analyses show how in planta pathogen incidence is strongly affected by vector abundance and infectivity. Meanwhile, biological control agent density negatively affects vector abundance and slows vector population build-up. Together, these relationships suggest that biological control lessens pathogen incidence by reducing vector abundance, though a paucity of data impedes direct, empirical demonstration of this effect. In particular, bipartite (mainly vector × pathogen) interactions have only been uncovered under field conditions for less than half of focal pathosystems. More so, just 5 % of studies simultaneously reported pathogen , vector, and biological control agent densities. Our study contests the long-standing dogma that arthropod-vectored pathogens cannot be mitigated through biological control, and accentuates how observational or manipulative field studies are imperative to grasp its full potential.
... Floral resources offer nutrition to enhance longevity, reproductive capacity, and biological control impact of predators and parasitoids (Hatt et al. 2019;Lu et al. 2014;Wang et al. 2020;Xiong et al. 2021;Zhao et al. 2017). Because of these plants providing floral resources are often intercropped or planted on crop margins to improve biological control and reduce dependence on chemical pesticides in integrated pest management (IPM) programs worldwide, natural enemies easily get the floral resources (Parolin et al. 2012;Damien et al. 2017;Perovic et al. 2018Perovic et al. , 2021Gong et al. 2024;Gurr et al. 2016;Wang et al. 2022b). ...
Floral resources such as nectar are essential for increasing survival and population growth of synovigenic parasitic wasps in agroecosystems. Although the bottom-up effect of cadmium (Cd) has been identified as a major ecological force influencing multitrophic interactions of synovigenic parasitoids, information on the direct effects of Cd-contaminated floral resources on the fitness of natural enemies which might impact their fitness and effectiveness are still lacking. In this study, we assessed the performance of three commonly used Trichogramma species exposed to Cd-contaminated sucrose solutions. Female survival, longevity, the female/male adult proportion, and F1 emergence rate of T. japonicum were not affected by Cd concentrations. However, a decline in the survival rate of females, their longevity, and female/male adult proportion were observed for T. dendrolimi at high Cd concentration. No significant differences in female/male adult proporation and longevity of T. ostriniae were found at wide Cd concentration ranges. Our results suggest that Cd-contaminated nectar resources can negatively affect performance of some Trichogramma spp., indicating Cd contamination in nectar would directly reduce the potential value of these species in IPM programs. These results not only increase our understanding of interspecific variations in synovigeny of Trichogramma, but also suggest that releases of T. japonicum and T. ostriniae rather than T. dendrolimi should be considered at Cd-contaminated sites.
... Both conventional and organic Georgia blueberry farms use spinosyn and pyrethrum for control of SWD (Van Timmeren and Isaacs 2013), which are relatively similar in their toxicity to SWD (Cuthbertson et al. 2014, Noble et al. 2017. Besides this, parasitoids and natural enemies depend upon resource connectivity, and any management practice, such as the use of pesticides, that disrupts or limits the availability of food or host resources can impact parasitoid abundance or performance (Perovic et al. 2018, Schmidt et al. 2021. While the organic farms surveyed contained a ground cover of grass or mixed vegetation between the plants and rows, the conventional fields lacked vegetation cover. ...
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), commonly known as spotted-wing Drosophila (SWD), is an invasive insect pest threatening the economy of many small fruit farms in the Americas and Europe. Biological control using parasitoids is a promising strategy for improving the sustainable management of SWD. To use the parasitoids as biocontrol agents, recognizing and understanding the presence and preference of North American native parasitoids and their local adaptation is necessary. We conducted 2 season-long field explorations of North American native parasitoids of SWD during 2021 and 2022 at major blueberry-producing locations in southeast GA, USA. A total of 371 parasitoids of Drosophila were collected using fruit-baited sentinel traps and classified into 3 families: Figitidae, Pteromalidae, and Diapriidae. Leptopilina boulardi (Hymenoptera: Figitidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) were the most abundant species. The abundance of parasitoids was higher during the peak blueberry ripening period through the end of the harvest season compared to all other phenological stages. Out of the North American native parasitoids of SWD that we collected, Pachycrepoideus vindemmiae successfully parasitized SWD in its natural habitat, and L. boulardi only parasitized SWD larvae at a low rate of 7% in the laboratory, but it failed to emerge from all the parasitized SWD. Ultimately, we found that the existing North American native parasitoids were inadequate to suppress the SWD in these locations. Planned intervention with the classical release of Asian native specialist parasitoids in addition to the existing SWD management approaches was deemed necessary in these areas.
... adjacent vegetation and ground covers) and olive orchards. However, the trend resulting from this synergistic relationship may be modulated by the complexity and functionality of the vegetation (Haddad et al., 2001;Hatt et al., 2017Hatt et al., , 2019Knops et al., 1999;Perovic et al., 2018). In olive orchards, for example, plant richness and arrangement affect key arthropods that prey on or parasitize olive pests differently, suggesting that each key arthropod taxon responds to its individual needs for plant resources but forms groups modulated by the gradient of complexity, which particularly affects predators and omnivores (Álvarez, Morente, & Ruano, 2021). ...
Biological control of pests can be enhanced by the presence of semi-natural habitats within agricultural landscapes. However, this assumption remains controversial due to inconsistencies related to the type of agroecosystems and the natural enemies studied. Within olive orchards, there is a lack of information regarding the interaction among natural enemies and their relation with habitat structure to control pests at the landscape scale. Here, we investigate the effects of the natural habitat on the pest, pest damage and the interaction of pests and natural enemies-using a trophic guild approach, in organic olive orchards. For this, we decomposed the natural habitats into vegetation structures and analysed their effects with a multi-scale perspective. Our results show that (1) greater proportions of natural habitats increase the abundance of ants (omnivores) and predators and diminish pest pressures-reducing the impact of Prays oleae on olive fruits. (2) Vegetation structures within natural habitats were grouped, based on their effects, into three main vegetation groups: grassland and forest , scrublands and olive trees. However, the dense scrubland and the dense forest improve the abundance of natural enemies that are linked to pest damage the most. (3) Prays oleae increases in landscapes dominated by low numbers of patches that are highly aggregated. Conversely, ants and predators increased in landscapes dominated by high numbers of patches that have a less edge-resembling shape. (4) Within the olive canopy, the abundance of lacewing larvae and salticid spiders is related to lower pest damage and a reduction in P. oleae adults respectively. However, when ants and predators interact with the natural habitat, they can cope with pest pressures without the need for high abundances, supporting 'the more-effective natural enemy hypoth-esis' in agroecosystems.
... Trait-based predictions for hymenopteran parasitoids are premised on the assumption that the agricultural habitat will contain species that are adapted to harsh environments. For example, a generalist feeding strategy, small body size, and relatively longer activity periods are associated with intensified agricultural environments (G amez- Virués et al., 2015;Perovi c et al., 2018). Furthermore, differences in senescence are often associated with differences in environmental conditions; habitats with higher adult mortality risk often contain species with lower adult longevity and earlier senescence (Bryant & Reznick, 2004;Stearns et al., 2000;Williams, 1957). ...
Agricultural habitats are frequently disturbed, and disturbances could have major effects on species in upper trophic levels such as hymenopteran parasitoids that are important for biological control. A strategy for conservation biological control is to provide a diversified agricultural landscape which increases the availability of resources such as sugar required by parasitoid biological control agents. Here, we ask whether parasitoids occurring in agriculture benefit from sugar resources more or less than parasitoids occurring in natural habitats surrounding agricultural fields. We collected parasitoids from agricultural alfalfa fields, field margins, and natural prairies, and in the lab we randomly divided them into two treatments: half were given a constant supply of a sugar source to test their residual lifespan, and half were given neither sugar nor water to test their hardiness. Collected individuals were monitored daily and their day of death recorded. Parasitoids receiving a sugar source lived substantially longer than those without. Parasitoids collected in prairies lived longer than those from alfalfa fields in both the residual lifespan and hardiness treatments, with parasitoids from field margins being intermediate between them. Furthermore, the benefits of a sugar source to increase longevity was lower for parasitoids collected in agriculture than in natural habitats. This suggests that, even though parasitoid biological control agents benefit from sugar resources, their short lifespans make the benefit of sugar resources small compared to parasitoids that occur in natural habitats and have longer lifespans, and are adapted to consistent sugar sources.
... Nowadays, the studies related with ecosystem services in agroecosystems are focused on understanding the functional features provided by insects, like biological control (Perović et al., 2018;Demestihas et al., 2017). It is estimated that 20 to 40 % of the global crop production is annually lost by the action of insect pests (FAO, 2020), increasing in recent years due to the climate warming that alters relevant biological insect features (Deutsch et al., 2018). ...
... Meanwhile, traits that capture response diversity or extinction proneness may be especially important in highly disturbed (farm) settings (Redhead et al., 2018;Walker et al., 2023). While extensive trait databases exist for plants, invertebrate or microbial trait data tend to be scarce, uncurated and scattered across the literature (Perović et al., 2018;Segoli et al., 2023). Trait-based approaches however are imperative to reliably pinpoint tipping points for network collapse (Bascompte and Scheffer, 2023) e.g., in which the respective loss of endemic macromoth or parasitoids may either trigger farm-level pest outbreaks or lower restoration success (Villar, 2023). ...
Biodiversity loss, as driven by anthropogenic global change, imperils biosphere intactness and integrity.
Ecosystem services such as top-down regulation (or biological control; BC) are susceptible to loss of extinction-prone
taxa at upper trophic levels and secondary ‘support’ species e.g., herbivores. Here, drawing upon curated
open-access interaction data, we structurally analyze trophic networks centered on the fall armyworm Spodoptera
frugiperda (Lepidoptera: Noctuidae) and assess their robustness to species loss. Tri-partite networks link 80 BC
organisms (invertebrate or microbial), 512 lepidopteran hosts and 1194 plants (including 147 cultivated crops)
in the Neotropics. These comprise threatened herbaceous or woody plants and conservation flagships such as
saturniid moths. Treating all interaction partners functionally equivalent, random herbivore loss exerts a
respective 26 % or 108 % higher impact on top-down regulation in crop and non-crop settings than that of BC organisms (at 50 % loss). Equally, random loss of BC organisms affects herbivore regulation to a greater extent
(13.8 % at 50 % loss) than herbivore loss mediates their preservation (11.4 %). Yet, under moderate biodiversity
loss, (non-pest) herbivores prove highly susceptible to loss of BC organisms. Our topological approach spotlights
how agriculturally-subsidized BC agents benefit vegetation restoration, while non-pest herbivores uphold biological
control in on- and off-farm settings alike. Our work underlines how the on-farm usage of endemic biological
control organisms can advance conservation, restoration, and agricultural sustainability imperatives. We
discuss how integrative approaches and close interdisciplinary cooperation can spawn desirable outcomes for
science, policy and practice.
... The activity of ES providers may be influenced by a variety of direct and indirect factors operating at different spatial scales, ultimately affecting plant reproductive success (Klein et al. 2007, Bartomeus et al. 2014, Dainese et al. 2019, Martin et al. 2019. Resource availability at relevant activity distances is a major factor directly shaping the overall abundance and composition of ES providers across landscapes, as well as the provision of ecosystem services, including herbivore population control and pollination (Isaacs et al. 2009, Woodard and Jha 2017, Perović et al. 2018, Albrecht et al. 2020). In addition, biotic and abiotic factors influencing plant properties may indirectly affect the activity of ES providers by altering the attractiveness of these plants (Dale and Polasky 2007, Brittain et al. 2010, van der Sluijs et al. 2013, Burkle and Runyon 2016, Liere et al. 2017. ...
Pollinator activity is affected by landscape‐scale flower availability, and by pollinator interactions with co‐occurring organisms. Of special interest are potentially detrimental effects of herbivores on the attractiveness of plants to pollinators. While insect herbivores are abundant in natural and agro‐ecosystems, the combined effect of herbivory and landscape floral resources on pollinator activity and the delivery of pollination services is little studied and understood. Here we investigated the combined effects of surrounding flower cover and aphid herbivory on pollination services in agricultural landscapes. We apply a resource landscape approach for mapping the spatial distribution of floral resources across landscapes, using neighbourhood modelling and empirical data on flower availability in specific land‐use types. In each of 25 Mediterranean landscapes spanning a gradient of land‐use intensity ranging from natural to agricultural, we established paired patches of potted aphid‐infested or aphid‐free phytometer plants Diplotaxis erucoides. In each patch, we recorded the activity of insects visiting flowers and subsequent seed set. We also recorded the relative abundance of flowers in dominant land‐use locales within a 1 km radius of each patch. Neighbourhood analyses revealed that plant–pollinator interactions in our study system are shaped by herbivory, distribution of floral resources across the landscape, and the interaction between these factors. We found a negative competitive effect of flower cover on pollinator activity and phytometer seed‐set; this effect was stronger on aphid‐infested than aphid‐free plants. The main pollinator guilds in the study sites (wild bees, honeybees and non‐bee pollinators) responded differently to these factors. Our results highlight the importance of combining a resource landscape approach with the exploration of interactions among different organisms, when mapping pollination services and identifying the scale at which pollinators respond to foraging resources.
... This spillover of arthropods can result from their periodic or annual movements across habitat edges (Blitzer et al., 2012;Tscharntke et al., 2012), leading to a substantial variation in community structures along the gradient from field edges towards arable field interiors (Fagan et al., 1999;González et al., 2016;Rand et al., 2006). Thus, cross-habitat movements of organisms can be crucial for promoting in-field diversity (Galpern et al., 2020;González et al., 2020a;Knapp et al., 2019) and ecosystem services such as biological control (Ollivier et al., 2020;Perović et al., 2018), pollination (Castro et al., 2021), and organic matter decomposition (Benbow et al., 2019). However, this can be strongly influenced by the dispersal abilities of different species. ...
Agricultural intensification and landscape simplification are among the major drivers of biodiversity loss in agricultural landscapes. Increasing field edges might be a key solution for enhancing biodiversity and related ecosystem services within arable fields. In this study, we investigated the spatial distribution of nine arthropod groups and weed seed and pest predation rates across different distances from field edges and crop types. Furthermore, we tested the relationship between local carabid abundance and species richness and directly measured weed seed and pest predation rates. Most of the investigated taxa were not affected by field margin proximity, except for carabid species richness and the abundance of bees and wasps, hoverflies, and myriapods, which were high near the edge. We found a higher abundance of carabids and herbivores in oilseed rape compared to other crops, while hoverflies, bees and wasps were more abundant in cereal. True bug abundance was significantly higher in oilseed rape interiors compared to edges. Weed seed predation and pest predation by small mammals were the highest at 36 m from the field margin, probably due to small mammal distribution, while pest predation by arthropods did not show any significant pattern. Both weed seed predation rate and arthropod pest predation were positively related to carabid abundance and negatively to species richness. Contrasting responses across nine investigated arthropod taxa indicate that redesigning agricultural landscapes to support biodiversity across taxa will be challenging, and further studies are needed to fully understand the spatial distribution of arthropods and related ecosystem services in agricultural landscapes.
... Further to selecting forb species known to attract and support natural enemies of crop pests, a trait-based approach has been proposed to tailor flowering mixtures towards enhancing biological control (Gardarin et al., 2018;Perovic et al., 2018). An initial hypothesis was that an increase in the functional diversity of flower mixtures would provide more niches for floral food consumers, promoting niche complementarity and lowering competition, thereby leading to an increase in the diversity of flower visitors, particularly if the species concerned have different ecological requirements. ...
In an attempt to restore functional biodiversity-delivering ecosystem services, several alternative agricultural approaches have emerged. Among these, two have been particularly acknowledged in recent decades: organic agriculture, with its aim to restrict the use of synthetic intrants, and conservation agriculture, promoting soil health via reduced soil tillage, permanent soil cover and crop diversification. Both approaches share the same overarching objective of restoring ecological functions and services to reach higher autonomy and resilience, yet, they have long represented two distinct communities. Today, interests from both parties are starting to converge: organic farmers are willing to provide more attention to their soils and conservation farmers are willing to decrease their dependency on synthetic intrants. However, when combining both approaches, farmers are left with no curative tools to combat pests and preventive agroecological practices become of the uttermost importance. This chapter reviews the challenge of controlling pests when opting for a combination of organic and conservation agriculture principles, reviewing the scientific knowledge on agroecological practices managing pests, then presenting the feedback of eight farmers in Belgium who have opted for this ambitious approach of organic-conservation agricultures combined.
... Regarding our fourth prediction, we expected that arthropod species with higher dispersal capacities could cope better with more perturbed and fragmented habitats (Perović et al., 2018). Therefore, low dispersal capacity should be associated with higher vulnerability to such land-use modifications and face higher local extinction risks (Tscharntke et al., 2012;Wong et al., 2019). ...
Understanding how anthropogenic activities induce changes in the functional traits of arthropod communities is critical to assessing their ecological consequences. However, we largely lack comprehensive assessments of the long‐term impact of global‐change drivers on the trait composition of arthropod communities across a large number of species and sites. This knowledge gap critically hampers our ability to predict human‐driven impacts on communities and ecosystems.
Here, we use a dataset of 1.73 million individuals from 877 species to study how four functionally important traits of carabid beetles and spiders (i.e. body size, duration of activity period, tolerance to drought, and dispersal capacity) have changed at the community level across ~40 years in different types of land use and as a consequence of land use changes (that is, urbanisation and loss of woody vegetation) at the landscape scale in Switzerland.
The results show that the mean body size in carabid communities declined in all types of land use, with particularly stronger declines in croplands compared to forests. Furthermore, the length of the activity period and the tolerance to drought of spider communities decreased in most land use types. The average body size of carabid communities in landscapes with increased urbanisation in the last ~40 years tended to decrease. However, the length of the activity period, the tolerance to drought, and the dispersal capacity did not change significantly. Furthermore, urbanisation promoted increases in the average dispersal capacities of spider communities. Additionally, urbanisation favoured spider communities with larger body sizes and longer activity periods. The loss of woody areas at the landscape level was associated with trait shifts to carabid communities with larger body sizes, shorter activity periods, higher drought tolerances and strongly decreased dispersal capacities. Decreases in activity periods and dispersal capacities were also found in spider communities.
Our study demonstrates that human‐induced changes in land use alter key functional traits of carabid and spider communities in the long term. The detected trait shifts in arthropod communities likely have important consequences for their functional roles in ecosystems.
... Most studies on functional traits have focused on their relationships with arthropod communities (Greenop et al. 2023), but studies on plant functional traits in agroecosystems are still limited (Perović et al. 2018), although they are expected to play a crucial role in influencing arthropod community composition. Plant functional traits associated with plant resource use, growth, and life history strategies (e.g., leaf area, leaf toughness and palatability, and leaf C and N content) are often studied to explore plant-environment and plant-plant interactions (e.g., Blumenthal et al. 2020;Fantinato et al. 2023); however, being also related to leaf nutritional value (e.g., C:N ratio; Pérez-Harguindeguy et al. 2013) and resistance to herbivory (e.g., leaf toughness; Pérez-Harguindeguy et al. 2013), these traits can help explain the richness and abundance of herbivorous (Storkey et al. 2013) and saprophagous arthropods (Ganault et al. 2022). ...
Flower strips are a fundamental part of agri-environment schemes in the Common Agricultural Policy (CAP). Although vegetation is central for many arthropod groups, a few studies have evaluated the effects of flower strip structural and functional attributes on arthropod communities. In this study, we explored the relationship between flower strip attributes and the abundance of different arthropod functional groups in annual flower strips located in an organic apple orchard. We surveyed plant and arthropod communities in 30 1 m × 6 m plots. In each plot, we collected data on species composition and vegetation structure (e.g., total cover, density, number of floral displays). For each plant species, we also retrieved data on leaf palatability and nutritional value. Arthropods were collected using sweep netting technique. Structural and functional attributes of the flower strip revealed a crucial role in regulating arthropod abundance, which however depended on the specific arthropod functional group. We identified three main attributes (plant species richness, composition, and vegetation density) of flower strips that should be considered when implementing multifunctional flower strips. Specifically, plant species richness to ensure complementarity of resources and niches, plant species composition to ensure complementary floral resources, and vegetation density to ensure sheltering microhabitats and suitable microclimatic conditions and to increase the density of floral resources. Our results suggest that by considering structural and functional attributes of flower strips, it is possible to design multifunctional flower strips with greater effectiveness as measures for ecological intensification.
... In-field organismal abundance irregularly informs laboratory-level scrutiny, where up to eight metrics may (or may not) shine light on their actual efficacy. This decision-making process has to be sharpened and trait-based approaches are often touted as a game-changer (Perović et al., 2018). While such tools are being developed, demographic analyses can clarify the impact of individual BCAs or gauge their (collective) contribution to pest population regulation (Bellows et al., 1992;Carey, 2001). ...
Since 2016, the fall armyworm (FAW) Spodoptera frugiperda has spread over extensive areas of the tropics and subtropics, imperiling food security, economic progress and the livelihoods of millions of cereal farmers. Although FAW has received long-standing scientific attention in its home range in the Americas, chemical inputs feature prominently in its mitigation and biological control uptake is globally lagging. Here, building upon a quantitative review of the global literature, we methodically dissect FAW biological control science. Of the known entomopathogens (46), parasitoids (304) and predators (215) of FAW, approx. 40% have been subject to laboratory-or field-level scrutiny. Laboratory-level performance has partially been assessed for 14-18% of the above invertebrate taxa. Yet, organismal, geographic, methodological and thematic biases hamper efforts to relate in-field biodiversity to actual ecosystem service delivery. Often, single-guild 'snapshot' surveys are preferred over comprehensive bio-inventories or population dynamics appraisals, trophic interactions are wrongly inferred from co-occurrence, standard pest infestation metrics are lacking and natural enemy censuses are performed arbitrarily. Diurnal biota receive inordinate attention, while egg and pupal predation-the main biotic sources of mortality-are routinely overlooked. Multiple microbial and invertebrate biota are investigated with a view towards mass-rearing and augmentative release, but the basis for agent selection is often unclear. Lastly, conservation biological control receives marginal attention and cross-disciplinary engagement with the agroecology domain is lagging. We lay out several steps, including standardized methodologies, smart use of biodemographic toolkits, networked field trials and a fortification of its ecological underpinnings, to sharpen the science of (FAW) biological control and urge further momentum in its global implementation.
... In-field organismal abundance irregularly informs laboratory-level scrutiny, where up to eight metrics may (or may not) shine light on their actual efficacy. This decision-making process has to be sharpened and trait-based approaches are often touted as a game-changer (Perović et al., 2018). While such tools are being developed, demographic analyses can clarify the impact of individual BCAs or gauge their (collective) contribution to pest population regulation (Bellows et al., 1992;Carey, 2001). ...
Since 2016, the fall armyworm (FAW) Spodoptera frugiperda has spread over extensive areas of the tropics and subtropics, imperiling food security, economic progress and the livelihoods of millions of cereal farmers. Although FAW has received long-standing scientific attention in its home range in the Americas, chemical inputs
feature prominently in its mitigation and biological control uptake is globally lagging. Here, building upon a quantitative review of the global literature, we methodically dissect FAW biological control science. Of the known entomopathogens (46), parasitoids (304) and predators (215) of FAW, approx. 40% have been subject to
laboratory- or field-level scrutiny. Laboratory-level performance has partially been assessed for 14–18% of the above invertebrate taxa. Yet, organismal, geographic, methodological and thematic biases hamper efforts to relate in-field biodiversity to actual ecosystem service delivery. Often, single-guild ‘snapshot’ surveys are
preferred over comprehensive bio-inventories or population dynamics appraisals, trophic interactions are wrongly inferred from co-occurrence, standard pest infestation metrics are lacking and natural enemy censuses are performed arbitrarily. Diurnal biota receive inordinate attention, while egg and pupal predation - the main biotic sources of mortality - are routinely overlooked. Multiple microbial and invertebrate biota are investigated with a view towards mass-rearing and augmentative release, but the basis for agent selection is often unclear. Lastly, conservation biological control receives marginal attention and cross-disciplinary engagement with the
agroecology domain is lagging. We lay out several steps, including standardized methodologies, smart use of biodemographic toolkits, networked field trials and a fortification of its ecological underpinnings, to sharpen the science of (FAW) biological control and urge further momentum in its global implementation.
... In-field organismal abundance irregularly informs laboratory-level scrutiny, where up to eight metrics may (or may not) shine light on their actual efficacy. This decision-making process has to be sharpened and trait-based approaches are often touted as a game-changer (Perović et al., 2018). While such tools are being developed, demographic analyses can clarify the impact of individual BCAs or gauge their (collective) contribution to pest population regulation (Bellows et al., 1992;Carey, 2001). ...
Since 2016, the fall armyworm (FAW) Spodoptera frugiperda has spread over extensive areas of the tropics and subtropics, imperiling food security, economic progress and the livelihoods of millions of cereal farmers. Although FAW has received long-standing scientific attention in its home range in the Americas, chemical inputs feature prominently in its mitigation and biological control uptake is globally lagging. Here, building upon a quantitative review of the global literature, we methodically dissect FAW biological control science. Of the known entomopathogens (46), parasitoids (304) and predators (215) of FAW, approx. 40% have been subject to laboratory- or field-level scrutiny. Laboratory-level performance has partially been assessed for 14–18% of the above invertebrate taxa. Yet, organismal, geographic, methodological and thematic biases hamper efforts to relate in-field biodiversity to actual ecosystem service delivery. Often, single-guild ‘snapshot’ surveys are preferred over comprehensive bio-inventories or population dynamics appraisals, trophic interactions are wrongly inferred from co-occurrence, standard pest infestation metrics are lacking and natural enemy censuses are performed arbitrarily. Diurnal biota receive inordinate attention, while egg and pupal predation - the main biotic sources of mortality - are routinely overlooked. Multiple microbial and invertebrate biota are investigated with a view towards mass-rearing and augmentative release, but the basis for agent selection is often unclear. Lastly, conservation biological control receives marginal attention and cross-disciplinary engagement with the agroecology domain is lagging. We lay out several steps, including standardized methodologies, smart use of biodemographic toolkits, networked field trials and a fortification of its ecological underpinnings, to sharpen the science of (FAW) biological control and urge further momentum in its global implementation.
... Alternative management strategies have been suggested to make the agroecosystem more supportive of local biodiversity, with the hope of boosting ESs (e.g., ecological intensification [3]). The effectiveness of such measures is routinely tracked by monitoring the abundance or diversity of the identified ES providers, which does not always reflect the levels of ESs [4,5]. A confounding factor is that a species cannot always be unequivocally labeled beneficial or harmful, as the same can be an ES provider and, at other times, an ED provider [6]. ...
Simple Summary
Ecosystem services (ESs) and disservices (EDs) are routinely estimated from changes in service provider densities without measuring their actual levels. By using the sentinel approach (i.e., exposing a plant, seeds, and prey models in a standardized way), we tested how coriander (Coriandrum sativum) strips planted in mixed orchards on Terceira Island (Azores, Portugal) affected ESs/EDs via herbivory on lettuce plants, seed predation on wheat and weed seeds, and predation on artificial caterpillars. Vertebrates had more influence than invertebrates on ESs and EDs. Herbivory (ED) after 2 weeks was similar in the coriander and the control plots, while seed predation was higher in the control than in the coriander plots on both wheat grain (an ED: 30.8% vs. 15.3%) and weed seeds (an ES: 2.5% vs. 0.4%). Vertebrate predation (ES) rates after 48 h were significantly higher in the control (9%) than in the coriander plots (3%), while no difference was observed for invertebrate predation. Coriander strips did not support increased ES/reduced ED levels in this habitat. The sentinel approach is effective to quantitatively compare multiple ESs/EDs under different farming management strategies.
Abstract
The effect of flower strips on ecosystem services (ESs) and disservices (EDs) is routinely assessed following changes in service provider densities without measuring the associated levels of ES/EDs. By using the sentinel approach (i.e., exposing a plant, seeds, and prey models in a standardized way), we tested how coriander (Coriandrum sativum) strips planted in mixed orchards on Terceira Island (Azores, Portugal) affected herbivory on lettuce plants, seed predation on wheat and weed seeds, and predation on artificial caterpillars. Vertebrates had more influence than invertebrates on ESs/EDs. Herbivory (ED) after 2 weeks was similar in the coriander and the control plots (mean ± SD; 2.3% ± 3.3% vs. 2.2% ± 2.9%, n = 32 for both). Seed predation was higher in the control than in the coriander plots for both grain (ED; 30.8% ± 38.9% vs. 15.3% ± 10.8%, n = 18 for both) and weed seeds (ES; 2.5% ± 4.1% vs. 0.4% ± 0.5%, n = 18 for both). Vertebrate predation (ES) rates after 48 h were significantly higher in the control (estimate 9%, 95% CI: 4–20%) than in the coriander plots (3%, 1–8%), while no difference was observed for invertebrate predation. Coriander strips did not support increased ES/reduced ED levels in this setting. The tools used can be effective to quantitatively compare multiple ESs/EDs under different farming management strategies.
... 57 These inconsistent patterns likely can be explained by space, time and gene dimensions of given intercrop system, 58 and a myriad of traits of the plant species that are paired. 59 Herbivores employ multiple olfactory and visual cues to locate their host plants and guide their foraging decisions. Companion plants regularly emit volatile repellents or arrestants that influence herbivore colonization processes, 60 and can also reduce the visual attractivity of a crop for flying aphids, for example, in sugar beet. ...
Background
The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is an important pest of cotton and horticultural crops globally. In China, smallholder farmers regularly intercrop cotton with garlic or onion. Aside from higher farm‐level revenue, cotton intercrops are typified by lower Aphis gossypii abundance than monocrops. So far, the mechanistic basis of this lowered pest pressure has not been empirically assessed.
Results
Field trials showed that Aphis gossypii abundance is lower and (relative) abundance of aphid predators higher in early‐season cotton intercrops than in monocrops. Cage trials and Y‐tube olfactometer tests further indicated that garlic and onion volatiles repel Aphis gossypii alates. Electrophysiological bioassays and gas chromatography–mass spectrometry (GC–MS) identified two physiologically active volatiles, that is, diallyl disulfide and propyl disulfide from garlic and onion respectively. Next, behavioral tests confirmed that both sulfur compounds exert a repellent effect on alate Aphis gossypii.
Conclusion
Garlic and onion volatiles interfere with Aphis gossypii settling, but do not affect its main (ladybird) predators. Meanwhile, early‐season cotton/onion intercrops bear higher numbers of Aphis gossypii predators and fewer aphids. By thus unveiling the ecological underpinnings of aphid biological control in diversified cropping systems, our work advances non‐chemical management of a globally‐important crop pest. © 2023 Society of Chemical Industry.
... In contrast, a study of urban greenspaces in Australia reporting strong positive associations between native plants and insect biodiversity found over 96% native insect species [80]. One important note is that beyond species-level diversity, composition, or the origin of plant species, it is vital to understand the functional diversity and composition of plant traits, such as growth form, floral attraction, and the presence of structures such as trichomes, spines, and nectaries, as such factors can critically impact arthropods such as pollinators and natural enemies [81][82][83], and may be more important than species identity. For bees in particular, our only sampled group of plant mutualists, co-evolutionary processes may shape their interactions with native plants [84]. ...
Simple Summary
Urban sprawl contributes to biodiversity loss, but the presence of native plants in urban areas may help to support diversity. In urban gardens, where non-native plants are common, the role of native plants may be especially important in providing resources to pollinators and other beneficial arthropods, like natural enemies of pests, but little research has examined how native plants affect non-pollinators in gardens. We sampled plants, bees, and three groups of natural enemies (ladybeetles, ants, and ground-foraging spiders) in gardens in California. We found that native plants represented about 10% of the species and only 2.5% of the plants found. The native plants present did not have large impacts on the numbers or diversity of bees, ladybeetles, or ants, but did have an unexpected negative effect on non-native spiders. Other garden features, such as garden size, flowers, mulch, and trees and shrubs, did have mostly positive impacts on the biodiversity of bees, ants, and spiders, but the impacts of each feature differed by organism type. Natural habitat near to gardens was also important for native ants, non-native bees, and ladybeetles. In sum, native plants, when rare within gardens, likely have little benefit, but other garden features can be manipulated in order to promote beneficial arthropods in gardens.
Abstract
(1) Urbanization threatens biodiversity, yet urban native plants support native biodiversity, contributing to conservation and ecosystem services. Within urban agroecosystems, where non-native plants are abundant, native plants may boost the abundance and richness of beneficial arthropods. Nevertheless, current information focuses on pollinators, with little attention being paid to other beneficials, like natural enemies. (2) We examined how the species richness of native plants, garden management, and landscape composition influence the abundance and species richness of all, native, and non-native bees, ladybeetles, ants, and ground-foraging spiders in urban agroecosystems (i.e., urban community gardens) in California. (3) We found that native plants (~10% of species, but only ~2.5% of plant cover) had little influence on arthropods, with negative effects only on non-native spider richness, likely due to the low plant cover provided by native plants. Garden size boosted native and non-native bee abundance and richness and non-native spider richness; floral abundance boosted non-native spider abundance and native and non-native spider richness; and mulch cover and tree and shrub abundance boosted non-native spider richness. Natural habitat cover promoted non-native bee and native ant abundance, but fewer native ladybeetle species were observed. (4) While native plant richness may not strongly influence the abundance and richness of beneficial arthropods, other garden management features could be manipulated to promote the conservation of native organisms or ecosystem services provided by native and non-native organisms within urban agroecosystems.
... The above two species possibly cannot compete with the locally dominant T. brassicae and fail to persist in the harsh and ecologically fragile (desert) settings. Overall, temporal shifts in host and parasitoid community carry implications for crop protection, and habitat management schemes will need to be attuned to the locally prevailing parasitoid species and (a-) biotic conditions (Gurr et al. 2017;Perović et al. 2018). Applied ecological research is thus essential to ensure that (biodiversity-based) management strategies are well-suited to local farming contexts. ...
Globally, insect abundance and diversity are experiencing a rapid decline. Despite important inter-taxa and geographical variability, this can entail an extinction of ecological interactions and a decay of ecosystem functions. In this study, we compared the spatial distribution, abundance and species composition of Trichogramma spp. egg parasitoids (Hymenoptera: Trichogrammatidae) over a 30-year time period in China. During the 1980s and in 2016–2018, egg masses of the Asian corn borer (ACB), Ostrinia furnacalis, were systematically sampled from corn fields across the country. In 2018, five species were identified with Trichogramma ostriniae representing 90% of the species complex. Since the 1980s, two new species have made their appearance while nine (out of 12; i.e., 75%) species disappeared. These include comparative specialists but also generalists such as T. evanescens and T. exiguum. Across sites, species richness (R) and diversity (Shannon-Weiner index) have declined by a respective 25–86% and 56–100% (except for Heilongjiang province) over this time frame. We hypothesize that this is attributed to land use change, pesticide use and plant diversity decline in agro-landscapes. Conversely, no negative impacts were detected of augmentative biological control. Given the drastic reduction in ACB parasitoid richness, agro-ecological measures and diversification strategies should be deployed to restore the ecological resilience of local farming systems. Our work carries major implications for food security and helps to muster support for more nature-friendly, pest-resilient farming systems in China and abroad.
... In the case of conservation biological control by entomopathogens, emphasis has been given to aphid control with Entomophthorales fungi (Meyling and Eilenberg 2007). Natural-enemy diversity and biological control have also been studied at the landscape scale (Bianchi, Booij and Tscharntke, 2006;Tscharntke et al., 2008;Shackelford et al., 2013;Grez et al., 2014;Landis, 2017;Perović et al., 2018;Martin et al., 2019). Several landscape studies have targeted the control of aphids by coccinellids (e.g. ...
Interest in the use of microbial and invertebrate biological control agents (BCAs) in food and agriculture is increasing. Growing concerns about the impact of pesticide use on biodiversity and human health – and increasing demand for products from biodiversity-friendly production systems, including organic systems – have led to growing interest in alternative methods of pest control, including particularly the use of microbial and invertebrate BCAs.
... This approach provides a unique framework to understand how environmental variables affect the function of arthropod communities (Mammola et al., 2021;Moretti et al., 2017;Wood et al., 2015). Investigating trait distributions in communities also can pinpoint how habitat mosaics and different agricultural intensification levels affect biodiversity and alter ecosystem services in agroecosystems (Fournier et al., 2015;Perović et al., 2018). For instance, studies have shown that small species with a shorter life cycle and higher dispersal ability have the advantage of avoiding frequent disturbance, and, as a consequence, these traits, highly adapted to the disturbed environment, were selected for in intensively managed grasslands (Simons et al., 2016). ...
Agricultural intensification and land use transformation are among the main driving forces of the unprecedented decline of biodiversity and ecosystem services in croplands. Trait-based approaches provide a unique framework to detect the potential mechanisms of how this intensification affects biodiversity and alter ecosystem services. However, the potential relationship between arthropod traits and various types of habitats is still poorly understood , especially in subtropical vegetable agroecosystems. Here, we conducted a trait-based approach to evaluate the variable roles of different habitats on functional trait diversity and the structure of the arthropod community in brassica vegetable crops. Twenty-three conventional cruciferous vegetables fields were sampled over two years in three regions in Fujian, China. We found that the increasing proportion of non-brassica vegetable plantations and water bodies negatively affected the functional diversity of arthropods, whereas forest and grassland habitats showed a positive correlation, indicating habitat filtering for certain traits or trait combinations. This study demonstrates the importance of landscape composition as an ecological filter for vegetable arthropod community, and identifies how the proportion of different habitats selected for or against specific functional traits. Our findings support that increasing forest and grassland areas adjacent to vegetable fields can play a vital role in promoting the functional diversity of arthropod communities. Since the natural enemy assemblages supported by these habitats bear combinations of diverse traits adapted to disturbance, they have the potential to enhance pest suppression in the highly variable environment of vegetable crops.
... Studying the ecological mechanisms underlying novel species interactions is a significant challenge to understanding fluctuation in population and community assemblage, such as species colonization and range expansion (Strauss et al., 2006;Wang et al., 2013). However, the ecological outcomes of species interactions can only be fully understood after considering the multi-trophic approaches in which the species are embedded, i.e. beyond the simple pairwise interactions, the emergent features of interactions visible at least at a tri-trophic should also be considered (Fortuna et al., 2012;Harvey et al., 2003;Perović et al., 2018;Price et al., 1980;Singh, 2003). Understanding multi-trophic interactions are fundamental in the context of biological control and pest invasions (Schulz et al., 2019;Tylianakis & Binzer, 2014). ...
When several polyphagous herbivore species share a parasitoid, the tri-trophic interaction networks can be difficult to predict. In addition to direct effects, the parasitoid may influence the herbivore community by mediating indirect interactions among hosts. The plant species can also modulate the parasitoid preference for a specific host. One of the indirect effects is apparent competition, a negative interaction between individuals as a result of the action of shared natural enemies. Here, we focus on the interactions between the parasitoid Fopius arisanus (Braconidae) and two generalist fruit fly pests: Bactrocera dorsalis and Bactrocera zonata (Tephritidae). This parasitoid was introduced into La Réunion in 2003 to control populations of B. zonata and can also interact with B. dorsalis since its invasion in 2017. Our main objective is to characterize the tri-trophic interactions between F. arisanus, fruit fly and host plant species. We developed a long-term field database of fruit collected before and after the parasitoid introduction and after the B. dorsalis invasion in order to compare parasitism rate and fruit fly infestation for the different periods. In laboratory assays, we investigated how the combination of fruit fly species and fruit can influence the preference of F. arisanus. In the field, before the invasion of B. dorsalis, the parasitism rate of F. arisanus was low and had a little impact on the fruit fly infestation rate. After the B. dorsalis invasion, we observed an increase in parasitism rate from 5% to 17%. A bioassay showed that females of F. arisanus could discriminate between eggs of different fruit fly and host plant species. The host plant species preference changed in relation to the fruit fly species inoculated. Field observations and laboratory experiments suggest the possible existence of apparent competition between B. dorsalis and B. zonata via F. arisanus.
... While non-crop habitat tends to enhance parasitism in rice (Gurr et al., 2011;Haan et al., 2020), our results show that individual parasitoid species respond differently to landscape variables. Species-specific responses are likely mediated by differences in functional traits with host range, dispersal range, foraging habits and overwintering behavior all playing prominent roles (e.g., Schmitz et al., 2017;Perović et al., 2018;Heimpel et al., 2021). Specialist parasitoids respond strongly to target host abundance (Sann et al., 2018) as reflected in a positive association between C. chilonis parasitism rate and RSB overwintering larval density . ...
The rice stem borer (RSB), Chilo suppressalis (Walker), is an economically important pest of rice in subtropical Asia. Up till present, it remains unknown how pest abundance and parasitoid-mediated biological control are modulated by landscape composition. In this study, 20 rice fields with varying proportion of non-crop habitat in (2000 m radius) landscape sectors were selected in China’s Jiangxi province. RSB infestation levels were highest in agriculture-dominated landscapes. Meanwhile, parasitism rate increased with pest pressure but was not related to landscape-level non-crop habitat cover. Landscape-level responses of parasitoids were species-specific and likely modulated by functional traits. The specialist parasitoid Cotesia chilonis (Munakata) responded negatively to non-crop habitat, while positive responses were recorded for the generalists Eriborus sinicus (Holmgren) and Microgaster russata (Haliday). Our work unveils the occurrence of a bottom-up cascade in which spatiotemporal rice cropping patterns shape pest pressure and parasitism dynamics, with more diverse landscapes experiencing lower RSB infestation levels. Non-crop habitats within the landscape matrix equally retained parasitoid species with varying feeding modes and attack strategies. Hence, despite its (globally) inconsistent impacts on biological control, agricultural landscape diversification can directly benefit pest suppression and thus remains a valuable component of the ecological intensification toolbox.
This chapter explores the influence of high-throughput technologies on enhancing the biological control of insect pests. Given the criticism of the environmental and health effects of traditional pest control methods, high-throughput techniques offer alternative options for pest management. This chapter provides an overview of various high-throughput methods, such as genomics, metagenomics, and phonomics, which facilitate rapid identification and investigation of biocontrol agents and their interactions with pests. This chapter also addresses significant concerns such as the absence of robust data analysis frameworks and the failure to incorporate genetic data into practical applications. Furthermore, this chapter explores potential methods to improve the efficacy and efficiency of biological control tactics by utilizing these technologies, such as developing targeted interventions and optimizing the microbial communities associated with biocontrol organisms. In this chapter, the authors provide a comprehensive overview of how the integration of high-throughput technologies and biological control might enhance pest management and promote agricultural sustainability.
Accurate and high-resolution mapping of land cover is essential for modeling species response, guiding habitat management practices, and prioritizing conservation efforts, especially in restricted and remote areas. Geographic information systems (GIS) and remote sensing (RS) techniques offer potential solutions. This study assessed the utility of GIS and RS techniques to map and predict grassland bird species in Nairobi National Park (NNP), Kenya. We utilized Sentinel-2B median imagery, which was accessible through Google Earth Engine (GEE), for January 2022 to classify six land cover classes: forest, shrubland, woodland, grassland, water, and bare soil. Grassland bird data were extracted from Kenya Bird Map (KBM) website for the period between 2015 and 2022, using full protocol card records. We hypothesized that grassland and shrubland would cover a larger portion of NNP and that grassland birds would respond positively to grassland, shrubland and woodland. We tested the second hypothesis using KBM data. Training samples for various land cover types were collected and used to train a Random Forest (RF) classifier on Sentinel-2B imagery. Model accuracy was evaluated with a confusion matrix, showing an overall accuracy of 99.93 % and a Kappa statistic of 0.9989. Land cover composition indicated that grassland had the highest composition (44.9 %), while water had the least (0.003 %). Woodland, shrubland, forest and bare soil comprised 33.7 %, 15.4 %, 5.9 % and 0.2 %, respectively. Logistic regression results showed that grassland birds responded positively to grassland and shrubland but tended to avoid woodland and bare soil. These findings demonstrate that land cover maps derived from GIS and RS techniques are fundamental tools for studying the abundance and distribution of grassland bird species, especially in remote areas. These tools are also essential for conservation and habitat management.
La agricultura industrial ha sido reconocida como uno de los principales impulsores de la pérdida de biodiversidad y la disminución de múltiples contribuciones de la naturaleza a las personas. Al mismo tiempo, se asocia con profundos impactos sociales como la pérdida de autogestión, despoblamiento rural, erosión cultural, pérdida de me-dios de vida, confliictos sociales y desterritorialización de tramas productivas. El abordaje de la sustentabilidad ha estado centrado en aspectos económicos y ambientales, invisibilizando los componentes sociales y su interacción con los componentes ecológicos. Sin embargo , en las últimas décadas las aproximaciones avanzaron sobre esta visión reduccionista para integrar una comprensión de los niveles ecológicos y sociales de coevolución, estructura y función. La agroecología proporciona un marco al aplicar la teoría ecológica a la gestión de los agroecosistemas de acuerdo con recursos y realidades socioeconómicas específicos, y al proporcionar una metodología para establecer las conexiones transdis-ciplinarias requeridas. Este paradigma aspira a volver a ciclos más cerrados de energía y materiales, maximizando la reutilización y promoviendo los flujos locales fuertemente anclados en el territorio, para lo que se requiere que agricultorxs, técnicxs, consumidorxs e investigadorxs cambien la escala (ecología del paisaje, territorio) y los objetos de re exión. Las instituciones formales y no formales del sistema social pueden contener, apoyar y promover procesos de construcción democrática del sistema alimentario a través de políticas públicas de ordenamiento territorial y de apoyo a las transiciones hacia sistemas equitativos y sustentables. En este manuscrito tenemos como objetivo revisar los intereses actuales que intentan restringir conceptualmente el significado de la Agroecología. Proponemos un marco conceptual que analice la sustentabilidad multidimensional de los sistemas agroecológicos, buscando mejorar la comprensión de cómo el sistema social en el que están inmersos lxs actorxs puede modificar el devenir de las iniciativas en la transición hacia sistemas alimentarios equitativos y sustentables.
In agriculture, spontaneous field border vegetation can engender several benefits, including mitigating soil erosion, increasing carbon retention, conserving pollinators, and promoting biological control. The extension of these benefits can, however, often depend on the context of location and time. As for biological control, field borders can promote natural enemy conservation if the plants therein can provide adequate resources (e.g. shelter, alternative food, microclimate). In the context of location, field borders can be adjacent to areas with varying degrees of agricultural intensification, including fields with annual crops, perennial crops, or forest areas. While many studies have investigated how field borders can influence arthropod communities in adjacent crops, the opposite direction of effect (i.e. how crop areas can influence adjacent field borders) remains an underexplored topic. Therefore, in this three-season study we selected vegetated field borders next to annual crops, perennial crops, and forest areas, to study their communities of spontaneous plants (weeds) and arthropods as well as their potential to engender biological control. In general, our results show that the community composition of plants and arthropods was affected by land use type and season. Furthermore, field border vegetation next to areas with higher level of agricultural intensification (i.e. annual or perennial crops) harbored more herbivores, flowers and natural enemies; although some of these results were season dependent. Lastly, field borders next to annual or perennial crop areas engendered stronger biological control of aphids; possibly due to the alternative food (herbivores/aphids and flowers) provided by the plants therein. Taken altogether, our results reinforce the importance of preserving spontaneous field border vegetation, especially in areas under intensive agriculture management.
Fruits and vegetables can vary significantly in their dependence upon insect pollinators to transfer pollen. Raspberry and blackberry are two fruits that are regarded as highly-pollinator dependent. This means that knowledge of pollinator foraging behaviour, efficiency at transferring pollen, and interactions between pollinators, flowers, and the surrounding environment, are all critical factors to understand in depth to ensure that pollination service delivery is optimised. Bees have generally been acknowledged as the most important crop pollinators, yet their efficiency can vary in response to various factors including timing of the visit, previous visits, hive health, flowers available and interactions with other taxa. Further, even though we know other insects visit crop flowers, little is known about the pollination services provided by animals other than bees (i.e., non-bees) and their capacity to transfer pollen effectively. We also have a limited understanding about the number and quality of flower visits required in different cultivars and systems to achieve the best fruit quality. Finally, the resources pollinators require in different seasons and landscapes and the environmental conditions in which berry plants are grown, can also mediate the likelihood of pollination success. This presentation will outline a number of research findings that could be used to support greater resiliency with regard to insect pollination needs of Rubus and Ribes. These include understanding the contribution of different flower visitors and their efficiency in providing pollination services, a greater understanding of pollinator resource needs to improve their longevity in orchard environments, the conditions in which plants are most responsive to pollination service delivery and the importance of collaborations between industry and researchers to manage the system sustainably and to optimise fruit production and quality.
While many pesticides are detrimental to human health and the environment, drastically reducing their use and risks in agriculture has been set as a key target for global environmental policies. To this end, redesigning agroecosystems by increasing plant diversity at the cropping system and landscape levels is increasingly seen as imperative. Positive evidence that diversifying agroecosystems suppresses pests is accumulating and many ecological mechanisms driving pest suppression are known. Yet, variability in effects, risks of failure, and the limited adoption of diversification practices, call for improving diversification science. The overarching challenge lies in shifting from homogeneous production systems targeting yield at the cost of high input uses, to complex biodiversity-based environments resilient to pest pressure and delivering multifunctional performances. Therefore, a new conceptual umbrella to guide future agroecosystem design is proposed, which consists of integrating four principles: (i) embracing complexity, by jointly considering the multiple pests and their enemies; (ii) considering traits, in mobilizing the functional grammar; (iii) stacking diversification practices, by strategically combining the multiple facets of plant diversity at multiple scales; (iv) translating ecological processes into socio-economic benefits to adopt a multifunctional perspective. While addressing the associated implications for science and research, the present review critically discusses how to mobilize the spatio-temporal cross-scale dependencies of interactions in agroecosystems. Promoting synergies and building on the functional complementarities of ecological processes is proposed as a way to strengthen agroecosystem resilience to pest outbreaks.
Increasing plant diversity in agroecosystems is well‐known to strengthen natural pest suppression, yet reliably predicting which non‐crop management practices best support natural enemies remains a challenge. Farmers often supplement diversity with managed flower patches or by allowing weedy non‐crop plant growth, both of which may support diverse, abundant and balanced communities of insect predators that provide biocontrol.
At the same time, evenness among predators and effectiveness of biocontrol may be compromised by dominant arthropod invaders that co‐benefit from non‐crop diversity.
We examined whether floral resources or adjacent weeds had stronger effects on the evenness and abundance of natural enemies by surveying plants and insects on zucchini crops at 37 organic farms.
Neither flower richness nor weed richness affected insect predator evenness. Instead, the abundance of an invasive predator, the red imported fire ant ( Solenopsis invicta Buren), increased with floral resource diversity, which negatively predicted the evenness and abundance of non‐invasive predators.
These results suggest that floral diversity might be a less reliable predictor of natural enemy diversity when invasive predators interfere. Habitat management recommendations for bolstering biocontrol services should consider and potentially mitigate unintended consequences of floral resource provisions on farms where invasive predators dominate.
Plant diversity drives the trophic ecology of arthropod communities, and is the focus of thousands of studies and a growing field of meta-analysis. Although syntheses of plant diversity studies have yielded valuable insights, their sheer number and complexity limits broader interpretation. Here we scrutinize 23 syntheses published over three decades to identify common themes and contrasting results. We find that plant diversity consistently attracts more abundant and diverse communities of predators. Herbivore diversity tends to increase in response to plant diversity treatments, while herbivore abundance and plant damage generally decrease. Yet, these net effects often mask nuanced responses to plant diversity that depend on ecosystem, scale, and specialization. For instance, specialist herbivores often respond negatively to plant diversity, while generalists more often mount positive or neutral responses. Studies conducted at greater spatial scales show a dilution of effects on herbivores, but reveal conflicting effects on predators. Despite complexity in outcomes, syntheses show that diversifying plant communities holds great promise for enhancing the resilience of managed ecosystems. A closer examination of how insect diet breadth, spatial scale, and plant arrangement interactively determine the strength of trophic cascades will improve reliability and precision in how we leverage biodiversity for conservation and biocontrol.
Diversification measures are widely recognized for their potential to enhance the resilience of agri-food production systems under global change. Nitrogen-fixing legumes commonly feature in diversification schemes, where they exert positive impacts on soil structure, nutrient retention, carbon sequestration or fertilizer reduction. Though legumes are premier tools for conservation agriculture, their impacts on (invertebrate, microbial) biological control are far less clear. As legumes secrete copious amounts of energy-rich (floral, extra-floral) nectar and provide alternative host or prey items for resident natural enemies, their deployment is expected to benefit biological control. Yet, its mechanistic basis is poorly understood and scientific underpinnings weak. In this Perspective piece, we collate data from the published literature and open-access databases on the extent to which different natural enemy guilds interact with 25 legume species that are commonly used as intercrops in the (sub)tropics. Our work unveils how natural enemies regularly forage on legumes, but the portrayal of those interaction linkages-or "biostructure" data-is profoundly incomplete and their ensuing implications for biological control are under-investigated. For instance, merely 4 (out of 167) parasitoids of the globally invasive fall armyworm Spodoptera frugiperda have been recorded in association with legumes. We hope that this Perspective piece will stimulate further thought, drive a new wave of biodiversity x ecosystem function research, and ultimately result in the design and implementation (or preservation) of more resilient, resource-frugal and pest-suppres-sive farming systems.
Diet can have a direct influence on the reproductive success of parasitoid wasps. For synovigenic parasitoids, the nutrients obtained from floral resources, such as nectar and pollen, play a vital role in fueling bodily functions and physiological energy expenditure incurred from reproduction. Insufficient access to nutrient-rich diets can lead to lower rates of reproductive fitness, therefore reducing the efficacy of biocontrol. Here, a study was conducted to evaluate the influence of diet quality on nutrient retention and reproductive fitness of the egg parasitoid Hadronotus pennsylvanicus (Hymenoptera: Scelionidae), a prospective biocontrol agent for the leaffooted bug Leptoglossus zonatus (Heteroptera: Coreidae), a primary pest of almonds and pistachios. Newly emerged parasitoid females were provided host eggs every other day accompanied by diets of varying sucrose concentrations (source of carbohydrates) and pollen (source of lipid and proteins). The sucrose concentration in the diet, regardless of pollen content, significantly increased the survival and lifetime fecundity of female H. pennsylvanicus. While wasps fed high sucrose diets depleted bodily sugars, glycogen, and lipids at a slower rate than wasps fed low sucrose diets, there was no effect on bodily protein levels. Given these findings, further research is now needed to identify floral resources that are compatible, attractive, and nutritionally-sufficient for optimal H. pennsylvanicus reproductive fitness, which could lead to enhanced parasitism of L. zonatus in crop systems.
CONTEXT: Agricultural intensification contributes to global food security and well-being by supplying the food demand of a growing human population. However, ongoing land-use change and intensification seriously affect the abundance, diversity and distribution of species, besides many other impacts, thereby threatening the functioning of ecosystems worldwide. Despite the accumulating evidence that the current agricultural model is unsustainable, we are far from understanding the consequences of functional diversity loss for functioning and
ecosystem service supply and the potential long-term threats to food security and human well-being.
OBJECTIVE: In this review, we propose a conceptual framework to understand the relationships between functional diversity and human well-being that also considers agroecosystem health. To this end, we identify the most commonly assumed relationships linking functional diversity to regulating and provisioning agroecosystem services and their importance for human well-being, emphasising the most serious knowledge gaps in the individual pathways of the conceptual framework.
METHODS: A consortium formed by an international panel of experts from different disciplines including functional diversity, ecosystem services and human health compiled 275 articles. Members of the consortium proposed literature to exemplify each specific aspect of the conceptual framework in the text, in accordance with
his/her field of expertise. The guideline for all experts was to focus mostly in current literature (38% of the references are from the last 5 years and 66% from the last decade), with special interest in reviews and synthesis articles (42% of the references), as well as meta-analyses and global studies (10% of the references).
RESULTS AND CONCLUSIONS: The factors that influence agroecosystem health are extremely complex, involving both services and disservices related to land-use management and environmental conditions. The global human population needs sustainable and resilient agroecosystems and a concerted effort is needed to fundamentally redesign agricultural practices to feed the growing human population without further jeopardising the quality of life for future generations. We highlight the potential effects of land-use change and ecological intensification on
the functional diversity of plant and animal communities, and the resulting consequences for ecosystem services and ultimately human health.
SIGNIFICANCE: The resulting conceptual model is developed for researchers as well as policy makers highlighting the need for a holistic approach to understand diversity impacts on human well-being. Finally, we document a major knowledge gap due to the lack of any studies focusing on the full pathway from diversity to
human well-being.
We propose that a growing research base considering pest management as an ecosystem service can be leveraged to expand areawide pest management (AWPM) to an agroecological-oriented framework when addressing pest arthropods in cropping systems. This AWPM framework centers on the innate capacity of the agroecosystem to suppress pests and is supported with strategic insertion of AWPM tactics. Recent studies on agroecological pest management are valuable to identify AWPM candidates. The estimation and predictability of AWPM outcomes may be improved by measuring effects of interactions of pest and pest suppression agents, and mediating factors such as landscape and weather. This knowledge helps formulate selection and strategic insertion of AWPM tactics into the system to support innate pest suppression. Advances in biotechnology and agricultural engineering have increased effectiveness of AWPM tactics, further improving positive AWPM outcomes. Furthermore, multifunctional agricultural, environmental, and economic benefits may be seen when adopting this framework.
ContextManipulating crop diversity in the landscape has been suggested as a promising management option to enhance biocontrol but how crop diversity independently of other important aspects of landscape structure affects predator and pest abundances remain largely unexplored.Objectives
Our study assessed the relative and interactive effects of crop composition and configuration on aphids and their generalist predators, i.e. ladybirds, spiders and lacewings.Methods
We sampled arthropods in 47 cotton fields and 21 wheat fields in Hebei, China, located along three landscape gradients: crop diversity (Shannon diversity of crops ranging from 0.27 to 1.32 corresponding to a crop richness varying from 2 to 7 different crops), crop configurational (crop edge density varying from 0.0012 m/ha to 0.066 m/ha) and proportion of semi-natural habitats (varying from 0.5% to 56%).ResultsCrop diversity never had any effect on arthropod communities and we found no effect of the proportion of semi-natural habitats on natural enemies’ abundances. Aphid abundance was positively correlated with the proportion of semi-natural habitats both in cotton and wheat fields. Lacewing abundance benefited from configurational heterogeneity as abundances increased with crop edge density.Conclusions
Our result provide evidence that crop diversity is probably not the best management option to enhance biocontrol of aphids in Chinese landscapes and confirms that the amount of semi-natural habitats in the landscape is a critical aspect shaping arthropod communities. It also indicates that manipulating crop edge density by promoting agricultural landscapes with small field size for instance can benefit natural enemies of crop pests.
In recent years the focus in ecology has shifted from species to a greater emphasis on functional traits. In tandem with this shift, a number of trait databases have been developed covering a range of taxa. Here, we introduce the GlobalAnts database.
Globally, ants are dominant, diverse and provide a range of ecosystem functions. The database represents a significant tool for ecology in that it (i) contributes to a global archive of ant traits (morphology, ecology and life history) which complements existing ant databases and (ii) promotes a trait‐based approach in ant and other insect ecology through a broad set of standardised traits.
The GlobalAnts database is unique in that it represents the largest online database of functional traits with associated georeferenced assemblage‐level data (abundance and/or occupancy) for any animal group with 9056 ant species and morphospecies records for entire local assemblages across 4416 sites.
We describe the structure of the database, types of traits included and present a summary of data coverage. The value of the database is demonstrated through an initial examination of trait distributions across subfamilies, continents and biomes.
Striking biogeographic differences in ant traits are highlighted which raise intriguing questions as to the mechanisms generating them.
Predatory arthropods contribute to biological control, but to become an integral part of agricultural management, it is essential to identify drivers of their spatio-temporal distribution at the landscape scale. This study focuses on how agricultural land use affects the community composition, emergence and dispersal tendency of predatory arthropods. The arthropods were collected in emergence traps during the growing season (14 weeks) in a gradient of agricultural land uses from intensively managed sugar beet fields, over winter wheat fields, to less intensively managed grasslands. The emergence traps were equipped with one pitfall trap and a collecting bottle at the top. The distribution of the arthropods between these two collecting methods was assumed to represent their tendency to move out of the habitat. The grasslands had the highest numbers of spiders, while the winter wheat fields had the highest numbers of omnivorous rove beetles and macropterous predaceous ground beetles. The phenology of emergence differed between the land-use types, resulting in seasonal differences in community composition. The overall dispersal tendency of predatory arthropods was higher in crop fields than in grasslands. This study suggests that only a diverse mix of agricultural land uses will provide high levels of predators from different functional groups, throughout the growing season.
Habitat management involving manipulation of farmland vegetation can exert direct suppressive effects on pests and promote natural enemies. Advances in theory and practical techniques have allowed habitat management to become an important subdiscipline of pest management. Improved understanding of biodiversity-ecosystem function relationships means that researchers now have a firmer theoretical foundation on which to design habitat management strategies for pest suppression in agricultural systems, including landscape-scale effects. Supporting natural enemies with shelter, nectar, alternative prey/hosts, and pollen (SNAP) has emerged as a major research topic and applied tactic with field tests and adoption often preceded by rigorous laboratory experimentation. As a result, the promise of habitat management is increasingly being realized in the form of practical worldwide implementation. Uptake is facilitated by farmer participation in research and is made more likely by the simultaneous delivery of ecosystem services other than pest suppression. Expected final online publication date for the Annual Review of Entomology Volume 62 is January 07, 2017. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Trait‐based approaches are increasingly being used to test mechanisms underlying species assemblages and biotic interactions across a wide range of organisms including terrestrial arthropods and to investigate consequences for ecosystem processes. Such an approach relies on the standardized measurement of functional traits that can be applied across taxa and regions. Currently, however, unified methods of trait measurements are lacking for terrestrial arthropods and related macroinvertebrates (terrestrial invertebrates hereafter).
Here, we present a comprehensive review and detailed protocol for a set of 29 traits known to be sensitive to global stressors and to affect ecosystem processes and services. We give recommendations how to measure these traits under standardized conditions across various terrestrial invertebrate taxonomic groups.
We provide considerations and approaches that apply to almost all traits described, such as the selection of species and individuals needed for the measurements, the importance of intraspecific trait variability, how many populations or communities to sample and over which spatial scales.
The approaches outlined here provide a means to improve the reliability and predictive power of functional traits to explain community assembly, species diversity patterns and ecosystem processes and services within and across taxa and trophic levels, allowing comparison of studies and running meta‐analyses across regions and ecosystems.
This handbook is a crucial first step towards standardizing trait methodology across the most studied terrestrial invertebrate groups, and the protocols are aimed to balance general applicability and requirements for special cases or particular taxa. Therefore, we envision this handbook as a common platform to which researchers can further provide methodological input for additional special cases.
A lay summary is available for this article.
To meet their carbohydrate requirements, adult parasitoids exploit a broad range of sugar resources, including floral and extrafloral nectar and honeydew. Although honeydew might be the predominant sugar source, especially in agricultural systems, it is often nutritionally inferior to sugar sources like nectar. Given its broad availability, it may be expected that sugar-feeding insects have evolved specialized adaptations to deal with this often inferior sugar source. This would apply especially to organisms that have a close association with honeydew producers. Here, we hypothesized that parasitoids of honeydew-producing insects show a particularly pronounced response to sugars that predominantly occur in honeydew such as fructose, sucrose, melezitose and trehalose, and to a lesser extent glucose. To test this hypothesis, we investigated sugar consumption, feeding behavior and survival of the aphid parasitoid Aphidius ervi on several sugars (equiweight solutions). Our results show that A. ervi adults consumed typical honeydew sugars the most (sucrose, fructose, trehalose and melezitose), whereas intake of glucose or melibiose was considerably lower. Rhamnose, which does not occur in aphid honeydew, was not or only marginally consumed. When different sugars were provided at the same time, A. ervi adults preferred sucrose or fructose over glucose or melezitose. Furthermore, a pre-exposure to sucrose or fructose significantly reduced subsequent intake of glucose, suggesting an acquired distaste for glucose after being exposed to highly preferred sugars such as sucrose and fructose. Altogether, this study shows that A. ervi adults mainly prefer sugars that are overrepresented in aphid honeydew (fructose, melezitose, trehalose and sucrose) and to a lesser extent sugars that are underrepresented (glucose).
Specialization is a central concept in ecology and one of the fundamental properties of parasitoids. Highly specialized parasitoids tend to be more efficient in host-use compared to generalized parasitoids, presumably owing to the trade-off between host range and host-use efficiency. However, it remains unknown how parasitoid host specificity and host-use depends on host traits related to susceptibility to parasitoid attack. To address this question, we used data from a 13-year survey of interactions among 142 aphid and 75 parasitoid species in nine European countries. We found that only aphid traits related to local resource characteristics seem to influence the trade-off between host-range and efficiency: more specialized parasitoids had an apparent advantage (higher abundance on shared hosts) on aphids with sparse colonies, ant-attendance and without concealment, and this was more evident when host relatedness was included in calculation of parasitoid specificity. More traits influenced average assemblage specialization, which was highest in aphids that are monophagous, monoecious, large, highly mobile (easily drop from a plant), without myrmecophily, habitat specialists, inhabit non-agricultural habitats and have sparse colonies. Differences in aphid wax production did not influence parasitoid host specificity and host-use. Our study is the first step in identifying host traits important for aphid parasitoid host specificity and host-use and improves our understanding of bottom-up effects of aphid traits on aphid-parasitoid food web structure.
Functional traits are morphological, biochemical, physiological, structural, phenological or behavioural characteristics of organisms that influence performance or fitness. Grouping species by functional characteristics is a long‐standing idea, but there has more recently been rapid development in the application of trait‐based approaches to diverse topics in ecology. Two common applications of functional traits are to characterise community responses to changes in the environment, including community assembly processes, and to quantify the influence of community shifts on ecosystem processes. Practical decisions include: What types of traits should be considered? How can traits be measured or inferred? Are traits correlated or traded‐off? Which, and how many, traits should be assessed? How should trait data be analysed? Functional trait approaches enhance ecological understanding by focusing on the mechanisms that govern interactions between organisms and their environments. Measuring and understanding traits increases our understanding of ecological processes, thus also informing conservation and restoration.
Key Concepts
Functional traits are morphological, biochemical, physiological, structural, phenological or behavioural characteristics that influence organism performance or fitness.
Traits can be broadly classified either as having an effect on ecosystem properties and the services that human societies derive from them, or as characterising a response to environmental change or with respect to processes affecting community assembly.
Common data types for traits include continuous, categorical, ordinal and binary variable formats. The data type has repercussions for subsequent data analyses.
Methods for measuring traits vary from time‐consuming (hard traits) to rapid (soft traits), and in turn the information content of the resulting data also varies.
Trait syndromes describe patterns of inter‐trait correlation that define differences and trade‐offs in ecological strategies.
When choosing traits for calculating functional diversity it is important to consider which, and how many, traits are included, as well as what insights they will provide into the ecosystem processes, community structure or assembly processes under consideration.
Functional traits are at the forefront of efforts to develop a mechanistic understanding of how species diversity influences ecosystem functioning, and the current ecological literature presents many indices by which functional diversity can be computed.
Global food security requires increased crop productivity to meet escalating demand(1-3). Current food production systems are heavily dependent on synthetic inputs that threaten the environment and human well-being(2,4,5). Biodiversity, for instance, is key to the provision of ecosystem services such as pest control(6,7), but is eroded in conventional agricultural systems. Yet the conservation and reinstatement of biodiversity is challenging(5,8,9), and it remains unclear whether the promotion of biodiversity can reduce reliance on inputs without penalizing yields on a regional scale. Here we present results from multi-site field studies replicated in Thailand, China and Vietnam over a period of four years, in which we grew nectar-producing plants around rice fields, and monitored levels of pest infestation, insecticide use and yields. Compiling the data from all sites, we report that this inexpensive intervention significantly reduced populations of two key pests, reduced insecticide applications by 70%, increased grain yields by 5% and delivered an economic advantage of 7.5%. Additional field studies showed that predators and parasitoids of the main rice pests, together with detritivores, were more abundant in the presence of nectar-producing plants. We conclude that a simple diversification approach, in this case the growth of nectar-producing plants, can contribute to the ecological intensification of agricultural systems.
Cardamom flowers offer nectar in a corolla tube which is 23 (±2.08) mm long and the style passes through the corolla tube. The honey-bee pollinators, Apis cerana and A. dorsata, despite their short tongue lengths (4.5 and 5.5 mm, respectively) drew nectar up to 11.45 (±2.65) and 11.65 (±1.85) mm. In controlled experiments, using capillary tubes of similar dimensions as cardamom corolla tubes, the depth of feeding by the two species of bees corresponded to their tongue lengths when there was no style. However, when a natural or an artificial style was introduced into the capillary tube the depth of feeding increased with increase in style thickness. We show here that the presence of style inside the corolla tube helps bees to draw more nectar from cardamom flowers. We also suggest that the plant facilitates pollinators to draw more nectar than it is possible with their short tongues, by keeping the style within, and that the thickness of style may have some significance in the evolution of the system.
The promise of “trait-based” plant ecology is one of generalized prediction across organizational and spatial scales, independent of taxonomy. This promise is a major reason for the increased popularity of this approach. Here, we argue that some important foundational assumptions of trait-based ecology have not received sufficient empirical evaluation. We identify three such assumptions and, where possible, suggest methods of improvement: (i) traits are functional to the degree that they determine individual fitness, (ii) intraspecific variation in functional traits can be largely ignored, and (iii) functional traits show general predictive relationships to measurable environmental gradients.
Phylogenetically related species share a common evolutionary history and may therefore have similar traits. In terms of interaction networks, where traits are a major determinant, related species should therefore interact with other species which are also related. However, this prediction is challenged by current evidence that there is a weak, albeit significant, phylogenetic signal in species' taxonomic niche, i.e., the identity of interacting species. We studied mutualistic and antagonistic plant-insect interaction networks in species-rich alpine meadows and show that there is instead a very strong phylogenetic signal in species' functional niches-i.e., the mean functional traits of their interactors. This pattern emerges because related species tend to interact with species bearing certain traits that allow biotic interactions (pollination, herbivory) but not necessarily with species from all the same evolutionary lineages. Those traits define a set of potential interactors and show clear patterns of phylogenetic clustering on several portions of plants and insect phylogenies. Thus, this emerging pattern of low phylogenetic signal in taxonomic niches but high phylogenetic signal in functional niches may be driven by the interplay between functional trait convergence across plants' and insects' phylogenies and random sampling of the potential interactors.
In order to improve biological control of agricultural pests, it is fundamental to understand which factors influence the composition of natural enemies in agricultural landscapes. In this study, we aimed to understand how agricultural land use affects a number of different traits in ground beetle communities to better predict potential consequences of land-use change for ecosystem functioning. We studied ground beetles in fields with different agricultural land use ranging from frequently managed sugar beet fields, winter wheat fields to less intensively managed grasslands. The ground beetles were collected in emergence tents that catch individuals overwintering locally in different life stages and with pitfall traps that catch individuals that could have a local origin or may have dispersed into the field. Community weighted mean values for ground beetle traits such as body size, flight ability and feeding preference were estimated for each land-use type and sampling method. In fields with high land-use intensity the average body length of emerging ground beetle communities was lower than in the grasslands while the average body length of actively moving communities did not differ between the land-use types. The proportion of ground beetles with good flight ability or a carnivorous diet was higher in the crop fields as compared to the grasslands. Our study highlights that increasing management intensity reduces the average body size of emerging ground beetles and the proportion of mixed feeders. Our results also suggest that the dispersal ability of ground beetles enables them to compensate for local management intensities.
In modern agricultural landscapes, many organisms providing ecosystem services such as pollination and natural pest control are likely constrained by shortage of nectar and/or pollen required for adult nutrition. More and more flower‐rich field margin strips and other habitats are created to eliminate these constraints. For most target organisms, however, it is not well known which (types of) flowers are effective in providing suitable pollen and nectar.
We studied the suitability of a wide range of flowers as a food source for zoophagous hoverflies (hoverflies with predatory larvae) at five different levels: nectar accessibility (based on flower morphology), realized adult fitness, flower choice (both based on cage experiments), flower visitation and hoverfly abundance in mixed vegetation (both based on field observations).
Realized survival of Episyrphus balteatus is related to effective flower depth by a sigmoid function. The critical flower depth is 1·6 mm, which is less than the proboscis size of the hoverfly. For Asteraceae, the critical floret depth is even less than 1·0 mm, which – in contrast to common knowledge – rules out most species within this family.
Both flower choice in the laboratory and flower visitation rates in the field are well correlated with nectar accessibility and realized adult survival.
In mixed floral vegetation, the number of zoophagous hoverflies is highly correlated with the abundance of only those flowers that have accessible nectar for these hoverflies.
Synthesis and applications . This comparative study demonstrates that nectar (and not pollen) accessibility is the main driver determining flower resource suitability, flower choice and abundance of zoophagous hoverflies in arable field margins. The study identifies the limited range of plant species that can effectively support these beneficial insects. Preserving the right flowers in and around agricultural fields could enhance local populations and the pest control and pollination services they provide.
Web-building spiders are abundant generalist predators in agroecosystems that primarily forage on insects including economically important pests. Local management and landscape composition influence spider and prey communities and thereby their trophic interactions and functional role in arthropod food webs. We compared predator-prey interactions between organically managed cereal fields and sown flower-rich fields, both supported by agri-environmental schemes. The surrounding landscape of twelve study sites differed in the percentage of arable crops within a radius of 500 m around each site. We analyzed 1036 hand-collected web-building spiders with 5270 prey items from webs and 6777 potentially available prey items sampled by fenced suction sampling. Thysanoptera significantly dominated prey composition of web-building spiders in cereal fields located in landscapes with low percentages of arable crops, while Nematocera dominated prey composition in sown flower-rich fields. The captured prey numbers per spider web, irrespective of taxonomic identity, increased with the availability of potential prey, independent of habitat type or landscape composition. We did not find any effect on the compositions of web-building spiders and potential prey. Our results suggest that spider webs act as traps for prey that depend on prey density. However, this simple interpretation is only valid for the overall prey quantity, while capture success of single prey taxa may be habitat-specific and depend on landscape features. The impact of land use at different spatial scales on the functional role of web-building spiders should caution us towards density-based estimates of predation processes, e.g. when assessing the impact of agri-environmental schemes on arthropod food webs.
Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions, but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear. Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits-wood density, specific leaf area and maximum height-consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies. Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our trait-based approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.
Earth is home to a remarkable diversity of plant forms and life histories, yet comparatively few essential trait combinations have proved evolutionarily viable in today’s terrestrial biosphere. By analysing worldwide variation in six major traits critical to growth, survival and reproduction within the largest sample of vascular plant species ever compiled, we found that occupancy of six-dimensional trait space is strongly concentrated, indicating coordination and trade-offs. Three-quarters of trait variation is captured in a two-dimensional global spectrum of plant form and function. One major dimension within this plane reflects the size of whole plants and their parts; the other represents the leaf economics spectrum, which balances leaf construction costs against growth potential. The global plant trait spectrum provides a backdrop for elucidating constraints on evolution, for functionally qualifying species and ecosystems, and for improving models that predict future vegetation based on continuous variation in plant form and function.
Ecologists and evolutionary biologists are increasingly using big-data approaches to tackle questions at large spatial, taxonomic, and temporal scales. However, despite recent efforts to gather two centuries of biodiversity inventories into comprehensive databases, many crucial research questions remain unanswered. Here, we update the concept of knowledge shortfalls and review the tradeoffs between generality and uncertainty. We present seven key shortfalls of current biodiversity data. Four previously proposed shortfalls pinpoint knowledge gaps for species taxonomy (Linnean), distribution (Wallacean), abundance (Prestonian), and evolutionary patterns (Darwinian). We also redefine the Hutchinsonian shortfall to apply to the abiotic tolerances of species and propose new shortfalls relating to limited knowledge of species traits (Raunkiæran) and biotic interactions (Eltonian). We conclude with a general framework for the combined impacts and consequences of shortfalls of large-scale biodiversity knowledge for evolutionary and ecological research and consider ways of overcoming the seven shortfalls and dealing with the uncertainty they generate.
Biodiversity loss can affect the viability of ecosystems by decreasing the ability of communities to respond to environmental change and disturbances. Agricultural intensification is a major driver of biodiversity loss and has multiple components operating at different spatial scales: from in-field management intensity to landscape-scale simplification. Here we show that landscape-level effects dominate functional community composition and can even buffer the effects of in-field management intensification on functional homogenization, and that animal communities in real-world managed landscapes show a unified response (across orders and guilds) to both landscape-scale simplification and in-field intensification. Adults and larvae with specialized feeding habits, species with shorter activity periods and relatively small body sizes are selected against in simplified landscapes with intense in-field management. Our results demonstrate that the diversity of land cover types at the landscape scale is critical for maintaining communities, which are functionally diverse, even in landscapes where in-field management intensity is high.
Cover crops are sown to provide a number of ecosystem services including nutrient
management, mitigation of diffuse pollution, improving soil structure and organic matter
content, weed suppression, nitrogen fixation and provision of resources for biodiversity.
Although the decision to sow a cover crop may be driven by a desire to achieve just one
of these objectives, the diversity of cover crops species and mixtures available means that
there is potential to combine a number of ecosystem services within the same crop and
growing season. Designing multi-functional cover crops would potentially help to reconcile
the often conflicting agronomic and environmental agendas and contribute to the optimal
use of land. We present a framework for integrating multiple ecosystem services delivered
by cover crops that aims to design a mixture of species with complementary growth habit
and functionality. The optimal number and identity of species will depend on the services
included in the analysis, the functional space represented by the available species pool and
the community dynamics of the crop in terms of dominance and co-existence. Experience
from a project that applied the framework to fertility building leys in organic systems
demonstrated its potential and emphasised the importance of the initial choice of species
to include in the analysis.
We develop methods for quantifying habitat connectivity at multiple scales and assigning conservation priority to habitat patches based on their contribution to connectivity. By representing the habitat mosaic as a mathematical "graph," we show that percolation theory can be used to quantify connectivity at multiple scales from empirical landscape data. Our results indicate that connectivity of landscapes is highly scale dependent, exhibiting a marked transition at a characteristic distance and varying significantly for organisms with different dispersal behavior. More importantly, we show that the sensitivity and importance of landscape pattern is also scale dependent, peaking at scales associated with the percolation transition. In addition, the sensitivity analysis allows us to identify critical "stepping stone" patches that, when removed from the landscape, cause large changes in connectivity.
Ecologists are familiar with two data structures commonly used to represent landscapes. Vector-based maps delineate land cover types as polygons, while raster lattices represent the landscape as a grid. Here we adopt a third lattice data structure, the graph. A graph represents a landscape as a set of nodes (e.g., habitat patches) connected to some degree by edges that join pairs of nodes functionally (e.g., via dispersal). Graph theory is well developed in other fields, including geography (transportation networks, routing applications, siting problems) and computer science (circuitry and network optimization). We present an overview of basic elements of graph theory as it might be applied to issues of connectivity in heterogeneous landscapes, focusing especially on applications of metapopulation theory in conservation biology. We develop a general set of analyses using a hypothetical landscape mosaic of habitat patches in a nonhabitat matrix. Our results suggest that a simple graph construct, the minimum spanning tree, can serve as a powerful guide to decisions about the relative importance of individual patches to overall landscape connectivity. We then apply this approach to an actual conservation scenario involving the threatened Mexican Spotted Owl (Strix occidentalis lucida). Simulations with an incidence-function metapopulation model suggest that population persistence can be maintained despite substantial losses of habitat area, so long as the minimum spanning tree is protected. We believe that graph theory has considerable promise for applications concerned with connectivity and ecological flows in general. Because the theory is already well developed in other disciplines, it might be brought to bear immediately on pressing ecological applications in conservation biology and landscape ecology.
Colonies of web building social spiders may persist at a site for several generations; therefore, their placement in the habitat is critical for survival. This study focuses on the development of spatial distribution patterns by means of different dispersal modes in a social spider species (Stegodyphus dumicola Pocock, 1898, Eresidae) in central Namibia. Social spiders disperse varying distances from the parent colony by ballooning or short distances by budding. Using spatial point pattern analyses we aimed to identify the dispersal pattern from source colonies and what drivers affect the resulting distribution patterns. The distribution of suitable vegetation constrained pattern development in the three study plots with mapped colonies. In a plot with isolated large trees, colonies were only aggregated over short distances and the average cluster size was small. First generation colonies were established within the same clusters by solitary ballooning females. In the two study plots with more evenly distributed shrubs, clusters were generally larger and new colonies were formed mainly by budding. In these plots, newly established colonies and older source colonies were either associated in suitable habitat patches or segregated from each other. Possible explanations include high mortality of either older colonies and replacement by newly established colonies or of dispersers in the vicinity of established colonies, or selection of “empty” sites by dispersing individuals based on cues from conspecific colonies. In conclusion, both the distribution of the vegetation and the mode of dispersal may explain the development of spatial patterns in S. dumicola. Our results highlight the importance of spatial pattern analyses for inferring underlying causes of distribution of sedentary organisms.
Body surfaces of organisms must prevent desiccation and inhibit the intrusion of harmful compounds and organisms. In insects, these functions are fulfilled by their cuticle, of which the external one represents a lipid layer that comprises different compound groups with various functions. In the highly social stingless bees, cuticular compounds are either produced by the bees themselves (i.e., genetically determined) or acquired from plant resins (i.e., environmentally derived). While genetically determined compounds protect their bearers against desiccation and convey information among and between species and colonies, environmentally derived compounds substantially increase the surface’s chemical diversity, but their functional role remains unclear. We investigated whether resin-derived compounds may affect predators by testing whether ants showed a different behavior when offered a choice between one bee species with and one without resin-derived cuticular compounds and when faced with cuticular extracts of these two species. We additionally compared weight loss through desiccation of living bees and the rate of developing mold of dead bees between the two bee species. We found that ants preferred bees without resin-derived compounds and were more repelled by extracts of bees with resin-derived compounds. The rate of developing mold did not differ between the two bee species and weight loss through desiccation primarily depended on the bees’ body sizes, but not the species and thus cuticular chemistry. We therefore suggest that environmentally derived compounds may provide an advantage to their bearers as they can protect them against predators.
In its simplest case, omnivory involves a top consumer, an intermediate consumer, and a resource that is common to both consumers. Simple models predict that the intermediate consumer can only coexist with the top consumer if the former is more efficient in exploiting the common resource, which would imply a net positive effect of the top consumer on the equilibrium density of resources (compared to the situation where only the intermediate consumer is present). Among 22 experimental manipulations of omnivorous top consumers there were only two studies in which top consumers had significant positive effects on resources. Considerations of relative body sizes of intermediate and top consumers suggest, that top consumers having negative net effects on the basic resources are relatively similar in size, but both are much smaller than omnivorous top consumers (eg vertebrate omnivores feeding on benthos, soil invertebrates, terrestrial insects etc), the direct negative effect on top consumers on basic resources should not be outweighed by negative positive effects, and that other mechanisms (eg prey refuges) must be invoked to explain the persistence of intermediate consumers in many natural systems. -from Author
There are many reasons why it is important that we find ways to conserve, and better utilise natural enemies of invertebrate crop pests. Currently, measures of natural enemy impact are rarely incorporated into studies that purport to examine pest control. Most studies examine pest and natural enemy presence and/or abundance and then qualitatively infer impact. Whilst this provides useful data to address a range of ecological questions, a measure of impact is critical for guiding pest management decision-making. Often some very simple techniques can be used to obtain an estimate of natural enemy impact. We present examples of field based studies that have used cages, barriers to restrict natural enemy or prey movement, direct observation of natural enemy attack, and sentinel prey items to estimate mortality. The measure of natural enemy impact used in each study needs to be tailored to the needs of farmers and the specific pest problems they face. For example, the magnitude of mortality attributed to natural enemies may be less important than the timing and consistency of that mortality between seasons. Tailoring impact assessments will lead to research outcomes that do not simply provide general information about how to conserve natural enemies, but how to use these natural enemies as an integral part of decision-making.This article is protected by copyright. All rights reserved.
Agricultural intensification is recognised as a major driver of biodiversity loss in human-modified landscapes. Several agro-environmental measures at different spatial scales have been suggested to mitigate the negative impact of intensification on biodiversity and ecosystem services. The effect of these measures on the functional structure of service-providing communities remains, however, largely unexplored. Using two distinct landscape designs, we examined how the management options of organic farming at the field scale and crop diversification at the landscape level affect the taxonomic and functional structure of generalist predator communities and how these effects vary along a landscape complexity gradient. Organic farming as well as landscapes with longer and more diversified crop rotations enhanced the activity-density of spiders and rove beetles, but not the species richness or evenness. Our results indicate that the two management options affected the functional composition of communities, as they primarily enhanced the activity-density of functionally similar species. The two management options increased the functional similarity between spider species in regards to hunting mode and habitat preference. Organic farming enhanced the functional similarity of rove beetles. Management options at field and landscape levels were generally more important predictors of community structure when compared to landscape complexity. Our study highlights the importance of considering the functional composition of generalist predators in order to understand how agro-environmental measures at various scales shape community assemblages and ecosystem functioning in agricultural landscapes.
Species traits may provide a short-cut to predicting generalities in species turnover in response to environmental change, particularly for poorly known taxa. We ask if morphological traits of assemblages respond predictably to macrohabitats across a large scale. Ant assemblages were collected at nine paired pasture and remnant sites from within three areas along a 300 km distance. We measured ten functional morphological traits for replicate individuals of each species. We used a fourth corner model to test associations between microhabitat variables, macrohabitats (pastures and remnants) and traits. In addition, we tested the phylogenetic independence of traits, to determine if responses were likely to be due to filtering by morphology or phylogeny. Nine of ten traits were predicted by macrohabitat and the majority of these traits were independent of phylogeny. Surprisingly, microhabitat variables were not associated with morphological traits. Traits which were associated with macrohabitats were involved in locomotion, feeding behaviour and sensory ability. Ants in remnants had more maxillary palp segments, longer scapes and wider eyes, while having shorter femurs, smaller apical mandibular teeth and shorter Weber's lengths. A clear relationship between traits and macrohabitats across a large scale suggests that species are filtered by coarse environmental differences. In contrast to the findings of previous studies, fine-scale filtering of morphological traits was not apparent. If such generalities in morphological trait responses to habitat hold across even larger scales, traits may prove critical in predicting the response of species assemblages to global change.
IntroductionMethods of Studying Flower ExploitationFloral Food Requirements for different Groups of Biological Control AgentsConclusion
References
Earlier this year, the first global thematic assessment from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) evaluated the state of knowledge about pollinators and pollination ( 1 , 2 ). It confirmed evidence of large-scale wild pollinator declines in northwest Europe and North America and identified data shortfalls and an urgent need for monitoring elsewhere in the world. With high-level political commitments to support pollinators in the United States ( 3 ), the United Kingdom ( 4 ), and France ( 5 ); encouragement from the Convention on Biological Diversity's (CBD's) scientific advice body ( 6 ); and the issue on the agenda for next month's Conference of the Parties to the CBD, we see a chance for global-scale policy change. We extend beyond the IPBES report, which we helped to write, and suggest 10 policies that governments should seriously consider to protect pollinators and secure pollination services. Our suggestions are not the only available responses but are those we consider most likely to succeed, because of synergy with international policy objectives and strategies or formulation of international policy creating opportunities for change. We make these suggestions as independent scientists and not on behalf of IPBES.
Spiders, a group of predominantly insectivorous predators, occasionally use plant food to supplement their insect prey. In the current review, we tracked down 95 reported incidents of spiders feeding on plant food under natural conditions. Globally, >60 spider species representing ten families have been observed feeding on plant materials from over 20 plant families. Cursorial spiders including the families Anyphaenidae, Clubionidae, Eutichuridae, Salticidae, Thomisidae, and Trachelidae dominate among the spiders feeding on plant food (>80% of reported incidents). Spiders feed on a wide diversity of plant-derived products including floral nectar, extrafloral nectar, stigmatic exudate, plant sap, honeydew, seeds, Beltian bodies, Müllerian bodies and pollen (originating from very different plant types such as coniferous and deciduous trees, herbaceous plants and shrubs, annual weeds, grasses, climbing plants, orchids, carnivorous plants, and ferns). Furthermore, spiders have been shown to consume fungal spores in laboratory trials. Supplementary feeding on plant materials by spiders was shown to be global in extent and widespread across spider taxa, plant taxa and plant materials; however, the extent to which the different categories of plant food contribute to the spiders’ diet and how this may affect their behavior and life history is still largely unexplored. This review is expected to lay a foundation for future research on this topic.
Global assessments of variation in plant functional traits and the way that these traits influence competitive interactions provide a launching pad for future ecological studies.
The expansion of intensive agricultural practices is a major threat to biodiversity and to the delivery of ecosystem services on which humans depend. Local‐scale conservation management strategies, such as agri‐environment schemes to preserve biodiversity, have been widely adopted to reduce the negative impacts of agricultural intensification. However, it is likely that the effectiveness of these local‐scale management actions depend on the structure and composition of the surrounding landscape.
We experimentally tested the utility of floral resource strips to improve local‐scale biological control of crop pests, when placed within a gradient of moderately simple through to highly complex landscapes.
We found that experimental provision of floral resources enhanced parasitism rates of two globally important crop pests in moderately simple landscapes but not in highly complex ones, and this translated into reduced pest abundances and increased crop yield.
Synthesis and applications . Our results lend experimental support for the ‘intermediate landscape complexity hypothesis’, which predicts that local conservation management will be most effective in moderately simple agricultural landscapes, and less effective in either very simple landscapes where there is no capacity for response, or in highly complex landscapes where response potential is already saturated. This knowledge will allow more targeted and cost‐effective implementation of conservation biological control programs based on an improved understanding of landscape‐dependent processes, which will reduce the negative impacts of agricultural intensification.
Functional trait research has led to greater understanding of the impacts of biodiversity in ecosystems. Yet, functional trait approaches have not been widely applied to agroecosystems and understanding of the importance of agrobiodiversity remains limited to a few ecosystem processes and services. To improve this understanding, we argue here for a functional trait approach to agroecology that adopts recent advances in trait research for multitrophic and spatially heterogeneous ecosystems. We suggest that trait values should be measured across environmental conditions and agricultural management regimes to predict how ecosystem services vary with farm practices and environment. This knowledge should be used to develop management strategies that can be easily implemented by farmers to manage agriculture to provide multiple ecosystem services.
Copyright © 2015. Published by Elsevier Ltd.
The strength and prevalence of trophic cascades, defined as positive, indirect effects of natural enemies (predatory and parasitic arthropods) on plants, is highly variable in agroecosystems. This variation may in part be due to the spatial or landscape context in which these trophic cascades occur. In 2011 and 2012, we conducted a natural-enemy exclusion experiment in soybean fields along a gradient of landscape composition across southern Wisconsin and Michigan. We used structural equation modeling to ask (1) whether natural enemies influence biocontrol of soybean aphids (SBA) and soybean yield and (2) whether landscape effects on natural enemies influence the strength of the trophic cascades. We found that natural enemies (NE) suppressed aphid populations in both years of our study and, in 2011, the yield of soybean plants exposed to natural enemies was 37% higher than the yield of plants with aphid populations protected from natural enemies. The strength of the trophic cascade was also influenced by landscape context. We found that landscapes with a higher proportion of soybean and higher diversity habitats resulted in more NE, fewer aphids, and in some cases a trend toward greater soybean yield. These results indicate that landscape context is important for understanding spatial variability in biocontrol and yield, but other factors, such as environmental variability and compensatory growth, might overwhelm the beneficial effects of biocontrol on crop yield.
The sustainable delivery of multiple ecosystem services requires the management of functionally diverse biological communities. In an agricultural context, where conflicting services often need to be reconciled on the same parcel of land, growing species mixtures may improve multi-functionality when compared to monocultures. In this case, the optimum number and identity of species will be determined by trade-offs between ecosystem services, functional composition of the available species pool and competitive dynamics. A combination of functional trait / ecosystem service relationships and a process-based model of plant competition was used to engineer a plant community that delivered the optimal balance of services using the case study of a legume-based fertility building cover crop. An experimental species pool of 12 cultivated legume species was screened for a range of functional traits and ecosystem services at five sites across a geographical gradient in the UK. All possible species combinations were then analysed to identify the community that delivered the best balance of services at each site. In our system, low to intermediate levels of species richness (1-4 species) that exploited functional contrasts in growth habit and phenology, were identified as being optimal. The optimal solution was determined largely by the number of species and functional diversity represented by the starting species pool emphasising the importance of the initial selection of species for the screening experiments. The approach of applying functional traits / ecosystem service relationships to the design of multi-functional biological communities has the potential to inform the design of agricultural systems that better balance agronomic and environmental services and meet the current objective of European agricultural policy, to maintain viable food production in the context of the sustainable management of natural resources.
Top-down control of pest populations by their natural enemies is a crucial ecosystem service supporting agricultural production. The relationship between predator community composition and predation rates of pests remains poorly investigated. A deeper understanding of the processes shaping interaction strength in agroecosystems is needed if we are to accurately predict natural pest control services. Functional traits in a community can provide insights into processes shaping community assembly and ecosystem functioning. Functional diversity indices can be constructed from a single trait, such as body length, or from the integration of multiple traits, such as body length, hunting mode and habitat preference. However, their performance in predicting ecosystem functioning and services remains largely unexplored. We used empirical data replicated at landscape scales to examine which component of ground-dwelling predator community structure (activity-density, species richness, evenness, taxonomic distinctness and functional diversity) of spiders, carabids and staphylinids best predicted predation rates of aphids in spring cereals. Functional diversity explained a greater part of variation in predation rates than any other taxonomic or activity-density component. Among the indices for functional diversity, single-trait indices better predicted variation in aphid predation rates compared with multiple-trait indices. In particular, we found that the community-average value of body-size of ground-dwelling predators was negatively related to predation rates of aphids, whereas the proportion of spiders with a preference for arable land was positively related to predation rates. Additional analyses of body-size distributions of ground-dwelling predators suggested that intraguild predation was a key process shaping the relationship between predator community composition and the level of aphid pest control. Considering the functional trait composition of communities provides a more mechanistic understanding of the processes shaping the strength of trophic interactions in terrestrial ecosystems, thus improving predictive power. Body-size distribution and habitat preference appear to be particularly valuable in predicting the level of natural pest control by ground-dwelling predators in an agroecosystem.
We observed 5 nectar-collecting behaviors of Diadegma insulare (Cresson), a major parasitoid of diamondback moth, Plutella xylostella (L.). The most striking behavior of D. insulare was chewing at the base of Barbarea vulgaris R. Br. and Brassica napus L. flowers and creating holes that probably released the floral nectar. D. insulare visited more frequently and spent longer times on flower species that supported longer life and high fecundity (B. vulgaris, Brassica kaber (D.C.) Wheeler, B. napus and Daucus carota L.). Time spent per visit was positively correlated with the number of previous visits for B. vulgaris and B. kaber, flowers that support long life and high fecundity. Time spent per visit was negatively correlated with the number of previous visits for Berteroa incana L. (D.C.) and Erysimum cheiranthoides L. (flowers that cause shorter lives and low fecundity of D. insulare). This suggests that D. insulare, after experience, was able to positively correlate nectar rewards with the flower characters. Flower color did not affect parasitoid choice of flowers. D. insulare spent significantly longer time at the upper one-third of D. carota corolla and at the lower one-third of B. kaber and B. vulgaris corollas than other flowers. Behavioral flexibility of D. insulare to flower characters and its nectar-collecting behaviors should be considered for increased impact of this parasitoid in diamondback moth management programs.
An effective means of supplying food to Cotesia vestalis, the larval endoparasitoid of the diamondback moth, Plutella xylostella, was examined in a laboratory and an experimental small greenhouse. Compared to the red and blue boards, yellow boards significantly attracted parasitoids in the laboratory and in the small greenhouse, the yellow feeding site was more effectively utilized by parasitoids than the white one. The parasitoid tended to utilize a feeding site hung 50 cm above ground more than one hung 200 cm above ground, hence we concluded that color and height were important factors for the recognition of the feeding sites by C. vestalis.
Landscape heterogeneity represents two aspects of landscape simplification: (i) compositional heterogeneity (diversity of habitat types); and (ii) configurational heterogeneity (number, size and arrangement of habitat patches), both with different ecological implications for community composition.
We examined how independent gradients of compositional and configurational landscape heterogeneity, at eight spatial scales, shape taxonomic and functional composition of butterfly communities in 91 managed grasslands across Germany. We used landscape metrics that were calculated from functional maps based on habitat preferences of individual species during different life stages. The relative effects of compositional and configurational landscape heterogeneity were compared with those of local land‐use intensity on butterfly taxonomic diversity, community composition and functional diversity of traits related to body size, feeding breadth and migratory tendency.
As expected, compositional heterogeneity had strong positive effects on taxonomic diversity, while configurational heterogeneity had strong positive effects on trait dominance within the community. When landscapes had smaller mean patch size and greater boundary area, communities were dominated by species with more specialized larval feeding, decreased forewing length and limited migratory tendency.
The positive effects of increased configurational landscape heterogeneity outweighed the negative effects of local land‐use intensity on larval‐feeding specialization, at all spatial scales, highlighting its importance for specialists of all dispersal capabilities.
Synthesis and applications . We show that landscapes with high compositional heterogeneity support communities with greater taxonomic diversity, while landscapes with high configurational heterogeneity support communities that include vulnerable species (feeding specialists with larger body size, sedentary nature and more negatively affected by local management intensity). A decline in functional community composition can lead to functional homogenization, affecting the viability of the ecosystems by decreasing the variability in their responses to disturbance and altering their functioning. A landscape management for grasslands that promotes the maintenance of small patch sizes and a diversity of land uses in the surrounding landscape (within 250–1000 m) is recommended for the conservation of diverse butterfly communities. These strategies could also benefit government programmes such as the EU 2020 Biodiversity Strategy in their efforts to reduce the loss of biodiversity in agricultural landscapes.
Research linking biodiversity and ecosystem functioning (BEF) has been mostly centred on the influence of species richness on ecosystem functions in small-scale experiments with single trophic levels. In natural ecosystems, many ecosystem functions are mediated by interactions between plants and animals, such as pollination and seed dispersal by animals, for which BEF relationships are little understood. Largely disconnected from BEF research, network ecology has examined the structural diversity of complex ecological networks of interacting species. Here, we provide an overview of the most important concepts in BEF and ecological network research and exemplify their applicability to natural ecosystems with examples from pollination and seed-dispersal studies. In a synthesis, we connect the structural approaches of network analysis with the trait-based approaches of BEF research and propose a conceptual trait-based model for understanding BEF relationships of plant-animal interactions in natural ecosystems. The model describes the sequential processes that determine the BEF relationship, i.e. the responses of species to environmental filters, the matching of species in ecological networks and the functionality of species in terms of their quantitative and qualitative contributions to plant demography and ecosystem functioning. We illustrate this conceptual integration with examples from mutualistic interactions and highlight its value for predicting the consequences of biodiversity loss for multispecies interactions and ecosystem functions. We foresee that a better integration between BEF and network research will improve our mechanistic understanding of how biodiversity relates to the functioning of natural ecosystems. Our conceptual model is a step towards this integration between structural and functional biodiversity research.
AimPollination services are at risk from land use change and intensification, but responses of individual pollinator species are often variable, making it difficult to detect and understand community-level impacts on pollination. We investigated changes in community composition and functional diversity of insect pollinator communities under land use change in a highly modified landscape.LocationCanterbury region, South Island, New Zealand.Methods
We trapped insect pollinators every month for 1 year at 24 sites across four land use types of increasing intensity in New Zealand: gardens with native vegetation, blackcurrant orchards, dairy farms, and rotational cropping farms. We investigated changes in pollinator species and functional richness and differences in species and functional composition.ResultsUnder increasing land use intensity, both species and functional richness declined markedly. Changes in functional richness, however, were overall not significantly different than expected based on the observed declines in species richness. Nevertheless, there was a significant trend towards greater than expected functional richness within less-intensive land use types and lower than expected functional richness within intensive land use types. The order of species loss under increasing land use intensity was non-random, as pollinators with a narrow diet breadth, large body size, solitary behaviour and a preference for non-floral larval food resources were lost first.Main conclusionsOur study shows that pollinator species bearing particular trait attributes are susceptible to differences in land use. Our study suggests that pollination services may be more vulnerable to environmental changes and disturbances in more intensive land use types as a result of lower pollinator functional richness.
Monocultures typical of intensive agriculture offer ideal conditions to specialized herbivores while depriving their natural enemies of habitat and nutritional resources. The resulting release of herbivores from both bottom-up and top-down control causes pest outbreaks in economically important crops. Boosting locally occurring natural enemy populations through species-specific habitat management to restore natural herbivore control has been much advocated but remains rarely tested in the field. Here, we investigated whether adding specifically selected flowering plants to monocultures increases parasitation rates of herbivores and crop yield. We performed replicated field experiments in 2 years and found that adding cornflowers (Centaurea cyanus) into cabbage (Brassica oleracea) fields significantly increased larval and egg parasitation and egg predation of the herbivore, reduced herbivory rates, and increased crop biomass in at least 1 year. These findings show that addition of a single, well-chosen flowering plant species can significantly increase natural top-down pest control in monocultures but success is variable. This is relevant on two applied levels. First, well chosen companion plants may partially substitute pesticides in agriculture if the approach is optimized, reducing negative effects such as unspecific killing of non-target organisms, residues in food, contamination of soils and water-bodies and increasing pesticide resistances. Our results suggest that, from an agro-economical point of view, egg parasitoids or predators may be the best targets for habitat management because strong natural selection acts on larval parasitoids to keep their hosts alive for their own development. Second, the addition of non-crop vegetation to monocultures benefits biodiversity conservation directly through resource diversification and indirectly through the reduction of pesticide application that increased natural control makes possible.