Invertebrate functional traits and terrestrial nutrient cycling: Insights from a global meta-analysis

Diltiazem disrupts Ca2+-homeostasis and exerts immunotoxic effects on a marine bivalve mollusc, the blood clam (Tegillarca granosa)

The prevalence of pharmaceutical residues like diltiazem in environments raises concerns over their potential threat to non-target organisms. While the immune system poses as a potential target, little is known about the immunotoxicity of diltiazem to aquatic species such as bivalve molluscs. In this study, the binding affinity of diltiazem to the calcium channels of several aquatic species was evaluated by molecular docking. Taking blood clam as a representative, the impacts of diltiazem on Ca2+-homeostasis and immune parameters were also assessed. Our results illustrated diltiazem exhibit a high binding affinity to calcium channels of representative aquatic species. Moreover, Ca2+-homeostasis in the haemocytes of blood clam was significantly disrupted by 4-week exposure to diltiazem. Additionally, apart from exhibiting significantly lower survival rates upon pathogenic challenge, diltiazem-exposed blood clams also suffered markedly impaired immune-related hematic parameters and lower levels of immune factors. Furthermore, diltiazem exposure generally altered the expression of key Ca2+-homeostasis and immune-related genes. Collectively, our data suggest that diltiazem at environmentally relevant concentrations could severely undermine the immunity of blood clam by disrupting Ca2+-homeostasis. Given the high binding affinities of diltiazem to calcium channels of diverse aquatic species and the critical role of Ca2+-homeostasis, the far-reaching impacts of diltiazem pollution on non-target aquatic species warrant closer attention and monitoring.

Environmental yeasts differentially impact the development and oviposition behavior of the Asian tiger mosquito Aedes albopictus

BACKGROUND

While the Asian tiger mosquito (Aedes albopictus), a known vector of many arboviruses, establishes symbiotic associations with environmentally acquired yeasts, their impact on mosquito biology remains poorly investigated. To better understand these associations, we hypothesized that waterborne yeasts colonizing the larval gut differentially support mosquito development based on their capacity to produce riboflavin or recycle nitrogen waste into proteins by secreting uricase, as B vitamins and amino acids are crucial for mosquito development. To address this hypothesis, we used axenic and gnotobiotic insects to gauge the specific impact of different environmental yeasts on Ae. albopictus development and survival. We then evaluated whether the observed variations across yeast species could be linked to differential uricolytic activities and varying quantities of riboflavin and proteins in insecta. Finally, given that mosquito oviposition site selection favors conditions that enhance offspring performance, we tested whether yeasts that promote faster development mediate oviposition site selection by gravid females.

RESULTS

Differences in mosquito development times were observed based on the environmental yeast used. Yeasts like Rhodotorula mucilaginosa and Aureobasidium pullulans promoted rapid development and were associated with improved survival. Conversely, yeasts such as Torulaspora delbrueckii and Martiniozyma asiatica, which led to slower development, produced smaller adults. Notably, R. mucilaginosa, which promoted the fastest development, provided high riboflavin intakes and enhance nitrogenous waste recycling and protein synthesis through strong uricolytic-ureolytic activity. Behavioral experiments indicated that yeasts promoting rapid development "attract gravid females.

CONCLUSIONS

Our findings highlight that a set of environmental yeasts present in natural larval breeding sites can be associated with improved mosquito development and survival by enhancing nutritional intake, thereby attracting gravid females. Variations in mosquito development time are likely linked to the differential levels of riboflavin production and nitrogenous waste recycling capacities among yeast species. This study opens new perspectives on the trophic interactions between mosquitoes and their mycobiota, emphasizing the importance of nitrogen-containing molecules such as essential amino acids, proteins, or vitamins provided by the mycobiota. Video Abstract.

Radiocaesium and radiostrontium transfer to an insect herbivore and an insect detritivore through holometabolous development: A comparison between the cabbage butterfly (Pieris brassicae) and the black soldier fly (Hermetia illucens)

The presence of the long-lived radionuclides 137Cs and 90Sr in ecosystems is a major environmental concern because bioavailable forms of the radionuclides are readily transferred to living organisms. The present study investigated how holometabolous insect development influences the fate of radiocaesium and radiostrontium by examining the behaviour of tracers (134Cs and 84Sr) and stable elements during the larval feeding stage (21-23 days old), the pupal stage, and the adult stage. We aimed to evaluate the degree to which an herbivore or a detritivore food chain could serve as transfer pathways to higher trophic levels in terms of accumulation potential, and during which stage of development the accumulation potential is highest. We used the Cabbage butterfly (Pieris brassicae) and the Black soldier fly (Hermetia illucens) as model insects in the herbivore food chain and the detritivore food chain, respectively. Both food chains showed similar patterns of radiocaesium transfer to the larvae, with concentration ratios of 0.26 to 1.15. Radiocaesium levels then gradually decreased during the transition from larva to adult. We also found strontium in the larvae of both model insects. However, while the transfer to P. brassicae was low and the majority of retained strontium was removed prior to the pupal stage, we found that strontium biomagnified in H. illucens larvae and pupae, showing high accumulation potentials. Overall, our results suggest that radiocaesium transfer to terrestrial holometabolous insects is predominantly determined by radiocaesium levels in their diet, whereas radiostrontium transfer is influenced by the insects' dietary need for calcium and the concentration of calcium in the diet.

Replacing native grazers with livestock influences arthropods to have implications for ecosystem functions and disease

Grazing by large mammalian herbivores influences ecosystem structure and functions through its impacts on vegetation and soil, as well as by the influence on other animals such as arthropods. As livestock progressively replace native grazers around the world, it is pertinent to ask whether they have comparable influence over arthropods, or not. We use a replicated landscape-level, long-term grazer-exclusion experiment (14 years) to address how ground-dwelling arthropods respond to such a change in grazing regime where livestock replace native grazers in the cold deserts of the Trans-Himalayan ecosystem of northern India. We analyze spatial and temporal variation in the abundance of 25,604 arthropods sampled using pitfall traps across 2765 trap-days through the duration of the growing season spanning spring, summer, and autumn. These were from 88 operational taxonomic units covering six orders from 33 families (ants, wasps, bees, ticks and mites, spiders, grasshoppers, and beetles). We find that grazer assemblage-whether livestock or native herbivores-had a strong influence on both vegetation and arthropods. Partial redundancy analysis (RDA) showed that 53.6% of the spatial and temporal variation in arthropod communities could be explained by grazing and by grazer assemblage identity, alongside covariation with vegetation composition and soil variables. Structural equation models revealed that grazing and grazer assemblage identity have direct effects on arthropods, as well as indirect effects that are mediated through vegetation. Importantly, spiders (predators) were less abundant under livestock, whereas grasshoppers (leaf eaters) and ticks and mites (parasitic disease vectors) were more abundant, compared with native grazers. Reduction in spiders can fundamentally alter material and energy flow through the cascading effects of losing predators, and an abundance of grasshoppers may even contribute to vegetation degradation that is often associated with livestock. Parallelly, increases in ticks and mites lead to concerns over vector-borne disease that require planned interventions to align animal husbandry with One Health. Thus, losing native grazers to livestock expansion can have wide-ranging repercussions via arthropods. This may not only affect ecosystem structure and functions, but also offer challenges and opportunities to mitigate risks from vector-borne disease.

Descriptive Mappings of Global-Related Research Studies on Invertebrates in the Context of Agriculture

Invertebrates form a vital component of agricultural ecosystems, and they are chief actors in sustaining the functions of the ecosystem and soil health. Scholarly publications that concentrated on visualizing the research outputs and trends on invertebrates and agriculture are scarce. In this paper, we adopted a bibliometric model to extract trends/research studies on invertebrates and agriculture between 1991 and 2022, using scholarly studies retrieved from the Web of Science (WoS) databank. Therefore, the aim of the study is to assess and analyse publications and findings on research studies/trends on invertebrates and agriculture. A total of 1201 articles were recovered from the WoS databank with average citations per doc and coauthors per document ratio of 31.22 and 4.79, respectively. Studies on invertebrates and agriculture research studies were positively correlated with the number of years (R 2 = 0.7803; y = 3.4661x - 19.659) signifying an upsurge in the amount of publications on this topic in the near future. The United States maintained a top position in terms of published outputs (n = 312) and citations (n = 14,113), followed by Germany (n = 75; n = 3686) and the United Kingdom (n = 70; n = 3117), respectively. Articles from the United States (n = 67) and China (n = 32) had strong networks with other nations of the world. Top subject priorities in this research field in terms of author keywords are agriculture (n = 141), biodiversity (n = 66), arthropods (n = 66) and biological control/ecosystem services (n = 46). From our findings, economically stable nations such as the United States, Germany, China, the United Kingdom and Australia are carrying out more research on this subject matter compared to the developing countries. We also found out that from the thematic evolution and literature results, invertebrate research in the context of agriculture is tending towards biogeography, farmland biodiversity, insecticides and organic agriculture, which are of immense importance to scientists and researchers in this research domain, thus signifying the direction/path of future research.

Beyond correlation: Understanding the causal link between microbiome and plant health

Understanding the causal link between the microbiome and plant health is crucial for the future of crop production. Established studies have shown a symbiotic relationship between microbes and plants, reshaping our knowledge of plant microbiomes' role in health and disease. Addressing confounding factors in microbiome study is essential, as standardization enables precise identification of microbiome features that influence outcomes. The microbiome significantly impacts plant development, necessitating holistic investigation for maintaining plant health. Mechanistic studies have deepened our understanding of microbiome structure and function related to plant health, though much research still needs to be carried out. This review, therefore, discusses current challenges and proposes advancing studies from correlation to causation and translation. We explore current knowledge on the microbiome and plant health, emphasizing multi-omics approaches and hypothesis-driven research. Future studies should focus on developing translational research for producing probiotics and prebiotics from biomarkers that regulate the microbiome-plant health connection, promoting sustainable crop production through microbiome applications.

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.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

Global contribution of invertebrates to forest litter decomposition

Forest litter decomposition is an essential component of global carbon and nutrient turnover. Invertebrates play important roles in litter decomposition, but the regional pattern of their effects is poorly understood. We examined 476 case studies across 93 sites and performed a meta-analysis to estimate regional effects of invertebrates on forest litter decomposition. We then assessed how invertebrate diversity, climate and soil pH drive regional variations in invertebrate-mediated decomposition. We found that (1) invertebrate contributions to litter decomposition are 1.4 times higher in tropical and subtropical forests than in forests elsewhere, with an overall contribution of 31% to global forest litter decomposition; and (2) termite diversity, together with warm, humid and acidic environments in the tropics and subtropics are positively associated with forest litter decomposition by invertebrates. Our results demonstrate the significant difference in invertebrate effects on mediating forest litter decomposition among regions. We demonstrate, also, the significance of termites in driving litter mass loss in the tropics and subtropics. These results are particularly pertinent in the tropics and subtropics where climate change and human disturbance threaten invertebrate biodiversity and the ecosystem services it provides.

Structural and Functional Shifts in the Microbial Community of a Heavy Metal-Contaminated Soil Exposed to Short-Term Changes in Air Temperature, Soil Moisture and UV Radiation

The interplay between metal contamination and climate change may exacerbate the negative impact on the soil microbiome and, consequently, on soil health and ecosystem services. We assessed the response of the microbial community of a heavy metal-contaminated soil when exposed to short-term (48 h) variations in air temperature, soil humidity or ultraviolet (UV) radiation in the absence and presence of Enchytraeus crypticus (soil invertebrate). Each of the climate scenarios simulated significantly altered at least one of the microbial parameters measured. Irrespective of the presence or absence of invertebrates, the effects were particularly marked upon exposure to increased air temperature and alterations in soil moisture levels (drought and flood scenarios). The observed effects can be partly explained by significant alterations in soil properties such as pH, dissolved organic carbon, and water-extractable heavy metals, which were observed for all scenarios in comparison to standard conditions. The occurrence of invertebrates mitigated some of the impacts observed on the soil microbial community, particularly in bacterial abundance, richness, diversity, and metabolic activity. Our findings emphasize the importance of considering the interplay between climate change, anthropogenic pressures, and soil biotic components to assess the impact of climate change on terrestrial ecosystems and to develop and implement effective management strategies.

Climate dependence of the macrofaunal effect on litter decomposition-A global meta-regression analysis

Litter decomposition by microorganisms and animals is influenced by climate and has been found to be higher in warm and wet than in cold and dry biomes. We, however, hypothesized that the macrofaunal effect on decomposition should increase with temperature and aridity since larger animals are more tolerant to aridity than smaller organisms. This hypothesis was supported by our global analysis of macrofauna exclusion studies. Macrofauna increased litter mass loss on average by 40%, twofold higher than the highest previous estimation of macrofaunal effect on decomposition. The strongest effect was found in subtropical deserts where faunal decomposition had not been considered important. Our results highlight the need to consider animal size when exploring climate dependence of faunal decomposition, and the disproportionately large role of macrofauna in regulating litter decomposition in warm drylands. This new realization is critical for understanding element cycling in the face of global warming and aridification.

Isopod mouthpart traits respond to a tropical forest recovery gradient

Functional trait ecology has the potential to provide generalizable and mechanistic predictions of ecosystem function from data of species distributions and traits. The traits that are selected should both respond to environmental factors and influence ecosystem functioning. Invertebrate mouthpart traits fulfill these criteria, but are seldom collected, lack standardized measurement protocols, and have infrequently been investigated in response to environmental factors. We surveyed isopod species that consume plant detritus, and tree communities in 58 plots across primary and secondary forests in Singapore. We measured body dimensions (body size traits), pereopod and antennae lengths (locomotory traits), dimensions of mandible structures (morphological mouthpart traits), and mechanical advantages generated by mandible shape (mechanical mouthpart traits) for six isopod species found in these plots and investigated if these traits respond to changes in tree community composition, tree diversity, and forest structure. Morphological mouthpart traits responded to a tree compositional gradient reflecting forest recovery degree. Mouthpart features associated with greater consumption of litter (broader but less serrated/rugose lacinia mobilis [an important cutting and chewing structure on the mandible]) were most prevalent in abandoned plantation and young secondary forests containing disturbance-associated tree species. Feeding strategies associated with fungi grazing (narrower and more serrated/rugose lacinia mobilis) were most prevalent in late secondary forests containing later successional tree species. Since morphological mouthpart traits likely also predict consumption and excretion rates of isopods, these traits advance our understanding of environment-trait-ecosystem functioning relationships across contrasting tropical forest plots that vary in composition, disturbance history, and post-disturbance recovery.

Arachnid Fauna (Araneae and Opiliones) from the Castro Verde Special Protection Area, southern Portugal

Background

With the increasing recognition of the significance of arachnid conservation, it is crucial to allocate greater efforts towards implementing targeted monitoring programmes. Despite recent studies, our understanding of arachnid populations in Portugal remains limited. This study serves as the initial inventory of arachnids (Araneae and Opiliones) within the Castro Verde Special Protection Area (SPA) located in Beja, southern Portugal. The surveys were conducted during the spring of 2012 across 80 open grasslands that were grazed by cattle and sheep.

New information

A total of 71 species of Araneae and two species of Opiliones have been identified. Notably, three spider species, namely Argennasubnigra, Civizelotesibericus and Walckenaeriacucullata, are documented for the first time in Portugal. Additionally, two harvestmen species (Dasylobusibericus and Homalenotusbuchneri) and 14 spider species (Cheiracanthiumpennatum, Haplodrassusrhodanicus, Marinarozelotesminutus, Tapinocybaalgirica, Agraecinalineata, Tibellusmacellus, Talaverapetrensis, Tetragnathaintermedia, Dipoenaumbratilis, Enoplognathadiversa, Neottiurauncinata, Ruborridionmusivum, Theridionpinastri and Xysticusgrallator) are recorded for the first time in the Beja District. The occurrence of each documented species within the SPA, including family and species details, is presented, underscoring the significance of the Castro Verde SPA for arachnid conservation. These findings contribute novel insights into the biodiversity of the Castro Verde SPA, emphasising the necessity of incorporating this area into arachnid diversity conservation efforts.

Consequences of climate-induced range expansions on multiple ecosystem functions

Climate-driven species range shifts and expansions are changing community composition, yet the functional consequences in natural systems are mostly unknown. By combining a 30-year survey of subalpine pond larval caddisfly assemblages with species-specific functional traits (nitrogen and phosphorus excretion, and detritus processing rates), we tested how three upslope range expansions affected species' relative contributions to caddisfly-driven nutrient supply and detritus processing. A subdominant resident species (Ag. deflata) consistently made large relative contributions to caddisfly-driven nitrogen supply throughout all range expansions, thus "regulating" the caddisfly-driven nitrogen supply. Whereas, phosphorus supply and detritus processing were regulated by the dominant resident species (L. externus) until the third range expansion (by N. hostilis). Since the third range expansion, N. hostilis's relative contribution to caddisfly-driven phosphorus supply increased, displacing L. externus's role in regulating caddisfly-driven phosphorus supply. Meanwhile, detritus processing contributions became similar among the dominant resident, subdominant residents, and range expanding species. Total ecosystem process rates did not change throughout any of the range expansions. Thus, shifts in species' relative functional roles may occur before shifts in total ecosystem process rates, and changes in species' functional roles may stabilize processes in ecosystems undergoing change.

Impacts of extreme weather events on terrestrial carbon and nitrogen cycling: A global meta-analysis

Some weather events like drought, increased precipitation, and warming exert substantial impact on the terrestrial C and N cycling. However, it remains largely unclear about the effect of extreme weather events (extreme drought, heavy rainfall, extreme heat, and extreme cold) on terrestrial C and N cycling. This study aims to analyze the responses of pools and fluxes of C and N in plants, soil, and microbes to extreme weather events by conducting a global meta-analysis of 656 pairwise observations. Results showed that extreme weather events (extreme drought, heavy rainfall, and extreme heat) decreased plant biomass and C flux, and extreme drought and heavy rainfall decreased the plant N pool and soil N flux. These results suggest that extreme weather events weaken the C and N cycling process in terrestrial ecosystems. However, this study did not determine the impact of extreme cold on ecosystem C and N cycling. Additional field experiments are needed to reveal the effects of extreme cold on global C and N cycling patterns.

Herbivores in Arctic ecosystems: Effects of climate change and implications for carbon and nutrient cycling

Arctic terrestrial herbivores influence tundra carbon and nutrient dynamics through their consumption of resources, waste production, and habitat-modifying behaviors. The strength of these effects is likely to change spatially and temporally as climate change drives shifts in herbivore abundance, distribution, and activity timing. Here, we review how herbivores influence tundra carbon and nutrient dynamics through their consumptive and nonconsumptive effects. We also present evidence for herbivore responses to climate change and discuss how these responses may alter the spatial and temporal distribution of herbivore impacts. Several current knowledge gaps limit our understanding of the changing functional roles of herbivores; these include limited characterization of the spatial and temporal variability in herbivore impacts and of how herbivore activities influence the cycling of elements beyond carbon. We conclude by highlighting approaches that will promote better understanding of herbivore effects on tundra ecosystems, including their integration into existing biogeochemical models, new applications of remote sensing techniques, and the continued use of distributed experiments.

The global distribution of known and undiscovered ant biodiversity

Invertebrates constitute the majority of animal species and are critical for ecosystem functioning and services. Nonetheless, global invertebrate biodiversity patterns and their congruences with vertebrates remain largely unknown. We resolve the first high-resolution (~20-km) global diversity map for a major invertebrate clade, ants, using biodiversity informatics, range modeling, and machine learning to synthesize existing knowledge and predict the distribution of undiscovered diversity. We find that ants and different vertebrate groups have distinct features in their patterns of richness and rarity, underscoring the need to consider a diversity of taxa in conservation. However, despite their phylogenetic and physiological divergence, ant distributions are not highly anomalous relative to variation among vertebrate clades. Furthermore, our models predict that rarity centers largely overlap (78%), suggesting that general forces shape endemism patterns across taxa. This raises confidence that conservation of areas important for small-ranged vertebrates will benefit invertebrates while providing a "treasure map" to guide future discovery.

Effects of enhanced productivity of resources shared by predators in a food-web module: Comparing results of a field experiment to predictions of mathematical models of intra-guild predation

We compared the response to resource enhancement of a simple empirical model of intra-guild predation (IGP) to the predictions of published, simple mathematical models of asymmetric IGP (a generalist IG Predator that feeds both on a specialist IG Prey and a Resource that it shares with the IG Prey). The empirical model was a food-web module created by pooling species abundances across many families in a speciose community of soil micro-arthropods into three categories: IG Predator (large predatory mites), IG Prey (small predatory mites), and a shared Resource (fungivorous mites and springtails). By pooling abundances of species belonging to broadly defined functional groups, we tested the hypothesis that IGP is a dominant organizing principle in this community. Simple mathematical models of asymmetric IGP predict that increased input of nutrients and energy to the shared Resource will increase the equilibrium density of Resource and IG Predator, but will decrease that of IG Prey. In a field experiment, we observed how the three categories of the empirical model responded to two rates of addition of artificial detritus, which enhanced the food of fungivores, the Resource of the IGP module. By the experiment's end, fungivore densities had increased ~1.5× (ratio of pooled fungivore densities in the higher-input treatment to plots with no addition of detritus), and densities of IG Predators had increased ~4×. Contrary to the prediction of mathematical models, IG Prey had not decreased, but instead had increased ~1.5×. We discuss possible reasons for the failure of the empirical model to agree with IGP theory. We then explore analogies between the behavior of the empirical model and another mathematical model of trophic interactions as one way to gain insights into the trophic connections in this community. We also propose one way forward for reporting comparisons of simple empirical and mathematical models.