Competition, predation and species responses to environmental change

Despite much effort over the past decade on the ecological consequences of global warming, ecologists still have little understanding of the importance of interspecific interactions in species responses to environmental change. Models predict that predation should mitigate species responses to environmental change, and that interspecific competition should aggravate species responses to environmental change. To test this prediction, we studied how predation and competition affected the responses of two ciliates, Colpidium striatum and Paramecium tetraurelia , to temperature change in laboratory microcosms. We found that neither predation nor competition altered the responses of Colpidium striatum to temperature change, and that competition but not predation altered the responses of Paramecium tetraurelia to temperature change. Asymmetric interactions and temperature-dependent interactions may have contributed to the disparity between model predictions and experimental results. Our results suggest that models ignoring inherent complexities in ecological communities may be inadequate in forecasting species responses to environmental change.     

Richness–productivity relationships between trophic levels in a detritus-based system: significance of abundance and trophic linkage

Most theoretical and empirical studies of productivity–species richness relationships fail to consider linkages among trophic levels. We quantified productivity–richness relationships in detritus-based, water-filled tree-hole communities for two trophic levels: invertebrate consumers and the protozoans on which they feed. By analogy to theory for biomass partitioning among trophic levels, we predicted that consumer control would result in richness of protozoans in the lower trophic level being unaffected by increases in productivity, whereas richness of invertebrate consumers would increase with productivity. Our data were consistent with this prediction: consumer richness increased linearly, but protozoan richness was unrelated to changes in productivity. The productivity–richness relationships for all taxa combined were not necessarily consistent with relationships within each trophic level. We used path analysis to investigate the mechanisms that may produce the observed responses of trophic levels to changes in productivity. We tested the importance of the direct effect of productivity on richness and the indirect effect of productivity mediated by effects on total abundance. For protozoans, only direct effects of productivity on richness were important, but both direct and indirect effects of productivity on richness were important for invertebrates. Protozoan richness was strongly affected by top-down impacts of abundance of invertebrates. These results are consistent with theory on biomass partitioning among trophic levels and suggest a strong link between richness and abundance within and between trophic levels. Understanding how trophic level interactions determine productivity–richness relationships will likely be necessary in order for us to achieve a comprehensive understanding of the determinants of diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Temperature fluctuation facilitates coexistence of competing species in experimental microbial communities

1. Temperature fluctuation is a general phenomenon affecting many, if not all, species in nature. While a few studies have shown that temperature fluctuation can promote species coexistence, little is known about the effects of different regimes of temperature fluctuation on coexistence. 2. We experimentally investigated how temperature fluctuation and different regimes of temperature fluctuation ('red' environments in which temperature series exhibited positive temporal autocorrelation vs. 'white' environments in which temperature series showed little autocorrelation) affected the coexistence of two ciliated protists, Colpidium striatum Stein and Paramecium tetraurelia Sonneborn, which competed for bacterial resources. 3. We have previously shown that the two species differed in their growth responses to changes in temperature and in their resource utilization patterns. The two species were not always able to coexist at constant temperatures (22, 24, 26, 28 and 30 degrees C), with Paramecium being competitively excluded at 26 and 28 degrees C. This indicated that resource partitioning was insufficient to maintain coexistence at these temperatures. 4. Here we show that in both red and white environments in which temperature varied between 22 and 32 degrees C, Paramecium coexisted with Colpidium. Consistent with the differential effects of temperature on their intrinsic growth rates, Paramecium population dynamics were largely unaffected by temperature regimes, and Colpidium showed more variable population dynamics in the red environments. 5. Temperature-dependent competitive effects of Colpidium on Paramecium, together with resource partitioning, appeared to be responsible for the coexistence in the white environments; resource partitioning and the storage effect appeared to account for the coexistence in the red environments. 6. These results suggest that temperature fluctuation may play important roles in regulating species coexistence and diversity in ecological communities.     

A cross‐system meta‐analysis reveals coupled predation effects on prey biomass and diversity

Predator diversity and abundance are under strong human pressure in all types of ecosystems. Whereas predator potentially control standing biomass and species interactions in food webs, their effects on prey biomass and especially prey biodiversity have not yet been systematically quantified. Here, we test the effects of predation in a cross‐system meta‐analysis of prey diversity and biomass responses to local manipulation of predator presence. We found 291 predator removal experiments from 87 studies assessing both diversity and biomass responses. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey across ecosystems. Predation effects were highly similar between ecosystem types, whereas previous studies had shown that herbivory or decomposition effects differed fundamentally between terrestrial and aquatic systems based on different stoichiometry of plant material. Such stoichiometric differences between systems are unlikely for carnivorous predators, where effect sizes on species richness strongly correlated to effect sizes on biomass. However, the negative predation effect on prey biomass was ameliorated significantly with increasing prey richness and increasing species richness of the manipulated predator assemblage. Moreover, with increasing richness of the predator assemblage present, the overall negative effects of predation on prey richness switched to positive effects. Our meta‐analysis revealed strong general relationships between predator diversity, prey diversity and the interaction strength between trophic levels in terms of biomass. This study indicates that anthropogenic changes in predator abundance and diversity will potentially have strong effects on trophic interactions across ecosystems. Synthesis The past centuries we have experienced a dramatic loss of top–predator abundance and diversity in most types of ecosystems. To understand the direct consequences of predator loss on a global scale, we quantitatively summarized experiments testing predation effects on prey communities in a cross‐system meta‐analysis. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey, and predation effects were highly similar. However, with increasing predator richness, the overall negative effects of predation on prey richness switched to positive ones. Anthropogenic changes in predator communities will potentially have strong effects on prey diversity, biomass, and trophic interactions across ecosystems.     

Biodiversity effects of the predation gauntlet

The ubiquity of trophic downgrading has led to interest in the consequences of mesopredator release on prey communities and ecosystems. This issue is of particular concern for reef-fish communities, where predation is a key process driving ecological and evolutionary dynamics. Here, we synthesize existing experiments that have isolated the effects of mesopredators to quantify the role of predation in driving changes in the abundance and biodiversity of recently settled reef fishes. On average, predators reduced prey abundance through generalist foraging behavior, which, through a statistical sampling artifact, caused a reduction in alpha diversity and an increase in beta diversity. Thus, the synthesized experiments provide evidence that predation reduces overall abundance within prey communities, but—after accounting for sampling effects—does not cause disproportionate effects on biodiversity.

     

Effects of enrichment on protist abundances and bacterial composition in simple microbial communities

We experimentally investigated effects of nutrient enrichment and trophic structure in a microbial food web consisting of mixed bacteria, two bacterivorous ciliates ( Tetrahymena sp. and Colpidium sp.) and an omnivorous ciliate ( Blepharisma sp.) feeding on both trophic levels. We assembled all possible food webs including one or more of the ciliate species and cross-classified them with four levels of enrichment of the bacterial medium. The qualitative outcome of food web interactions was independent of enrichment and always the same: Tetrahymena strongly depressed or excluded Colpidium , and Blepharisma strongly depressed or excluded both bacterivores. Consequently, in all sub-webs only the dominant ciliate species responded positively to enrichment. The total density of bacteria increased with enrichment irrespective of food web composition. In contrast, the response of single-celled bacteria to enrichment depended on food web composition and was only weakly positive in most food webs with the omnivore. Enrichment had a positive effect on the relative success of (presumably more defended) bacterial aggregates. The outcome of interspecific interactions among ciliates could not be predicted from monoculture experiments and deviated from earlier experiments in which each bacterivore coexisted separately with the omnivore. As a potential explanation we suggest that changes in experimental protocol reduced spatial heterogeneity and increased attack rates. A simple, dynamical model shows that increased attack rates can indeed greatly decrease the upper limit and range of enrichment over which intermediate consumers can coexist with omnivores.     

The invasive mud crab enforces a major shift in a rocky littoral invertebrate community of the Baltic Sea

In rocky littoral communities, intense herbivory allows for the occurrence of trophic cascades where higher trophic levels influence producer communities. Invasive predators can be especially effective in imposing trophic cascades. The North American mud crab Rhithropanopeus harrisii is a recent invader in the Baltic Sea, with an expanding distribution range. Here, we document the effects of mud crab on the native invertebrate community associated with the key foundation species Fucus vesiculosus. During the initial 3 years of invasion, mud crab abundance in F. vesiculosus increased from 2 % to about 25 % of the algae being inhabited by crabs. Simultaneously, the invertebrate community underwent a major transition: Species richness and diversity dropped as a consequence of decreasing abundance and the loss of certain taxa. The abundance of gastropods decreased by 99 % and that of crustaceans by 75 %, while chironomids completely disappeared. Consequently, the community dominated earlier by herbivorous and periphyton-grazing gastropods and crustaceans shifted to a mussel dominated community with overall low abundances of herbivores. At the same time filamentous epiphytic algae prospered and the growth rate of F. vesiculosus decreased. We suggest that this shift in the invertebrate community may have far reaching consequences on ecosystem functioning. These arise through changes in the strength of producer–herbivore interaction, caused by mud crab predation on the dominating grazer taxa. This interaction is a major determinant of ecological function of ecosystems, i.e. productivity and energy flow to higher trophic levels. Therefore, the decrease in herbivory can be expected to have a major structuring role in producer communities of the rocky littoral macroalgal assemblages.     

Plant Diversity Impacts Decomposition and Herbivory via Changes in Aboveground Arthropods

Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning.     

The rise of a marine generalist predator and the fall of beta diversity

Determining the importance of physical and biological drivers in shaping biodiversity in diverse ecosystems remains a global challenge. Advancements have been made towards this end in large marine ecosystems with several studies suggesting environmental forcing as the primary driver. However, both empirical and theoretical studies point to additional drivers of changes in diversity involving trophic interactions and, in particular, predation. Moreover, a more integrated but less common approach to the assessment of biodiversity changes involves analyses of spatial β diversity, whereas most studies to date assess only changes in species richness (α diversity). Recent research has established that when cod, a dominant generalist predator, was overfished and collapsed in a northwest Atlantic food web, spatial β diversity increased; that is, the spatial structure of the fish assemblage became increasingly heterogeneous. If cod were to recover, would this situation be reversible, given the inherent complexity and non‐linear dynamics that typify such systems? A dramatic increase of cod in an ecologically similar large marine ecosystem may provide an answer. Here we show that spatial β diversity of fish assemblages in the Barents Sea decreased with increasing cod abundance, while decadal scale changes in temperature did not play a significant role. These findings indicate a reversibility of the fish assemblage structure in response to changing levels of an apex predator and highlight the frequently overlooked importance of trophic interactions in determining large‐scale biodiversity patterns. As increased cod abundance was largely driven by changes in fisheries management, our study also shows that management policies and practices, particularly those involving apex predators, can have a strong effect in shaping spatial diversity patterns, and one should not restrict the focus to effects of climate change alone.     

Predator diversity strengthens trophic cascades in kelp forests by modifying herbivore behaviour

Although human-mediated extinctions disproportionately affect higher trophic levels, the ecosystem consequences of declining diversity are best known for plants and herbivores. We combined field surveys and experimental manipulations to examine the consequences of changing predator diversity for trophic cascades in kelp forests. In field surveys we found that predator diversity was negatively correlated with herbivore abundance and positively correlated with kelp abundance. To assess whether this relationship was causal, we manipulated predator richness in kelp mesocosms, and found that decreasing predator richness increased herbivore grazing, leading to a decrease in the biomass of the giant kelp Macrocystis. The presence of different predators caused different herbivores to alter their behaviour by reducing grazing, such that total grazing was lowest at highest predator diversity. Our results suggest that declining predator diversity can have cascading effects on community structure by reducing the abundance of key habitat-providing species.     

Woody plant phylogenetic diversity mediates bottom–up control of arthropod biomass in species-rich forests

Global change is predicted to cause non-random species loss in plant communities, with consequences for ecosystem functioning. However, beyond the simple effects of plant species richness, little is known about how plant diversity and its loss influence higher trophic levels, which are crucial to the functioning of many species-rich ecosystems. We analyzed to what extent woody plant phylogenetic diversity and species richness contribute to explaining the biomass and abundance of herbivorous and predatory arthropods in a species-rich forest in subtropical China. The biomass and abundance of leaf-chewing herbivores, and the biomass dispersion of herbivores within plots, increased with woody plant phylogenetic diversity. Woody plant species richness had much weaker effects on arthropods, but interacted with plant phylogenetic diversity to negatively affect the ratio of predator to herbivore biomass. Overall, our results point to a strong bottom–up control of functionally important herbivores mediated particularly by plant phylogenetic diversity, but do not support the general expectation that top–down predator effects increase with plant diversity. The observed effects appear to be driven primarily by increasing resource diversity rather than diversity-dependent primary productivity, as the latter did not affect arthropods. The strong effects of plant phylogenetic diversity and the overall weaker effects of plant species richness show that the diversity-dependence of ecosystem processes and interactions across trophic levels can depend fundamentally on non-random species associations. This has important implications for the regulation of ecosystem functions via trophic interaction pathways and for the way species loss may impact these pathways in species-rich forests.     

Predation and disturbance interact to shape prey species diversity

Though predation, productivity (nutrient richness), spatial heterogeneity, and disturbance regimes are known to influence species diversity, interactions between these factors remain largely unknown. Predation has been shown to interact with productivity and with spatial heterogeneity, but few experimental studies have focused on how predation and disturbance interact to influence prey diversity. We used theory and experiments to investigate how these factors influence diversification of Pseudomonas fluorescens by manipulating both predation (presence or absence of Bdellovibrio bacteriovorus) and disturbance (frequency and intensity of disturbance). Our results show that in a homogeneous environment, predation is essential to promote prey species diversity. However, in most but not all treatments, elevated diversity was transitory, implying that the effect of predation on diversity was strongly influenced by disturbance. Both our experimental and theoretical results suggest that disturbance interacts with predation by modifying the interplay of resource and apparent competition among prey.     

Between‐lake variation in the trophic ecology of an invasive crayfish

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The alpine cushion plant Silene acaulis as foundation species: a bug's-eye view to facilitation and microclimate

Alpine ecosystems are important globally with high levels of endemic and rare species. Given that they will be highly impacted by climate change, understanding biotic factors that maintain diversity is critical. Silene acaulis is a common alpine nurse plant shown to positively influence the diversity and abundance of organisms--predominantly other plant species. The hypothesis that cushion or nurse plants in general are important to multiple trophic levels has been proposed but rarely tested. Alpine arthropod diversity is also largely understudied worldwide, and the plant-arthropod interactions reported are mostly negative, that is,. herbivory. Plant and arthropod diversity and abundance were sampled on S. acaulis and at paired adjacent microsites with other non-cushion forming vegetation present on Whistler Mountain, B.C., Canada to examine the relative trophic effects of cushion plants. Plant species richness and abundance but not Simpson's diversity index was higher on cushion microsites relative to other vegetation. Arthropod richness, abundance, and diversity were all higher on cushion microsites relative to other vegetated sites. On a microclimatic scale, S. acaulis ameliorated stressful conditions for plants and invertebrates living inside it, but the highest levels of arthropod diversity were observed on cushions with tall plant growth. Hence, alpine cushion plants can be foundation species not only for other plant species but other trophic levels, and these impacts are expressed through both direct and indirect effects associated with altered environmental conditions and localized productivity. Whilst this case study tests a limited subset of the membership of alpine animal communities, it clearly demonstrates that cushion-forming plant species are an important consideration in understanding resilience to global changes for many organisms in addition to other plants.     

Resource Availability and Spatial Heterogeneity Control Bacterial Community Response to Nutrient Enrichment in Lakes

The diversity and composition of ecological communities often co-vary with ecosystem productivity. However, the relative importance of productivity, or resource abundance, versus the spatial distribution of resources in shaping those ecological patterns is not well understood, particularly for the bacterial communities that underlie most important ecosystem functions. Increasing ecosystem productivity in lakes has been shown to influence the composition and ecology of bacterial communities, but existing work has only evaluated the effect of increasing resource supply and not heterogeneity in how those resources are distributed. We quantified how bacterial communities varied with the trophic status of lakes and whether community responses differed in surface and deep habitats in response to heterogeneity in nutrient resources. Using ARISA fingerprinting, we found that bacterial communities were more abundant, richer, and more distinct among habitats as lake trophic state and vertical heterogeneity in nutrients increased, and that spatial resource variation produced habitat specific responses of bacteria in response to increased productivity. Furthermore, changes in communities in high nutrient lakes were not produced by turnover in community composition but from additional taxa augmenting core bacterial communities found in lower productivity lakes. These data suggests that bacterial community responses to nutrient enrichment in lakes vary spatially and are likely influenced disproportionately by rare taxa.     

Richness and species composition of arboreal arthropods affected by nutrients and predators: a press experiment

A longstanding goal for ecologists is to understand the processes that maintain biological diversity in communities, yet few studies have investigated the combined effects of predators and resources on biodiversity in natural ecosystems. We fertilized nutrient limited plots and excluded insectivorous birds in a randomized block design, and examined the impacts on arthropods associated with the dominant tree in the Hawaiian Islands, Metrosideros polymorpha (Myrtaceae). After 33 months, the species load (per foliage mass) of herbivores and carnivores increased with fertilization, but rarified richness (standardized to abundance) did not change. Fertilization depressed species richness of arboreal detritivores, and carnivore richness dropped in caged, unfertilized plots, both because of the increased dominance of common, introduced species with treatments. Herbivore species abundance distributions were more equitable than other trophic levels following treatments, and fertilization added specialized native species without changing relativized species richness. Overall, bird removal and nutrient addition treatments on arthropod richness acted largely independently, but with countervailing influences that obscured distinct top-down and bottom-up effects on different trophic levels. This study demonstrates that species composition, biological invasions, and the individuality of species traits may complicate efforts to predict the interactive effects of resources and predation on species diversity in food webs.     

Experimental Manipulation of Grassland Plant Diversity Induces Complex Shifts in Aboveground Arthropod Diversity

Changes in producer diversity cause multiple changes in consumer communities through various mechanisms. However, past analyses investigating the relationship between plant diversity and arthropod consumers focused only on few aspects of arthropod diversity, e.g. species richness and abundance. Yet, shifts in understudied facets of arthropod diversity like relative abundances or species dominance may have strong effects on arthropod-mediated ecosystem functions. Here we analyze the relationship between plant species richness and arthropod diversity using four complementary diversity indices, namely: abundance, species richness, evenness (equitability of the abundance distribution) and dominance (relative abundance of the dominant species). Along an experimental gradient of plant species richness (1, 2, 4, 8, 16 and 60 plant species), we sampled herbivorous and carnivorous arthropods using pitfall traps and suction sampling during a whole vegetation period. We tested whether plant species richness affects consumer diversity directly (i), or indirectly through increased productivity (ii). Further, we tested the impact of plant community composition on arthropod diversity by testing for the effects of plant functional groups (iii). Abundance and species richness of both herbivores and carnivores increased with increasing plant species richness, but the underlying mechanisms differed between the two trophic groups. While higher species richness in herbivores was caused by an increase in resource diversity, carnivore richness was driven by plant productivity. Evenness of herbivore communities did not change along the gradient in plant species richness, whereas evenness of carnivores declined. The abundance of dominant herbivore species showed no response to changes in plant species richness, but the dominant carnivores were more abundant in species-rich plant communities. The functional composition of plant communities had small impacts on herbivore communities, whereas carnivore communities were affected by forbs of small stature, grasses and legumes. Contrasting patterns in the abundance of dominant species imply different levels of resource specialization for dominant herbivores (narrow food spectrum) and carnivores (broad food spectrum). That in turn could heavily affect ecosystem functions mediated by herbivorous and carnivorous arthropods, such as herbivory or biological pest control.     

Water temperature determines strength of top-down control in a stream food web

1. We examined effects of water temperature on the community structure of a three trophic level food chain (predatory fish, herbivorous caddisfly larvae and periphyton) in boreal streams. We used laboratory experiments to examine (i) the effects of water temperature on feeding activities of fish and caddisfly larvae and on periphyton productivity, to evaluate the thermal effects on each trophic level (species‐level experiment), and (ii) the effects of water temperature on predation pressure of fish on abundance of the lower trophic levels, to evaluate how temperature affects top‐down control by fish (community‐level experiment). 2. In the species‐level experiment, feeding activity of fish was high at 12 °C, which coincides with the mean summer temperature in forested streams of Hokkaido, Japan, but was depressed at 3 °C, which coincides with the mean winter temperature, and also above 18 °C, which coincides with the near maximum summer temperatures. Periphyton productivity increased over the range of water temperatures. 3. In the community‐level experiments, a top‐down effect of fish on the abundance of caddisfly larvae and periphyton was clear at 12 °C. This effect was not observed at 3 and 21 °C because of low predation pressure of fish at these temperatures. 4. These experiments revealed that trophic cascading effects may vary with temperature even in the presence of abundant predators. Physiological depression of predators because of thermal stress can alter top‐down control and lead to changes in community structure. 5. We suggest that thermal habitat alteration can change food web structure via combinations of direct and indirect trophic interactions.     

Effects of temperature, salinity and fish in structuring the macroinvertebrate community in shallow lakes: implications for effects of climate change

Climate warming may lead to changes in the trophic structure and diversity of shallow lakes as a combined effect of increased temperature and salinity and likely increased strength of trophic interactions. We investigated the potential effects of temperature, salinity and fish on the plant-associated macroinvertebrate community by introducing artificial plants in eight comparable shallow brackish lakes located in two climatic regions of contrasting temperature: cold-temperate and Mediterranean. In both regions, lakes covered a salinity gradient from freshwater to oligohaline waters. We undertook day and night-time sampling of macroinvertebrates associated with the artificial plants and fish and free-swimming macroinvertebrate predators within artificial plants and in pelagic areas. Our results showed marked differences in the trophic structure between cold and warm shallow lakes. Plant-associated macroinvertebrates and free-swimming macroinvertebrate predators were more abundant and the communities richer in species in the cold compared to the warm climate, most probably as a result of differences in fish predation pressure. Submerged plants in warm brackish lakes did not seem to counteract the effect of fish predation on macroinvertebrates to the same extent as in temperate freshwater lakes, since small fish were abundant and tended to aggregate within the macrophytes. The richness and abundance of most plant-associated macroinvertebrate taxa decreased with salinity. Despite the lower densities of plant-associated macroinvertebrates in the Mediterranean lakes, periphyton biomass was lower than in cold temperate systems, a fact that was mainly attributed to grazing and disturbance by fish. Our results suggest that, if the current process of warming entails higher chances of shallow lakes becoming warmer and more saline, climatic change may result in a decrease in macroinvertebrate species richness and abundance in shallow lakes.     

Trophic and Non-Trophic Interactions in a Biodiversity Experiment Assessed by Next-Generation Sequencing

Plant diversity affects species richness and abundance of taxa at higher trophic levels. However, plant diversity effects on omnivores (feeding on multiple trophic levels) and their trophic and non-trophic interactions are not yet studied because appropriate methods were lacking. A promising approach is the DNA-based analysis of gut contents using next generation sequencing (NGS) technologies. Here, we integrate NGS-based analysis into the framework of a biodiversity experiment where plant taxonomic and functional diversity were manipulated to directly assess environmental interactions involving the omnivorous ground beetle Pterostichus melanarius. Beetle regurgitates were used for NGS-based analysis with universal 18S rDNA primers for eukaryotes. We detected a wide range of taxa with the NGS approach in regurgitates, including organisms representing trophic, phoretic, parasitic, and neutral interactions with P. melanarius. Our findings suggest that the frequency of (i) trophic interactions increased with plant diversity and vegetation cover; (ii) intraguild predation increased with vegetation cover, and (iii) neutral interactions with organisms such as fungi and protists increased with vegetation cover. Experimentally manipulated plant diversity likely affects multitrophic interactions involving omnivorous consumers. Our study therefore shows that trophic and non-trophic interactions can be assessed via NGS to address fundamental questions in biodiversity research.