Predator Richness Research Articles

Fire frequency shapes diversity in multi‐guild communities through direct and indirect pathways

Abstract Human‐induced changes in fire regimes worldwide are leading to changes in the diversity and composition of plant and insect communities through alterations in vegetation and habitat characteristics. As species interact in complex networks, environmental disturbances, such as an increase in fire frequency, can affect species directly and indirectly through cascading effects across trophic levels. This study examines the effects of fire frequency on multi‐guild communities in the Chaco region in Argentina, aiming to disentangle the direct and indirect pathways of influence between five different species groups: plants, phytophagous insects, ants, predators, and parasitoids. We assess cross‐taxon congruence by analysing α and β diversity indices and performing a structural equation model and Procrustes tests, respectively, trying to elucidate the pathways of influence between fire frequency and the different guilds. Multi‐guild communities responded to environmental changes produced by fire frequency via direct and indirect effects. Fire has both negative and positive, but weak indirect effects on predator richness through a bottom‐up cascading effect from plant richness across phytophagous insects and ants. However, when species relative abundances were considered, no effects have been observed on Shannon and Simpson diversity indices. A positive correlation between species composition of different guilds and fire frequency indicated congruence between connected guilds suggesting that changes in beta diversity propagate across all trophic chains. Given an increase in fire frequency, changes posed to vegetation translated in weak changes via species richness but through pronounced effects on species composition across different trophic levels. Our findings emphasise the importance of a multi‐guild approach to understanding biodiversity responses to environmental changes, highlighting the complexity and intricate dynamics of ecological communities in fire‐prone ecosystems.

Soil arthropod diversity, richness, and abundance in agroecological and conventional cotton production systems in Chaco, Argentina

In Argentina, agroecology has grown in last years as a scientific paradigm that seeks to design and evaluate agroecosystems considering sustainability, complexity, and uncertainty. Diversity is a key factor in the design and management of production systems and a necessary component for conservation biological control and the reduction of agrochemicals use. Cotton (Gossypium hirsutum) crop in northern Argentina is usually managed with high load of agrochemicals: agroecological production arises as an alternative. This study evaluated the diversity, richness, and abundance of soil arthropods using pitfall traps in two experimental cotton plots under conventional (CONV) and agroecological management (AE) in Chaco, Argentina. AE system presented higher diversity and richness of predators compared with CONV, even when natural preparations were used for pest control. The phytophagous arthropods showed higher diversity and richness in CONV, even when pyrethroid insecticides were applied for pest control and preventively. The abundance in AE was lower for predators and higher for phytophagous arthropods. Agroecological production of cotton can be a tool that favors conservative biological control and an alternative for areas where protecting the health of farmers and the ecosystem is a priority.

Insect conservation in agricultural landscapes needs both high crop heterogeneity and semi-natural habitats

Identifying landscapes that are suitable for both biodiversity conservation and agricultural production is a major challenge. Traditionally, much research has focused on biodiversity conservation outside of agricultural production areas, e.g., in semi-natural habitats. In contrast, recent research has mainly focused on the potential of crop heterogeneity. This includes both compositional (crop diversity) and configurational heterogeneity (field border density). However, if and how crop heterogeneity, and semi-natural habitats interact to shape insect diversity in agricultural landscapes remains poorly understood. Here we investigated the combined effects of crop diversity, field border density, and semi-natural habitats (i.e., grassland proportion, hedge density) on insect diversity. We sampled insect communities from 14 – 17 June 2021 with pan traps in 27 study landscapes (500 m x 500 m) covering independent gradients of these landscape variables and identified a total of 587 insect species with DNA metabarcoding. We found that field border density mediated the effects of crop diversity, grassland proportion, and hedge density on insect richness. At low levels of field border density (i.e., landscapes with mostly large fields), effects were either neutral (crop diversity), negative (grassland proportion) or weakly positive (hedge density). By contrast, at high levels of field border density, crop diversity, grassland proportion, and hedge density all exerted positive effects on insect richness. Responses to crop heterogeneity and semi-natural habitat differed among trophic groups of insects (decomposers, herbivores, parasitoids, predators). While variation in richness of herbivorous insects followed the patterns of the overall richness, decomposer richness was not related to any of the investigated variables. Predator richness increased with hedge density in landscapes, whereas parasitoid richness increased when high levels of field border density and grassland proportion coincided. Our study shows that increasing crop heterogeneity is a viable strategy for promoting insect diversity in agricultural landscapes. However, the effects of the amount of remaining semi-natural habitats, such as grassland or hedges, are mediated by configurational heterogeneity, and vary between trophic groups. Efforts to conserve insects in agricultural landscapes must therefore focus on both increasing the heterogeneity of the crop matrix by promoting crop diversity and increasing the density of field borders, while also maintaining or restoring semi-natural habitats as important source habitats for insect species.

Digest: Cooperative breeding strategies in birds are shaped by avian predator richness.

Despite their prevalence, family-living and cooperative breeding in birds have received little examination as to how and why they vary across species. Investigating the evolution of these social systems, Bliard et al. (2024) found that the presence of avian predators is associated with birds' social systems, with increases in predator presence corresponding to multiple shifts from non-family-living to cooperative breeding. Phylogenetic comparative analyses indicate that factors outside the breeding season can be selected for family-living and cooperative breeding.

Beyond predator richness: How diversified cropping can enhance pest regulation

AbstractResearch Highlight discussing: Heinen, J.; Dominguez, V.; Aguilera, G.; Malsher, G.; Vesterinen, E.; Roslin, T.; Bommarco, R.; Bartomeus, I. (2024). Diversified cropping strengthens herbivore regulation by providing seasonal resource continuity to predators. Journal of Applied Ecology, https://doi.org/10.1111/1365‐2664.14674. Crop monocultures consist of homogenous agroecosystems highly dependent on pesticides for pest regulation and mineral fertilisation for maintaining plant nutrition, representing the least resilient system. Agricultural diversification practices can increase heterogeneity in agroecosystems, resulting in greater richness of arthropod predators and enhanced ecological services. Among natural enemies of pests, generalist predators are important for pest regulation as they prey on diverse arthropod pests and be present throughout the season. However, since they consume other predators (intraguild predation) and soil fauna, it is uncertain whether enhanced richness of generalist predators translates into improved pest regulation. The study by Heinen et al. examined how diversified crop rotation and organic fertilisation influenced predator–prey interactions throughout the cropping cycle in cereal fields. The predators' diet preference shifted over the growing season, indicating that soil fauna is an important resource for recruitment and maintenance of predators early in the season. Although intraguild predation was considerably high, it decreased across the season in fields with the greatest level of diversification, where predation of pests remained stable. This study demonstrated how diversified cropping is important for providing resource continuity with alternative prey (soil fauna and predators) over crop‐growing season, enhancing predator richness and herbivore regulation.

Diversified cropping strengthens herbivore regulation by providing seasonal resource continuity to predators

Abstract Agricultural practices shape arthropod communities in arable fields, consequently influencing their interactions and the resulting ecosystem services, in particular pest regulation. Predatory arthropods play a pivotal role by preying on herbivores, soil fauna, and on other predators. However, the intricate mechanisms through which agricultural practices shape the dietary preferences of predators, and regulate herbivore populations remain complex and inadequately understood. We assessed how fertilisation with organic fertiliser and extending crop rotations with perennial ley affected predation pressure across prey taxa. We mapped predator and prey trophic linkages with molecular analysis of carabid predator gut contents, and measured densities and taxonomic richness of predators, herbivores, and soil fauna in 19 cereal fields during three samplings across the growing season. We derived two food web structure metrics: prey vulnerability that is the average number of predators feeding on a selected prey, and predator trophic redundancy, that is dietary overlap. Prey vulnerability was compared among soil fauna, herbivores, and other predator species (that is interspecific intraguild predation) over the growing season, and across treatments. The mechanistic underpinnings of observed shifts in vulnerability of herbivorous prey at different crop stages were identified using information criteria to select among candidate variables related to the richness, density and interaction structure of the different guilds during both the current, and the previous crop stages. Agricultural diversification via organic fertilisation combined with perennial ley in the crop rotation decreased the vulnerability of both intraguild prey and soil fauna prey, and stabilised herbivore vulnerability. Mechanistically, the vulnerability of herbivorous prey at crop ripening emerges from the combination of predator richness and trophic redundancy during this sampling round, rather than from carryover effects from previous crop stages. Synthesis and applications: Our results suggest that locally provided resource continuity through diversified cropping practices bolster biological pest regulation, thus underline the importance of lesser disturbance in arable ecosystems for the provision of ecosystem services. Enhanced predator species richness together with availability of alternative prey through the season underpins this enhanced pest regulation.

Seasonal abundance of key alfalfa (Fabaceae) seed production pests and their natural enemies in southern Alberta, Canada

Abstract The economic importance of insect pests in agricultural fields and the potential biological control by their natural enemies warrant foundational studies for the development of integrated pest management strategies. An insect survey was conducted in alfalfa (Fabaceae) seed production fields in southern Alberta, Canada, during the bud, flowering, and seed crop stages in 2020 and 2021. We examined the seasonal abundance of Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae), Lygus spp. Hahn (Hemiptera: Miridae), and 12 natural enemy taxa. We also examined the seasonal abundance, richness, and diversity of generalist predators and the seasonality of the two H. postica parasitoids, Bathyplectes curculionis (Thomson) (Hymenoptera: Ichneumonidae) and Oomyzus incertus (Ratzeburg) (Hymenoptera: Eulophidae). The seasonality of pests and natural enemies was inconsistent between years. Hypera postica larvae, B. curculionis, and O. incertus were present from mid-June to mid-August. However, we detected no correlations between H. postica larvae and its two parasitoids in either year. A number of generalist predators were correlated with A. lineolatus and Lygus spp. Further research is needed to understand the effects of environmental and biotic factors on the seasonality of pests and natural enemies in alfalfa seed production fields, and the insects’ trophic interactions.

Evaluation of pongamia oil soap against red spider mites, Tetranychus urticae Koch and its effect on mite predators in brinjal ecosystem

The efficacy of pongamia oil soap was tested on red spider mites and on its predators (rove beetle, Oligota sp. and predatory gall midge, Feltiella acarisuga Vallot). Pongamia oil soap at 0.6, 1, 2 and 3 per cent along with neem oil 0.6 per cent, soap solution 0.5 per cent and thiamethoxam 25 WG were investigated and observations were recorded on, a day prior to and, 1, 3, 5, 7 and 14 days after spray application. The results revealed that pongamia oil soap @ 3, 2 and 1 per cent shown mite population reduction up to 86.50, 84.57 and 79.27 per cent respectively. Richness of mite predators didn’t vary significantly at one day after spray and the maximum population was observed in soap solution - (4.33/5 plants). Population of mite predators was relatively high at 14 days after spray with soap solution (35.67 per five plants) which was at par with pongamia oil soap @ 0.6, 1 and 2 per cent.

Influences of conservation tillage on soil macrofaunal biodiversity and trophic structure in the Mollisol region of Northeast China

Tillage regimes directly impact soil disturbance and crop residue levels in the field, subsequently affecting soil macrofauna abundance and diversity, crucial for maintaining soil health and ecosystem functionality. The present study aimed to investigate the effects of different tillage regimes (no-tillage (NT), conventional tillage (CT) and reduced-tillage (RT)) on soil properties and macrofaunal communities in a typical black soil region of Northeast China. Our study revealed that, in comparison to CT and RT, NT significantly enhanced soil macrofauna biodiversity and brought about modification in the community composition. Additionally, it reduced changes in the soil physical–chemical properties. Furthermore, the choice of tillage regimes impacted the trophic structure of soil macrofauna, manifesting in great density and species richness of herbivores and predators in NT plots with crop residue retention when compared to those managed with tillage. Overall, soil organic carbon (SOC) and pH played pivotal roles in regulating the soil macrofaunal community. The alternations observed in the soil macrofaunal community represented a comprehensive response to tillage practices and residue return, which in turn influenced soil properties and microenvironments, including food resources and microhabitats. Therefore, our findings indicated that conservation tillage exerted a notable influence on the soil macrofaunal community. This underscores the significance of soil environments and properties in molding the structure and composition of the soil macrofaunal community. The study will enhance comprehension of soil management practices and advocate for diversity within soil macrofaunal communities.

Fine‐scale spatial and temporal distribution patterns of large marine predators in a biodiversity hotspot

AbstractAimLarge marine predators, such as cetaceans and sharks, play a crucial role in maintaining biodiversity patterns and ecosystem function, yet few estimates of their spatial distribution exist. We aimed to determine the species richness of large marine predators and investigate their fine‐scale spatiotemporal distribution patterns to inform conservation management.LocationThe Hauraki Gulf/Tīkapa Moana/Te Moananui‐ā‐Toi, Aotearoa/New Zealand.MethodsWe conducted a replicate systematic aerial survey over 12 months. Flexible machine learning models were used to explore relationships between large marine predator occurrence (Bryde's whales, common and bottlenose dolphins, bronze whaler, pelagic and immature hammerhead sharks) and environmental and biotic variables, and predict their monthly distribution and associated spatially explicit uncertainty.ResultsWe revealed that temporally dynamic variables, such as prey distribution and sea surface temperature, were important for predicting the occurrence of the study species and species groups. While there was variation in temporal and spatial distribution, predicted richness peaked in summer and was the highest in coastal habitats during that time, providing insight into changes in distributions over time and between species.Main ConclusionsTemporal changes in distribution are not routinely accounted for in species distribution studies. Our approach highlights the value of multispecies surveys and the importance of considering temporally variable abiotic and biotic drivers for understanding biodiversity patterns when informing ecosystem‐scale conservation planning and dynamic ocean management.

Multitrophic arthropod diversity mediates tree diversity effects on primary productivity.

Forests sustain 80% of terrestrial biodiversity and provide essential ecosystem services. Biodiversity experiments have demonstrated that plant diversity correlates with both primary productivity and higher trophic diversity. However, whether higher trophic diversity can mediate the effects of plant diversity on productivity remains unclear. Here, using 5 years of data on aboveground herbivorous, predatory and parasitoid arthropods along with tree growth data within a large-scale forest biodiversity experiment in southeast China, we provide evidence of multidirectional enhancement among the diversity of trees and higher trophic groups and tree productivity. We show that the effects of experimentally increased tree species richness were consistently positive for species richness and abundance of herbivores, predators and parasitoids. Richness effects decreased as trophic levels increased for species richness and abundance of all trophic groups. Multitrophic species richness and abundance of arthropods were important mediators of plant diversity effects on tree productivity, suggesting that optimizing forest management for increased carbon capture can be more effective when the diversity of higher trophic groups is promoted in concert with that of trees.

Combining organic fertilisation and perennial crops in the rotation enhances arthropod communities

Single and combined diversification practices in crop fields and their effects on arthropod predators, decomposers and herbivores have mainly been assessed in small plot and cage experiments. In particular, effects of diversification on arthropod predators and their food resources, such as soil fauna, weed seeds and herbivorous prey in entire crop fields across the growing season, remain unclear. We explored how organic fertilisers, with or without the legacy of perennial ley in the crop rotation, and mineral fertiliser without the legacy of perennial ley, affected below- and aboveground communities in 19 spring cereal crop fields. In each field, we determined the abundance of the soil mesofauna, communities of arthropod prey aboveground and of the predator guilds carabids, staphylinids and spiders. We sampled at three crop stages: tillering, heading and ripening. Weed cover and soil characteristics, such as carbon and nitrogen content, were assessed. For most soil mesofauna groups, the combination of organic fertiliser with the legacy of ley gave highest, organic fertiliser with annual crop rotations intermediate, and mineral fertiliser with annual crop rotations the lowest total abundance. Aboveground arthropod prey abundances were similar across treatments. The legacy of ley increased richness of all aboveground arthropod predators. Staphylinid communities’ abundance increased additively as diversification treatments were combined during tillering of the crop. Increasing organic amendments, alongside the reduced disturbances through inclusion of perennial ley in the rotation, led to more abundant communities below- and aboveground as well as more richness in aboveground predator communities.

Multiple Fish Species Supplement Predation in Estuaries Despite the Dominance of a Single Consumer

Predation is important in maintaining the community structure, functioning and ecological resilience of estuarine seascapes. Understanding how predator community structure, seascape context and habitat condition combine to influence predation is vital in managing estuarine ecosystems. We measured relationships between predator species richness, predator abundance and individual species abundances as well as seascape context and habitat condition, on relative predation probability in mangrove forests, seagrass meadows and unvegetated sediment across 11 estuaries in Queensland, Australia. Predation was quantified using videoed assays of tethered invertebrates (i.e. ghost nippers, Trypaea australiensis) and fish assemblages were surveyed using remote underwater video systems. Yellowfin bream (Acanthopagrus australis) dominated predation in all three habitats; however, predation was not correlated with yellowfin bream abundance. Instead, predation increased fourfold in mangroves and threefold in unvegetated sediment when predatory species richness was highest (> 3 species), and increased threefold in seagrass when predator abundance was highest (> 10 individuals). Predation in mangroves increased fourfold in forests with a lower pneumatophore density (< 50/m2). In seagrass, predation increased threefold at sites that had a greater extent (> 2000 m2) of seagrass, with longer shoot lengths (> 30 cm) and at sites that were closer to (< 2000 m) the estuary mouth. Predation on unvegetated sediment increased threefold when more extensive salt marshes (> 15000 m2) were nearby. These findings demonstrate the importance of predator richness and abundance in supplementing predation in estuaries, despite the dominance of a single species, and highlight how seascape context and habitat condition can have strong effects on predation in estuaries.

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.

Species richness, diversity and evenness of predators in Bt cotton in Maharashtra, India

Species richness, diversity and evenness of predators in Bt cotton in Maharashtra, India

Invertebrate predators in Sitka spruce plantations managed by clear-cutting or continuous-cover silvicultural systems

Invertebrate predators of aphids were sampled at ground level and in the canopy in 13 even-aged Sitka spruce Picea sitchensis forest stands managed by clear-cutting and replanting, and in 11 Sitka spruce stands managed as continuous cover forestry using either shelterwood or group selection silvicultural systems. The expectation was that stands managed using shelterwood or group selection systems would support a greater abundance and diversity of invertebrate predators, because of their more complex internal structure, but results were mixed. Hoverflies (Syrphidae), predatory bugs (Hemiptera), ladybird beetles (Coccinellidae) and spiders (Araneae) were more abundant in shelterwood and group selection stands, but soldier beetles (Cantharidae), lacewings (Neuroptera) and harvestmen (Opiliones) were more abundant in mid-rotation and mature even-aged stands, and vespid wasps (Vespidae) showed a similar abundance across all stand types. In contrast, species richness and diversity of the insect predator groups were higher in shelterwood and group selection stands, even for groups that were less abundant in those stands. It was not clear, however, whether the greater species richness of insect predators in shelterwood and group selection was the result of these stands supporting breeding populations of a wider range of species, including less common species, or was because the more open structure of these stands allowed introgression of species from other habitats within the forest.

Local and landscape factors determining the abundance and richness of insect pests and arthropod predators in Bt and non-Bt soybean

Agricultural landscapes of the Pampas and Campos biome have changed considerably due to the expansion of annual crops over non-crop areas, soybean seeding and the adoption of lepidopteran-resistant varieties (Bt technology). These changes have a great impact on predatory and phytophagous arthropods, which have been scarcely studied in Uruguay. The following aspects were evaluated: (a) the effect of vegetation cover composition (landscape factor), Bt technology (varieties expressing Cry1Ac protein) and field margins (local factors), on the abundance of the main pests and predators of soybean; b) the role of refuge areas (non-Bt soybean) in determining the abundance and richness of arthropod predators in Bt soybean crops, and c) the effect of Cry1Ac protein on the biology, reproduction and feeding behavior of Piezodorus guildinii (Hemiptera: Pentatomidae). In the northern Uruguayan littoral, during two years, predators and pests were sampled in 90 commercial non-Bt and Bt soybean fields and refuge areas. Biological and reproductive parameters of P. guildinii fed with Bt soybean pods and their possible effect on feeding behavior were evaluated using the electrical penetration graph technique. The main results obtained were: a) i. Bt soybean presented lower abundance of defoliating lepidoptera, without affecting predator abundance; ii. Soybean predators’ abundance was negatively related to the proportion of this crop in the landscape, but positively related to natural grassland and other crops; iii. Predators’ abundance between margins and within soybean fields was positively associated; b) Bt predators’ abundance and richness was positively associated with their values in refuge areas, evidencing for the first time their role in the conservation of beneficial fauna; c) biological and reproductive parameters and feeding behavior of P. guildinii were not affected by the ingestion of Cry1Ac protein expressed in Bt soybean pods. These results contribute to the possibilities of ecological intensification designs of national and regional production systems through pest management approached from a landscape perspective.

Effect of Cosmos, Crotalaria, Foeniculum, and Canavalia species, single-cropped or mixes, on the community of predatory arthropods.

Some plants can attract natural enemy by offering resources such as alternative food and refuge. However, studies need to be conducted before agricultural landscape diversification is implement. Our objective was to determine the best floristic compositions of cosmos (Cosmos sulphureus—Asteraceae), showy rattlepod (Crotalaria spectabilis—Fabaceae), fennel (Foeniculum vulgare—Apiaceae), and jack bean (Canavalia ensiformis—Fabaceae) to attract and maintain predatory arthropods, and know the potential of these treatments for future use in diversifying agricultural systems. The experimental design consisted in seven treatments of four species in single-crop, intercrops in three densities called mix1, mix2, and mix3, and the control (weeds). For the arthropod families classified as very frequent and constant, population dynamics in intercropping treatments was plotted according to the plant phenology. We conclude that all plants cultivated in single-cropping and intercropping treatments showed high predator richness and can potentially be used to diversify cultivated areas. Sulfur cosmos as a single crop and three mixes attracts higher numbers and greater family richness. Spider families—Oxyopidae, Araneidae and Thomisidae—and insects—Chrysopidae and Coccinellidae are more frequents. The dynamics of the predator populations varied according to the mixes treatment.

Bottom‐up effects of plant quantity and quality on arthropod diversity across multiple trophic levels in a semi‐arid grassland

Abstract Plant quantity and quality can independently affect the diversity of the entire arthropod communities and multiple arthropod taxa in grassland ecosystems. However, it remains unclear how these effects on arthropod taxa at one trophic level propagate through food web to influence the diversity of higher trophic levels. We performed a monoculture experiment with 15 herbaceous species in the Inner Mongolian grassland to investigate how natural variations in plant productivity and host leaf traits affect herbivore taxon richness, which, in turn, affects predator taxon richness. For herbivores, plant productivity indirectly promoted herbivore taxon richness by increasing herbivore biomass, which was attributed to the increases in the richness of dominant sucking herbivores and endophytes with high food requirements. However, the high plant quality indicator (e.g. high leaf protein, phosphorus and water contents, and high leaf protein to carbohydrate ratio) directly increased, whereas the low plant quality indicator (e.g. high leaf lignin content) directly decreased herbivore taxon richness. Taxon richness of chewing and sucking herbivores with specific feeding modes (tearing or sucking mouthparts) showed strong positive responses to increasing plant quality. For predators, herbivore taxon richness, rather than herbivore biomass, mainly mediated the positive effects of plant productivity and the high plant quality indicator, but the negative effect of the low plant quality indicator, on predator taxon richness. At the feeding guild level, the taxon richness of parasitoids, other predators and spiders exhibited positive responses to different herbivores, which was attributed to their different diet preferences. Predator diversity could be promoted by prey partitioning among predator guilds facilitating species coexistence. At the family level, the taxon richness of most predator families was positively correlated with that of more than one herbivore family, suggesting that high predator diversity may be caused by balanced diets owing to high prey diversity. Synthesis. Natural variations in plant quantity and quality can substantially affect the diversity of herbivores and cascade up the food web to affect predators. Specificity and mechanisms of feeding have a large impact on the responses of arthropod guilds at each trophic level.

Increasing Levels of Physical Disturbance Affect Soil Nematode Community Composition in a Previously Undisturbed Ecosystem.

Soil is essential for the sustenance of life. Diverse soil organisms support several biological processes such as organic matter decomposition, mineralization, nutrient cycling, and controlling pests and diseases. Among multicellular soil organisms, nematodes are ubiquitous, functionally diverse, and abundant. Notably, agricultural practices have diverse impacts on plants, soils, and soil organisms. Tillage affects nematodes directly by altering pore size and disrupting the continuity of water films and indirectly by affecting the lower trophic groups such as bacteria and fungi. The primary goal of this study was to examine the effect of increasing levels of physical disturbance on nematode communities in an undisturbed forest ecosystem. The experiment included four treatments: control with no disturbance, surface litter removed with no litter and no vegetation, tilling the soil with a rototiller every 2 mon, and every 2 wk. Tillage significantly reduced the overall abundance and overall richness of nematode communities over time. Among nematode trophic groups, tillage significantly reduced the abundance and richness of bacterial feeders, predators, and omnivores over time. The abundance and richness of c-p 2, c-p 4, and c-p 5 class nematodes were significantly decreased by tillage. Unlike tillage, minimal disturbance such as removal of surface litter resulted in a significant decrease in the abundance of only three genera: Acrobeles, Aporcelaimellus, and Boleodorus. Nonmetric multidimensional scaling analysis revealed that nematodes of higher c-p classes such as Dorylaimida, Aporcelaimellus, Alaimus, Clarkus, and Tripyla were sensitive to physical disturbances. Bacterial feeders belonging to the c-p 2 class such as Tylocephalus, Acrobeles, Ceratoplectus, Plectus, and Pseudacrobeles were significantly reduced by tillage. Moreover, tillage significantly reduced the functional metabolic footprint of nematodes, which indicates decreased metabolic activity, reduced C inflow, and poorly structured soil food webs. Previous studies conducted in agricultural ecosystems determined that Clarkus, Filenchus, and Plectus were tolerant to tillage; however, they were found sensitive to tillage in our study. Overall, our study suggests that increasing levels of physical disturbance are detrimental to nematode community abundance and diversity that could affect soil ecosystem stability and sustainability.