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Free-living soil nematodes span several trophic levels and play a key role in soil food webs. As such, the relative abundances and diversity of nematode feeding groups, along with nematode body size that is correlated with trophic transfer efficiency may provide useful information in understanding carbon and nitrogen cycling in soil systems. Yet, despite their role in soil carbon dynamics, there is a lack of knowledge regarding nematode trophic diversity in high carbon storage systems such as boreal peatlands. Here we assessed nematode communities using feeding groups (bacterivores, fungivores, herbivores, omnivores, and predators) based on mouthpart morphology, and their body sizes (length and mass) in two contrasting boreal peatlands in Northern Ontario, Canada that differ in vegetation (Sphagnum vs Carex), hydrology, nutrient availability, and microbial decomposition. We found that nematode trophic diversity was higher in the Sphagnum -dominated fen, and that the dominant nematode group corresponded to the dominant microbial group at each site. Predatory nematodes were significantly more abundant and larger in the Sphagnum -dominated fen, consistent with greater food web complexity, but the average body size of nematodes (all feeding groups included) was not significantly different between the fens. Taken together, these observed trends in nematode feeding groups and body sizes, along with higher microbial biomass in the Sphagnum -dominated fen supports the idea that the two sites may differ ecologically, and generally follow differences in microbial communities. Our study provides important baseline information for understanding peatland soil food web dynamics and their implications for carbon and nutrient dynamics. • Nematode feeding group and body size were explored at contrasting peatlands. • Predators were more abundant and larger in a Sphagnum -dominated fen. • Nematode functional diversity parallels overall soil food web trophic structure. • Nematode communities from contrasting peatlands imply different ecological function. [ABSTRACT FROM AUTHOR]

Climate warming may alter predator–prey interactions and predator feeding behaviour due to increased metabolic demands. How predators meet these increased demands may depend on trade‐offs in prey energy content and body size, handling time and other functional constraints.We tested hypotheses associated with these trade‐offs with the predatory mite Stratiolaelaps scimitus, and three prey that differed in body size, energy content, and defenses (Folsomia candida, Oppia nitens, and Carpoglyphus lactis). We estimated metabolic rate, predation in choice and no choice feeding trials, movement rate, and lipid and protein content for all four species at 16°C and 24°C. We used these data to estimate the predator's energy demands and compared these to estimated energy intake in the choice feeding trials.Predators had greater metabolic demands at 24°C than at 16°C, but temperature did not affect predator or prey movement rates. Warming decreased lipid content, but not protein content, of all three prey species, leading to lower energy content for C. lactis and O. nitens, but not F. candida. In both feeding trials at 24°C, predators increased their feeding on the smaller, energy‐poor C. lactis, but not the larger, energy‐rich F. candida, resulting in lower estimated energy intake. S. scimitus did not feed on O. nitens at either temperature.Predators increasingly fed on small‐bodied prey under warming and not the large‐bodied prey despite the potential for greater energetic gains from larger prey. We posit that predators minimized energy lost during feeding through lower handling costs associated with C. lactis, rather than maximize energy gain. We conclude that selection of prey based on body size changes with temperature as a trade‐off for predators to balance increased metabolic demands. As predators provide top‐down control and regulate energy flow through the consumption of their prey, changes to predator feeding behaviour with climate warming may affect food web dynamics and ecosystem‐level processes. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

• Both Mesostigmata adult and juvenile abundance increased under warming. • Mesostigmata assemblages shifted and average individual body mass increased. • Assemblages shifted due to the increased abundances of parthenogenetic species. • These results align with previous studies on Oribatida assemblages under warming. Increasing global mean surface temperatures from climate change will coincide with longer and more frequent short-term, extreme warming events. Because of this, habitats like boreal forests are predicted to have new temperature regimes. Boreal forest soils contain a diverse array of microarthropods and nematodes, which include the main soil predators, mesostigmatic mites (Acari: Parasitiformes: Mesostigmata). Although extensive research exists on how climate warming affects oribatid mite and collembolan communities, fewer studies have examined how warming effects Mesostigmata communities. We tested the effect of short-term (three months), intensive warming (+8 °C) on Mesostigmata communities from the boreal forest using experimental mesocosms containing forest-floor material. We collected moss mats and underlying forest floor organic material from a boreal forest and incubated them within individual mesocosms at 12 °C and 20 °C for three months, where 12 °C represented the long-term average growing season temperature and 20 °C corresponds to the potential extreme surface temperature from climate warming for the region. We enumerated all extracted microarthropods and nematodes, and identified all Mesostigmata adults to the species-level. In total, we counted 24,080 nematode individuals, and 19,582 total microarthropod individuals, of which 3349 individuals (1899 adults and 1450 juveniles) were mesostigmatic mites, consisting of 14 species. Mesostigmatic juvenile and adult abundances, along with adult community-level body mass were higher under warming, which lead to a shift in community composition. Changes to Mesostigmata communities were driven by the greater abundances of parthenogenetic species, primarily Veigaia mitis (Berlese), under warming—a response that has been shown in oribatid mite communities, but not mesostigmatic communities, before. Overall, we found that warming shifted mesostigmatic mite communities in the boreal forest, which has wide ranging implications for the soil food web. [ABSTRACT FROM AUTHOR]

Boreal peatlands play an important role in terrestrial carbon storage. Soil fauna and their trophic interactions play a key role in regulating microbial communities and the flux of carbon (C) and nitrogen (N) belowground, thus controlling the storage/release of C and N in soil systems. At northern latitudes, soil temperature and moisture conditions under climate change are predicted to become more extreme and more variable, and these factors will play an important role in regulating decomposition and ecosystem functioning, like C and N dynamics, in boreal peatlands. The objective of this research is to quantify and model the effects of experimentally imposed temperature and moisture conditions that simulate potential future climate extremes on peatland soil fauna food webs and soil C and N fluxes. Results suggest that increases in temperature and soil saturation will alter total faunal biomasses with warming increasing and soil saturation decreasing biomasses. Shifts in fauna biomass drove changes in C flux, C mineralization, and N mineralization. However, under warming, increased population turnover rate alongside decreased feeding efficiencies increased the proportion of total C flux that is lost as respiration (i.e., C mineralization). Future research is needed to better resolve the opposing changes in potential future boreal peatland C and N dynamics threatened by potential future warming and climate-mediated changes in peatland hydrology. [ABSTRACT FROM AUTHOR]

Cannibalism imperfectly recycles resources back to the same species and so decreases trophic transfer efficiency in food webs. As such, viable populations have some limit on how much of their diet can come from cannibalism. We applied a Lotka-Volterra model to derive a theoretical maximum for the proportion of the diet coming from cannibalism. This proportion is set by the food conversion efficiency for both cannibalism and alternative prey. We apply the result to sixteen published soil food web models and find that cannibalism cannot exceed 20% of the diet of most organisms, which includes eating conspecifics that were already dead. However, predators can show a strong (>80%) preference for cannibalism because encountering conspecifics is rare. Cannibalism increased carbon and nitrogen mineralization in fifteen soil food webs and had non-monotonic effects in the remaining one. Our estimates map a physiological parameter (conversion efficiency) to an ecological one (cannibalism) to help to improve model fit and to help soil ecologists identify taxa where cannibalism may be most important. - Physiological inefficiency lets us calculate a theoretical limit for cannibalism. - Maximum cannibalism rate is about 20% of the diet for most soil organisms. - Cannibalism decreases the efficiency of carbon and nitrogen flow in soil food webs. - Ignoring cannibalism biases carbon loss estimates by up to 10% and nitrogen by up to 30%. [ABSTRACT FROM AUTHOR]

• Oribatid mite community composition is driven to an extent by interactions between temperature and moisture. • Communities in the Sphagnum- and Carex -dominated fens showed contrasting responses to warming. • Warming-induced soil moisture reduction facilitated the establishment of terrestrial species and impacted semi-aquatic species. Climate warming is expected to disproportionately affect high latitude and alpine systems such as boreal peatlands. Previous studies observing changes in both plant and microbial communities suggest boreal peatlands may shift from carbon sinks to sources under warming. But few studies have investigated oribatid mites (Acari: Oribatida) under climate change scenarios in peatland systems, despite oribatid mites being well represented in terms of diversity in boreal peatlands. We performed a large-scale experimental field manipulation of warming in two contrasting peatland sites in Northern Ontario, Canada, and sampled oribatid mites over four years following three years of passive warming and one full growing season of active warming. We found that warming had contrasting effects on the oribatid mite community at both peatland sites, and depended on the peatland type. Specifically, we observed an increase in species richness at the drier, Sphagnum -dominated site and a reduction in species richness at the wetter, Carex -dominated site. That said, we suggest that these outcomes arise from the same mechanism, namely warming-induced reductions in soil moisture that impacted semi-aquatic species and facilitated the establishment of new species, likely from surrounding forests. We also observed increases in small-bodied species suggesting direct metabolic effects from warming. As such, we show that peatland oribatid mite community composition is driven to an extent by interactions between temperature and moisture but dependant on peatland type. As oribatid mite communities are responsive to multiple environmental changes, and play important mid-trophic level roles in soil food webs, changes in oribatid mite community composition may have consequences for carbon flux in peatland systems. [ABSTRACT FROM AUTHOR]

• Major soil microarthropod taxa responded differently to simulated climate change. • Oribatida and Collembola diversity increased under warming in a high rainfall year. • Mesostigmata diversity showed no response to either warming or elevated CO 2. • Annual rainfall may dictate soil faunal responses to simulated climate change. Soils systems provide essential ecosystem functions and services performed by a hyperdiverse array of fauna, but how soil communities respond to climate change remains an understudied topic. Although previous long-term studies have found variable effects of climate change manipulations on soil communities, precipitation often yields strong responses from fauna. In this study we used a field-based experiment to test how soil communities respond to active warming (+4 °C) and elevated atmospheric CO 2 concentrations (800 ppm) in the boreal forest over two consecutive years in a full factorial experimental design. We sampled and identified soil fauna across multiple taxonomic groups to determine how species abundance, richness, diversity, evenness, and community composition were affected by these simulated global climate change factors. Fauna were minimally affected by experimental treatments in the first year of sampling. However, in the second year of treatment, richness and diversity increased and soil community composition shifted as oribatid mites responded to both warming and elevated CO 2 and springtails responded to warming treatments. We propose that the enhanced response of soil communities in the second year of experimental treatment was due to greater than normal precipitation, suggesting that annual variability in weather conditions can influence soil fauna response to climate change. [ABSTRACT FROM AUTHOR]

Springtails (Collembola) inhabit soils from the Arctic to the Antarctic and comprise an estimated ~32% of all terrestrial arthropods on Earth. Here, we present a global, spatially-explicit database on springtail communities that includes 249,912 occurrences from 44,999 samples and 2,990 sites. These data are mainly raw sample-level records at the species level collected predominantly from private archives of the authors that were quality-controlled and taxonomically-standardised. Despite covering all continents, most of the sample-level data come from the European continent (82.5% of all samples) and represent four habitats: woodlands (57.4%), grasslands (14.0%), agrosystems (13.7%) and scrublands (9.0%). We included sampling by soil layers, and across seasons and years, representing temporal and spatial within-site variation in springtail communities. We also provided data use and sharing guidelines and R code to facilitate the use of the database by other researchers. This data paper describes a static version of the database at the publication date, but the database will be further expanded to include underrepresented regions and linked with trait data., (© 2024. The Author(s).)

Climate change can alter predator-prey interactions when predators and prey have different thermal preferences as temperature change can exacerbate thermal mismatches (also called thermal asymmetry) with population-level consequences. We tested this using micro-arthropod predators (Stratiolaelaps scimitus) and prey (Folsomia candida) that differ in their temperature optima to examine predator-prey interactions across two temperature ranges, a cool (12 and 20 °C) and warm (20 and 26 °C) range. We predict that the lower thermal preference and optimum in F. candida will alter top-down control (i.e., interaction strength) by predators with interaction strength being strongest at intermediate temperatures, coinciding with F. candida thermal optimum. Predators and prey were placed in mesocosms, whereafter we measured population (predator and prey abundance), trait-based (average predator and prey body mass, and prey body length distribution), and predator-prey indices (predator-prey mass ratio (PPMR), Dynamic Index, and Log Response Ratio) to determine how temperature affected their interactions. Prey populations were the highest at intermediate temperatures (average temperature exposure: 16-23 °C) but declined at warmer temperatures (average temperature exposure: 24.5-26 °C). Predators consistently lowered prey abundances and average prey mass increased when predators were added. Top-down control was the greatest at intermediate temperatures (indicated by Log Response Ratio) when temperatures were near or below the thermal optimum for both species. Temperature-related prey declines negated top-down control under the warmest conditions suggesting that mismatches in thermal performance between predators and their prey will alter the strength and dominance of top-down or bottom-up forces of predator-prey interactions in a warmer world., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Summaries of taxonomic knowledge are provided for all acarine groups in Canada, accompanied by references to relevant publications, changes in classification at the family level since 1979, and notes on biology relevant to estimating their diversity. Nearly 3000 described species from 269 families are recorded in the country, representing a 56% increase from the 1917 species reported by Lindquist et al. (1979). An additional 42 families are known from Canada only from material identified to family- or genus-level. Of the total 311 families known in Canada, 69 are newly recorded since 1979, excluding apparent new records due solely to classification changes. This substantial progress is most evident in Oribatida and Hydrachnidia, for which many regional checklists and family-level revisions have been published. Except for recent taxonomic leaps in a few other groups, particularly of symbiotic mites (Astigmata: feather mites; Mesostigmata: Rhinonyssidae), knowledge remains limited for most other taxa, for which most species records are unpublished and may require verification. Taxonomic revisions are greatly needed for a large majority of families in Canada. Based in part on species recorded in adjacent areas of the USA and on hosts known to be present here, we conservatively estimate that nearly 10,000 species of mites occur in Canada, but the actual number could be 15,000 or more. This means that at least 70% of Canada's mite fauna is yet unrecorded. Much work also remains to match existing molecular data with species names, as less than 10% of the ~7500 Barcode Index Numbers for Canadian mites in the Barcode of Life Database are associated with named species. Understudied hosts and terrestrial and aquatic habitats require investigation across Canada to uncover new species and to clarify geographic and ecological distributions of known species.

Considerable progress has been made in ecological and evolutionary genetics with studies demonstrating how genes underlying plant and microbial traits can influence adaptation and even 'extend' to influence community structure and ecosystem level processes. Progress in this area is limited to model systems with deep genetic and genomic resources that often have negligible ecological impact or interest. Thus, important linkages between genetic adaptations and their consequences at organismal and ecological scales are often lacking. Here we introduce the Sphagnome Project, which incorporates genomics into a long-running history of Sphagnum research that has documented unparalleled contributions to peatland ecology, carbon sequestration, biogeochemistry, microbiome research, niche construction, and ecosystem engineering. The Sphagnome Project encompasses a genus-level sequencing effort that represents a new type of model system driven not only by genetic tractability, but by ecologically relevant questions and hypotheses., (© 2017 UT-Battelle New Phytologist © 2017 New Phytologist Trust.)

Habitat transformation is one of the leading causes of changes in biodiversity and the breakdown of ecosystem function and services. The impacts of habitat transformation on biodiversity are complex and can be difficult to test and demonstrate. Network approaches to biodiversity science have provided a powerful set of tools and models that are beginning to present new insight into the structural and functional effects of habitat transformation on complex ecological systems. We propose a framework for studying the ways in which habitat loss and fragmentation jointly affect biodiversity by altering both habitat and ecological interaction networks. That is, the explicit study of "networks of networks" is required to understand the impacts of habitat change on biodiversity. We conduct a broad review of network methods and results, with the aim of revealing the common approaches used by landscape ecology and community ecology. We find that while a lot is known about the consequences of habitat transformation for habitat network topology and for the structure and function of simple antagonistic and mutualistic interaction networks, few studies have evaluated the consequences for large interaction networks with complex and spatially explicit architectures. Moreover, almost no studies have been focused on the continuous feedback between the spatial structure and dynamics of the habitat network and the structure and dynamics of the interaction networks inhabiting the habitat network. We conclude that theory and experiments that tackle the ecology of networks of networks are needed to provide a deeper understanding of biodiversity change in fragmented landscapes.