Predation can be a great source of mortality for insect eggs. Thus, female insects use multiple strategies to reduce it. Two common strategies are to aggregate eggs, which may function to satiate egg predators, and various deterrence strategies, such as the addition of faecal strings on top of the egg. We tested the hypothesis that these two strategies work best in combination, where egg aggregation may strengthen the effect of deterrence strategies. We compared egg predation by the predator Paederus riparius both within the species Galerucella lineola (cleaned eggs versus eggs with faecal strings), and between the species G. lineola and G. sagittariae (where the latter species naturally lack faecal strings). Our findings revealed a robust treatment interaction, where faecal strings and egg density affected egg survival when exposed to Paederus riparius. Egg survival increased with egg density for eggs with faecal strings but was constantly low on eggs without faecal strings (cleaned G. lineola eggs or G. sagittariae eggs). This study emphasised that a combination of insect traits may be needed to defend insect eggs against their natural predators.

Volatile plant compounds are essential for host plant selection by herbivores and particularly important for the behaviour of parasitoids seeking larvae in which to lay eggs. Headspace extracts were collected from intact plants of four Brassica oleracea genotypes, as well as from plants damaged by larvae of Mamestra brassicae or Pieris rapae. In total, 52 volatiles present in the headspaces of four genotypes were selected for multivariate analyses. The most abundant groups of volatiles were terpenes and esters, represented by 20 and 14 compounds, respectively. The qualitative and quantitative differences in odour profiles between the four genotypes were sufficient to differentiate between groups using multivariate analysis techniques. The most distinct volatile blends originated from curly kale, followed by cabbage, cauliflower and broccoli. Multivariate analysis revealed that genotypes affected the composition of the volatile blends to a large extent compared to the herbivore damage by the different species tested. In curly kale, broccoli and cauliflower, the differences in odour bouquets were more expressed between plants with and without active feeding, independent of the herbivore identity, while in cabbage, larger differences were observed between odour profiles with different herbivore feedings, independent of whether the herbivore was present or removed.

Aim: Aquatic-terrestrial transition zones contain features essential for many species that often benefit wetland biodiversity. Shallow flood-zone areas and reed beds are indicative of natural wetland habitats; however, how such features affect the native arthropod biodiversity in constructed wetlands is scarcely investigated. We asked how these shoreline features, as well as wetland shoreline properties and grazing management, influence riparian arthropod diversities and habitat specializations. Location: Constructed wetlands, Sweden. Taxa: Araneae, Coleoptera, Diptera. Methods: Taxonomic-, phylogenetic- and trait diversities, along with habitat specialist species richness, were measured in riparian spiders, beetles and selected Diptera in 68 constructed wetlands in two regions of Sweden. We ran structural equation models to estimate direct and indirect effects from shoreline slope, flooded grassland, reed areas and grazing management on group diversities, and used multivariate models to determine drivers on habitat specialist species richness. Results: Flooded grassland and reed area, along with shoreline slope influenced arthropod diversities, and responses differed between arthropod groups and diversity metrics. Spider trait diversity was greater in wetlands with larger flooded grassland areas, whilst beetle trait diversity was reduced. Spider phylogenetic diversity was greater in wetlands containing larger reed areas and in wetlands with steeper shorelines. However, species richness in predatory flies was greater in wetlands with more gentle shorelines. Grazing management had limited effects on arthropod diversities; however, species richness in wetland specialist and generalist predatory dipterans was greater in the absence of grazers in wetlands with greater flooded grassland areas. Main Conclusions: As requirements vary considerably among arthropods, care must be taken when constructing and managing wetlands to benefit arthropod biodiversity. The present results suggest wetlands with a varied shoreline, albeit with greater proportions of flood areas, or multiple adjacent wetlands with varying shores in a wet landscape and a mild grazing regiment, would accommodate a more diverse arthropod fauna.

In aquatic ecosystems, zooplankton-associated bacteria potentially have a great impact on the structure of ecosystems and trophic networks by providing various metabolic pathways and altering the ecological niche of host species. To understand the composition and drivers of zooplankton gut microbiota, we investigated the associated microbial communities of four zooplankton genera from different seasons in the Baltic Sea using the 16S rRNA gene. Among the 143 ASVs (amplified sequence variants) observed belonging to heterotrophic bacteria, 28 ASVs were shared across all zooplankton hosts over the season, and these shared core ASVs represented more than 25% and up to 60% of relative abundance in zooplankton hosts but were present at low relative abundance in the filtered water. Zooplankton host identity had stronger effects on bacterial composition than seasonal variation, with the composition of gut bacterial communities showing host-specific clustering patterns. Although bacterial compositions and dominating core bacteria were different between zooplankton hosts, higher gut bacteria diversity and more bacteria contributing to the temporal variation were found in Temora and Pseudocalanus, compared to Acartia and Synchaeta. Diet diatom and filamentous cyanobacteria negatively correlated with gut bacteria diversity, but the difference in diet composition did not explain the dissimilarity of gut bacteria composition, suggesting a general effect of diet on the inner conditions in the zooplankton gut. Synchaeta maintained high stability of gut bacterial communities with unexpectedly low bacteria-bacteria interactions as compared to the copepods, indicating host-specific regulation traits. Our results suggest that the patterns of gut bacteria dynamics are host-specific and the variability of gut bacteria is not only related to host taxonomy but also related to host behavior and life history traits.

Wetland hydrological dynamics often dictate the composition of biological communities found in or near wetlands, either directly or through changes in vegetation composition. However, much remains unknown, particularly regarding how riparian arthropods respond to such dynamics. In this study, we used high-resolution hydrological data, along with presence of grazing livestock and shoreline vegetation height from 41 constructed wetlands in south-western Sweden to explore flood zone areas, flood frequencies, vegetation and grazing as drivers of the resident arthropod communities. The collected material consisted of 26,817 arthropods, where the dominant groups were Diptera (13,258 specimens), spiders (6,207) and Coleoptera (2,858), which were collected using SLAM (Sea Land and Air Malaise) trapping, along with pitfall trapping and vacuum sampling of riparian arthropods. We found group-specific responses to inundation frequencies, where wetlands with higher frequencies had lower abundances of some beetles and tipulids, and where wetlands with longer low-water table periods contained less trichopterans and heteropterans. In contrast, the size of flood zone areas only affected some wolf spider groups, that were more abundant in wetlands with intermediately sized flood zones. Shoreline vegetation height affected multiple groups, spiders, beetles and dipterans, but in different directions, whereas presence of grazing livestock had limited impact on abundances and community compositions. Given the variable responses to wetland hydrological and structural drivers, it seems that wetland arthropod communities would benefit from a high local wetland habitat variability, or wetlandscapes where individual wetlands have differing hydrological dynamics, morphology and vegetation.

The restoration and creation of wetlands is being discussed as a way to solve several societal crises. It can mitigate climate change by preventing greenhouse gas emissions, but also reduce eutrophication, prevent floods and droughts and favour biodiversity. However, a single wetland cannot fulfil all environmental requirements; a diversity of wetland types is needed, where the right wetland is put in the right place.

Restaurering och anläggning av våtmarker diskuteras som ett sätt att lösa flera samhälleliga kriser. Det kan mildra klimatförändringarna genom att motverka läckage av växthusgaser men också minska övergödning, förhindra översvämning och torka samt gynna biologisk mångfald. Samtidigt kan en enskild våtmark inte uppfylla alla miljökrav utan det krävs en mångfald av våtmarkstyper där rätt våtmark placeras på rätt plats.

Terrestrial insectivores in riparian areas, such as spiders, can depend on emergent aquatic insects as high-quality prey. However, chemical pollution entering streams from agricultural and urban sources can alter the dynamics and composition of aquatic insect emergence, which may also affect the riparian food web. Few studies have examined the effects of stressor-induced alterations in aquatic insect emergence on spiders, especially in terms of chemical pollution and diet composition. We used DNA metabarcoding of gut content to describe the diet of Tetragnatha montana spiders collected from 10 forested streams with differing levels of pesticide and wastewater pollution. We found that spiders consumed more Chironomidae and fewer other aquatic Diptera, including Tipulidae, Ptychopteridae and Culicidae, at more polluted streams. Pollution-related effects were mainly observed in the spider diet, and were not significant for the number nor composition of flying insects trapped at each site. Our results indicate that the composition of riparian spider diets is sensitive to stream pollution, even in the absence of a change in the overall proportion of aquatic prey consumed. A high reliance on aquatic prey at polluted streams may give spiders an increased risk of dietary exposure to chemical pollutants retained by emergent insects.

1. Null models provide a valuable baseline against which fundamental ecological hypotheses can be tested and foraging choices that cannot be explained by neutral processes or sampling biases can be highlighted. In this way, null models can advance our understanding beyond simplistic dietary descriptions to identify drivers of interactions. This method, however, requires estimates of resource availability, which are generally imperfect representations of highly dynamic systems. Optimising method selection is crucial for study design, but the precise effects of different resource availability data on the efficacy of null models are poorly understood.
2. Using spider–prey networks as a model, we used prey abundance (suction sample) and activity density (sticky trap) data, and combinations of the two, to simulate null networks. We compared null diet composition, network properties (e.g., connectance and nestedness) and deviations of simulations from metabarcoding-based spider dietary data to ascertain how different prey availability data alter ecological interpretation.
3. Different sampling methods produced different null networks and inferred distinct prey selectivity. Null models based on prey abundance and combined frequency-of-occurrence data generated null diet compositions, which more closely resembled the diet composition determined by metabarcoding. Null models based on prey abundance, activity density and proportionally combined data generated null network properties most like the networks constructed via dietary metabarcoding.
4. We show that survey method choice impacts all aspects of null network analyses, the precise effects varying between methods but ultimately altering ecological interpretation by increasing disparity in network properties or trophic niches between null and directly constructed networks. Merging datasets can generate more complete prey availability data but is not a panacea because it introduces different biases. The choice of method should reflect the research hypotheses and study system being investigated. Ultimately, survey methods should emulate the foraging mode of the focal predator as closely as possible, informed by the known ecology, natural history and behaviour of the predator.

Flood dynamics are important drivers of wetland biodiversity. With current climate and land-use changes affecting overall water cycling, many wetland ecosystems are at risk of degradation, affecting biodiversity support negatively. This emphasizes a need for understanding possible correlations between specific hydrological conditions and biodiversity support in wetlands, at least in terms of species composition. In this study, we used high resolution hydrological monitoring of water levels and insect sampling in a depressional wetland to investigate possible correlations between inundation patterns and insect abundance. Our results show that there is a high spatial and temporal heterogeneity in wetland inundation patterns and that this heterogeneity explains variation in insect abundance. This creates episodes of downstream wet and upstream dry conditions. In addition, the spatial variability was high between grid cells of 2 meter’s resolution. There were also indications that distance to stream affected insect community structure. The findings from this work show that that the local hydrological conditions can create heterogeneity in habitat conditions, which in turn lead to refuge habitats for species vulnerable to changes in inundation condition. This study also highlights the importance of acknowledging quantitative hydrological methods when assessing the relation to insect communities.