Invertebrate Functional Groups Research Articles

Air pollution disproportionately impairs beneficial invertebrates: a meta-analysis

Air pollution has the potential to disrupt ecologically- and economically-beneficial services provided by invertebrates, including pollination and natural pest regulation. To effectively predict and mitigate this disruption requires an understanding of how the impacts of air pollution vary between invertebrate groups. Here we conduct a global meta-analysis of 120 publications comparing the performance of different invertebrate functional groups in unpolluted and polluted atmospheres. We focus on the pollutants ozone, nitrogen oxides, sulfur dioxide and particulate matter. We show that beneficial invertebrate performance is reduced by air pollution, whereas the performance of plant pest invertebrates is not significantly affected. Ozone pollution has the most detrimental impacts, and these occur at concentrations below national and international air quality standards. Changes in invertebrate performance are not dependent on air pollutant concentrations, indicating that even low levels of pollution are damaging. Predicted increases in tropospheric ozone could result in unintended consequences to global invertebrate populations and their valuable ecological services.

Interactive effects of drought and deforestation on multitrophic communities and aquatic ecosystem functions in the Neotropics-a test using tank bromeliads.

Together with the intensification of dry seasons in Neotropical regions, increasing deforestation is expected to exacerbate species extinctions, something that could lead to dramatic shifts in multitrophic communities and ecosystem functions. Recent studies suggest that the effects of habitat loss are greater where precipitation has decreased. Yet, experimental studies of the pure and interactive effects of drought and deforestation at ecosystem level remain scarce. Here, we used rainshelters and transplantation from rainforest to open areas of natural microcosms (the aquatic ecosystem and microbial-faunal food web found within the rainwater-filled leaves of tank bromeliads) to emulate drought and deforestation in a full factorial experimental design. We analysed the pure and interactive effects of our treatments on functional community structure (including microorganisms, detritivore and predatory invertebrates), and on leaf litter decomposition in tank bromeliad ecosystems. Drought or deforestation alone had a moderate impact on biomass at the various trophic level, but did not eliminate species. However, their interaction synergistically reduced the biomass of all invertebrate functional groups and bacteria. Predators were the most impacted trophic group as they were totally eliminated, while detritivore biomass was reduced by about 95%. Fungal biomass was either unaffected or boosted by our treatments. Decomposition was essentially driven by microbial activity, and did not change across treatments involving deforestation and/or drought. Our results suggest that highly resistant microorganisms such as fungi (plus a few detritivores) maintain key ecosystem functions in the face of drought and habitat change. We conclude that habitat destruction compounds the problems of climate change, that the impacts of the two phenomena on food webs are mutually reinforcing, and that the stability of ecosystem functions depends on the resistance of a core group of organisms. Assuming that taking global action is more challenging than taking local-regional actions, policy-makers should be encouraged to implement environmental action plans that will halt habitat destruction, to dampen any detrimental interactive effect with the impacts of global climate change.

ECOfast – An integrative ecological evaluation index for an ecosystem-based assessment of shallow rocky reefs

The degradation of marine ecosystems is a growing concern worldwide, emphasizing the need for efficient tools to assess their ecological status. Herein, a novel ecosystem-based ecological evaluation index of shallow rocky reefs is introduced and tested in the Aegean and Ionian Seas (NE Mediterranean). The index focuses on a specific set of pre-selected species, including habitat-forming, key, commercially important, and non-indigenous species, across a wide range of trophic levels (1.00–4.53). Data acquisition is conducted through rapid non-destructive SCUBA diving surveys to assess all macroscopic food web components (macroalgae, invertebrates, and fish). Two versions of the index, ECOfast and ECOfast-NIS, were developed, each applying a different approach to account for the impact of non-indigenous species. In our case study, the correlations between the two versions of the index and sea surface temperature, protection status, occurrence of carnivorous fish, and non-indigenous herbivores were assessed through generalized additive models (GAMs). The assessment assigned 93% (ECOfast) or 96% (ECOfast-NIS) of the sites to a moderate to bad ecological status, indicating an alarming situation in the shallow rocky reefs of the NE Mediterranean. Sites evaluated as poor or bad were characterized by extensive coverage of ephemeral macroalgae, absence or minimal presence of large indigenous carnivorous fish, and complete absence of one to three out of five invertebrate functional trophic groups. The community composition of macroalgae, herbivorous species, and carnivorous fishes differed between the 5 m and 15 m depth zones. Surface temperature and carnivorous fish occurrence were the most important tested predictors of the ecological status of shallow rocky reefs. The best GAMs showed that the ECOfast score declined with sea surface temperature and increased with the occurrence of carnivorous fish; ECOfast-NIS declined with sea surface temperature and the occurrence of non-indigenous fish and increased with the occurrence of carnivorous fish. The non-destructive and integrative nature of this approach, its speed of data acquisition and analysis, and its capacity to account for highly mobile predatory fish and non-indigenous species render the ECOfast index a novel, robust, and valuable tool for assessing the ecological status of shallow rocky reefs.

Meta‐ecosystem dynamics drive the spatial distribution of functional groups in river networks

The meta‐ecosystem concept provides a theoretical framework to study the effect of local and regional flows of resources on ecosystem dynamics. Meta‐ecosystem theory has hitherto been applied to highly abstract landscapes, and meta‐ecosystem dynamics in real‐world landscapes remain largely unexplored. River networks constitute a prime example of meta‐ecosystems, being characterized by directional resource flows from upstream to downstream communities and between the terrestrial and the aquatic realm. These flows have been thoroughly described by the River continuum concept (RCC), a seminal concept in freshwater ecology, stating that observed spatial variations in the relative abundances of invertebrate functional groups reflect systematic shifts in types and locations of food resources, which are in turn determined by the physical attributes of river reaches. Hence, the RCC represents a solid conceptual basis for determining how changes in landscape structure and resource flows will translate into local and regional changes in community composition. Here, we develop and analyse a riverine meta‐ecosystem model inspired by the RCC, which builds upon a physically‐based landscape model of dendritic river networks. We show that the spatial distributions and regional biomass of invertebrate functional groups observed in stream communities are determined by the spatial structure and scaling attributes of dendritic river networks, as well as by specific rates of resource flows. Neglecting any of these aspects in modelling river meta‐ecosystems would result in different community patterns. Moreover, we observed that high rates of resource flow, for example due to river anthropization, have a negative effect on the regional biomass of all functional groups studied, and can lead to cascading extinctions at the meta‐ecosystem scale. Our work paves the way for the development of physically‐based meta‐ecosystem models to understand the structure and functioning of real‐world ecosystems.

Comparison Between Trophic Positions in the Barents Sea Estimated From Stable Isotope Data and a Mass Balance Model

The trophic position concept is central in system ecology, and in this study, trophic position (TP) estimates from stable-isotopes and an Ecopath mass-balance food web model for the Barents Sea were compared. Two alternative models for estimating TP from stable isotopes, with fixed or scaled trophic fractionation were applied. The mass-balance model was parametrized and balanced for year 2000, was comprised of 108 functional groups (Gs), and was based on biomass and diet data largely based on predator stomach data. Literature search for the Barents Sea Large Marine Ecosystem revealed 93 sources with stable isotope data (δ15N values) for 83 FGs, and 25 of the publications had trophic position estimated from nitrogen stable isotopes. Trophic positions estimated from the mass-balance model ranged to 5.1 TP and were highly correlated with group mean δ15N values, and also highly correlated with the original literature estimates of trophic positions from stable isotopes. On average, TP from the mass-balance model was 0.1 TP higher than the original literature TP estimates (TPSIR) from stable isotopes. A trophic enrichment factor (TEF) was estimated assuming fixed fractionation and minimizing differences between trophic positions from Ecopath and TP predicted from δ15N values assuming a baseline value for δ15N calculated for pelagic particulate organic matter at a baseline TP of 1.0. The estimated TEF of 3.0‰ was lower than the most commonly used TEF of 3.4 and 3.8‰ in the literature. The pelagic whales and pelagic invertebrates functional groups tended to have higher trophic positions from Ecopath than from stable isotopes while benthic invertebrate functional groups tended to show an opposite pattern. Trophic positions calculated using the scaled trophic fractionation approach resulted in lower TP than from Ecopath for intermediate TPs and also a larger TP range in the BS. It is concluded that TPs estimated from δ15N values using a linear model compared better to the Ecopath model than the TPs from scaled fractionation approach.

Macroinvertebrate community composition and richness along extreme gradients: The role of local, catchment, and climatic variables in Patagonian headwater streams

Abstract We investigated how interacting multi‐scale environmental variables affect taxonomic composition and functional feeding groups of macroinvertebrates in headwater streams of western Patagonia in southern Chile (45–47°S), a region characterised by extreme climatic gradients, intact forested catchments, and recent intense land use change. The opportunity of establishing biological/functional diversity patterns for near‐reference conditions of headwaters streams is paramount. We used multi‐dimensional scaling ordination and boosted regression tree analysis to evaluate the link between reach, catchment, spatial, and regional climatic variables and macroinvertebrate community structure. The high diversity of predators in low productivity streams, together with genera previously unreported for this latitudinal range underscore the unique characteristics and very limited understanding of Patagonian freshwater stream communities. Two main groups of environmental variables were linked to both taxonomic and functional feeding group diversity. The strongly associated variables were related to forest cover (and inversely alpine zone) at the catchment scale, together with stream velocity at the local scale. The second group reflected local indicators of productivity and weathering inputs, associated with the regional east–west precipitation gradient. We present a conceptual model for the catchment scale effects on invertebrate functional groups in forested headwater streams. While the results highlight potentially singular characteristics of the study region, they also suggest a macro‐ecological generalisation of how global change variables, operating on mountain catchments, may differentially affect stream ecosystems as a consequence of the variations in the forest/alpine gradient, across both deciduous and evergreen temperate biomes.

Aerial invertebrate functional groups respond to landscape composition with only detritivores and predators responding to agri-environment scheme management

Landscape-scale agricultural intensification is a major driver of biodiversity loss. Highly mobile species, such as aerial invertebrates may be disproportionately affected by land cover at large spatial scales due to their ability to disperse. Assessing the efficacy of environmentally friendly farming, such as Agri-Environment Schemes (AES), therefore, requires establishing the influence of land cover beyond focal farms or fields, contextualising the impact of agricultural management. This study measured the response of aerial invertebrate functional groups to AES management in improved and semi-improved upland grasslands accounting for spatial autocorrelation and multi-scale effects of land cover within buffers varying from 100 m to 5 km at 88 paired fields. Total aerial invertebrate abundance and diversity, including detritivores, herbivores, nectivores, predators and parasitoids all responded to different land cover types at varying scales indicative of highly complex and idiosyncratic functional group responses to landscape.After accounting for spatial autocorrelation and multi-scale landscape composition, total aerial invertebrate abundance was unaffected by agricultural management but diversity was (5%) higher in AES than conventionally managed fields. Detritivore (mostly Mycetophilidae fungus gnat) diversity and abundance were higher in AES than conventional fields, but only on improved grasslands, while predator (adult Muscidae house fly, Scathophagidae dung fly and Dolichopodidae long-legged fly) diversity was lower but abundance higher in AES than conventional fields. Aerial invertebrate herbivores (Anthomyiidae root-maggot flies and Cecidomyiidae gall midges and gnats), nectivores (Syrphidae hoverflies and Apoidea bees) and parasitoids (Ichneumonidae wasps) responded to landscape composition, but not agricultural management. Synthesis and Applications: this study suggests that landscape composition drives aerial invertebrate functional group diversity and abundance at multiple spatial scales. Nevertheless, the responses of some functional groups (detritivores and predators) to local agricultural management suggest that AES management may contribute to the maintenance or enhancement of ecosystem service delivery (nutrient cycling and pest biocontrol). Explicitly accounting for multi-scale landscape effects is necessary when assessing the impact of agricultural management on highly mobile taxa.

Global meta‐analysis reveals incomplete recovery of soil conditions and invertebrate assemblages after ecological restoration in agricultural landscapes

Abstract Restoration of old fields in agricultural landscapes has become increasingly important for conservation of species and their habitats owing to habitat destruction and rapid environmental change. Studies examining the outcomes of old field restoration predominantly focus on plant, and sometimes, vertebrate communities. Fewer studies have systematically investigated the effects of restoration efforts on soil properties or ground‐dwelling invertebrates and there is limited synthesis of these data. We conducted a global meta‐analysis of published studies to assess the effects of old field restoration on soil properties and soil invertebrate abundance and richness. We anticipated increased vegetation cover would improve soil properties towards reference condition and in turn, this would promote invertebrate abundance and richness. Studies were included if field sites had a history of cropping or livestock grazing. We identified 42 studies (1994–2019) from 16 countries that met our criteria. More studies assessed passive restoration methods than active planting, and native species were more commonly planted than exotic species. Results showed that restoration improved soil conditions with respect to total nitrogen, magnesium, soil carbon, bulk density and porosity when compared to controls; however, conditions similar to those in reference ecosystems were generally not achieved, even 50+ years after restoration had been initiated. Moderator analyses showed few significant tends, however, bulk density improved with age, and in passively restored versus reference ecosystems. Outcomes for soil carbon and bulk density were most predominant in the top soil when compared to the degraded ecosystem. We detected no consistent trends for the effect of restoration on soil invertebrate richness and abundance compared to the control or reference ecosystems. Synthesis and applications. Our global meta‐analysis found strong evidence that old field restoration in agricultural landscapes had positive effects on soil condition but did not lead to full recovery when compared to a reference ecosystem. We detected few and idiosyncratic effects for invertebrates. Further research is needed to understand effects of restoration on soil invertebrate functional groups and to develop management interventions that accelerate the restoration of soil condition.

Soil macroinvertebrates alter the fate of root and rhizosphere carbon and nitrogen in a turfgrass lawn

Soil invertebrates, especially larger macroinvertebrates, move soil, fragment organic matter and change resource accessibility for soil microorganisms. Macroinvertebrates also affect the formation and turnover of aggregates, which are important controls of soil organic matter dynamics because they physically protect organic matter from degradation and influence many belowground processes ranging from microbial activity to nutrient sorption and water flow. We still lack a complete understanding of how different soil invertebrate functional groups affect the incorporation of root derived carbon and nitrogen into belowground pools. We assessed the effects of macroinvertebrates on soil aggregate abundance and composition and quantified the fate of organic matter derived from roots using a two-year macroinvertebrate exclusion-based field mesocosm study coupled with stable isotope labeling in a turfgrass lawn ecosystem. We hypothesized that macroinvertebrates change soil aggregates dynamics by increasing macroaggregates and decreasing microaggregates and enhancing the incorporation of root-derived organic matter into macroaggregates. We found that within the turfgrass root zone, macroinvertebrates increased the proportion of macroaggregates and decreased free microaggregates. In addition, macroinvertebrates increased carbon and nitrogen incorporation into macroaggregates, microaggregates and coarse particulate organic matter, detected via isotopic enrichment of those soil fractions. We found that macroinvertebrates affect the fate of recently fixed root- and rhizodeposit-derived organic matter in a turfgrass lawn ecosystem, and particularly its incorporation into soil aggregates, similar to findings in forest and agricultural systems.

Monitoring programs of the U.S. Gulf of Mexico: inventory, development and use of a large monitoring database to map fish and invertebrate spatial distributions

Since the onset of fisheries science, monitoring programs have been implemented to support stock assessments and fisheries management. Here, we take inventory of the monitoring programs of the U.S. Gulf of Mexico (GOM) surveying fish and invertebrates and conduct a gap analysis of these programs. We also compile a large monitoring database encompassing much of the monitoring data collected in the U.S. GOM using random sampling schemes and employ this database to fit statistical models to then map the spatial distributions of 61 fish and invertebrate functional groups, species and life stages of the U.S. GOM. Finally, we provide recommendations for improving current monitoring programs and designing new programs, and guidance for more comprehensive use and sharing of monitoring data, with the ultimate goal of enhancing the inputs provided to stock assessments and ecosystem-based fisheries management (EBFM) projects in the U.S. GOM. Our inventory revealed that 73 fisheries-independent and fisheries-dependent programs have been conducted in the U.S. GOM, most of which (85%) are still active. One distinctive feature of monitoring programs of the U.S. GOM is that they include many fisheries-independent surveys conducted almost year-round, contrasting with most other marine regions. A major sampling recommendation is the development of a coordinated strategy for collecting diet information by existing U.S. GOM monitoring programs for advancing EBFM.

Environmental drivers explain regional variation of changes in fish and invertebrate functional groups across the Mediterranean Sea from 1994 to 2012

Functional groups are sets of species that play a similar role in a food web. We defined functional groups of fish species based on their morphological characteristics, while using expert knowledge for invertebrates. We measured 9 morphological traits of 72 fish species, and carried out multivariate analyses to assign fish species to functional groups. The analysis identified 9 trait-based fish functional groups to which were added 3 expert-based invertebrate functional groups. The habitat (position in the water column) and potential diet of each group were identified from the literature. Using the MEDITS bottom trawl survey data collected at 10 to 800 m depth, we calculated relative change in the 12 fish and invertebrate functional group biomasses for 12 Mediterranean areas over the period 1994 to 2012. Multiple regression trees identified 4 regions with similar changes: (1) the Adriatic and the Ionian Sea; (2) the Tyrrhenian Sea and the Strait of Sicily; (3) the Balearic Islands and other enclosed areas such as the Gulf of Lions and Aegean Sea; and (4) the Ligurian Sea and Sardinia. The biomass of all functional groups increased or remained stable in the first 2 regions, while around half the functional group biomasses decreased in the other 2 regions. These regional differences in functional group biomass changes were mainly associated with regional variations in the time trends of bottom water temperature (37%), bottom water dissolved oxygen (23%) and mean catch levels (9%). This study contributes to the EU Marine Strategy Framework Directive by proposing food web indicators based on morphologically and habitat defined functional groups.

Impacts on invertebrate fungivores: a predictable consequence of ground-cover weed invasion?

Empirical impact evidence exists for few of New Zealand’s environmental weeds. Financial constraints prevent managers examining all impacts of all weeds. Therefore it is useful to seek generalisable rules which allow managers to predict impacts of new invasions. Invasive weeds may indirectly affect fungivorous invertebrates through mechanisms such as altered litter-fall, decomposition rates, and microclimate, all of which may alter fungal activity. I tested the hypothesis that fungivorous invertebrates would be consistently affected by three invasive weeds, and that this effect would be more pronounced than for other invertebrate functional groups. Using pitfall traps, I compared invertebrates beneath climbing asparagus, tradescantia and ginger with invertebrates of uninvaded lowland forest. Five out of six Coleoptera taxa which differed in abundance between invaded and uninvaded sites were fungivores; the remaining taxon was a saprophage. At least two taxa of fungivorous Coleoptera responded to each of the three weed species. Acari (mainly Oribatids, some of which are fungivores), Isopoda and Amphipoda (decomposers) were the only taxa to respond to the presence of all three weed species. These results provide some support for the hypothesis that fungivores are particularly responsive to ground-cover weed invasion, but suggest this could be extended to include decomposers as well. However, the direction of effect differed among weed species. Therefore, while changes in fungivore and decomposer abundance may be predicted as one of the more likely consequences of ground-cover weed invasion in New Zealand low-land forest, site- and taxa-specific effects make it difficult to predict the direction of effect.

Utilisation of agri-environment scheme habitats to enhance invertebrate ecosystem service providers

The impact of habitat management (project-managed, farmer-managed or organic), quantity (proportion of uncropped land) and spatial configuration of habitats (arranged as strips or blocks) on the density and biomass of invertebrate functional groups was studied at the farm (100-ha block) and plot scale. At the farm scale, invertebrate abundance and biomass per unit area of uncropped land, responded positively to the presence of project-managed habitats for a number of invertebrate groups (including parasitoids and chick food). The abundance of different invertebrate functional groups varied considerably between habitat types; no single habitat provided the highest densities of all groups, suggesting that a diversity of habitats is beneficial for ecosystem service delivery. Grassy habitats supported the highest densities of predatory invertebrates, wild bird seed the most parasitoids and annual plant habitats the highest levels of chick food for farmland birds. Vegetation characteristics influenced total invertebrate biomass and levels of chick food, but not the total number of invertebrates or the abundance of those providing biocontrol.

Benthic diversity and assemblage structure of a north Patagonian rocky shore: a monitoring legacy of the NaGISA project

The rocky shore of Punta Este, Golfo Nuevo (Patagonia, Argentina), was sampled by means of the standardized NaGISA (CoML) protocol, that was aimed to generate biodiversity baseline data in six levels, from high intertidal to 10 m depth. Based on the generated data, we analysed the benthic assemblage structure, species richness, mean abundance and the distribution pattern of invertebrate functional groups, typifying species in each intertidal and subtidal level. The intertidal sampled is exposed to extreme physical conditions higher than any other rocky shore system studied, with air temperature variation of 40°C during the year, maximum winds of 90 km/h and semidiurnal tides of 5 m amplitude; on the other hand subtidal presents less thermal variation (ΔT 10°C throughout the year) and more homogeneous physical conditions. We identified 64 taxa represented by six animal phyla: Mollusca, Arthropoda, Annelida (Polychaeta), Echinodermata, Cnidaria and Nemertea; and three algal phyla: Chlorophyta, Rhodophyta and Heterokontophyta (class: Phaeophyceae). Ordination non-metric multidimensional scaling plots showed three different assemblages in terms of species composition (intertidal, subtidal 1 m level and subtidal 5–10 m levels). The intertidal was represented by suspension feeders, mainly Mollusca. The tiny mussels Brachidontes rodriguezii and Brachidontes purpuratus, and the algae Corallina officinalis dominated the intertidal and promote positive interaction (amelioration), preventing other species from the extreme physical stress. The subtidal was mainly represented by grazers. Our results showed a tendency of suspension feeders to decrease and grazers and predators to increase from high intertidal to subtidal, probably driven by decreasing physical stress. The gastropod Tegula patagonica, the sea urchins Arbacia dufresnii and Pseudechinus magellanicus and the invasive algae Undaria pinnatifida were the most abundant species in 1 m–10 m levels. Based on previous work performed in the region, we hypothesize that the differences registered between intertidal and subtidal levels could be explained in part by an increase in physical stress at the intertidal, with low predation pressure that promotes positive interactions, while in the subtidal the increase in consumers and decrease of physical stress could lead to associational defences. Our results could be useful as baseline data to develop a sustainable network for long-term monitoring of benthic community changes due to anthropogenic activities.

Disease-Driven Amphibian Declines Alter Ecosystem Processes in a Tropical Stream

Predicting the ecological consequences of declining biodiversity is an urgent challenge, particularly in freshwater habitats where species declines and losses are among the highest. Small-scale experiments suggest potential ecosystem responses to losses of species, but definitive conclusions require verification at larger scales. We measured ecosystem metabolism and used whole-ecosystem stable isotope tracer additions to quantify nitrogen cycling in a tropical headwater stream before and after the sudden loss of amphibians to the fungal pathogen Batrachochytrium dendrobatidis. Tadpoles are normally dominant grazers in such streams, where greater than 18 species may co-occur and densities often exceed 50 individuals m−2. Loss of 98% of tadpole biomass corresponded with greater than 2× increases in algae and fine detritus biomass in the stream and a greater than 50% reduction in nitrogen uptake rate. Nitrogen turnover rates in suspended and deposited organic sediments were also significantly lower after the decline. As a consequence, the stream cycled nitrogen less rapidly, and downstream exports of particulate N were reduced. Whole stream respiration was significantly lower following the decline, indicating less biological activity in the stream sediments. Contrary to our predictions, biomass of grazing invertebrates, or any invertebrate functional groups, did not increase over 2 years following loss of tadpoles. Thus, reductions in ecosystem processes linked to the amphibian decline were not compensated for by other, functionally redundant consumers. Declining animal biodiversity has ecosystem-level consequences that may not be offset by ecological redundancy, even in biologically diverse regions such as the Neotropics.

Grazing management in saltmarsh ecosystems drives invertebrate diversity, abundance and functional group structure

Abstract. 1. Saltmarsh conservation management often involves livestock grazing to maximise plant diversity and provide suitable breeding habitat for over‐wintering coastal birds. The effect of grazing on invertebrates is rarely quantified, but results from limited studies of terrestrial and coastal grasslands demonstrate greater abundance and species richness in un‐grazed grassland.2. The impact of short sward (<8 cm) cattle grazing on the ground dwelling invertebrate community was assessed on an English inter‐tidal upper salt marsh using pitfall traps. Abundance, species richness, functional group structure, abundance of coastal specialists, environmental factors that influence invertebrate habitat choice and food web composition were compared for grazed and un‐grazed marsh.3. In total, 90 000 invertebrates were sampled. Predatory, zoophagus and detritivorous Coleoptera were significantly more abundant on the un‐grazed marsh. In contrast, predatory Hemiptera and Araneae were significantly more abundant on the grazed marsh. Sheet weaver spiders were significantly more abundant on the grazed marsh, foliage running hunters and space web builders more abundant on the un‐grazed marsh. Most inter‐tidal coastal specialist species exhibited clear habitat preference for the grazed marsh. Total species richness was not significantly different between grazing treatments.4. Linear direct gradient analysis showed that two environmental variables influenced by grazing intensity, soil temperature and vegetation height, significantly explained the composition of invertebrate functional groups. Larger bodied invertebrates dominated the un‐grazed food web.5. We conclude that both short sward cattle grazed and un‐grazed saltmarsh habitat should be maintained to maximise invertebrate abundance and diversity and provide suitable habitat for coastal specialists.

Contribution of scale-dependent environmental variability on the biomass patterns of drift algae and associated invertebrates in the Gulf of Riga, northern Baltic Sea

Increased eutrophication has caused a bloom of opportunistic macroalgae and development of drift algal mats in coastal seas worldwide including the Baltic Sea. To date the patterns of the drift algae have been described at one scale (usually at a sampling unit scale i.e. < 100 m) ignoring an infinite variety of other possibilities. Therefore, these analyses do not capture a substantial fraction of overall variance and thus, have limited ecological significance and descriptive power. The objective of this study was to investigate in which of studied spatial scales (sampling unit, 100, 1000 and 10,000 m scales) abiotic environmental variability explained best the biomass patterns of drifting algae and associated invertebrates in the Gulf of Riga, northern Baltic Sea. In addition we assessed whether the species composition and biomass structure of drift algae were related to the biomass structure of three invertebrate functional groups. The biomass distribution of drift algae was better explained by large-scale environmental variability than small-scale environmental variability. The occurrence of topographic depressions at 10,000 m scale seems very important for drifting algal mats to remain in the study area. Non-migrating herbivore community was more strongly related to the biomass patterns of drift algae than mobile herbivore community. The biomass pattern of non-migrating suspension feeders was mainly explained by coastal morphology at different spatial scales indicating that the drift algae had minor or no effects on this functional group.

Soil aggregation in a laboratory experiment: Interactions between earthworms, woodlice and litter palatability

Summary Interactions between soil invertebrate functional groups are still poorly understood. In this study, the effect of the soil dwelling earthworm Aporrectodea caliginosa and the woodlouse Porcellio scaber (litter inhabitant), alone or in combination, on soil aggregation was investigated in laboratory microcosms with litter of different quality (Quercus robur and Fagus sylvatica). After 4 months of incubation, the aggregate size distribution was measured using a dry-sieving method. A. caliginosa played an important role in the formation of large aggregates (>2 mm), whereas P. scaber greatly influenced litter disappearance. A. caliginosa individuals formed a greater number of large aggregates when fed with beech leaves compared to oak leaves even though they preferred the latter. In the presence of beech and P. scaber, A. caliginosa produced significantly fewer large aggregates than expected.

Functional approaches for assessing plant and invertebrate abundance patterns in arable systems

A functional group approach was developed for plant and invertebrate assemblages from UK arable fields to assess the variation in functional composition of these highly disturbed, managed systems. Data were taken from the Farm-Scale Evaluations (FSE) of genetically modified herbicide-tolerant (GMHT) crops where the impact of management of the GMHT crop has been assessed for winter and spring sown oilseed rape, beet and maize. Twenty plant and 36 invertebrate functional groups were defined according to trophic behaviour and traits that affect resource capture, quality and availability. The functional composition of the plant community was significantly affected by season of sowing, the type of crop sown and, to a lesser extent, herbicide management. The invertebrate community composition was also affected by crop type and sowing season, but not by management. Resource and consumer groups were positively related, and data provide strong evidence for top-down control of herbivore populations. Two main interaction groups were identified within the arable food web: one between omnivores, generalist predators and detritivores, which are positively associated with monocots, and one between omnivores, parasitoids, sap feeders and leaf chewers, which have a stronger association with dicots. Although management has an impact on within-field arable biodiversity, crop type and sowing season have an overriding effect on the functional composition of plant and invertebrate assemblages in arable systems. Für Pflanzen- und Invertebratengesellschaften auf Kulturflächen in Großbritannien wurde ein Ansatz über funktionelle Gruppen entwickelt, um die Variation in der funktionalen Zusammensetzung dieser hochgradig gestörten, bewirtschafteten Systeme zu bestimmen. Die Daten stammen aus der “Farm-Scale-Evaluation” von genetisch modifizierten herbizidtoleranten Feldfrüchten (GMHT), bei der der Einfluss der Bewirtschaftung der GHMT-Feldfrüchte für Winter- und Sommerraps, Rüben und Mais abgeschätzt wurde. Es wurden 20 funktionelle Gruppen von Pflanzen und 36 von Invertebraten unter Berücksichtigung der trophischen Stellung und Eigenschaften definiert, welche die Ressourcennutzung, Qualität und Verfügbarkeit beeinflussen. Die funktionelle Zusammensetzung der Pflanzengemeinschaften wurde signifikant durch die Aussaatsaison, durch den ausgesäten Nutzpflanzentyp und in geringerem Maße durch das Herbizidmanagement beeinflusst. Die Zusammensetzung der Invertebratengemeinschaften wurde ebenfalls durch den Nutzpflanzentyp und die Aussaatsaison beeinflusst, aber nicht durch das Management. Die Ressourcen- und Konsumentengruppen standen in einer positiven Beziehung zueinander und die Daten liefern starke Hinweise auf eine top-down Kontrolle der Herbivorenpopulationen. Es wurden zwei wesentliche Interaktionsgruppen innerhalb des Kulturnahrungsnetzes gefunden: Eine zwischen den Omnivoren, unspezialisierten Prädatoren und Detritivoren, die positiv mit Monokotylen assoziiert sind, und eine zwischen Omnivoren, Parasitoiden, Saftsaugern und Blattfressern, die eine stärkere Assoziation mit Dikotylen zeigen. Obwohl die Bewirtschaftung einen Einfluss auf die Biodiversität innerhalb der Kulturfelder hat, zeigen Kulturpflanzentyp und Aussaatsaison eine überwältigenden Einfluss auf die funktionale Zusammensetzung der Pflanzen- und Invertebratengemeinschaften in Kultursystemen.

The importance of sward architectural complexity in structuring predatory and phytophagous invertebrate assemblages

Abstract 1. Although the importance of plant community assemblages in structuring invertebrate assemblages is well known, the role that architectural complexity plays is less well understood. In particular, direct empirical data for a range of invertebrate taxa showing how functional groups respond to plant architecture is largely absent from the literature.2. The significance of sward architectural complexity in determining the species richness of predatory and phytophagous functional groups of spiders, beetles, and true bugs, sampled from 135 field margin plots over 2 years was tested. The present study compares the relative importance of sward architectural complexity to that of plant community assemblage.3. Sward architectural complexity was found to be a determinant of species richness for all phytophagous and predatory functional groups. When individual species responses were investigated, 62.5% of the spider and beetle species, and 50.0% of the true bugs responded to sward architectural complexity.4. Interactions between sward architectural complexity and plant community assemblage indicate that the number of invertebrate species supported by the plant community alone could be increased by modification of sward architecture. Management practices could therefore play a key role in diversifying the architectural structure of existing floral assemblages for the benefit of invertebrate assemblages.5. The contrasting effects of sward architecture on invertebrate functional groups characterised by either direct (phytophagous species) or indirect (predatory species) dependence on plant communities is discussed. It is suggested that for phytophagous taxa, plant community assemblage alone is likely to be insufficient to ensure successful species colonisation or persistence without appropriate development of sward architecture.