The concept of critical age group for density dependence: bridging the gap between demographers, evolutionary biologists and behavioural ecologists

Density dependence plays an important role in population regulation in the wild. It involves a decrease in population growth rate when the population size increases. Fifty years ago, Charlesworth introduced the concept of 'critical age group', denoting the age classes in which variation in the number of individuals most strongly contributes to density regulation. Since this pioneering work, this concept has rarely been used. In light of Charlesworth's concept, we discuss the need to develop work between behavioural ecology, demography and evolutionary biology to better understand the mechanisms acting in density-regulated age-structured populations. We highlight demographic studies that explored age-specific contributions to density dependence and discuss the underlying evolutionary processes. Understanding competitive interactions among individuals is pivotal to identify the ages contributing most strongly to density regulation, highlighting the need to move towards behavioural ecology to decipher mechanisms acting in density-regulated age-structured populations. Because individual characteristics other than age can be linked to competitive abilities, expanding the concept of critical age to other structures (e.g. sex, dominance rank) offers interesting perspectives. Linking research fields based on the concept of the critical age group is key to move from a pattern-oriented view of density regulation to a process-oriented approach.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Forest plant indicator values for moisture reflect atmospheric vapour pressure deficit rather than soil water content

Soil moisture shapes ecological patterns and processes, but it is difficult to continuously measure soil moisture variability across the landscape. To overcome these limitations, soil moisture is often bioindicated using community-weighted means of the Ellenberg indicator values of vascular plant species. However, the ecology and distribution of plant species reflect soil water supply as well as atmospheric water demand. Therefore, we hypothesized that Ellenberg moisture values can also reflect atmospheric water demand expressed as a vapour pressure deficit (VPD). To test this hypothesis, we disentangled the relationships among soil water content, atmospheric vapour pressure deficit, and Ellenberg moisture values in the understory plant communities of temperate broadleaved forests in central Europe. Ellenberg moisture values reflected atmospheric VPD rather than soil water content consistently across local, landscape, and regional spatial scales, regardless of vegetation plot size, depth as well as method of soil moisture measurement. Using in situ microclimate measurements, we discovered that forest plant indicator values for moisture reflect an atmospheric VPD rather than soil water content. Many ecological patterns and processes correlated with Ellenberg moisture values and previously attributed to soil water supply are thus more likely driven by atmospheric water demand.

Holocene precipitation variations in the northwestern half of the Chinese Loess Plateau: Pollen-based reconstructions

The northwestern half of the Chinese Loess Plateau (i.e., the examined area) is reported to have been sensitive to the East Asian Summer Monsoon (EASM) and might have also been exposed to the influence of the Indian Summer Monsoon (ISM) during the Holocene. This study utilizes the already reported pollen data from four high-resolution fossil pollen sequences to quantitatively reconstruct the Holocene mean annual precipitation (Pann) in the examined area. It also incorporates those quantitative precipitation reconstructions from the same area reported by others to delineate the regional Pann patterns. It finally brings the regional Pann patterns into the perceived forcing contexts to explore the underlying mechanisms. Our delineation shows that the Holocene Pann exhibits different temporal trends between the western part and the northern part of the Chinese Loess Plateau. That is, the "higher-than-average" Pann occurred in the early mid-Holocene from ~10.0 to ~5.5 cal. kyr BP in the western part and the "higher-than-average" Pann occurred in the late mid-Holocene from ~8.0 to ~2.5 cal. kyr BP in the northern part. We propose that the Pann differences between the western part and the northern part might have been associated with two mechanisms: (1) differences in the thermal sensitivity to the solar insolation between the Indian Ocean and the Pacific Ocean, and (2) differences in terms of the relative importance of precipitable water vapor transports either from the ISM or from the EASM between the western part and the northern part.

Biodiversity of multi-trophic biological communities within riverine sediments impacted by PAHs contamination and land use changes

River ecosystems currently face a significant threat of degradation and loss of biodiversity resulting from continuous emissions of persistent organic pollutants and human activities. In this study, multi-trophic communities were assessed using DNA metabarcoding in a relatively stable riverine sediment compartment to investigate the biodiversity dynamics in the Beiluo River, followed by an evaluation of their response to polycyclic aromatic hydrocarbons (PAHs) and land use changes. A total of 48 bacterial phyla, 4 fungal phyla, 4 protist phyla, 9 algal phyla, 31 metazoan phyla, and 12 orders of fish were identified. The total concentration of PAHs in the Beiluo River sediments ranged from 25.95 to 1141.35 ng/g, with low molecular weight PAHs constituting the highest proportion (68.67%), followed by medium (22.19%) and high (9.14%) molecular weight PAHs. Notably, in contrast to lower trophic level aquatic communities such as bacteria, algae, and metazoans, PAHs exhibited a significant inhibitory effect on fish. Furthermore, the diversity of aquatic communities displayed obvious heterogeneity across distinct land use groups. A high proportion of cultivated land reduced the biodiversity of fish communities but increased that of metazoans. Conversely, an elevated proportion of built-up land reduced metazoan biodiversity, while simultaneously enhancing that of fungi and bacteria. Generally, land use changes exert both indirect and direct effects on aquatic communities. The direct effects primarily influence the abundance of aquatic communities rather than their diversity. Nevertheless, PAHs pollution may have limited potential to disrupt community structures through complex species interactions, as the hub species identified in the co-occurrence network did not align with those significantly affected by PAHs. This study indicates the potential of PAHs and land use changes to cause biodiversity losses. However, it also highlights the possibility of mitigating these negative effects in riverine sediments through optimal land use management and the promotion of enhanced species interactions.

Trophic fate and biomagnification of organic micropollutants from staple food to a specialized predator

The environmental burden of organic micropollutants has been shown in aquatic ecosystems, while trophic fate of many compounds in terrestrial food chains remains highly elusive. We therefore studied concentrations of 108 organic micropollutants in a common European mammal, the bank vole (Clethrionomys glareolus), and 82 of the compounds in a specialized predator, Tengmalm's owl (Aegolius funereus) relying to >90 % on voles as its prey. We studied compounds in whole voles (n = 19), pools of 4-8 bank voles (npools = 4), owl blood (n = 10) and in owl eggs (n = 10) in two regions in Sweden. For comparison, we also included previously published data on 23 PFAS (per- and polyfluoroalkyl substances) in bank vole liver (npools = 4) from the same regions. In voles, concentrations of the organic micropollutants caffeine (maxIndividual 220 ng/g ww) and DEET (N,N-diethyl-m-toluamide) (maxPool 150 ng/g ww) were 2-200 times higher in voles relative to owl blood and eggs. Conversely, concentrations of nicotine, oxazepam, salicylic acid, and tributyl citrate acetate were 1.3-440 times higher in owls. Several PFAS showed biomagnification in owls as revealed by maximum biomagnification factors (BMFs); PFNA (perfluorononanoate) BMF = 5.6, PFTeDA (perfluorotetradecanoic acid) BMF = 5.9, and PFOS (perfluorooctane sulfonate) BMF = 6.1. Concentrations of organic micropollutants, alongside calculated BMFs, and Tengmalm's owl's heavy reliance on bank vole as staple food, suggest, despite small sample size and potential spatio-temporal mismatch, accumulation of PFAS (especially PFNA, PFTeDA, and PFOS) in owls and biomagnification along the food chain. Concentrations of PFAS in owl eggs (e.g., 21 ng/g ww PFOS) highlight the likely pivotal role of maternal transfer in contaminant exposure for avian embryos. These concentrations are also of concern considering that certain predators frequently consume owl eggs, potentially leading to additional biomagnification of PFAS with yet undetermined consequences for ecosystem health.

Enhancing nitrate removal from small wetlands via regulating bacterial-algal symbiosis with macrophyte coverage

With increasing land resource constraints, wetlands, as ecological hotspots, are expected to enhance biogeochemical processes to mitigate nitrogen (N) pollution, particularly nitrate-nitrogen (NO3--N). However, the interactions among bacteria, algae, and macrophytes in wetlands, which are crucial for N removal, remain largely unknown. This study explored how macrophyte coverage influences bacterial-algal interactions, shifting from mutualism to inhibition, thereby affecting N removal. Moderate coverage enhanced NO3--N and total nitrogen (TN) removal (P < 0.05), which was correlated with increased microbial abundance (P < 0.05). This may have resulted from moderate algal photosynthesis, reduced physiological stress, and the expansion of ecological niches for microbes. Insufficient coverage promoted algal growth (chlorophyll-a > 31.8 μg·L-1), leading to increased competition for substrates and elevated pH, which further inhibited bacterial activity. Excessive coverage also inhibited bacterial activity by reducing illumination and oxidation-reduction potential. Consequently, insufficient and excessive coverage decreased N removal efficiencies by 2.7-15.7 % (NO3--N) and 3.7-11.1 % (TN) while increasing methane emission potential by 1.4-6.9 times compared with moderate coverage. These findings offer insights into solving NO3--N contamination using near-natural methods and balancing the ecological and practical considerations for small wetlands.

Behavioural response to boat noise weakens the strength of a trophic link in coral reefs

In oceans, the noise generated by human activities has reached phenomenal proportions, with considerable harmful effects on marine life. Measuring this impact to achieve a sustainable balance for highly vulnerable marine ecosystems, such as coral reefs, is a critical environmental policy objective. Here, we demonstrate that anthropogenic noise alters the interactions of a coral reef fish with its environment and how this behavioural response to noise impairs foraging. In situ observations on the Moorea reef revealed that the damselfish Dascyllus emamo reacts to boat passage by moving closer to its coral bommie, considerably reducing the volume of water available to search for prey. Using boat noise playback experiments in microcosms, we studied D. emamo's behaviour and modeled its functional response (FR), which is the relationship between resource use and resource density, when feeding on juvenile shrimps. Similar to field observations, noise reduced D. emamo's spatial occupancy, accompanied by a lower FR, indicating a reduction in predation independent of prey density. Overall, noise-induced behavioural changes are likely to influence predator-prey interaction dynamics and ultimately the fitness of both protagonists. While there is an urgent need to assess the effect of anthropogenic noise on coral reefs, the ecological framework of the FR approach combined with behavioural metrics provides an essential tool for evaluating the cascading effects of noise on nested ecological interactions at the community level.

Influence of migration range and foraging ecology on mercury accumulation in Southern Ocean penguins

In order to evaluate mercury (Hg) accumulation patterns in Southern Ocean penguins, we measured Hg concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in body feathers of adult Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua), and chinstrap (Pygoscelis antarctica) penguins living near Anvers Island, West Antarctic Peninsula (WAP) collected in the 2010/2011 austral summer. With these and data from Pygoscelis and other penguin genera (Eudyptes and Aptenodytes) throughout the Southern Ocean, we modelled Hg variation using δ13C and δ15N values. Mean concentrations of Hg in feathers of Adélie (0.09 ± 0.05 μg g-1) and gentoo (0.16 ± 0.08 μg g-1) penguins from Anvers Island were among the lowest ever reported for the Southern Ocean. However, Hg concentrations in chinstrap penguins (0.80 ± 0.20 μg g-1), which undertake relatively broad longitudinal winter migrations north of expanding sea ice, were significantly higher (P < 0.001) than those in gentoo or Adélie penguins. δ13C and δ15N values for feathers from all three Anvers Island populations were also the lowest among those previously reported for Southern Ocean penguins foraging within Antarctic and subantarctic waters. These observations, along with size distributions of WAP krill, suggest foraging during non-breeding seasons as a primary contributor to higher Hg accumulation in chinstraps relative to other sympatric Pygoscelis along the WAP. δ13C values for all Southern Ocean penguin populations, alone best explained feather Hg concentrations among possible generalized linear models (GLMs) for populations grouped by either breeding site (AICc = 36.9, wi = 0.0590) or Antarctic Frontal Zone (AICc = 36.9, wi = 0.0537). Although Hg feather concentrations can vary locally by species, there was an insignificant species-level effect (wi < 0.001) across the full latitudinal range examined. Therefore, feeding ecology at breeding locations, as tracked by δ13C, control Hg accumulation in penguin populations across the Southern Ocean.

High-resolution temporal NDVI data reveal contrasting intratidal, spring-neap and seasonal biomass dynamics in euglenoid- and diatom-dominated biofilms

Intertidal microphytobenthos (MPB) are a major contributor to primary production in estuarine ecosystems. While their biomass is highly variable at multiple spatial and temporal scales, the underlying drivers are as yet little understood. Both in situ sampling and remote-sensing techniques often lack the temporal resolution or coverage to simultaneously capture short-term (intratidal to daily) and longer-term (weekly to annual) biomass changes. Our field setup with in-situ NDVI sensors allowed us to study MPB surface biomass variability at high temporal resolution (10 mins) for up to two years in a freshwater euglenoid dominated mudflat, and a brackish and a marine diatom dominated mudflat. MPB biomass showed marked periodicities at multiple temporal scales: seasonal, spring-neap and intratidal. The diatom-dominated MPB community showed a seasonal biomass peak in winter, while the euglenoid-dominated community showed biomass peaks during spring and summer, probably caused by underlying divergent responses to mainly irradiance, temperature and wind-induced resuspension, and macrobenthos grazing. Spring-neap periodicity likely resulted from differential migratory responses of the MPB communities to variation in timing and duration of daylight exposure. In the freshwater community, upward migration only occurred when exposure duration was sufficiently long (≥4 h). In the diatom-dominated community, morning daylight exposure resulted in highest NDVI values. This study highlights the differences in MPB biomass dynamics between MPB communities within estuarine ecosystems, and underscores the great potential of high-resolution temporal NDVI monitoring for more accurate estimates of MPB biomass and primary production.

The impact of anthropogenic pressures on microbial diversity and river multifunctionality relationships on a global scale

Conserving biodiversity is crucial for maintaining essential ecosystem functions, as indicated by the positive relationships between biodiversity and ecosystem functioning. However, the impacts of declining biodiversity on ecosystem functions in response to mounting human pressures remain uncertain. This uncertainty arises from the complexity of trade-offs among human activities, climate change, river properties, and biodiversity, which have not been comprehensively addressed collectively. Here, we provide evidence that river biodiversity was significantly and positively associated with multifunctionality and contributed to key ecosystem functions such as microbially driven water purification, leaf litter decomposition and pathogen control. However, human pressure led to abrupt changes in microbial diversity and river multifunctionality relationships at a human pressure value of 0.5. In approximately 30 % (N = 58) of countries globally, the ratio of area above this threshold exceeded the global average (∼11 %), especially in Europe. Results show that human pressure affected ecosystem functions through direct effects and interactive effects. We provide more direct evidence that the nonadditive effects triggered by prevailing human pressure impact the multifunctionality of rivers globally. Under high levels of human stress, the beneficial effects of biodiversity on nutrient cycling, carbon storage, gross primary productivity, leaf litter decomposition, and pathogen control tend to diminish. Our findings highlight that considering interactions between human pressure and local abiotic and biotic factors is key for understanding the fate of river ecosystems under climate change and increasing human pressure.

A systematic review of poeciliid fish invasions in Africa

BACKGROUND

This review compiles and synthesises the existing information concerning non-native poeciliid introductions to Africa. The recent upsurge in research on invasive poeciliids has revealed their widespread occurrence in Africa.

RESULTS

Within the 87 relevant articles, 74% reported on the presence of Gambusia spp., 33% on P. reticulata, 19% on X. hellerii, 11% on X. maculatus, and 5% on other ornamental poeciliids. Overall, poeciliids have been documented as introduced to 25 different countries in Africa. With Gambusia spp. being introduced to 16 countries and P. reticulata to 19 countries. Our results are representative of the current state of research on invasive poeciliids in Africa. There was a concentration of studies in South Africa, with limited research elsewhere. Current distribution data is relatively patchy, although widespread surveys of multiple river systems in Morocco and South Africa, confirmed widespread and abundant established poeciliid populations. The ecological impacts of invasive poeciliids in Africa remain understudied but evidence indicates deleterious effects on native fish, invertebrates, and amphibians, many of which are critically endangered or endemic.

CONCLUSION

Current research is limited in reporting from certain countries and ecological impacts. An increased effort to monitor species composition in vulnerable waterbodies, especially in the many African countries where invasive poeciliids are reported, should be completed to reveal further established populations. Future research should prioritise quantifying the ecological impacts of invasive poeciliids in the field and identifying both vulnerable and resistant native ecosystems to guide future management decisions.

Adaptation to different temperatures results in wing size divergence of the invading species Drosophila nasuta (Diptera: Drosophilidae) in Brazil

Invasive species threaten biodiversity on a global scale. The success of invasions depends on the species' adaptation to the different environmental conditions of new territories. Studies show that invasive insects present evolutionary changes in wing morphology in areas they are introduced to in response to abiotic conditions. In the last decade, the Asian Drosophila nasuta fly invaded and spread widely throughout Brazil. This insect has preferences for conserved environments and is related to the likely reduction in the abundance of native drosophilids in the Atlantic Forest. Ecological niche modelling analyses showed that rainfall and temperature are the main factors which delimit the geographic distribution of this species. Herein, we verified the existence of significant differences in the wing sizes of D. nasuta in Brazil and evaluated the influence of abiotic factors (rainfall and temperature) on the observed patterns. We conducted 11 measurements on the right-side wings of 240 D. nasuta males collected in the Amazon Forest, Caatinga, Cerrado and Atlantic Forest. Statistical analyses revealed the existence of two groups: one with larger wings, which brought together samples from locations with the lowest temperatures; and one with smaller wings, which corresponded to places with a hotter climate. One explanation for this result is the fact that large wings favour greater heat capture by flies in colder climates, increasing their survival chances in these environments. These rapid evolutionary changes in D. nasuta in this first decade of invasion in Brazil reveal the enormous adaptive potential of this species in this megadiverse country.

A modeling approach to forecast local demographic trends in metapopulations

Predicting animal population trajectories into the future has become a central exercise in both applied and fundamental ecology. Because demographic models classically assume population closure, they tend to provide inaccurate predictions when applied locally to interconnected subpopulations that are part of a larger metapopulation. Ideally, one should explicitly model dispersal among subpopulations, but in practice this is prevented by the difficulty of estimating dispersal rates in the wild. To forecast the local demography of connected subpopulations, we developed a new demographic model (hereafter, the two-scale model) that disentangles two processes occurring at different spatial scales. First, at the larger scale, a closed population model describes changes in metapopulation size over time. Second, total metapopulation size is redistributed among subpopulations, using time-varying proportionality parameters. This two-step approach ensures that the long-term growth of every subpopulation is constrained by the overall metapopulation growth rate. It implicitly accounts for the interconnectedness among subpopulations and avoids unrealistic trajectories. Using realistic simulations, we compared the performance of this new model with that of a classical closed population model at predicting subpopulations' trajectories over 30 years. While the classical model predicted future subpopulation sizes with an average bias of 30% and produced predictive errors sometimes >500%, the two-scale model showed very little bias (<3%) and never produced predictive errors >20%. We also applied both models to a real dataset on European shags (Gulosus aristotelis) breeding along the Atlantic coast of France. Again, the classical model predicted highly unrealistic growths, as large as a 200-fold increase over 30 years for some subpopulations. The two-scale model predicted very sensible growths, never larger than a threefold increase over the 30-year time horizon, which is more in accordance with this species' life history. This two-scale model provides an effective solution to forecast the local demography of connected subpopulations in the absence of data on dispersal rates. In this context, it is a better alternative than closed population models and a more parsimonious option than full-dispersal models. Because the only data required are simple counts, this model could be useful to many large-scale wildlife monitoring programs.

Influence of shifting thermal regimes on tomato fruit borer, Helicoverpa armigera (Hubner) in the Eastern Himalaya: implications for pest management strategies

Climate change, particularly temperature fluctuations, profoundly impacts pest populations. This study focuses on the tomato, a crucial commercial crop in the Eastern Himalayan Region of India. The study examined the impact of varying thermal regimes on tomato fruit borers. Field experiments were conducted at three locations, with altitudes ranging from < 500 to > 1500 m. At lower altitudes, fruit borer incidence commenced earlier (5th - 18th March) and peaked higher (1.47 ± 0.34 to 1.73 ± 0.37 larvae/plant), causing more damage (26-29%) as compared to the highest location (~ 9%). The generalized linear mixed model (GLMM) analysis indicated that maximum temperature had significant positive impacts on the H. armigera incidence and fruit damage. Climatic datasets indicate an increase in the temperature of the region during the tomato growing season, thereby increasing the risk of fruit borer impact. As an adaptation option, we evaluated eight different tomato varieties/genotypes and studied biochemical parameters to understand their tolerance. Results showed a strong positive association of fruit borer incidence with total soluble solids whereas negative association with acidity. Cherry tomato (7.62%) and MT-2 (10.04%) had relatively lower fruit damage; MT-3 (50.92 t/ha) and MT-2 (50.57 t/ha) consistently yielded the highest across all locations. Hence, the selection of appropriate genotypes and the development of varieties with suitable characteristics hold the key to fruit borer management. This insight is crucial for developing effective pest management strategies and ensuring sustainable agricultural practices in the region.

Haemoglobin Gene Repertoire in Teleost and Cichlid Fishes Shaped by Gene Duplications and Genome Rearrangements

Haemoglobin is a key molecule for oxygen transport in vertebrates. It exhibits remarkable gene diversity in teleost fishes, reflecting adaptation to various aquatic environments. In this study, we present the dynamic evolution of haemoglobin subunit genes based on a comparison of high-quality genome assemblies of 24 vertebrate species, including 17 teleosts (of which six are cichlids). Our findings indicate that teleost genomes contain a range of haemoglobin genes, from as few as five in fugu to as many as 43 in salmon, with the latter being the largest repertoire found in vertebrates. We find evidence that the teleost ancestor had at least four Hbα and three or four Hbβ subunit genes, and that the current gene diversity emerged during teleost radiation, driven primarily by (tandem) gene duplications, genome compaction, and rearrangement dynamics. We provide insights into the genomic organisation of haemoglobin clusters in different teleost species. We further show that the evolution of paralogous rhbdf1 genes flanking both teleost clusters (LA and MN) supports the hypothesis for the origin of the LA cluster by rearrangement within teleosts, rather than by the teleost specific whole-genome duplication. We specifically focus on cichlid fishes, where adaptation to low oxygen environment plays role in species diversification. Our analysis of six cichlid genomes, including Pungu maclareni from the Barombi Mbo crater lake, for which we sequenced a representative genome, reveals 18-32 copies of the Hb genes, and elevated rates of non-synonymous substitutions compared to other teleosts. Overall, this work facilitates a deeper understanding of how haemoglobin genes contribute to the adaptive potential of teleosts.

Global patterns and controlling factors of tree bark C : N : P stoichiometry in forest ecosystems consistent with biogeochemical niche hypothesis

Bark serves crucial roles in safeguarding trees physically and chemically, while also contributing to nutrient cycling and carbon sequestration. Despite its importance, the broader biogeographical patterns and the potential factors influencing bark C : N : P stoichiometry in forest ecosystems remain largely unknown. In this study, we compiled a comprehensive dataset comprising carbon (C), nitrogen (N), and phosphorus (P) concentrations in bark with 1240 records from 550 diverse forest sites to systematically analyze the large-scale patterns and the factors controlling bark C : N : P stoichiometry. The geometric means of bark C, N, and P concentrations were found to be 493.17 ± 1.75, 3.91 ± 0.09, and 0.2 ± 0.01 mg g-1, respectively. Correspondingly, the C : N, C : P, and N : P mass ratios were 135.51 ± 8.11, 3313.19 ± 210.16, and 19.16 ± 0.6, respectively. Bark C : N : P stoichiometry exhibited conspicuous latitudinal trends, with the exception of N : P ratios. These patterns were primarily shaped by the significant impacts of climate, soil conditions, and plant functional groups. However, the impact of evolutionary history in shaping bark C : N : P stoichiometry outweigh climate, soil, and plant functional group, aligning with the biogeochemical niche (BN) hypothesis. These finding enhance our understanding of the spatial distribution of bark nutrient stoichiometry and have important implications for modeling of global forest ecosystem nutrient cycles in a changing environment.

Phenology mediates direct and indirect interactions among co-occurring invasive plant species

Why nonnative invasive plant species commonly co-occur, despite their competitive superiority and propensity to displace native species, remains a paradox in invasion biology. Negative interactions among competitively dominant invaders are potentially alleviated by two understudied mechanisms: seasonal priority effects, where phenological separation weakens the effect of competition on species with early phenology; and indirect facilitation, where competition between two species is mitigated by a third species. Although phenological separation has been speculated as a mechanism for explaining co-occurrence patterns of invasive plants, it has never been directly tested. In a greenhouse experiment, we tested the effect of phenological separation on direct and indirect interactions between three co-occurring invasive plant species found in the riparian forests of North America. These species have distinct natural phenological separation with reproduction in early spring (Ficaria verna), mid-spring (Alliaria petiolata), and late summer (Microstegium vimineum). When phenology was experimentally synchronized, direct pairwise interactions among invasive species were overwhelmingly negative, asymmetric, and unlikely to promote co-occurrence. However, increasing phenological separation generated seasonal priority effects, which weakened the effect of competition on species with early phenology. Furthermore, the addition of a third species generated indirect facilitative effects, which balanced competitive outcomes among the two weakest competitors. Based on these findings, we conclude that phenological separation modulates the strength of both seasonal priority effects and indirect facilitation within species interaction networks and may promote the co-occurrence of three common invasive species within this study system. We articulate how future studies can test the external validity of these findings in more complex environmental conditions and with a larger range of invasive plants.

Plant diversity enhances ecosystem multifunctionality via multitrophic diversity

Ecosystem functioning depends on biodiversity at multiple trophic levels, yet relationships between multitrophic diversity and ecosystem multifunctionality have been poorly explored, with studies often focusing on individual trophic levels and functions and on specific ecosystem types. Here, we show that plant diversity can affect ecosystem functioning both directly and by affecting other trophic levels. Using data on 13 trophic groups and 13 ecosystem functions from two large biodiversity experiments-one representing temperate grasslands and the other subtropical forests-we found that plant diversity increases multifunctionality through elevated multitrophic diversity. Across both experiments, the association between multitrophic diversity and multifunctionality was stronger than the relationship between the diversity of individual trophic groups and multifunctionality. Our results also suggest that the role of multitrophic diversity is greater in forests than in grasslands. These findings imply that, to promote sustained ecosystem multifunctionality, conservation planning must consider the diversity of both plants and higher trophic levels.

Keystone individuals - linking predator traits to community ecology

Individual behavioral plasticity enables animals to adjust to different scenarios. Yet, personality traits limit this flexibility, leading to consistent interindividual differences in behavior. These individual behavioral traits have the potential to govern community interactions, although testing this is difficult in complex natural systems. For large predators who often exert strong effects on ecosystem functioning, this behavioral diversity may be especially important and lead to individualized ecosystem roles. We present a framework for quantifying individual behavioral plasticity and personality traits of large wild predators, revealing the extent to which certain natural behaviors are governed by these latent traits. The outcomes will reveal how the innate characteristics of wildlife can scale up to affect community interactions.

A continental-wide decline of occupancy and diversity in five Neotropical carnivores

The Neotropics are a global biodiversity hotspot that has undergone dramatic land use changes over the last decades. However, a temporal perspective on the continental-wide distributions of species in this region is still missing. To unveil it, we model the entire area of occupancy of five Neotropical carnivore species at two time periods (2000-2013 and 2014-2021) using integrated species distribution models (ISDMs) in a Bayesian framework. The carnivores are the jaguarundi (Herpailurus yagouaroundi), margay (Leopardus wiedii), maned wolf (Chrysocyon brachyurus), tayra (Eira barbara), and giant otter (Pteronura brasiliensis). We mapped the temporal change, the areas where gains and losses accumulated for all species (hotspots of change) and calculated the temporal species turnover and change in spatial turnover. We show that (1) most carnivore species have declined their area of occupancy (i.e., range size) in the last two decades, (2) their diversity has decreased over time, mostly in the Chaco region, and (3) that hotspots of fast species composition turnover are in Chaco, the Caatinga region, and northwest of Mexico. We discuss how these newly identified hotspots of change overlap with regions of well-known and pronounced land use transformation. These estimated patterns of overall decline are alarming, more so given that four out of the five species had been classified as not threatened by IUCN. The official global threat status of these species may need to be re-evaluated. All this would be invisible if standard forecasts, local expert knowledge, or static threat criteria, such as range size, were used. We thus provide a new approach to evaluate past species range dynamics based on multiple lines of evidence, which can be employed over more species in the future, particularly in under-sampled regions.

Sex-specific variation in species interactions matters in ecological communities

Understanding how natural communities and ecosystems are structured and respond to anthropogenic pressures in a rapidly changing world is key to successful management and conservation. A fundamental but often overlooked biological characteristic of organisms is sex. Sex-based responses are often considered when conducting studies at organismal and population levels, but are rarely investigated in community ecology. Focusing on kelp forests as a model system, and through a review of other marine and terrestrial ecosystems, we found evidence of widespread sex-based variation in species interactions. Sex-based variation in species interactions is expected to affect ecosystem structure and functioning via multiple trophic and nontrophic pathways. Understanding the drivers and consequences of sex-based variation in species interactions can inform more effective management and restoration.

Sublethal Effects Induced by a Cyflumetofen Formulation on Honeybee Apis mellifera L. Workers: Assessment of Midgut, Hypopharyngeal Glands, and Fat Body Integrity

Worldwide, both cultivated and wild plants are pollinated by the honey bee, Apis mellifera. Bee numbers are declining as a result of a variety of factors, including increased pesticide use. Cyflumetofen controls pest mites in some plantations pollinated by bees, which may be contaminated with residual sublethal concentrations of this pesticide, in nectar and pollen. We evaluated the effects of a sublethal concentration of a cyflumetofen formulation on the midgut, hypopharyngeal gland, and fat body of A. mellifera workers orally exposed for 72 h or 10 days. The midgut epithelium of treated bees presented digestive cells with cytoplasm vacuoles and some cell fragmentation, indicating autophagy and cell death. After being exposed to the cyflumetofen formulation for 72 h, the midgut showed a higher injury rate than the control bees, but after 10 days, the organs had recovered. In the hypopharyngeal gland of treated bees, the end apparatus was filled with secretion, suggesting that the acaricide interferes with the secretory regulation of this gland. Histochemical tests revealed differences in the treated bees in both exposure periods in the midgut and hypopharyngeal glands. The acaricide caused cytotoxic effects on the midgut digestive cells, with apical protrusions, plasma membrane rupture, and several vacuoles in the cytoplasm, features of cell degeneration. In the hypopharyngeal glands of the treated bees, the secretory cells presented small electron-dense and large electron-lucent secretory granules. The fat body cells had no changes in comparison with the control bees. In conclusion, the cyflumetofen formulation at sublethal concentrations causes damage to the midgut and the hypopharyngeal glands of honey bee, which may compromise the functions of these organs and colony fitness. Environ Toxicol Chem 2024;43:2455-2465. © 2024 SETAC.

Important Crop Pollinators Respond Less Negatively to Anthropogenic Land Use Than Other Animals

Animal-mediated pollination is a key ecosystem service required to some extent by almost three-quarters of the leading human food crops in global food production. Anthropogenic pressures such as habitat loss and land-use intensification are causing shifts in ecological community composition, potentially resulting in declines in pollination services and impacting crop production. Previous research has often overlooked interspecific differences in pollination contribution, yet such differences mean that biodiversity declines will not necessarily negatively impact pollination. Here, we use a novel species-level ecosystem service contribution matrix along with mixed-effects models to explore how groups of terrestrial species who contribute differently to crop pollination respond globally to land-use type, land-use intensity, and availability of natural habitats in the surrounding landscape. We find that the species whose contribution to crop pollination is higher generally respond less negatively (and in some cases positively) to human disturbance of land, compared to species that contribute less or not at all to pollination. This result may be due to these high-contribution species being less sensitive to anthropogenic land conversions, which has led humans to being more reliant on them for crop pollination. However, it also suggests that there is potential for crop pollination to be resilient in the face of anthropogenic land conversions. With such a high proportion of food crops requiring animal-mediated pollination to some extent, understanding how anthropogenic landscapes impact ecological communities and the consequences for pollination is critical for ensuring food security.

Sublethal pesticide exposure in non-target terrestrial ecosystems: From known effects on individuals to potential consequences on trophic interactions and network functioning

Over the last decades, the intensification of agriculture has resulted in an increasing use of pesticides, which has led to widespread contamination of non-target ecosystems in agricultural landscapes. Plants and arthropods inhabiting these systems are therefore chronically exposed to, at least, low levels of pesticides through direct pesticide drift, but also through the contamination of their nutrient sources (e.g. soil water or host/prey tissues). Pesticides (herbicides, acaricides/insecticides and fungicides) are chemical substances used to control pests, such as weeds, phytophagous arthropods and pathogenic microorganisms. These molecules are designed to disturb specific physiological mechanisms and induce mortality in targeted organisms. However, under sublethal exposure, pesticides also affect biological processes including metabolism, development, reproduction or inter-specific interactions even in organisms that do not possess the molecular target of the pesticide. Despite the broad current knowledge on sublethal effects of pesticides on organisms, their adverse effects on trophic interactions are less investigated, especially within terrestrial trophic networks. In this review, we provide an overview of the effects, both target and non-target, of sublethal exposures to pesticides on traits involved in trophic interactions between plants, phytophagous insects and their natural enemies. We also discuss how these effects may impact ecosystem functioning by analyzing studies investigating the responses of Plant-Phytophage-Natural enemy trophic networks to pesticides. Finally, we highlight the current challenges and research prospects in the understanding of the effects of pesticides on trophic interactions and networks in non-target terrestrial ecosystems.

Changes in gut microbiome can be associated with abrupt seizure exacerbation in epilepsy patients

OBJECTIVE

Seizures can be triggered by a variety of endogenous or exogenous factors. We hypothesized that alterations in the gut microbiome may be a seizure precipitant and analyzed the composition and characteristics of the gut microbiome in epilepsy patients who experienced an abrupt seizure exacerbation without a clear seizure precipitant.

METHODS

We prospectively enrolled 25 adult patients with epilepsy and collected fecal samples on the admission and after seizure recovery for next-generation sequencing analysis. We performed nonparametric paired t-test analysis to evaluate changes in the gut microbiota as seizures worsened and when it recovered and also estimated alpha and beta diversities in each category.

RESULTS

A total of 19 patients (13 males) aged between 19 and 78 years (mean 45.2 years) were included in the study. The composition of the gut microbiota underwent a significant change following an abrupt seizure exacerbation. At the phylum level, the relative abundance of Fusobacteria and Synergistetes was decreased in the seizure recovery state compared to the acute seizure exacerbation. A similar trend was observed at the lower hierarchical levels, with a decrease in the relative abundance of Fusobacteria, Tissierellia, and Synergistia at the class level, and that of Synergistales, Tissierellales, and Fusobacteriales at the order level. At the family level, the relative abundance of Fusobacteriaceae and Staphylococcaceae was decreased, whereas that of Leuconostocaceae was increased. No statistical differences were observed in alpha and beta diversity between the pre- and post-acute seizure exacerbation periods.

SIGNIFICANCE

Our study suggests that the changes in Fusobacteriaceae and Lecuonostocaceae may be associated with acute seizure exacerbation in epilepsy patients. Given that Fusobacteriaceae are associated with various systemic diseases due to their invasive properties and that Leuconostocaceae are known to produce GABA, our results may suggest a gut microbiome-based treatment option for epilepsy patients.

Transferability of ecological forecasting models to novel biotic conditions in a long-term experimental study

Ecological forecasting models play an increasingly important role for managing natural resources and assessing our fundamental knowledge of processes driving ecological dynamics. As global environmental change pushes ecosystems beyond their historical conditions, the utility of these models may depend on their transferability to novel conditions. Because species interactions can alter resource use, timing of reproduction, and other aspects of a species' realized niche, changes in biotic conditions, which can arise from community reorganization events in response to environmental change, have the potential to impact model transferability. Using a long-term experiment on desert rodents, we assessed model transferability under novel biotic conditions to better understand the limitations of ecological forecasting. We show that ecological forecasts can be less accurate when the models generating them are transferred to novel biotic conditions and that the extent of model transferability can depend on the species being forecast. We also demonstrate the importance of incorporating uncertainty into forecast evaluation with transferred models generating less accurate and more uncertain forecasts. These results suggest that how a species perceives its competitive landscape can influence model transferability and that when uncertainties are properly accounted for, transferred models may still be appropriate for decision making. Assessing the extent of the transferability of forecasting models is a crucial step to increase our understanding of the limitations of ecological forecasts.

Persistent interactive effects of developmental salinity and temperature in Atlantic killifish (Fundulus heteroclitus)

Climate change alters multiple abiotic environmental factors in aquatic environments but relatively little is known about their interacting impacts, particularly in developing organisms where these exposures have the potential to cause long-lasting effects. To explore these issues, we exposed developing killifish embryos (Fundulus heteroclitus) to 26 °C or 20 °C and 20 ppt or 3 ppt salinity in a fully-factorial design. After hatching, fish were transferred to common conditions of 20 °C and 20 ppt to assess the potential for persistent developmental plasticity. Warm temperature increased hatching success and decreased hatch time, whereas low salinity negatively affected hatching success, but this was only significant in fish developed at 20 °C. Temperature, salinity, or their interaction affected mRNA levels of genes typically associated with thermal and hypoxia tolerance (hif1a, hsp90b, hsp90a, hsc70, and hsp70.2) across multiple developmental timepoints. These differences were persistent into the juvenile stage, where the fish that developed at 26 °C had higher expression of hif1a, hsp90b, hsp90a, and hsp70.2 than fish developed at 20 °C, and this was particularly evident for the group developed at both high temperature and salinity. There were also long-lasting effects of developmental treatments on body size after four months of rearing under common conditions. Fish developed at low salinity or temperature were larger than fish developed at high temperature or salinity, but there was no interaction between the two factors. These data highlight the complex nature of the developmental effects of interacting stressors which has important implications for predicting the resilience of fishes in the context of climate change.

Ecological debts induced by heat extremes

Heat extremes have become the new norm in the Anthropocene. Their potential to trigger major ecological responses is widely acknowledged, but their unprecedented severity hinders our ability to predict the magnitude of such responses, both during and after extreme heat events. To address this challenge we propose a conceptual framework inspired by the core concepts of ecological stability and thermal biology to depict how responses of populations and communities accumulate at three response stages (exposure, resistance, and recovery). Biological mechanisms mitigating responses at a given stage incur associated costs that only become apparent at other response stages; these are known as 'ecological debts'. We outline several scenarios for how ecological responses associate with debts to better understand biodiversity changes caused by heat extremes.

A global dataset of salmonid biomass in streams

Salmonid fishes are arguably one of the most studied fish taxa on Earth, but little is known about their biomass range in many parts of the world. We created a dataset of estimated salmonid biomass using published material of over 1000 rivers, covering 27 countries and 11 species. The dataset, spanning 84 years of data, is the largest known compilation of published studies on salmonid biomass in streams, allowing detailed analyses of differences in biomass by species, region, period, and sampling techniques. Production is also recorded for 194 rivers, allowing further analyses and relationships between biomass and production to be explored. There is scope to expand the list of variables in the dataset, which would be useful to the scientific community as it would enable models to be developed to predict salmonid biomass and production, among many other analyses.

The potential impacts of exploitation on the ecological roles of fish species targeted by fisheries: A multifunctional perspective

Examining ecosystem functioning through the lens of trait diversity serves as a valuable proxy. It offers crucial insights into how exploitation affects the specific ecological roles played by fisheries targeted species. The present study investigates the potential impacts of exploitation on the ecological roles of fish species targeted by fisheries through an examination of trait diversity. It focuses on the trait diversity of fish landed by local and coastal fleets in the Azores archipelago over the past four decades. Fourteen functional traits were merged to data on fish assemblages landed by both fishing fleets from 1980 to 2020. These traits corresponded to four fundamental fish functions: habitat use, locomotion, feeding and life history. Variability in functional diversity metrics (i.e., functional richness- FRic, functional evenness- FEve, functional divergence-FDiv, and functional dispersion- FDis) among fleets, functions and across decades was assessed using null models. The results revealed similar trait diversity between assemblages landed by local and coastal fishing fleets with overall trait diversity remaining relatively stable over time. However, fishery activities targeted a wide range of functional traits. Additionally, seasonal availability and increased catches of certain fish species can significantly alter trait diversity and their associated functions. The findings highlight the importance of addressing fishing impacts on species traits and their ecological roles, which is crucial for long-term fisheries and ecological sustainability.

The LTAR Croplands Common Experiment at Upper Mississippi River Basin-Ames

Agricultural systems evolve from the interactions of climate, crops, soils, management practices (e.g., tillage, cover crops, nutrient management), and economic risks and rewards. Alternatives to the corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] (C-S) cropping systems that dominate in the US Midwest may provide more sustainable use of resources, reduce the documented environmental impacts of current C-S systems, and improve production efficiency and ecosystem services. Innovative management practices are needed to offer producers options to increase farm resilience to variable weather conditions and offset negative environmental impacts. In response to this need, the Upper Mississippi River Basin Long-Term Agroecosystem Research network site at Ames, IA, established a cropland experiment in 2016 to investigate an alternative crop management system that includes reduced tillage, cover crops, and right source, right rate, right time, and right place (4R) nitrogen (N) management. The experimental site is located on the Iowa State University Kelley Research Farm in Boone County, IA. Crop, soil, air, and tile drainage water measurements are made throughout the year using published methods for each agronomic and environmental metric. Our goal is to provide quantitative information to farmers, consultants, agribusiness partners, and state and federal agencies to help guide decisions on the effective use of alternative management practices. Future changes in experimental treatments will adopt a knowledge co-production approach whereby researchers and stakeholders will work collaboratively to identify problems, implement research protocols, and interpret results.

Spatially variable organic-matter-driven clogging in a stormwater infiltration pond: Isotopic, microbiological and hydrogeological evidence

Stormwater infiltration ponds (SIPs) are nature-based solutions which tend to decrease their infiltration capacity over time due to pore clogging. Organic matter (OM) is a well-known clogging driver, but how OM affects the physical and biochemical processes in a SIP remains largely unknown. An analysis encompassing soil organic carbon (SOC) stable isotopes, extracellular polymeric substances (EPS) of biofilms, DNA-based identification of microbiological communities and hydrogeological tests was carried out to elucidate the main clogging mechanisms in a large SIP in Italy. Open pits revealed a stratified soil composed of different textures and compositions, associated with artificial recharge sequences and on-site maintenance practices. A very different isotopic and microbiological signature of soil samples collected at different depths within the first meter of the soil surface was observed. Such diversity was linked to the spatially variable permeability of OM-enriched sediments limiting the infiltration. The isotopic signature beneath the more permeable (i.e., less clogged) OM-enriched layers was similar to that of the isotopic value of the biological surficial crust (δ13C → -27 ‰). Below the less permeable (i.e., more clogged) OM-enriched layers, isotopic values were more consistent with advanced degradation of organic matter (δ13C → -23 ‰). The selective hydraulic isolation of the analyzed trenches could lead to the formation of microbial microenvironments, with direct consequences on local composition of EPS and biofilm production. Based on this multidisciplinary approach, a new conceptual model could be proposed to the site managers and authorities dealing with the SIP's maintenance.

On the structure of species-function participation in multilayer ecological networks

Understanding how biotic interactions shape ecosystems and impact their functioning, resilience and biodiversity has been a sustained research priority in ecology. Yet, traditional assessments of ecological complexity typically focus on species-species interactions that mediate a particular function (e.g., pollination), overlooking both the synergistic effect that multiple functions might develop as well as the resulting species-function participation patterns that emerge in ecosystems that harbor multiple ecological functions. Here we propose a mathematical framework that integrates various types of biotic interactions observed between different species. Its application to recently collected data of an islet ecosystem-reporting 1537 interactions between 691 plants, animals and fungi across six different functions (pollination, herbivory, seed dispersal, decomposition, nutrient uptake, and fungal pathogenicity)-unveils a non-random, nested structure in the way plant species participate across different functions. The framework further allows us to identify a ranking of species and functions, where woody shrubs and fungal decomposition emerge as keystone actors whose removal have a larger-than-random effect on secondary extinctions. The dual insight-from species and functional perspectives-offered by the framework opens the door to a richer quantification of ecosystem complexity and to better calibrate the influence of multifunctionality on ecosystem functioning and biodiversity.

An improved dynamic metabolic model for application to biota

Any major nuclear facility must ensure the conservation of biodiversity regarding radiation protection of biota. A special concern is for tritium (3H) and radiocarbon (14C) transfer in wild mammals, birds and reptiles. Hydrogen and carbon are the main components of biological tissues and enter the life cycle. The present study improves the scientific bases of a previous model, analyses the uncertainty of input parameters and tests the model for a larger range of mammals and birds. The biological and metabolic half-times for organically bound tritium (OBT) and 14C are linked with energy metabolism and recent results are revised in relation with metabolic scaling. A large data base regarding basal metabolic rate (BMR), field metabolic rate (FMR), and organ mass is used for input information of the present model, which considers brain as a separate compartment. Metabolic energy partition in organs of active animal is defined and the factors affecting the metabolic rate are analysed. Body and ambient temperature, diet and habitat, and phylogeny are important factors considered in animal adaptation to environment. The available experimental data for carbon turnover rates in animals are analysed and it is observed that the experimental conditions are not appropriate for wild animals. The link between 13,14C and 134,137Cs turnover rate is analysed and the present metabolic approach is successfully tested for mammals and reptiles. Considering animal adaptation and the large data base for 134,137Cs, the radiological impact of accidental releases of 3H and 14C on biota can be pursued in the future research.

Mapping intertidal microphytobenthic biomass with very high-resolution remote sensing imagery in an estuarine system

Microphytobenthos (MPB) contributes significantly to estuarine primary production, so that quantifying its biomass is crucial for assessing their ecosystem functioning. Conventional sampling methods are labour-intensive, logistically challenging, and cannot provide a comprehensive spatial distribution map of MPB biomass. Satellite imagery has offered a feasible alternative for mapping large areas at various temporal and spatial resolutions. However, no imaging device with a spatial resolution consistent with the few square centimetres sampled in-situ has been used in the field. This makes it challenging to accurately relate field biomass measurements with remotely sensed radiometric observations. In this study, two similar multispectral sensors were mounted on an unmanned aerial vehicle (UAV) at different altitudes, as well as on a custom-built device specifically designed to acquire images at ∼1 m altitude, in order to collect very-high spatial resolution reflectance data of MPB biofilms at the Guadalquivir Estuary (Spain) mudflats. In addition, a hyperspectral spectroradiometer acquiring in-situ field reflectance was used for validation. Simultaneously, MPB samples were collected using a 2 mm depth contact corer method, which were analysed through high-performance liquid chromatography (HPLC) to measure the concentrations of major MPB pigments. To assess the relationship between the MPB pigments and different reflectance-based spectral indices, generalised linear mixed effects models (GLMMs) were used, achieving a significant positive relationship between chlorophylls and all spectral indices tested. These models were used to map microphytobenthic biomass, yielding a mean biomass in the range of 30-50 mg Chl-a m-2 in the Guadalquivir estuary during late winter. This study demonstrates the potential of low-altitude/high spatial resolution radiometric imaging as an efficient, rapid, and non-destructive addition to in-situ measurements of MPB biomass, providing exciting perspectives for the monitoring of estuarine systems on a millimetric scale of variability.

Weighing the risks and benefits of flowering early in the spring for the woody perennial Prunus pumila

PREMISE

There are advantages to flowering early in the spring, including greater pollinator fidelity and longer fruit maturation time. But plant phenology has advanced in recent years, making many plants vulnerable to freezing damage from late frosts.

METHODS

To determine the costs and benefits of flowering early in the growing season, we exposed Prunus pumila plants to two freezing treatments and a delayed flowering treatment in subsequent years. Data were collected on ovary swelling, fruit production, and pollinator visitation on hand- and open-pollinated plants in all treatments. We also measured tissue damage after freeze events.

RESULTS

Our results suggest that flowering time and temperature affect reproductive success, with fewer fruits produced after hard freezes. The same was not true for light freezes, which had minimal impact on reproduction. Freezing damage to plants after a hard freeze did affect the number of dipteran pollinators but not the overall pollinator visitation rate. Despite the clear impact of freezing temperatures on plant reproduction, flowering early provided an advantage in that reproductive output decreased with delayed flowering.

CONCLUSIONS

Our findings suggest that Prunus pumila will retain the ability to attract pollinators and produce viable seeds if exposed to false spring conditions that involve a light freeze, but hard freezes may reduce yield by an order of magnitude. Although the advantages to flowering early may outweigh the risk of freezing damage under current conditions, it is possible that flower viability may be constrained under continued climate warming.

Density-Dependent Mortality of the Diving Beetle, Rhantus elevatus (Dytiscidae: Coleoptera) Preyed Upon Culex pipiens Larvae: Effects of Prey and Predator Densities

Diving beetles (Coleoptera: Dytiscidae) are general predators that feed primarily on mosquito larvae and can control their populations, but the evidence for such an assumption remains weak. Rhantus elevatus is an important predator of this group distributed in Egypt with both larval and adult stages preying on immature mosquito. For determine predator effectiveness, it is requisite to identify the functional response (a = rate of attack and Th = time of handling) and searching efficacy (at = area of discovery and m = mutual interference) as both correlate with biocontrol efficacy. This study assessed the density-dependent mortality of Culex pipiens larvae by eliciting functional responses of third-instar and adult predators at prey density ranging from 100 to 500 larvae per arena. By contrast, a searching efficacy for the same predator stages was examined at densities ranging from one to five predators per 500 prey. Predation rates of third-instar and adult of R. elevatus were fitted by a model of Type II response with coefficients were: third-instar (a = 0.208 h-1 and Th = 2413 h) and adult (a = 0.1191 h-1 and Th = 3723 h). The maximum number of mosquitoes which can be devoured by an individual larva and adult of R. elevatus within 24 h was 99.46 and 64.46 prey, respectively. The area of discovery for the larval stage declined more steeply than the adult stage of the predator as their density increased from one to five individuals, indicating more interference estimated for the larval stage. Considering these characteristics, larvae would seem to be the most effective stage against low mosquito populations due to low predation risk compared to that generated at high predator densities in the same arena from intra-specific interference. Eventually, we suggested a ratio of 1:100 (predator per prey) must be considered in biocontrol plans for mosquitoes.

Conversion of Rice Field Ecosystems from Conventional to Ecological Farming: Effects on Pesticide Fate, Ecotoxicity and Soil Properties

Rice is an important staple food around the world, the cultivation as sustainable agriculture and food supply are key to achieving the Sustainable Development Goals (SDGs) of 2030. In order to analyze the sustainability of the rice paddy ecosystem, a comparative study was carried out during the rice growing season between paddies with conventional agriculture (CA) and ecological agriculture (EA), integrating analysis of physico-chemical characteristics of soil and soil pore water, pesticide residues, acute toxic effects and potential ecological risk, as well as aquatic invertebrate community structure dynamics. Our study found that total carbon and nitrogen present in soil were significantly higher in CA than in EA, while opposite results were found in soil pore water, implying the improvement on soil properties in EA. Neonicotinoid pesticides (thiamethoxam and thiacloprid) were still detected in EA, although no pesticides were applied after conversing CA to EA. Additionally, toxic effects to zebrafish embryos with a peak toxicity in summer (July, LC50 = 55.26 mg soil equivalent/L) were also found in EA, which was lower than in CA. The dynamics of the aquatic invertebrate community structure were correlated with the toxicity results, with higher diversity recorded in EA. Therefore, for the purpose of ecosystem sustainability, the long-term implementation of EA is highly recommended.

Larval growth rate is not a major determinant of adult wing shape and eyespot size in the seasonally polyphenic butterfly Melanitis leda

Background

Insects often show adaptive phenotypic plasticity where environmental cues during early stages are used to produce a phenotype that matches the environment experienced by adults. Many tropical satyrine butterflies (Nymphalidae: Satyrinae) are seasonally polyphenic and produce distinct wet- and dry-season form adults, providing tight environment-phenotype matching in seasonal environments. In studied Mycalesina butterflies, dry-season forms can be induced in the laboratory by growing larvae at low temperatures or on poor food quality. Since both these factors also tend to reduce larval growth rate, larval growth rate may be an internal cue that translates the environmental cues into the expression of phenotypes. If this is the case, we predict that slower-growing larvae would be more likely to develop a dry-season phenotype.

Methods

We performed the first experimental study on seasonal polyphenism of a butterfly in the tribe Melanitini. We measured both larval growth rate and adult phenotype (eyespot size and wing shape) of common evening brown butterflies (Melanitis leda), reared at various temperatures and on various host-plant species. We constructed provisional reaction norms, and tested the hypothesis that growth rate mediates between external cues and adult phenotype.

Results

Reaction norms were similar to those found in Mycalesina butterflies. We found that both among and within treatments, larvae with lower growth rates (low temperature, particular host plants) were more likely to develop dry-season phenotypes (small eyespots, falcate wing tips). However, among temperature treatments, similar growth rates could lead to very different wing phenotypes, and within treatments the relationships were weak. Moreover, males and females responded differently, and eyespot size and wing shape were not strongly correlated with each other. Overall, larval growth rate seems to be weakly related to eyespot size and wing shape, indicating that seasonal plasticity in M. leda is primarily mediated by other mechanisms.

Improvement of water quality through coordinated multi-trophic level biomanipulations: Application to a subtropical emergency water supply lake

Artificial emergency water source lakes have been built in most cities in the middle and lower reaches of the Yangtze River, China, to ensure water safety for residents. However, these new ecosystems are prone to algal blooms or other degraded water quality conditions. A newly built water supply lake in the lower reaches of the Yangtze River was selected as a model system to test whether the coordinated manipulation of fish and submerged macrophyte communities could enhance ecosystem function and quality. The coordinated manipulations spanned a five-year period, aiming to enhance both top-down and bottom-up control of phytoplankton. As a result of these manipulations, the catch per unit effort of small-bodied zooplanktivorous fishes decreased by >95 % from year two and remained low. The coverage and biomass of submerged macrophytes increased year by year. Water transparency increased from 1.07 to 3.33 m. Total phosphorus and total nitrogen showed a decreasing trend (not significant though). The annual mean biomass of Cyanophyta, Chlorophyta and Bacillariophyta decreased from 2.99 to 0.03 mg/L, 3.90 to 0.16 mg/L, and 3.50 to 0.3 mg/L, respectively. The biomass of phytoplankton in different groups decreased in all four seasons. The annual mean biomass of Cladocera and Copepoda remained low. The biomass of Cladocera and Copepoda decreased in summer, fall, and winter. The Ecosystem Health Index - increased from 15.9 to 32.0. The pros and cons of the various top-down and bottom-up control measures employed are discussed. This research presents a valuable case study on the enhancement of ecosystem structure and function in newly constructed emergency water supply lakes and offers insights into the restoration of other subtropical shallow lakes.

Campoe O, Deshar R, Franklin O, Henriksson N, Littke K, Lutter R, Maier CA, Palmroth S, Rosenvald K, Slesak RA, Tullus A, Oren R. Overlooked branch turnover creates a widespread bias in forest carbon accounting

Most measurements and models of forest carbon cycling neglect the carbon flux associated with the turnover of branch biomass, a physiological process quantified for other organs (fine roots, leaves, and stems). Synthesizing data from boreal, temperate, and tropical forests (184,815 trees), we found that including branch turnover increased empirical estimates of aboveground wood production by 16% (equivalent to 1.9 Pg Cy-1 globally), of similar magnitude to the observed global forest carbon sinks. In addition, reallocating carbon to branch turnover in model simulations reduced stem wood biomass, a long-lasting carbon storage, by 7 to 17%. This prevailing neglect of branch turnover suggests widespread biases in carbon flux estimates across global datasets and model simulations. Branch litterfall, sometimes used as a proxy for branch turnover, ignores carbon lost from attached dead branches, underestimating branch C turnover by 38% in a pine forest. Modifications to field measurement protocols and existing models are needed to allow a more realistic partitioning of wood production and forest carbon storage.

Increased adult movements and decreased juvenile apparent survival of urban crows during COVID-19 lockdowns

The increasing abundance of animal species thriving in urban environments is a source of conflicts with managers and users of public spaces. Although opportunistic urban species often use resources originating from human food leftovers, the potential impact of a reduction in these resources on their demography is hard to quantify. The COVID-19 epidemic, which led many countries to set up lockdowns, gave us the opportunity to estimate the impact of a drastic reduction in such food resources and human activities on the demography of an urban bird population. Based on 7 years (2015-2021) of capture-mark-recapture of carrion crows (Corvus corone) in the city of Paris, France, we used multi-state models to examine the intra-annual (3-month time steps) apparent survival and movement patterns of crows during and outside COVID-19 lockdowns. We showed that the apparent survival of juvenile carrion crows decreased down during lockdown, while adult movements increased during this period, with more adult crows moving out of the urban district. Lockdown modified the demography of this urban crow population, suggesting that the reduction in food resources was sufficient to affect fitness and reduce carrying capacity.

Direct and indirect effects of chemical pollution: Fungicides alter growth, feeding, and pigmentation of the freshwater detritivore Asellus aquaticus

Anthropogenic chemical pollutants, such as fungicides, pose significant threats to natural ecosystems. Although the direct impacts of numerous chemicals are well-documented in simple environmental contexts, their indirect impacts are poorly understood. This study used two individual level laboratory experiments to assess direct and indirect effects of fungicides on the isopod Asellus aquaticus, a keystone detritivore in freshwater systems. First, a range-finding assay on three widely used fungicides (Fluazinam, Tebuconazole, Urea) showed that Tebuconazole had the strongest concentration-dependent negative effects on A. aquaticus growth and food consumption. Second, a factorial experiment using Tebuconazole assessed its direct and diet-mediated effects and showed that Tebuconazole reduced growth, feeding, and pigmentation through both pathways. The results indicate that assessing only direct impacts of toxic chemicals could overlook critical interactions that are relevant in natural systems, such as those associated with diet. Our study highlights the importance of considering both direct and indirect effects in environmental toxicology to better understand the full impacts of chemical pollutants in nature.

The impacts of diet on cardiac performance under changing environments

Natural and anthropogenic stressors are dramatically altering environments, impacting key animal physiological traits, including cardiac performance. Animals require energy and nutrients from their diet to support cardiac performance and plasticity; however, the nutritional landscape is changing in response to environmental perturbations. Diet quantity, quality and options vary in space and time across heterogeneous environments, over the lifetime of an organism and in response to environmental stressors. Variation in dietary energy and nutrients (e.g. lipids, amino acids, vitamins, minerals) impact the heart's structure and performance, and thus whole-animal resilience to environmental change. Notably, many animals can alter their diet in response to environmental cues, depending on the context. Yet, most studies feed animals ad libitum using a fixed diet, thus underestimating the role of food in impacting cardiac performance and resilience. By applying an ecological lens to the study of cardiac plasticity, this Commentary aims to further our understanding of cardiac function in the context of environmental change.

Effects of Pirimiphos-Methyl on Non-Target Invertebrates

The effects of pirimiphos-methyl have previously been assessed on blood-sucking insect species, pollinating insects, and target crop pest species. The sensitivity of non-target zoophagous and saprophage species to this insecticide remains largely unstudied. In laboratory conditions, we assessed the susceptibility of 43 species of invertebrates to pirimiphos-methyl. The most tolerant species to this insecticide were Pyrrhocoris apterus (LC50 measured over 60 mg/m2), Cylindroiulus truncorum, Pterostichus niger, Harpalus rufipes, Lithobius forficatus, and Carabus hortensis (LC50 ranged from 25 to 50 mg/m2). Average tolerance to pirimiphos-methyl was displayed by Ophonus rufibarbis, Teuchestes fossor, Silpha carinata, Badister sodalis, Rugilus rufipes, Phosphuga atrata, Porcellio laevis, Pterostichus oblongopunctatus, Aphodius foetens, Lasius fuliginosus, Oxypselaphus obscurus, Platydracus fulvipes, Myrmica ruginodis, Xantholinus tricolor, and Megaphyllum sp. (LC50 for those species ranged from 12 to 24 mg/m2). Higher sensitivity to this insecticide was seen for Amara nitida, Leistus ferrugineus, Harpalus xanthopus winkleri, Philonthus nitidus, Pterostichus melanarius, Harpalus latus, Limodromus assimilis, Philonthus decorus, Tachinus signatus, Ponera coarctata, Carabus convexus, Philonthus coprophilus, Philonthus laevicollis, Platydracus latebricola, Labia minor, and Carabus granulatus (LC50 for those species ranged from 6 to 12 mg/m2). The greatest sensitivity to pirimiphos-methyl was observed in Hister fenestus, Drusilla canaliculata, Bisnius fimetarius, Oxytelus sculptus, Lasius niger, and Lasius flavus (LC50 ranged from 0.4 to 6 mg/m2). We found a relationship between the parameters of bodies of invertebrates (the average body length and dry body mass) and sensitivity to pirimiphos-methyl. With an increase in body sizes of invertebrates, the tolerance to the insecticide increased (per each mm of body length, LC50 increased by 0.82 mg/m2 on average). We identified no relationship between the trophic specialization and sensitivity to the insecticide.

Effects of High-Temperature Stress on Biological Characteristics of Coccophagus japonicus Compere

The parasitoid, Coccophagus japonicus Compere (Hymenoptera: Aphelinidae) is a dominant natural enemy of Parasaissetia nigra Nietner (Hemiptera: Coccidae), an important pest of rubber trees. Much of Chinese rubber is cultivated in hotter regions such as Yunnan and Hainan, exposing applied parasitoids to non-optimal temperatures. Therefore, C. japonicus must adapt to avoid temperature-related impacts on survival and population expansion. In this study, we monitored the survival rate, developmental duration, parasitism rate, and fecundity of C. japonicus during short-term exposures to 36 °C, 38 °C, and 40 °C for 2, 4, and 6 h, as well as continuous exposures to 32 °C and 34 °C for 3 days. The results show that short-term exposure to high-temperature stress leads to decreased survival rate of C. japonicus larvae and pupae, with survival rates declining as temperature and duration increase. High-temperature stress also delayed insect development, reduced mature egg production, shortened the body length of newly emerged females, and decreased female lifespans. Moreover, continuous high-temperature stress was found to significantly impact the development and reproduction of C. japonicus. Compared with the CK (27 °C), 3 d of continuous exposure to 34 °C prolonged developmental duration, shortened the body length and lifespan of newly emerged females, reduced survival rate and single female fecundity, and significantly decreased offspring numbers and parasitism rates. Temperatures of 36 °C, 38 °C, and 40 °C decreased the mortality time of adult females to 28.78, 16.04, and 7.91 h, respectively. Adverse temperatures also affected the insects' functional response, with 8 h of stress at 36 °C, 38 °C, and 40 °C causing the control efficiency of C. japonicus on P. nigra. This level of stress in the parasitoids was found to reduce the immediate attack rate and search effect, prolong processing time, and attenuate interference between small prey. Parasitoid efficiency was lowest following exposure to 40 °C. In this study, we determined the range of high temperatures that C. japonicus populations can tolerate under short- or long-term stress, providing guidance for future field applications.

Phenotypical aspects of Culex pipiens biotype pipiens during diapause: Lipid utilization, body size, insemination, and parity

In temperate regions, female Culex pipiens biotype pipiens mosquitoes undergo diapause in winter. Diapausing biotype pipiens mosquitoes are potentially important winter reservoirs for mosquito-borne viruses, such as West Nile virus (WNV), Usutu virus (USUV), and Sindbis virus (SINV). Mosquitoes in diapause have not taken a bloodmeal prior to winter. Therefore, they do not become infected by taking an infectious bloodmeal and as a consequence, vertical transmission is considered the primary mechanism of mosquito-borne virus overwintering. Prior to winter, biotype pipiens mosquitoes build up fat reserves, which they utilize throughout winter. Furthermore, earlier studies have indicated that larger body size is correlated with increased survival during winter. However, not much is known about lipid utilization and body size of wild biotype pipiens mosquitoes in diapause. Therefore, we performed monthly collections of diapausing biotype pipiens mosquitoes in two consecutive winters (2020/2021 and 2021/2022) in bunkers of the New Hollandic Waterline in the Netherlands. Every month, we checked the proportion of inseminated and parous females via microscopy. In addition, we measured wing length as proxy for body size, and assessed total lipid content. Furthermore, we monitored indoor temperature in the overwintering locations. We show that the overwintering sites in our study provide relatively stable environments, in which temperatures rarely drop below 0 °C. The vast majority of biotype pipiens females were inseminated (84.1 %) and nulliparous (97.5 %). We detected differences in body size between but not within the two years of sampling. Additionally, we detected a difference in lipid content between the sampling years. We confirm that the vast majority of diapausing biotype pipiens females are inseminated and nulliparous. This indicates that they did not blood feed prior to winter, which underscores the likeliness of vertical transmission being the primary mechanism behind virus overwintering. The detected difference in body size between years can most likely be attributed to differences in summer conditions the mosquitoes were exposed to as larvae, although this needs confirmation. The difference in lipid depletion could not be explained by differences in climatic conditions. To shed more light on the links between climatic conditions, body size, lipid depletion and the consequences for mosquito population dynamics and arbovirus transmission, future experimental work, for example by arbovirus exposure followed by artificially induced diapause, is desired.

Conserved responses of water use to evaporative demand in mixed forest across seasons in low subtropical China

The positive correlation between diversity and production has been extensively documented. Given the intrinsic relationship between production and plant water consumption, it was anticipated that mixed forests would exhibit different water use compared to pure forests. In this study, the responses of water use to vapour pressure deficit were analyzed by monitoring the sap flow of Schima superba in both pure and mixed forests, as well as Castanopsis chinensis in mixed forest. Additionally, the relationships among leaf and stem traits were examined by measuring specific leaf area (SLA), N and P concentration per unit leaf mass, leaf δ18O and δ13C and wood density of sapwood (WD) during both wet and dry seasons. The results showed that S. superba demonstrated a comparable regulation of water use during both wet and dry seasons in mixed forest, whereas it exhibited less strict water use regulation during the wet season in comparison to the dry season in pure forest. Regardless of whether the forests were pure or mixed, both leaf δ13C and WD remained consistent across seasons, while there was an increase in SLA during the wet season compared to the dry season for S. superba. There was a different seasonal change in leaf δ18O for S. superba in pure and mixed forests. Water use and leaf economic spectrum may determine the adaptive strategies of coexisting species, and the coexisting tree species in mixed forest exhibited a resource-use differentiation, as indicated by seasonal variations in leaf and stem traits, likely explaining the conserved responses of sap flow to evaporative demand. Our research might provide insights into the impact of tree interaction on water use strategies and the water use-based forest management under current climate change.

Factors shaping pelagic-benthic coupling in the process of settlement in an Arctic fjord

Benthic organisms typically possess a planktonic propagule stage in the form of larvae or spores, which enables them to spread over large distances before settlement, and promotes tight pelago-benthic coupling. However, factors driving dispersal and epibenthos recruitment in shallow hard-bottom Arctic communities are poorly known. We therefore conducted a year-round in situ colonization experiment in Isfjorden (Svalbard), and found out that variation in early-stage epibenthic assemblages was explained by the combination of: abiotic (45.9%) and biotic variables (23.9%), and their interactions (30.2%). The upward-facing experimental plates were dominated by coralline algae, and this is the first study showing that at high latitudes coralline algae Lithothamnion sp. settle in high numbers on available substrates during the polar night in winter. The downward-facing plates, which had much less exposure to light, contained more diverse organisms, with a predominance of polychaetas and bryozoans. However, in summer, the barnacle Semibalanus balanoides outcompeted all the other recruits, as a result of massive occurrence of meroplanktonic Cirripedia larvae, triggered by the phytoplankton bloom. In conclusion, the rate and success of epibenthic settlements were dependent mostly on light availability and temperature, suggesting that larval settlement will be impacted by global warming with some taxa benefitting, while others losing.

A global meta-analysis reveals a consistent reduction of soil fauna abundance and richness as a consequence of land use conversion

Land use conversion of natural to production systems is one of the most important threats to belowground communities and to the key ecosystem processes in which they are involved. Available literature shows positive, negative, and neutral effects of land use changes on soil fauna communities; and these varying effects may be due to different characteristics of natural and production systems and soil organisms. We hypothesize that land conversion from high to low plant biomass, diversity, and structural complexity systems may have the most negative impacts on soil fauna. Here, we performed the first meta-analysis evaluating the overall effects of land use conversion on soil invertebrate communities and the influence of factors related to characteristics of natural and production systems, of soil fauna communities and methods. We compiled a dataset of 260 publications that yielded 1732 observations for soil fauna abundance and 459 for richness. Both abundance and richness showed a global decline as a consequence of natural land conversion to production systems. These negative effects were stronger, in general, when the conversion occurred in tropical and subtropical sites, and when natural systems were replaced by croplands, pastures and grazing systems. The effects of land use conversion also depended on soil property changes. In addition, the abundance of most taxa and richness of Acari and Collembola were strongly reduced by land use changes while Annelida were not affected. The highest reduction in abundance was recorded in omnivores and predators, whereas detritivores showed a reduction in richness. Our meta-analysis shows consistent evidence of soil biodiversity decline due to different land use changes and the partial dependence of those effects on the magnitude of changes in vegetation. These findings stress the need to continue developing production modes that effectively preserve soil biodiversity and ecosystem processes, without hampering food production.