Group-specific Responses Research Articles

Hydrological dynamics, wetland morphology and vegetation structure determine riparian arthropod communities in constructed wetlands

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.

Trophic group specific responses of alpine nematode communities to 18 years of N addition and codominant plant removal

Trophic group specific responses of alpine nematode communities to 18 years of N addition and codominant plant removal

Co-Limitation of Phytoplankton by N and P in a Shallow Coastal Lagoon (Ria Formosa): Implications for Eutrophication Evaluation

AbstractThe Ria Formosa coastal lagoon is a highly productive shallow ecosystem in southern Portugal, subjected to nutrient inputs from anthropogenic and natural sources. Nutrients are major abiotic drivers of phytoplankton in this system, but their effects on phytoplankton assemblages and the occurrence of nutrient limitation are still poorly understood. The main goal of this study was, thus, to evaluate the occurrence, type, and effects of nutrient limitation on phytoplankton community and specific functional groups in the Ria Formosa coastal lagoon. We conducted nutrient enrichment experiments with factorial additions of nitrogen (N) and phosphorus (P) using natural phytoplankton assemblages from distinct locations in the Ria Formosa, throughout a yearly cycle. Phytoplankton composition and abundance were evaluated using inverted and epifluorescence microscopies, and spectrophotometric methods were used for biomass. Limitation was defined as higher phytoplankton growth following enrichment with a particular nutrient in relation to the non-enriched control. The most common type of phytoplankton limitation was simultaneous co-limitation by N and P; diatoms, as r-strategists, were the most frequently limited group. Single N and P limitation, and serial P limitation were also observed, as well as negative responses to nutrient enrichment. Group-specific responses to nutrient enrichment were not reflected in the relative abundance of phytoplankton groups within the whole assemblage, due to the numerical dominance of pico-sized groups (cyanobacteria and eukaryotic picophytoplankton). Ambient nutrient ratios and concentrations did not predict phytoplankton nutrient limitation, given the different nutrient utilisation traits among phytoplankton functional groups. Therefore, nutrient ratios should not be used as indicators of nutrient limitation in eutrophication assessment.

Emiliania huxleyi-Bacteria Interactions under Increasing CO2 Concentrations.

The interactions established between marine microbes, namely phytoplankton-bacteria, are key to the balance of organic matter export to depth and recycling in the surface ocean. Still, their role in the response of phytoplankton to rising CO2 concentrations is poorly understood. Here, we show that the response of the cosmopolitan Emiliania huxleyi (E. huxleyi) to increasing CO2 is affected by the coexistence with bacteria. Specifically, decreased growth rate of E. huxleyi at enhanced CO2 concentrations was amplified in the bloom phase (potentially also related to nutrient concentrations) and with the coexistence with Idiomarina abyssalis (I. abyssalis) and Brachybacterium sp. In addition, enhanced CO2 concentrations also affected E. huxleyi's cellular content estimates, increasing organic and decreasing inorganic carbon, in the presence of I. abyssalis, but not Brachybacterium sp. At the same time, the bacterial isolates only survived in coexistence with E. huxleyi, but exclusively I. abyssalis at present CO2 concentrations. Bacterial species or group-specific responses to the projected CO2 rise, together with the concomitant effect on E. huxleyi, might impact the balance between the microbial loop and the export of organic matter, with consequences for atmospheric carbon dioxide.

Taxon- and functional group-specific responses of ground beetles and spiders to landscape complexity and management intensity in apple orchards of the North China Plain

Agricultural intensification has caused severe declines in ground-dwelling arthropods and associated ecosystem services. The conservation and re-establishment of semi-natural habitats in agricultural landscapes represent widely accepted measures to counter these declines. The effectiveness of these measures nonetheless varies between target taxa and their functional traits, while also being affected by local management. Here, we studied how species richness and abundance of different functional groups of carabid beetles and spiders in apple orchards were affected by landscape complexity (% semi-natural habitat) and local management intensity (mowing and soil total nitrogen (STN) content). Both abundance and species richness of non-carnivorous carabids and carabids overall were negatively affected by STN, while the abundance of carnivorous carabids and carabids overall was affected by interactive effects of mowing and landscape complexity, showing a positive response to mowing where semi-natural habitats are scarce, but negative responses in landscapes with a higher proportion of semi-natural habitats. The abundance of ground-hunting spiders and spiders overall was generally positively related to % semi-natural habitats, while the abundance of web-building spiders and the species richness of ground-hunting spiders showed a positive correlation with STN at landscapes with a low or medium abundance of semi-natural habitats, but a negative correlation where semi-natural habitats were more abundant. Non-carnivorous carabid diversity benefitted from low nitrogen application, while carnivorous carabid abundance benefitted from mowing intensity especially in simple and structurally homogenous agricultural landscapes. Both web-building and ground-hunting spiders positively responded to low nitrogen applications and intermediate landscape complexity. Overall, a low local management intensity promoted carabid beetles, while spiders were favored by increasing landscape complexity. We conclude that taxon- and functional group-specific, multi-scale conservation strategies are therefore required to conserve invertebrate predators in apple orchards.

Trophic differences regulate grassland food webs: herbivores track food quality and predators select for habitat volume.

The impacts of altered biogeochemical cycles on ecological systems are likely to vary with trophic level. Predicting how these changes will affect ecological food webs is further complicated by human activities, which are simultaneously altering the availability of macronutrients like nitrogen (N) and phosphorus (P), and micronutrients such as sodium (Na). Here we contrast three hypotheses that predict how increasing nutrient availability will shape grassland food webs. We conducted a distributed factorial fertilization experiment (N and P crossed with NaCl) across four North American grasslands, quantifying the responses of aboveground plant biomass and volume, plant tissue and soil elemental concentrations, as well as the abundance of five arthropod functional groups. Fertilization with N and P increased plant biomass and foliar N and P concentrations in grasses but not forbs. Fertilization with Na had no effect on plant biomass but increased foliar Na concentrations. Consistent with the nutrient limitation hypothesis, we found strong evidence of nutrient limitation for insect herbivores across the four sites with sucking (phloem and xylem feeding) herbivores increasing in abundance with NP fertilization and chewing herbivores increasing in response to both Na and NP fertilization, and a trend for increased response of arthropods to lower plant nutrient availability. We found no evidence for an interaction of NaCl and NP on arthropod abundance as predicted by the serial colimitation hypothesis. Finally, consistent with the ecosystem size hypothesis, predator and parasitoid abundances increased with plant volume, but not fertilization. Our results suggest these functional group-specific responses to changes in plant nutrients and structure are key to predicting the future of grassland food webs in an era with increasing use of N and P fertilizers, and increasing terrestrial inputs of Na from road salt, saline irrigation water, and aerosols due to rising sea levels.

Viral lysis modifies seasonal phytoplankton dynamics and carbon flow in the Southern Ocean

Phytoplankton form the base of marine food webs and are a primary means for carbon export in the Southern Ocean, a key area for global pCO2 drawdown. Viral lysis and grazing have very different effects on microbial community dynamics and carbon export, yet, very little is known about the relative magnitude and ecological impact of viral lysis on natural phytoplankton communities, especially in Antarctic waters. Here, we report on the temporal dynamics and relative importance of viral lysis rates, in comparison to grazing, for Antarctic nano- and pico-sized phytoplankton of varied taxonomy and size over a full productive season. Our results show that viral lysis was a major loss factor throughout the season, responsible for roughly half (58%) of seasonal phytoplankton carbon losses. Viral lysis appeared critically important for explaining temporal dynamics and for obtaining a complete seasonal mass balance of Antarctic phytoplankton. Group-specific responses indicated a negative correlation between grazing and viral losses in Phaeocystis and picoeukaryotes, while for other phytoplankton groups losses were more evenly spread throughout the season. Cryptophyte mortality was dominated by viral lysis, whereas small diatoms were mostly grazed. Larger diatoms dominated algal carbon flow and a single ‘lysis event’ directed >100% of daily carbon production away from higher trophic levels. This study highlights the need to consider viral lysis of key Antarctic phytoplankton for a better understanding of microbial community interactions and more accurate predictions of organic matter flux in this climate-sensitive region.

Restoration strategies in boreal forests: Differing field and ground layer response to ecological restoration by burning and gap cutting

The boreal biome is one of the largest in the world and its forests have been widely exploited for centuries. Consequently, large areas have suffered ecological simplification and loss of biodiversity. Under the current circumstances passive conservation measures are no longer enough and active restoration techniques need to be developed and assessed to preserve and recover the loss of biodiversity. We evaluated short- and long-term effects of two restoration methods aimed at mimicking natural disturbances on species richness, Shannon Diversity and community composition of vascular plants in the field layer and bryophytes in the ground layer. The experiment consisted of 18 forest stands in northern Sweden; each assigned to a different treatment: prescribed burning, gap cutting and untreated stands left as controls. A before-after control-impact (BACI) study design was applied and data was collected on three occasions: once prior to restoration (2010) and twice post restoration; one year (2012) and eight years after (2019). We analysed the differences in species richness and Shannon Diversity with linear mixed effect models and community composition changes with multivariate methods. Fire treatment caused an initial decline in diversity for both field and ground layer, but in the long-term, field layer surpassed the species richness and Shannon Diversity values found prior to restoration. Ground layer bryophytes species richness and Shannon Diversity remained lower than pre-treatment. Prescribed burning should, therefore, be used with caution in core areas for bryophyte diversity. Community composition in burned stands differed significantly between each time point as well as when compared to other treatments, for both layers. By contrast, we found no significant differences in diversity measures or community composition after gap cutting. The absence of effects from gap cutting suggests that minor changes in canopy cover does not affect the vegetation structure of forest stands. The organism group-specific responses, and temporal variability to restoration, highlight the importance of including more than one organism group, different restoration methodologies, and long-term studies in order to properly assess restoration outcomes at landscape level.

Group-Specific Responses to Retrospective Economic Performance: A Multilevel Analysis of Parliamentary Elections

What is the relationship between electoral and economic performance? Previous literature posits that poor economic performance hurts the incumbent at the ballot box because overall economic performance serves as a competence signal, which voters can readily access at low costs. Building on an emerging economic voting literature exploring heterogeneity in the electorate, this article argues that social groups are affected differently by various dimensions of economic performance and that their sociotropic sanctioning of incumbents is contingent on the retrospective performance of these dimensions. It theorizes how four social groups—low-skilled workers, pensioners, public sector employees, and high-income individuals—are differently affected by each of four economic dimensions: unemployment, inflation, stock market performance, and public spending; as a result, they penalize the incumbent to varying extents. Results from a multilevel logistic regression analysis from four modules of the Comparative Study of Electoral Systems containing around seventy electoral contexts are consistent with the argument.

Combined experimental drought and nitrogen loading: the role of species-dependent leaf level control of carbon and water exchange in a temperate grassland.

Nitrogen (N) loading and extreme drought strongly alter biomass production, species composition and carbon and water fluxes of temperate grasslands. Such changes at the community level are often attributed to species- and functional group-specific responses in phenology and/or physiology. In a multifactorial field experiment, we studied the responses of three abundant grassland species (forb Centaurea jacea, grasses Arrhenatherum elatius and Dactylis glomerata) to N loading and extreme drought, focusing on responses of carbon and water relations at the leaf level. We analysed (1) changes in bulk leaf N (uptake efficiency of additional N), (2) adaptation of plant water status (leaf water potential) and (3) impact on leaf carbon and water fluxes. We observed more efficient N utilization in the two grasses compared to C. jacea. Naturally occurring summer drought significantly impacted the plant water status of all species, while extreme drought treatment only further affected water status during and after summer drought. C. jacea was able to maintain much lower leaf water potentials compared to the grasses during drought. Despite these clear species-specific responses to N loading and drought, the species were able to maintain homeostasis of leaf carbon and water fluxes. Thus, strong declines in the (community) carbon sequestration observed at this site during the (natural) summer drought were not related to leaf physiological responses in assimilation, but were driven by phenological adaptions of the species community: the drought-sensitive grasses, even though exhibiting higher N uptake efficiency, responded with a shortened life cycle to severe summer drought.

Considering change with archaeological data: Reevaluating local variation in the role of the ~4.2k BP event in Northwest China

Over the past two decades, environmental studies in research on prehistoric China have been gaining popularity and importance. For Northwest China in particular, climate change, especially the so-called ~4.2k BP event has been seen as the main reason for an alleged collapse of Late Neolithic societies and a transition to pastoral-heavy economies and mobile lifeways. Yet, these explanatory models tend to rely on limited archaeological and environmental data and non-contemporaneous historical data, resulting in simplistic causal relationships between environmental changes and social response. This paper re-evaluates the Incipient Bronze Age in China’s Northwestern region, discussing evidence for climate change and its exact dates, as well as textual and archaeological evidence. We argue that the old narratives perpetuating the image of a dichotomy between Steppe and Sown are inaccurate, while large-scale models of region-wide subsistence change in response to climate cooling tend to disregard local developments and group-specific responses as well as chronological issues. Focusing on the Xindian and Siwa archaeological phenomena, this paper provides a view into sub-regional responses to this climate event, warning against simplistic broad-brush reconstructions and calling for both a return to archaeological fundamentals and large-scale intensive fieldwork and interdisciplinary studies involving archaeologists, paleobotanists, zooarchaeologists, isotope specialists, and climate scientists.

Heterogeneity-diversity relationships differ between and within trophic levels in temperate forests.

The habitat heterogeneity hypothesis predicts that biodiversity increases with increasing habitat heterogeneity due to greater niche dimensionality. However, recent studies have reported that richness can decrease with high heterogeneity due to stochastic extinctions, creating trade-offs between area and heterogeneity. This suggests that greater complexity in heterogeneity-diversity relationships (HDRs) may exist, with potential for group-specific responses to different facets of heterogeneity that may only be partitioned out by a simultaneous test of HDRs of several species groups and several facets of heterogeneity. Here, we systematically decompose habitat heterogeneity into six major facets on ~500 temperate forest plots across Germany and quantify biodiversity of 12 different species groups, including bats, birds, arthropods, fungi, lichens and plants, representing 2,600 species. Heterogeneity in horizontal and vertical forest structure underpinned most HDRs, followed by plant diversity, deadwood and topographic heterogeneity, but the relative importance varied even within the same trophic level. Among substantial HDRs, 53% increased monotonically, consistent with the classical habitat heterogeneity hypothesis but 21% were hump-shaped, 25% had a monotonically decreasing slope and 1% showed no clear pattern. Overall, we found no evidence of a single generalizable mechanism determining HDR patterns.

Climate change effects on earthworms - a review.

Climate change can have a plethora of effects on organisms above and below the ground in terrestrial ecosystems. Given the tremendous biodiversity in the soil and the many ecosystem functions governed by soil organisms, the drivers of soil biodiversity have received increasing attention. Various climatic factors like temperature, precipitation, soil moisture, as well as extreme climate events like drought and flood have been shown to alter the composition and functioning of communities in the soil. Earthworms are important ecosystem engineers in the soils of temperate and tropical climates and play crucial roles for many ecosystem services, including decomposition, nutrient cycling, and crop yield. Here, we review the published literature on climate change effects on earthworm communities and activity. In general, we find highly species- and ecological group-specific responses to climate change, which are likely to result in altered earthworm community composition in future ecosystems. Earthworm activity, abundance, and biomass tend to increase with increasing temperature at sufficiently high soil water content, while climate extremes like drought and flooding have deleterious effects. Changing climate conditions may facilitate the invasion of earthworms at higher latitudes and altitudes, while dryer and warmer conditions may limit earthworm performance in other regions of the world. The present summary of available information provides a first baseline for predictions of future earthworm distribution. It also reveals the shortage of studies on interacting effects of multiple global change effects on earthworms, such as potential context-dependent effects of climate change at different soil pollution levels and across ecosystem types.

Marital instability in the context of dramatic societal change: the case of Kyrgyzstan

ABSTRACTHow do marriages fare during times of dramatic social, political and economic transition? Transitional societies offer a unique context for studying marital instability as they are often buffeted by countervailing forces of modernisation and re-traditionalisation, in addition to socio-economic and political changes. Using detailed and rich data from Kyrgyzstan, the study investigates trends over time in marital instability in response to societal upheavals and gradual secular transformations; ethnic group-specific responses in marital instability; and the role of changing gender regimes in marital instability. The findings reveal an increase in the rate of marital dissolution over time. However, ethnic group-specific differentials remained significant, mirroring the historically shaped relative positioning of the groups in the process of demographic change. The results also highlight gender differentials in the influence of education and employment on marital instability. The findings are discussed within the broader framework of demographic and social changes in transitional Central Asia.

Adult and offspring size in the ocean over 17 orders of magnitude follows two life history strategies.

Explaining variability in offspring vs. adult size among groups is a necessary step to determine the evolutionary and environmental constraints shaping variability in life history strategies. This is of particular interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical and biological forcing factors in space and time. We compiled adult and offspring size for 407 pelagic marine species covering more than 17 orders of magnitude in body mass including Cephalopoda, Cnidaria, Crustaceans, Ctenophora, Elasmobranchii, Mammalia, Sagittoidea, and Teleost. We find marine life following one of two distinct strategies, with offspring size being either proportional to adult size (e.g., Crustaceans, Elasmobranchii, and Mammalia) or invariant with adult size (e.g., Cephalopoda, Cnidaria, Sagittoidea, Teleosts, and possibly Ctenophora). We discuss where these two strategies occur and how these patterns (along with the relative size of the offspring) may be shaped by physical and biological constraints in the organism's environment. This adaptive environment along with the evolutionary history of the different groups shape observed life history strategies and possible group-specific responses to changing environmental conditions (e.g., production and distribution).

Susceptibility of pollinators to ongoing landscape changes depends on landscape history

Aim Pollinators play an important role in ecosystem functioning, affecting also crop production. Their decline may hence lead to serious ecological and economic impacts, making it essential to understand the processes that drive pollinator shifts in space and time. Land-use changes are thought to be one of the most important drivers of pollinators’ loss, and there is increasing investment on pollinator-friendly landscape management. However, it is still unclear whether landscape history of a given region determines how pollinator communities respond to further landscape modification. Location The Netherlands. Methods Using geographically explicit historical landscape and pollinator data from the Netherlands, we evaluated how species richness changes of three important pollinator groups (bees, hoverflies and butterflies) are affected by landscape changes related to habitat composition, fragmentation and species spillover potential and whether such effects depend on the historical characteristics of the landscape. Results The effect of landscape changes varied between different pollinator groups. While bumblebee richness benefited from increases in edges between managed and natural systems, other bees benefited from increases in landscape heterogeneity and hoverfly richness was fairly resistant to land-use changes. We found that for the majority of the pollinators past landscape characteristics conditioned, the more recent pollinator richness changes. Landscapes that historically had more suitable habitat were more susceptible to display hoverfly declines (caused by drivers not considered in this study). Landscapes that historically had greater spillover potential were more likely to suffer butterfly richness declines and the bumblebee assemblages were more susceptible to the effects of fragmentation. Main conclusions The diversity of responses of the pollinator groups suggest that multispecies approaches that take group-specific responses to land-use change into account are highly valuable. These findings emphasize the limited value of a one-size-fits-all biodiversity conservation measure and highlight the importance of considering landscape history when planning biodiversity conservation actions.

Developing Strategies to Treat Asthma Exacerbations Caused by Rhinovirus

Developing Strategies to Treat Asthma Exacerbations Caused by Rhinovirus

Muscle-Specific Overexpression of PGC-1α Does Not Augment Metabolic Improvements in Response to Exercise and Caloric Restriction.

This study used mice with muscle-specific overexpression of PGC-1α, a transcriptional coactivator that promotes mitochondrial biogenesis, to determine whether increased oxidative potential facilitates metabolic improvements in response to lifestyle modification. MCK-PGC1α mice and nontransgenic (NT) littermates were fed a high-fat diet (HFD) for 10 weeks, followed by stepwise exposures to voluntary wheel running (HFD+Ex) and then 25% caloric restriction with exercise (Ex/CR), each for an additional 10 weeks with continued HFD. Running and CR improved weight and glucose control similarly in MCK-PGC1α and NT mice. Sedentary MCK-PGC1α mice were more susceptible to diet-induced glucose intolerance, and insulin action measured in isolated skeletal muscles remained lower in the transgenic compared with the NT group, even after Ex/CR. Comprehensive profiling of >200 metabolites and lipid intermediates revealed dramatic group-specific responses to the intervention but did not produce a lead candidate that tracked with changes in glucose tolerance irrespective of genotype. Instead, principal components analysis identified a chemically diverse metabolite cluster that correlated with multiple measures of insulin responsiveness. These findings challenge the notion that increased oxidative capacity defends whole-body energy homeostasis and suggest that the interplay between mitochondrial performance, lipotoxicity, and insulin action is more complex than previously proposed.

Composition, diversity and distribution of microbenthos across the intertidal zones of Ryazhkov Island (the White Sea)

The composition and distribution of the main unicellular eukaryotic groups (diatom algae, ciliates, dinoflagellates (DF), other phototrophic (PF) and heterotrophic flagellates (HF)) were investigated in sandy sediments at five stations allocated across the tidal sheltered beach of the White Sea. Overall, 75 diatoms, 98 ciliates, 16 DF, 3 PF and 34 HF species were identified; some are new records for the White Sea. Common species for each group are illustrated. Diatoms and ciliates showed high alpha-diversity (species richness per sample), whereas flagellates were characterized by high beta-diversity (species turnover across the intertidal flat). Each group demonstrated its own spatial pattern that was best matched with its own subset of abiotic variables, reflecting group-specific responses to environmental gradients. Species richness increased from the upper intertidal zone seaward for ciliates but decreased for HF, whereas autotrophs showed a relatively uniform pattern with a slight peak at the mid-intertidal zone. Across the littoral zone, all groups showed distinct compositional changes; however, the position of the boundary between “upper” and “lower” intertidal communities varied among groups. Most of the species found at Ryazhkov Island are known from many other regions worldwide, indicating a wide geographic distribution of microbial eukaryotic species.

Party choice in hard times: Group-specific responses to economic downturns in Sweden

This article asks if, when, and why different groups of voters behave differently in the wake of economic downturns. We examine two Swedish elections (1994 and 2010) that were held just after two deep recessions (the financial crisis of 1991–1993 and the 2008–2009 Great Recession). We find that group differences were much larger in 2010 than they were in 1994. After the 1991–1993 recession, the government's electoral support declined across the board. In 2010, there were large differences between voters with low economic status (who were unlikely to support the government) and voters with high economic status (who were likely to do so). Our findings suggest that group differences in electoral behavior after an economic downturn depend on contextual differences across elections. We argue that future research should pay close attention to the magnitude of economic shocks, the development of asset prices (especially real estate), and changes in social policy.