Diversity Of Arthropod Predators Research Articles

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

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

Functional and phylogenetic relationships link predators to plant diversity via trophic and non-trophic pathways.

Human-induced biodiversity loss negatively affects ecosystem function, but the interactive effects of biodiversity change across trophic levels remain insufficiently understood. We sampled arboreal spiders and lepidopteran larvae across seasons in 2 years in a subtropical tree diversity experiment, and then disentangled the links between tree diversity and arthropod predator diversity by deconstructing the pathways among multiple components of diversity (taxonomic, phylogenetic and functional) with structural equation models. We found that herbivores were major mediators of plant species richness effects on abundance, species richness, functional and phylogenetic diversity of predators, while phylogenetic, functional and structural diversity of trees were also important mediators of this process. However, the strength and direction differed between functional, structural and phylogenetic diversity effects, indicating different underlying mechanisms for predator community assembly. Abundance and multiple diversity components of predators were consistently affected by tree functional diversity, indicating that the variation in structure and environment caused by plant functional composition might play key roles in predator community assembly. Our study highlights the importance of an integrated approach based on multiple biodiversity components in understanding the consequences of biodiversity loss in multitrophic communities.

Strip intercropping of wheat and oilseed rape enhances biodiversity and biological pest control in a conventionally managed farm scenario

Abstract Conventional agriculture in the global north is typically characterized by large monocultures, commonly managed with high levels of pesticide or fertilizer input and mechanization. Strip intercropping, that is, diversifying cropland by growing strips of different crops using conventional machinery, may be a viable strategy to promote natural predator diversity and associated biological pest control in such conventional farming systems. We tested the influence of strip intercropping of conventionally managed winter wheat with oilseed rape, using common machinery with 27–36 m broad strips, on arthropod predator diversity and biological pest control. We characterized spider and carabid beetle communities, calculated pest aphid and pollen beetle densities and recorded parasitism rates for both crops (number of mummified aphids on wheat and number of parasitized pollen beetle larvae on oilseed rape). We observed a significant reduction in the densities of wheat aphids (50% decrease) and pollen beetle larvae (20% decrease) in strip intercropping areas compared to monocultures. Parasitism rates of wheat aphids increased significantly from 10% in monocultures to 25% in strip intercropping areas. The number of parasitized pollen beetle larvae did not show the same pattern but was higher towards the centre of the oilseed rape strip. Overall, the composition of predator communities benefited from the close neighbourhood of the two crop species in the strips, as carabid beetles were more abundant in oilseed rape and spiders were more abundant in wheat fields. Overall, strip intercropping reduced the dominance of one predator group and allowed for an equal representation of both spiders and carabid beetles in the mixture. Synthesis and applications. Our study presents evidence of the benefits of adopting strip intercropping with relatively large strips (adapted to existing machinery) for natural predator diversity and biological pest control in a large‐scale conventionally managed farm scenario. Wheat–oilseed rape strip intercropping reduced pest densities, increased parasitism of wheat aphids and promoted equal representation of natural predator groups well beyond the areas of monoculture. Overall, by reducing the area dedicated to only one crop, the implementation of strip intercropping adapted to mechanized agricultural scenarios can be used to increase crop heterogeneity at regional scales and enhance biodiversity and biological control, even in simplified landscapes dominated by large‐scale conventional agriculture.

A Comparison of Flower and Grass Strips for Augmentation of Beneficial Arthropods in Apple Orchards

Sowing plants that provide food resources in orchards is a potential habitat management practice for enhancing biological control. Flowering plants (providing pollen and nectar) and grasses (providing alternative prey) can benefit natural enemies in orchards; however, little is known about their relative importance. We studied the effect of management practices (flower strips, grass strips, and spontaneous grass) on arthropod predators under organic apple management regimes in apple orchards in Beijing, China. Orchards located at two different sites were assessed for 3 years (2017–2019). The cover crops had a significant impact on the abundance and diversity of arthropod predators. The grass treatment consistently supported significantly greater densities of alternative prey resources for predators, and predators were more abundant in the grass than in the other treatments. The Shannon–Wiener diversity was significantly higher for the cover crop treatment than for the control. Community structure was somewhat similar between the grass and control, but it differed between the flower treatment and grass/control. Weak evidence for an increase in mobile predators (ladybirds and lacewings) in the orchard canopy was found. Ladybirds and lacewings were more abundant in the grass treatment than in the other treatments in 2019 only, while the aphid abundance in the grass treatment was lowest. The fact that grass strips promoted higher predator abundance and stronger aphid suppression in comparison to the flower strips suggests that providing alternative prey for predators has great biocontrol service potential. The selection of cover crops and necessary management for conserving natural enemies in orchards are discussed in this paper.

Organic farming promotes arthropod predators, but this depends on neighbouring patches of natural vegetation

Current global declines in insect populations emphasise the need for biodiversity appropriate farming. Organic farming can promote in-field biodiversity, yet this may depend on surrounding vegetation, which acts as a source habitat for arthropod predators that promote pest suppression. Here we assess the role that natural vegetation plays in relation to farm management type (conventional versus organic farming) for arthropod predator diversity in a perennial cropping system (citrus orchards). We also determine how environmental variables, specifically plant species richness, flower abundance, cover crop height, litter depth, as well as grass, herbaceous, woody plant and rock cover, influence arthropod predators across the orchard – natural vegetation landscape mosaic. Arthropod species richness and abundance were significantly higher on organic farms, but species composition varied with biotope (natural vegetation, orchards with associated natural vegetation and those without associated natural vegetation). There was an interesting interaction between farming type and surrounding biotope. Organic farms had greater arthropod predator species richness and abundance than conventional farms in the absence of natural vegetation, but there was no difference between organic and conventional orchards in the presence of natural vegetation. Thus, patches of remnant natural vegetation improve the biodiversity of arthropod predators within conventional orchards. The environmental variables sampled here were all significant drivers for some focal taxa in most biotopes, emphasising the need to conserve heterogeneity in agricultural systems. The value of organic farming depends on landscape context, particularly proximity of natural vegetation. It is therefore recommended that to improve predator species richness and abundance, farmers should aim to diversify both local- and landscape-level environmental heterogeneity.

How a Scorpion Toxin Selectively Captures a Prey Sodium Channel: The Molecular and Evolutionary Basis Uncovered.

The growing resistance of insects to chemical pesticides is reducing the effectiveness of conventional methods for pest control and thus, the development of novel insecticidal agents is imperative. Scorpion toxins specific for insect voltage-gated sodium channels (Navs) have been considered as one of the most promising insecticide alternatives due to their host specificity, rapidly evoked toxicity, biodegradability, and the lack of resistance. However, they have not been developed for uses in agriculture and public health, mainly because of a limited understanding of their molecular and evolutionary basis controlling their phylogenetic selectivity. Here, we show that the traditionally defined insect-selective scorpion toxin LqhIT2 specifically captures a prey Nav through a conserved trapping apparatus comprising a three-residue-formed cavity and a structurally adjacent leucine. The former serves as a detector to recognize and bind a highly exposed channel residue conserved in insects and spiders, two major prey items for scorpions; and the latter subsequently seizes the "moving" voltage sensor via hydrophobic interactions to reduce activation energy for channel opening, demonstrating its action in an enzyme-like manner. Based on the established toxin-channel interaction model in combination with toxicity assay, we enlarged the toxic spectrum of LqhIT2 to spiders and certain other arthropods. Furthermore, we found that genetic background-dependent cavity shapes determine the species selectivity of LqhIT2-related toxins. We expect that the discovery of the trapping apparatus will improve our understanding of the evolution and design principle of Nav-targeted toxins from a diversity of arthropod predators and accelerate their uses in pest control.

Insectivorous birds in the Neotropics: Ecological radiations, specialization, and coexistence in species-rich communities

AbstractInsectivorous birds reach their highest diversity in the tropics and represent a striking variety of morphological and behavioral specializations for foraging, yet explanations for these patterns are inadequate because of both our limited understanding of the drivers of ecological diversification within and among clades and of coexistence mechanisms in particular. Here we synthesize recent information on Neotropical insectivorous birds, including their diversity, evolutionary ages and locations of origin, phylogenies, and both competitive and predator–prey species interactions. We propose a novel evolutionary hypothesis for the origin and coexistence of the phenotypic diversity of insectivore foraging morphologies in species-rich communities, based on their extraordinary food-resource specializations. Specifically, we develop the Biotic Challenge Hypothesis to explain the evolution of these specializations, and we provide preliminary evidence in support of this hypothesis based on a synopsis of both Neotropical insectivore specializations by family and arthropod antipredator adaptations by category. We argue that, from the perspective of tropical insectivorous birds, and particularly in the most species-rich, mainland Neotropical communities, the environment is an arthropod desert. Coexistence with all of the other insectivores requires feeding specialization to compete exploitatively and diffusely against evolutionarily diverse species and far less frequently against sister species. The arthropod desert arises primarily because of (1) the tactical diversity of arthropod predators as insectivore competitors and (2) the evolutionary arms races involving arthropod predators with their prey, which render many arthropods inaccessible to most insectivorous predators. Our idea provides an explicit mechanism for pervasive, diffuse tropical interspecific competition, for evolutionary specialization, and for positive feedback on speciation rates at low latitudes, thereby generating new predictions and insights into tropical life histories and the Latitudinal Diversity Gradient. Other recent ideas concerning the coexistence of Neotropical insectivores, including positive species interactions within mixed species flocks, are recognized and evaluated. We discuss ways to test predictions resulting from the new view of communities developed here, including a case study of diet specialization by Costa Rican tyrannid flycatchers. Our synthesis of the origin and nature of Neotropical insectivore communities injects new life into the “zombie” idea that evolution works differently in the species-rich tropics.

Co-culture of multiple aquatic species enhances vegetable production in coastal Shanghai

Global societies witnessed rapid increase in population and accelerating demand for vegetables from cities along the coastal areas (e.g., Shanghai). Development of “multiculture”, “polyculture”, or “co-culture” systems along the coastal areas in Southeast Asia in turn become a preferred choice for installing future aquaculture. To build much needed knowledge guiding the design, ecological benefits, and performances of these newly explored vegetable-aquaculture systems, we designed a nested block experiment and conducted a 3-year study of cauliflower-aquaculture farming on the island. We found that farming type significantly affected the arthropod herbivores and predators, including herbivore abundance and the abundance, species richness and Shannon's diversity of the predators. More importantly, farming type had a significant effect on insecticide use, cauliflower yield and economic returns. The reduction in insecticide use promoted predator diversity and cauliflower yield in co-cultured cauliflower aquaculture as indicated by a significantly negative relationship between amount of commercial insecticides and arthropod predator diversity, as well as between amount of commercial insecticide and cauliflower yield. We conclude that co-culture practice in cauliflower-aquaculture enhanced agricultural production while decreasing use of insecticide and herbivore abundance, and increasing the abundance and diversity of predators, vegetable yield and economic value.

The Diversity of Arthropods Predator on Wild Plant of Rice Field with and without Pesticides

<p>Contaminated- agro ecosystem influences abundance and diversity of arthropods. The aims of this study were to analyze the diversity and abundance of pre-planting arthropod predators on wild plants in rice field with and without application of pesticides. The survey and direct observation of wild plants at the rice filed were conducted from January to March 2015, at 1 ha in Pemulutan and 1 ha in Musi 2 Palembang. Sampling of arthropod predator was conducted 8 times before the rice was grown, using insect nets. On the land without pesticide application was found 14 arthropod families which consists of 28 species and 15 families of wild plant consists of 25 species. On the land with pesticide application was found 8 arthropod families consists of 16 species and 15 wild plant families with 23 species. On the land without pesticide application was found High index of diversity (H’=3.121) and low dominance (D=0.095), while on the land with pesticide application low index of diversity (H’=2.602) and high dominance (D=0.171). It is the indicators of arthropods predator more varieties at the land without pesticide application compare to the land with pesticide application. This finding is very important for biological pest management in South Sumatra. </p>

Optimizing arthropod predator conservation in permanent grasslands by considering diversity components beyond species richness

Grasslands host large parts of Europe’s agricultural arthropod diversity. Considering the adverse effects of ongoing land use changes on many grassland taxa, there is an urgent need to establish measures that allow for optimizing the conservation of permanent grassland habitats and their climatic, environmental and ecological benefits. Here, data from 42 permanent grasslands were used to quantify the effect of individual management practices on different diversity components in spider and ground beetle communities. Intensive fertilization and frequent cutting reduced the species richness of spiders and the number of threatened spider species, but increased the average taxonomic distinctness of communities. Moreover, high grazing intensity reduced the average body size of individuals in local spider communities. Frequent cutting led to a higher abundance of predaceous and omnivorous ground beetles but a lower abundance of herbivorous species. These opposing responses of both different biodiversity components and different taxa to individual grassland management practices confirm that no single management practice maximizes the biodiversity of arthropod predators in permanent grasslands at the local scale. Rather, our study suggests that arthropod predator diversity can only be conserved by promoting a landscape-scale combination of different management practices and intensities in permanent grasslands. When considering conservation measures, conservation goals should not only be formulated in terms of local species richness, but also need to address other components of diversity such as taxonomic or functional diversity.

Survey of Diversity and Abundance of Ground-dwelling Arthropods in a Black Walnut-forage Alley-cropped System in the Mid-western United States

Abstract Alley cropping is an integrated land management practice growing economic crops between rows of trees. This paper examines the effects of alley cropping on carabid beetles and other ground dwelling arthropod predators on species diversity and abundance by testing for differences among ground vegetation treatments in alleyways. Arthropods were collected with pitfall traps in two alley-cropped areas using the ground cover treatments of alfalfa, smooth bromegrass, and a vegetation-free control. Although not generally statistically significant, brome had the lowest means of any of the ground vegetation treatments, possibly due to the relative impenetrability of the thick grass. We found few significant differences among treatments. Carabidae numbers were negatively correlated with relative humidity and positively correlated to soil temperature and moisture. Sampling methods other than pitfall trapping are needed in future studies to clarify the role of ground cover in arthropod predator diversity and...

Effects of aphids on foliar foraging by Argentine ants and the resulting effects on other arthropods

Abstract 1. Although interactions between ants and honeydew‐producing insects have received considerable study, relatively little is known about how these interactions alter the behaviour of ants in ways that affect other arthropods. In this study, field and greenhouse experiments were performed that examined how the presence of aphids (Aphis fabae solanella) on Solanum nigrum influenced the foraging behaviour of Argentine ants (Linepithema humile) and, in turn, modified the extent to which ants deter larval lacewings (Chrysoperla rufilabris), which are known aphid predators.2. A field experiment demonstrated that the level of foliar foraging by ants increased linearly with aphid abundance, whereas no relationship existed between the level of ground foraging by ants and aphid abundance.3. In the greenhouse, as in the field, foliar foraging by ants greatly increased when aphids were present. Higher levels of foliar foraging led to a twofold increase in the likelihood that ants contacted aphid predators. As a result of these increased encounters with ants, lacewing larvae were twice as likely to be removed from plants with aphids compared with plants without aphids. Once contact was made, however, the behaviour of ants towards lacewing larvae appeared similar between the two experimental groups.4. Argentine ants drive away or prey upon a diversity of arthropod predators and parasitoids, but they also exhibit aggression towards certain herbivores. Future work should attempt to quantify how the ecological effects that result from interactions between honeydew‐producing insects and invasive ants, such as L. humile, differ from those that result from interactions between honeydew‐producing insects and native ants.

Effects of Management Intensity and Season on Arboreal Ant Diversity and Abundance in Coffee Agroecosystems

Agricultural intensification decreases arthropod predator diversity, abundance and population stability, and may affect interactions between top predators and their arthropod prey – ultimately affecting ecosystem services. Coffee management intensification (reduction or removal of shade trees) reduces diversity of arthropod predators (ground-foraging ants). Because ants provide ecosystem services by controlling pests, influences of intensification on arboreal, coffee-foraging ant diversity and abundance are important. We here address how coffee intensification affects: (1) coffee-foraging ant diversity and abundance and (2) seasonal fluctuations in ant abundance. In each of four coffee sites of varying management intensity in Chiapas, Mexico, we sampled vegetation and using two methods, sampled ant diversity and abundance over two years. Sites significantly differed in vegetation and management intensity. Coffee-foraging ant diversity generally decreased with increasing management intensity (16–26% fewer species observed in the most intensively-managed site). Ant abundance was higher in the wet season. Management intensity, however, did not influence ant abundance or seasonal fluctuations in abundance. Our results highlight the importance of diverse agricultural systems in maintaining arthropod predator diversity, and point to one model system in which we may effectively test how diversity per se affects ecosystem services.

Arthropod Parasitoids and Predators of the Onion Maggot (Diptera: Anthomyiidae) in Southwestern Ontario

Miniature (1 m2) mass-rearing beds containing onion maggot, Delia antiqua (Meigen), were established during 1980 and 1981 at three commercial onion-growing fields and an experimental farm in southwestern Ontario to attract local parasites and predators. Onion maggot (OM) pupae from each of the three generations were collected from the beds before eclosion and allowed to complete development in the laboratory, enabling collection and identification of emerging parasitoids. Seven insect species (three staphylinid, four hymenopteran) were confirmed as parasitoids of OM, of which only Aphaereta pallipes (Say) and Aleochara bilineata (Gyllenhal) were significant mortality agents (parasitism rates up to 17 and 20.7%, respectively). Twenty carabid, 42 staphylinid, and 17 other (total 79) arthropod species of predatory habit were associated with OM in or near the miniature rearing beds. Twenty-one of the 79 species of mooted predators accepted OM eggs, larvae, or pupae as food under laboratory conditions. Diversity of arthropod predators and parasitoids was highest at the experimental farm at London (53 + 7 spp., respectively) > the three commercial onion-growing fields at Thedford (39 + 6) > Keswick (36 + 5) > Bradford (36 + 4).