Levels Of Environmental Stress Research Articles

Cadmium-induced hormesis effect in medicinal herbs improves the efficiency of safe utilization for low cadmium-contaminated farmland soil

Compared to other soil remediation technologies, Cd-contaminated farmland soil with low cadmium accumulation (LCA) plant-based safe utilization is more catered to developing countries with food in high demand. Hormesis, which describes the fortification of plant growth performance by a low level of environmental stress, can be innovatively used to achieve increases in crop yield and plant functional components, thus amplifying the safe utilization efficiency of low Cd-contaminated soil by LCA plants. In the present study, the growth and physiological responses of Polygonatum sibiricum, a traditional Chinese medicinal herb, were investigated under laboratory conditions of gradient Cd dosage concentrations and times. As a result, the growth performance of P. sibiricum reached the peak of an inverse U-shaped curve of hormesis under e0 mg kg−1 and 9 months of Cd stress, with elevations in tuber biomass (medicinal part), plant height and polysaccharide content (medicinal components) of 143%, 25% and 90%, respectively. Meanwhile, trace Cd accumulation (0.41 mg kg−1) in the tuber guaranteed medicinal edible safety. In addition, Cd-induced hormesis in P. sibiricum was verified to be overcompensated by antioxidation systems. In conclusion, such ‘win-win’ results, including low Cd accumulation and enhancement of plant pharmaceutical value, provided medicinal herbs with a possibility for safe soil utilization.

Effects on Heart Rate Variability of Stress Level Responses to the Properties of Indoor Environmental Colors: A Preliminary Study.

Color is the most potent stimulating factor affecting human vision, and the environmental color of an indoor space is a spatial component that affects the environmental stress level. As one of the methods of assessing the physiological response of the autonomic nervous system that influences stress, heart rate variability (HRV) has been utilized as a tool for measuring the user’s stress response in color environments. This study aims to identify the effects of the changes of hue, brightness, and saturation in environmental colors on the HRV of two groups with different stress levels—the stress potential group (n = 15) and the healthy group (n = 12)—based on their stress level indicated by the Psychosocial Well-being Index (PWI). The ln(LF), ln(HF), and RMSSD values collected during the subjects’ exposure to 12 environments colors of red and yellow with adjusted saturation and brightness, were statistically analyzed using t-test and two-way ANOVA. The results show that the HRV values in the two groups did not significantly vary in response to the changes in hue, brightness and saturation. The two groups’ stress factors distinguished according to the stress levels by the PWI scale affected the In(LF) parameter, which demonstrates that the PWI index can be utilized as a reliable scale for measuring stress levels. The ultra-short HRV measurement record and the use of a sole In(LF) parameter for stress assessment are regarded as the limitations of this study.

Токсичні моделі паркінсонізму: історія та перспективи

The review article presents data on the history of research of extrapyramidal system dysfunctions, modern ideas about the etiology and diagnosis of Parkinson's disease, as the most common disease of the group of extrapyramidal disorders. Currently, no concept of effective therapy for patients with extrapyramidal system dysfunction has been developed, but it has been proven that the probability of developing the disease largely depends on the genetic predisposition and the level of environmental pollution. In the early stages, the disease is slow and asymptomatic, but gradually more than half of patients with Parkinson's disease die, and others need outside care. According to experts, in the near future, Parkinson's disease will become a problem for a significant part of people, because today it affects more and more people of working age. Under such conditions, reliable and early diagnosis of the disease is of great importance, which guarantees timely and most effective treatment. Modern therapies fail to stop the progressive death of the dopaminergic neurons of the substantia nigra, but traditional treatment can achieve symptomatic relief. Currently, it is known that the probability of developing Parkinson's disease depends on the genetic predisposition and the level of man-made environmental stress. The researchers consider that the pathological development of Parkinson's disease in the brain begins in the lower structures of the brain stem with the involvement of the caudal-Rostral nuclei, as well as the involvement of the cortico-basal ganglia-cerebellar pathways. The pathological process affects the ascending pathways and gradually passes to the midbrain, directly to the black substance, spreads from there and weakens the mesocortex and neocortex. Injuries in the brain stem lead to disorganization of the cortico-basal ganglia and cerebellar pathways, followed by the formation of alternative pathways to compensate for the initial disorders in the early stages of the disease. In addition, in Parkinson's disease, intracellular Lewy bodies and neurites formed by the protein alpha-synuclein are created, which are found in the autopsy material of most patients. Poor results of diagnostic evaluation and treatment of Parkinson's disease are usually associated with a lack of understanding of the pathogenesis of Parkinson's disease. The study of the biological basis and pathogenesis of Parkinson's disease is an important task of a whole complex of scientific studies of extrapyramidal system dysfunction. Conclusion. The article discusses the creation of toxic models of Parkinson's disease in vivo and in vitro, which help to recreate the pathogenesis of the disease for early diagnosis and the development of new ways to treat neurodegenerative diseases. In toxic models of Parkinsonism, not only deficits of motor functions such as bradykinesia, tremor, and posture disorders are actively studied, but also non-motor symptoms such as sleep disorders, neuropsychiatric and cognitive abnormalities

Disentangling the relative influence of regeneration processes on marsh plant assembly with a stage-structured plant assembly model

In salt marshes, abiotic factors, interspecific competition or facilitation, and herbivory have been discussed extensively as important drivers of marsh plant distribution patterns. However, the relative importance of various regeneration processes across stress gradients received little attention, despite their importance in explaining plant community dynamics. In this study, we built a stage-structured plant assembly model to study how the influence of each regeneration process on plant assembly dynamics varies with environmental stress level, plant succession stage and initial seed availability, in a salt marsh in Yellow River Delta National Nature Reserve in China. We found plant assembly at higher saline conditions is mainly governed by stress tolerance regardless of the stage of succession and initial seed availability, as salinity stress can suppress biomass accumulation and propagule production of salt intolerant species. Under less saline conditions with high seed availability, juvenile competition plays the most important role throughout succession. When initial seed availability is low, dispersal is more important at the beginning, but juvenile competition is more important at later stage and determines the plant competition outcomes. Our findings imply seed availability is important in determining plant succession trajectories under less stressful conditions, and should be given more attention during restoration management in coastal marshes.

Spatial and temporal scales of exposure and sensitivity drive mortality risk patterns across life stages

AbstractImpacts of increases in extreme heat events under climate change may differ across ontogeny for species with complex life cycles. Different life stages may (1) experience unequal levels of environmental stress that vary across space and time (exposure) and (2) have different stress tolerances (sensitivity). We used a field experiment to investigate whether exposure, sensitivity, and overall mortality risk differed between life stages of a marine foundation species (the mussel Mytilus californianus) across thermal conditions that vary in space (habitat, elevation, and site) and time (season) in southern California, USA. We deployed temperature loggers to document habitat‐specific exposure patterns, conducted laboratory thermal tolerance assays to calculate sensitivity, and performed field surveys to determine whether risk patterns were reflected in distributions. Exposure to extreme temperatures was highest in solitary habitats and during spring. Juvenile mussels were more sensitive to extreme heat than adults, and sensitivity for both life stages was highest in December and March. Risk was largely seasonal for juveniles but was more temporally variable for adults. Spatial occurrence patterns were congruent with risk assessments for both life stages (i.e., higher occurrence in lower risk habitats). These results highlight the importance of incorporating life stage and temporal dynamics when predicting impacts of climate change.

Quantifying the Evolutionary Constraints and Potential of Hepatitis C Virus NS5A Protein.

ABSTRACTRNA viruses, such as hepatitis C virus (HCV), influenza virus, and SARS-CoV-2, are notorious for their ability to evolve rapidly under selection in novel environments. It is known that the high mutation rate of RNA viruses can generate huge genetic diversity to facilitate viral adaptation. However, less attention has been paid to the underlying fitness landscape that represents the selection forces on viral genomes, especially under different selection conditions. Here, we systematically quantified the distribution of fitness effects of about 1,600 single amino acid substitutions in the drug-targeted region of NS5A protein of HCV. We found that the majority of nonsynonymous substitutions incur large fitness costs, suggesting that NS5A protein is highly optimized. The replication fitness of viruses is correlated with the pattern of sequence conservation in nature, and viral evolution is constrained by the need to maintain protein stability. We characterized the adaptive potential of HCV by subjecting the mutant viruses to selection by the antiviral drug daclatasvir at multiple concentrations. Both the relative fitness values and the number of beneficial mutations were found to increase with the increasing concentrations of daclatasvir. The changes in the spectrum of beneficial mutations in NS5A protein can be explained by a pharmacodynamics model describing viral fitness as a function of drug concentration. Overall, our results show that the distribution of fitness effects of mutations is modulated by both the constraints on the biophysical properties of proteins (i.e., selection pressure for protein stability) and the level of environmental stress (i.e., selection pressure for drug resistance).IMPORTANCE Many viruses adapt rapidly to novel selection pressures, such as antiviral drugs. Understanding how pathogens evolve under drug selection is critical for the success of antiviral therapy against human pathogens. By combining deep sequencing with selection experiments in cell culture, we have quantified the distribution of fitness effects of mutations in hepatitis C virus (HCV) NS5A protein. Our results indicate that the majority of single amino acid substitutions in NS5A protein incur large fitness costs. Simulation of protein stability suggests viral evolution is constrained by the need to maintain protein stability. By subjecting the mutant viruses to selection under an antiviral drug, we find that the adaptive potential of viral proteins in a novel environment is modulated by the level of environmental stress, which can be explained by a pharmacodynamics model. Our comprehensive characterization of the fitness landscapes of NS5A can potentially guide the design of effective strategies to limit viral evolution.

The expanding world of tRNA modifications and their disease relevance.

Transfer RNA (tRNA) is an adapter molecule that links a specific codon in mRNA with its corresponding amino acid during protein synthesis. tRNAs are enzymatically modified post-transcriptionally. A wide variety of tRNA modifications are found in the tRNA anticodon, which are crucial for precise codon recognition and reading frame maintenance, thereby ensuring accurate and efficient protein synthesis. In addition, tRNA-body regions are also frequently modified and thus stabilized in the cell. Over the past two decades, 16 novel tRNA modifications were discovered in various organisms, and the chemical space of tRNA modification continues to expand. Recent studies have revealed that tRNA modifications can be dynamically altered in response to levels of cellular metabolites and environmental stresses. Importantly, we now understand that deficiencies in tRNA modification can have pathological consequences, which are termed 'RNA modopathies'. Dysregulation of tRNA modification is involved in mitochondrial diseases, neurological disorders and cancer.

Driving factors and spatiotemporal effects of environmental stress in urban agglomeration: Evidence from the Beijing-Tianjin-Hebei region of China

Environmental stress is used as an indicator of the overall pressure on regional environmental systems caused by the output of various pollutants as a result of human activities. Based on the pollutant emissions and socioeconomic databases of the counties in Beijing—Tianjin—Hebei region, this paper comprehensively calculates the environmental stress index (ESI) for the urban agglomeration using the entropy weight method (EWM) at the county scale and analyzes the spatiotemporal patterns and the differences among the four types of major functional zones (MFZ) for the period 2012–2016. In addition, the socioeconomic driving forces of environmental stress are quantitatively estimated using the geographically weighted regression (GWR) method based on the STIRPAT model framework. The results show that: (1) The level of environmental stress in the Beijing-Tianjin-Hebei region was significantly alleviated during that time period, with a decrease in ESI of 54.68% by 2016. This decrease was most significant in Beijing, Tangshan, Tianjin, Shijiazhuang, and other central urban areas, as well as the Binhai New Area. The level of environmental stress in counties decreased gradually from the central urban areas to the suburban areas, and the high-level stress counties were eliminated by 2016. (2) The spatial spillover effect of environmental stress increased further at the county scale from 2012 to 2016, and spatial locking and path dependence emerged in the cities of Tangshan and Tianjin. (3) Urbanized zones (development-optimized and development-prioritized zones) were the major areas bearing environmental pollution in the Beijing-Tianjin-Hebei region in that time period. The ESI accounted for 65.98% of the whole region, where there was a need to focus on the prevention and control of environmental pollution. (4) The driving factors of environmental stress at the county scale included population size and the level of economic development. In addition, the technical capacity of environmental waste disposal, the intensity of agricultural production input, the intensity of territorial development, and the level of urbanization also had a certain degree of influence. (5) There was spatial heterogeneity in the effects of the various driving factors on the level of environmental stress. Thus, it was necessary to adopt differentiated environmental governance and reduction countermeasures in respect of emission sources, according to the intensity and spatiotemporal differences in the driving forces in order to improve the accuracy and adaptability of environmental collaborative control in the Beijing-Tianjin-Hebei region.

Stress-related coping styles, anxiety, and neuroticism in university students with myalgia temporomandibular: A case control study.

Los pacientes que sufren dolor debido a trastornos temporomandibulares (TTM) presentan mayores niveles de distrés psicológico, estrés ambiental, síntomas somáticos, ansiedad, depression, cogniciones de catastrofización, y otras estrategias de afrontamiento al dolor alteradas, comparados con personas libres de dolor. Sin embargo, poco se conoce acerca de los factores psicológicos involucrados en diferentes tipos de TTM. Además, independientemente de la gravedad o el tipo de TTM, el papel de los estilos y estrategias de afrontamiento al estrés en los TTM todavía no está claro. El principal objetivo de este trabajo es estudiar los estilos de afrontamiento al estrés, ansiedad y rasgos de personalidad en un grupo de estudiantes de odontología que sufren mialgia temporomandibular. Una muestra de 102 estudiantes universitarios fue incialmente reclutada para este estudio. Tras una evaluación clínica, se formaron un grupo de estudiantes con mialgia (24 participantes) y un grupo de estudiantes control (24 participantes). Los participantes de ambos grupos fueron posteriormente evaluados en ansiedad, estrategias de afrontamiento al estrés, y rasgos de personalidad. El grupo con myalgia mostró mayor rasgo de ansiedad y neuroticismo que el grupo control. Los participantes con myalgia también mostaron un mayor uso de estrategias de afrontamiento evitativas. Las estrategias evitativas generalmente se han considerado como desadaptativas, y se ha visto que incrementan el estrés percibido, un fuerte predictor de TTM.

Ergonomic risks and prevalence of musculoskeletal disorders among dental surgeons in Nigeria: A descriptive survey

Aim: To determine the prevalence of musculoskeletal disorders (MSDs) among dentists in Nigeria, where it is underreported, and to correlate these MSDs with occupational and stress-related ergonomic challenges. Materials and Methods: This descriptive study was conducted among randomly selected dentists in Nigeria. A modification of the validated Nordic questionnaire was utilized to determine the prevalence of MSDs. Paired t-tests and analysis of variance tests were used to determine statistical differences between numerical variables. The logistic regression analysis was used to confirm significant effect of predictor variables on work-related MSDs (WMSDs). Difference at the 5% level was accepted as significant. Results: Most of the participants were males (58.8%), aged between 26 and 30 years (37.2%), had 40 years [Exp β: 1.003; confidence interval (CI): 0.848–1.187; P = 0.020], body mass index: obese (Exp β: 1.079; CI: 0.733–1.589; P = 0.027), average time spent on each patient: >50 min (Exp β: 0.903; CI: 0.313–2.609; P = 0.049), having dental nurses in the clinic: >10 (Exp β: 0.959; CI: 0.410–2.243; P = 0.000), and a high level of environmental stress (Exp β: 1.092; CI: 0.862–1.384; P = 0.029) were significantly associated with MSDs. Conclusion: Our study showed that dentists who were older than 40 years, those who were obese, those who spent an average of 50 min on each patient, and those who had few dental nurses in the clinic and had a high level of environmental stress had a significantly higher prevalence of MSDs. Modifiable chairs, correct sitting postures by the dental surgeon and the patient, adequate lighting, use of indirect vision, use of magnification loupes, and sufficient rest and breaks at work could help to ameliorate these conditions.

Description Of The Development Of Children Age 4-5 Years In TK Pelangi

There are several factors that can affect children's development that is not fulfilled, namely, poverty, malnutrition, high levels of family and environmental stress that cause children to be exposed to violence, abuse, and lack of attention and learning opportunities. Children who do not have enough learning time or even do not have the same opportunity to learn can affect their motor development, for example, the brain damage that does not support children to develop motor skills. Lack of research that discusses the developmental picture in children aged 4-5 years, so researchers are interested in doing this research. The purpose of this study was to determine the development of children aged 4-5 years in Pelangi Kindergarten, Anrang Village, Bonto Masunggu Hamlet, Bulukumba Regency in 2020. The method used in this research is descriptive design, which aims to get a picture of the development of children aged 4-5 years in Kindergarten Pelangi, Anrang Village, Kec. Rilau Ale. The population in this study was 31 respondents and the sample size was 31 child respondents in Kindergarten Pelangi, Anrang Village, Kec. Rilau ale. The results obtained are that the researcher found the results of 31 respondents with the highest motor development results in accordance with the number of 21 respondents (67.7%), while with the lowest development there were deviations with respondent 3 (9.7%). The conclusion and suggestion are that there is a description of the development of children in Kindergarten Pelangi, Anrang Village, Kec. Rilau Ale

Primary cilia safeguard cortical neurons in neonatal mouse forebrain from environmental stress-induced dendritic degeneration

The developing brain is under the risk of exposure to a multitude of environmental stressors. While perinatal exposure to excessive levels of environmental stress is responsible for a wide spectrum of neurological and psychiatric conditions, the developing brain is equipped with intrinsic cell protection, the mechanisms of which remain unknown. Here we show, using neonatal mouse as a model system, that primary cilia, hair-like protrusions from the neuronal cell body, play an essential role in protecting immature neurons from the negative impacts of exposure to environmental stress. More specifically, we found that primary cilia prevent the degeneration of dendritic arbors upon exposure to alcohol and ketamine, two major cell stressors, by activating cilia-localized insulin-like growth factor 1 receptor and downstream Akt signaling. We also found that activation of this pathway inhibits Caspase-3 activation and caspase-mediated cleavage/fragmentation of cytoskeletal proteins in stress-exposed neurons. These results indicate that primary cilia play an integral role in mitigating adverse impacts of environmental stressors such as drugs on perinatal brain development.

Satellite-Based Sensor for Environmental Heat-Stress Sweat Creatinine Monitoring: The Remote Artificial Intelligence-Assisted Epidermal Wearable Sensing for Health Evaluation.

Wearable human sweat sensors have offered a great prospect in epidermal detection for self-monitoring and health evaluation. These on-body epidermal sensors can be integrated with the Internet of Things (IoT) as augmented diagnostics tools for telehealth applications, especially for noninvasive health monitoring without using blood contents. One of many great benefits in utilizing sweat as biofluid is the capability of instantaneously continuous diagnosis during normal day-to-day activities. Here, we revealed a textile-based sweat sensor selective for perspired creatinine that is prepared by coating poly(vinyl alcohol) (PVA)-Cu2+-poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) and cuprous oxide nanoparticles on stretchable nylon, is equipped with heart rate monitoring and a satellite-communication device to locate wearers, and incorporates machine learning to predict the levels of environmental heat stress. Electrochemical impedance spectroscopy (EIS) was used to investigate different charge-transfer resistances of PVA and PEDOT:PSS with cuprous and cuprite ions induced by single-chain and ionic cross-linking. Furthermore, density function theory (DFT) studies predicted the catalytic binding of sweat creatinine with the sensing materials that occurred at thiophene rings. The hybrid sensor successfully achieved 96.3% selectivity efficacy toward the determination of creatinine contents from 0.4 to 960 μM in the presence of interfering species of glucose, urea, uric acid, and NaCl as well as retained 92.1% selectivity efficacy in the existence of unspecified human sweat interference. Ultimately, the hand-grip portable device can offer the great benefit of continuous health monitoring and provide the location of any wearer. This augmented telemedicine sensor may represent the first remote low-cost and artificial-intelligence-based sensing device selective for heat-stress sweat creatinine.

A habitat‐based assessment of the role of competition in plant invasions

Abstract Many invasion theories invoke resource competition as the primary mechanism of invader advantage. These include Darwin's naturalization hypothesis (DNH), which treats phylogenetic similarity as a proxy for niche overlap and competitive intensity, and the evolutionary imbalance hypothesis (EIH), which suggests the phylogenetic diversity (PD) of an introduced species’ native range is an indicator of its competitive ability. Few tests of invasion theory, however, consider habitat characteristics associated with the role of competition in community assembly. In particular, plant invasions of habitats characterized by high environmental stress and disturbance levels should rarely be driven by competition. This suggests tests of EIH and DNH are habitat dependent, and their relative importance in invasiveness models should be predictable based on habitat qualities related to competitive intensity. Using a dataset of plant invasions in New Zealand (NZ) natural areas that distinguishes naturalized species according to both habitat type and community impact, we evaluated the predictive ability of factors related to EIH, DNH and covariates including year of introduction, introduction mode and life history attributes, in driving species invasiveness. We hypothesized that EIH and DNH would be more important predictors of invasiveness in forested habitats and decline in importance as communities shifted towards those more dominated by herbaceous species and/or more sparsely vegetated. We found mixed support for the role of competition linked to DNH and EIH as a driver of invasions in relation to habitat type. Native range PD was among the best predictors of invasiveness in forests, and declined in importance in more disturbed habitats, supporting EIH. In contrast, phylogenetic nearest neighbour distance (PNND) of invaders to native communities was more important in disturbed environments, suggesting competition does not drive DNH. Further, for most habitats and across all of NZ, neither PD nor PNND was as important as year of introduction or life history and growth form attributes in predicting invasiveness. Synthesis. Although both native range PD and PNND predict the invasiveness of naturalized plants in NZ, the results of our habitat‐specific models indicate that only PD is consistent with an invasion mechanism based on competitive ability. Effects of PNND were greatest in grasslands that have been extensively modified by fire and grazing, suggesting they are more likely driven by invader pre‐adaptation to modified habitat conditions. Due to the importance of matching species' traits to environmental context, invasiveness risk assessments perform better when applied to invaders of particular habitats.

Bacterial Communities Show Algal Host (Fucus spp.)/Zone Differentiation Across the Stress Gradient of the Intertidal Zone.

The intertidal zone often has varying levels of environmental stresses (desiccation, temperature, light) that result in highly stress-tolerant macrobiota occupying the upper zone while less tolerant species occupy the lower zone, but little comparative information is available for intertidal bacteria. Here we describe natural (unmanipulated) bacterial communities of three Fucus congeners (F. spiralis, high zone; F. vesiculosus, mid zone; F. distichus, low zone) as well as those of F. vesiculosus transplanted to the high zone (Dry and Watered treatments) and to the mid zone (Procedural Control) during summer in Maine (United States). We predicted that bacterial communities would be different among the differently zoned natural congeners, and that higher levels of desiccation stress in the high zone would cause bacterial communities of Dry transplants to become similar to F. spiralis, whereas relieving desiccation stress on Watered transplants would maintain the mid-zone F. vesiculosus bacterial community. Bacteria were identified as amplicon sequence variants (ASVs) after sequencing the V4 hypervariable region of the 16S rRNA gene. Microbiome composition and structure were significantly different between the differently zoned congeners at each tissue type (holdfasts, receptacles, vegetative tips). ASVs significantly associated with the mid-zone congener were frequently also present on the high-zone or low-zone congener, whereas overlap in ASVs between the high-zone and low-zone congeners was rare. Only 7 of 6,320 total ASVs were shared among tissues over all congeners and transplant treatments. Holdfast bacterial community composition of Dry transplants was not significantly different from that of F. spiralis, but Watered holdfast communities were significantly different from those of F. spiralis and not significantly different from those of procedural controls. Additional stressor(s) appeared important, because bacterial communities of Dry and Watered transplants were only marginally different from each other (p = 0.059). The relative abundance of Rhodobacteraceae associated with holdfasts generally correlated with environmental stress with highest abundance associated with F. spiralis and the two high-zone transplant treatments. These findings suggest that the abiotic stressors that shape distributional patterns of host species also affect their bacterial communities.

Multiple paternity in the intertidal zone porcelain crabPetrolisthes cinctipesRandall, 1840 (Decapoda: Anomura: Porcellanidae) is a life-history strategy that increases fitness during heat stress

AbstractMultiple paternity is widespread across animal and plant taxa and can increase genetic diversity and enhance fitness, especially in unpredictable environments. A prior study of the intertidal zone porcelain crab, Petrolisthes cinctipes (Randall, 1840), found that most females carried polyandrous broods. We tested the hypothesis that multiple paternity in P. cinctipes enhances fitness through increased average brood tolerance to temperature stress. Embryonic survival of split broods (N = 27) was measured under ambient conditions and following a single one-hour heat shock at 30 °C. Two microsatellite loci were used to genotype embryos and mothers in order to distinguish multiple from single paternity in each brood. Mean overall hatching percentage did not differ between singly and multiply sired broods; however, when exposed to a heat-shock, single-sired broods experienced 11% lower hatching success. Though relative fitness was higher in single-sired broods under non-stressful conditions, extrapolation of our results to conditions where temperatures are at least 30 °C (present-day extremes for the California coast) for > 2 days of the embryonic brood period, multiply sired broods have a relative fitness that is approximately 24 times higher after 15 generations. Maternal quality (size) and the timing of the heat shock relative to developmental timing also influence the brood response to heat shock. Our results suggest that multiple paternity reduces embryo survival variance between ambient and heat-shock conditions and that polyandrous behavior could be an advantage for P. cinctipes in the thermally variable high-intertidal zone. We conclude that multiple paternity is an important strategy for increasing fitness by genetic diversification in organisms that experience severe and unpredictable levels of environmental stress.

Heat stress effects on sexual reproductive processes of a threatened halophyte

Sexual reproduction, a critical life history process in plants, can be altered by heat stress derived from global warming. Sexual reproduction increases genetic diversity, and the ability of plants to respond to environmental changes and dispersal. The capacity for these responses is especially relevant as plants are exposed to rising environmental stress levels imposed by climate change. We investigated the influence of environmental factors that impose physiological stress that may affect the fruit set of Spartina maritima, the sole native African and European cordgrass species. To achieve our objective, we acquired locally recorded air temperatures and tidal amplitude projections. Within population sites, we measured sedimentary conditions (pH, redox potential and electrical conductivity), and the phenological stage of S. maritima inflorescences, spikelets with non-exserted stamens and caryopses produced throughout its 10-week flowering period. Fruit set decreased as flowering period advanced, and as air temperatures and the proportion of spikelets with non-exserted stamens increased. Fruit set decreased with increased sediment anoxia. The proportion of reabsorbed caryopses increased with high air temperatures during the female phase of the inflorescence, and with higher tidal amplitudes during the male phase. These environmental stress factors could terminate caryopsis development that had commenced. Our results point to a severe potential impact of global warming on the reproductive process of native S. maritima. Mitigation of global warming will be essential to maintain population persistence and support conservation and recovery of this halophyte that provides important ecosystem services in salt marshes.

Coexistence of plant species under harsh environmental conditions: an evaluation of niche differentiation and stochasticity along salt marsh creeks

BackgroundEcologists have achieved much progress in the study of mechanisms that maintain species coexistence and diversity. In this paper, we reviewed a wide range of past research related to these topics, focusing on five theoretical bodies: (1) coexistence by niche differentiation, (2) coexistence without niche differentiation, (3) coexistence along environmental stress gradients, (4) coexistence under non-equilibrium versus equilibrium conditions, and (5) modern perspectives.ResultsFrom the review, we identified that there are few models that can be generally and confidently applicable to different ecological systems. This problem arises mainly because most theories have not been substantiated by enough empirical research based on field data to test various coexistence hypotheses at different spatial scales. We also found that little is still known about the mechanisms of species coexistence under harsh environmental conditions. This is because most previous models treat disturbance as a key factor shaping community structure, but they do not explicitly deal with stressful systems with non-lethal conditions. We evaluated the mainstream ideas of niche differentiation and stochasticity for the coexistence of plant species across salt marsh creeks in southwestern Denmark. The results showed that diversity indices, such as Shannon–Wiener diversity, richness, and evenness, decreased with increasing surface elevation and increased with increasing niche overlap and niche breadth. The two niche parameters linearly decreased with increasing elevation. These findings imply a substantial influence of an equalizing mechanism that reduces differences in relative fitness among species in the highly stressful environments of the marsh. We propose that species evenness increases under very harsh conditions if the associated stress is not lethal. Finally, we present a conceptual model of patterns related to the level of environmental stress and niche characteristics along a microhabitat gradient (i.e., surface elevation).ConclusionsThe ecology of stressful systems with non-lethal conditions will be increasingly important as ongoing global-scale climate change extends the period of chronic stresses that are not necessarily fatal to inhabiting plants. We recommend that more ecologists continue this line of research.

Phoenixin influences the excitability of nucleus of the solitary tract neurones, effects which are modified by environmental and glucocorticoid stress.

Phoenixin (PNX) is a neuropeptide shown to play roles in the control of reproduction. The nucleus of the solitary tract (NTS), a critical autonomic integrating centre in the hindbrain, is one of many areas with dense expression of PNX. Using coronal NTS slices obtained from male Sprague-Dawley rats, the present study characterised the effects of PNX on both spike frequency and membrane potential of NTS neurones. Extracellular recordings demonstrated that bath-applied 10nmolL-1 PNX increased the firing frequency in 32% of NTS neurones, effects which were confirmed with patch-clamp recordings showing that 50% of NTS neurones tested depolarised in response to application of the peptide. Surprisingly, the responsiveness to PNX in NTS neurones then declined suddenly to 9% (P<0.001). This effect was subsequently attributed to stress associated with construction in our animal care facility because PNX responsiveness was again observed in slices from rats delivered and maintained in a construction-free facility. We then examined whether this loss of PNX responsiveness could be replicated in rats placed on a chronic stress regimen involving ongoing corticosterone (CORT) treatment in the construction-free facility. Slices from animals treated in this way showed a similar lack of neuronal responsiveness to PNX (9.1±3.9%) within 2weeks of CORT treatment. These effects were specific to PNX responsiveness because CORT treatment had no effect on the responsiveness of NTS neurones to angiotensin II. These results are the first to implicate PNX with respect to directly controlling the excitability of NTS neurones and also provide intriguing data showing the plasticity of these effects associated with environmental and glucocorticoid stress levels of the animal.

Summer aridity rather than management shapes fitness-related functional traits of the threatened mountain plant Arnica montana.

Semi‐natural mountain grasslands are increasingly exposed to environmental stress under climate change. However, which are the environmental factors that limit plants in these grasslands? Also, is the present management effective against these changes? Fitness‐related functional traits may offer a way to detect changes in performance and provide new insights into their vulnerability to climate change. We investigated changes in performance and variability of functional traits of the mountain grassland target species Arnica montana along a climate gradient in Central German low mountain ranges. This gradient represents at its lower end climate conditions that are expected at its upper end under future climate change. We measured vegetative, generative, and physiological traits to account for multiple ways of plant responses to the environment. Using mixed effects and multivariate models, we evaluated changes in trait values among individuals as well as the variability of their populations in order to assess performance under changing summer aridity and different management regimes. Fitness‐related performance of most traits showed strongly positive associations with reduced summer aridity at higher elevations, while only specific leaf area and leaf dry matter content showed no association. This suggests a higher performance level at less arid montane sites and that the physiological traits are less sensitive to this climate change factor. The coefficient of variation of almost all traits declined steadily with decreasing site aridity. We suggest that this reduced variability indicates a lower environmental stress level for A. montana toward its environmental optimum at montane elevations, especially because the trait performance increased simultaneously. Surprisingly, management factors and habitat characteristics had only low influence on both trait performance and variability. In summary, summer aridity had a stronger effect to shape the trait performance and variability of A. montana under increased environmental stress than management and other habitat characteristics.