Priority Effects Research Articles

Survival of mechanically ventilated ward patients and association with organisational factors: a multicentre prospective study

ObjectivesDetermine 90-day mortality of mechanically ventilated ward patients outside the intensive care unit (ICU) and its association with organisational factors.DesignMulticentre prospective observational study of mechanically ventilated ward patients. Modified Poisson...

Patch size drives colonization by aquatic insects, with minor priority effects of a cohabitant.

Patch size is one of the most important factors affecting the distribution and abundance of species, and recent research has shown that patch size is an important niche dimension affecting community structure in aquatic insects. Building on this result, we examined the impact of patch size in conjunction with presence of larval anurans on colonization by aquatic insects. Hyla chrysoscelis (Cope's gray treefrog) larvae are abundant and early colonists in fishless lentic habitats, and these larvae can fill multiple ecological roles. By establishing larvae in mesocosms prior to colonization, we were able to assess whether H. chrysoscelis larvae have priority effects on aquatic insect assemblages. We conducted a series of three experiments in naturally colonized experimental landscapes to test whether (1) H. chrysoscelis larval density affects insect colonization, (2) variation in patch size affects insect colonization, and (3) the presence and larval density of H. chrysoscelis shift colonization of insects between patches of different size. Larval density independently had almost no effect on colonization, while patch size had species‐specific effects consistent with prior work. When larvae and patch size were tested in conjunction, patch size had numerous, often strong, species‐specific effects on colonization; larval density had effects largely limited to the assemblages of colonizing beetles and water bugs, with few effects on individual species. Higher larval densities in large mesocosms shifted some insect colonization to smaller patches, resulting in higher beta diversity among small patches in proximity to high density large mesocosms. This indicates establishing H. chrysoscelis larvae prior to insect colonization can likely create priority effects that slightly shape insect communities. Our results support the importance of patch size in studying species abundances and distributions and also indicate that colonization order plays an important role in determining the communities found within habitat patches.

Unexpected diversity among small-scale sample replicates of defined plant root compartments

Community assembly processes determine patterns of species distribution and abundance which are central to the ecology of microbiomes. When studying plant root microbiome assembly, it is typical to sample at the whole plant root system scale. However, sampling at these relatively large spatial scales may hinder the observability of intermediate processes. To study the relative importance of these processes, we employed millimetre-scale sampling of the cell elongation zone of individual roots. Both the rhizosphere and rhizoplane microbiomes were examined in fibrous and taproot model systems, represented by wheat and faba bean, respectively. Like others, we found that the plant root microbiome assembly is mainly driven by plant selection. However, based on variability between replicate millimetre-scale samples and comparisons with randomized null models, we infer that either priority effects during early root colonization or variable selection among replicate plant roots also determines root microbiome assembly.

No evidence for dominance–discovery trade-offs in Pheidole (Hymenoptera: Formicidae) assemblages

Understanding the mechanisms that allow species coexistence across spatial scales is of great interest to ecologists. Many such proposed mechanisms involve trade-offs between species in different life-history traits, with distinct trade-offs being expected to be prevalent at varying temporal and spatial scales. The dominance–discovery trade-off posits that species differ in their ability to find and use resources quickly, in contrast to their ability to monopolize those resources, a mechanism analogous to the competition-colonization trade-off. We investigated the occurrence of this structuring mechanism in the genus Pheidole Westwood, 1839 (Hymenoptera: Formicidae) assemblages in Atlantic Forest remnants. According to the dominance–discovery trade-off, consistent interspecific variation should be observed along the axis of discovery and dominance. We established 55 sampling units across two sites, with each unit consisting of a sardine bait monitored for 3 h. There was no distinction among Pheidole species in their ability to find or dominate food sources, suggesting that the dominance–discovery trade-off does not explain their coexistence. The low levels of aggression between Pheidole species could prevent the establishment of dominance hierarchies, whereas the species order of arrival at food sources could allow for resource partitioning through priority effects.

On the Rate and Age of Information for non-preemptive systems with prioritized arrivals and deterministic packet deadlines in IoT networks

In this paper, we consider two different classes of IoT sensors with high and low priorities in which both classes send their data to a Monitoring Center (MC) equipped with one server and a buffer to store the arrival packets waiting in the queue, representing an M/M/1/2 system. An error-free channel predominates the link between the sensors and MC. We assume a non-preemptive scheme applying priorities on the buffer in MC so that the packets with lower priority in the queue can be replaced by more urgent higher priority packets but not in the service, as well. The arrival packets are specified by deadline characteristic due to the great demand for fresh data. The deadline is provided to free the buffer and let the monitoring center be updated by the latest data. As significant parameters in calculating the throughput and freshness of data, Rate of Information (RoI) and system’s Age of Information (AoI) are investigated in the MC. Our goal is to study the effect of priority and packet deadlines on the rate and status update of the system. Thus, a Markov model is applied to derive the closed form expressions considering deterministic deadlines and the impact of high and low priority packets. Also, a new metric named the Age to Rate Ratio of Information (ARRoI) is introduced and discussed for better realization of the relation between effective arrival rate and AoI. Simulation results for various parameters confirm the analytical results and show that the newly introduced metric, ARRoI, could be employed in finding proper transmission rates.

Divergent Pathways of Nitrogen-Fixing Trees through Succession Depend on Starting Nitrogen Supply and Priority Effects.

AbstractNitrogen-fixing trees are a major potential source of nitrogen in terrestrial ecosystems. The degree to which they persist in older forests has considerable implications for forest nitrogen budgets. We characterized nitrogen-fixing tree abundance across stand age in the contiguous United States and analyzed a theoretical model to help understand competitive outcomes and successional trajectories of nitrogen-fixing and nonfixing trees. Nitrogen-fixing tree abundance is bimodal in all regions except the northeastern United States, even in older forests, suggesting that competitive exclusion (including priority effects) is more common than coexistence at the spatial scale of our analysis. Our model analysis suggests conditions under which alternative competitive outcomes are possible and when they are transient (lasting decades or centuries) versus persistent (millennia). Critically, the timescale of the feedbacks between nitrogen fixation and soil nitrogen supply, which is thought to drive the exclusion of nitrogen-fixing trees through succession, can be long. Therefore, the long transient outcomes of competition are more relevant for real forests than the long-term equilibrium. Within these long-term transients, the background soil nitrogen supply is a major determinant of competitive outcomes. Consistent with the expectations of resource ratio theory, competitive exclusion is more likely at high and low nitrogen supply, while intermediate nitrogen supply makes coexistence or priority effects possible. However, these outcomes are modified by the nitrogen fixation strategy: obligate nitrogen fixation makes coexistence more likely than priority effects, compared with perfectly facultative fixation. These results advance our understanding of the successional trajectories of nitrogen-fixing trees and their effects on ecosystem development in secondary succession.

Density-dependent plant-soil feedbacks of two plant species affected by plant competition

Both plant-soil feedbacks (PSF) and plant competition drive plant community assembly, but their interactive effects have rarely been investigated, and the role of community composition in modulating these interactions is unknown. We conducted a fully reciprocal experiment with two plant species (Polygonum criopolitanum and Carex thunbergii) and their associated soil biota communities to untangle the relative importance of PSF and competition. The two species were grown either in monoculture or in mixed plantings, with various densities of each plant's neighbor, and either in the presence or absence of the soil biota associated with either species. When grown individually, each plant species showed a neutral PSF in the presence of its own soil biota, while feedbacks in competition were predominantly negative. P. criopolitanum produced more biomass in the presence of soil biota than in autoclaved soil, but the opposite was observed for C. thunbergii. In competition, both plant species were suppressed by its presence of their own soil biota, and neither had a competitive advantage, resulting in a significant negative pairwise PSF in most cases. C. thunbergii also showed stronger per capita effects than did P. criopolitanum. The predication on species coexistence largely depended on the presence of soil biota, the soil origin, and the plant species ratio. When planted in equal proportion, P. criopolitanum and C. thunbergii only coexisted in the presence of soil biota of P. criopolitanum, while C. thunbergii usually excluded P. criopolitanum under all other conditions. When the density of the neighboring plant increased, either species was excluded in the presence of their own soil biota. However, in the absence of a soil biota, there was a priority effect, giving an advantage to the species that was planted first. Our study revealed that the strength and direction of these interactions were altered by interspecific competition at the community level, and both the identity and the density of the competitors must be taken into account in interpreting plant community assembly processes.

Complex relationships between beta diversity and dispersal in meta‐community models

Dispersal is one of the most important drivers of community assembly. Understanding how dispersal impacts spatial variations in community composition (beta diversity) is crucial for predicting biodiversity change during the Anthropocene. Classic theories and a large amount of empirical evidence have led to a common belief that increasing dispersal rate should lead to regional community homogenization (lower beta diversity). However, recent empirical studies show that increasing dispersal can also lead to regional community divergence when interacting with other processes such as disturbance and priority effect. The underappreciation of the complex relationship between beta diversity and dispersal might impede our ability to make accurate ecological forecasts. To address this concern, I examine the beta diversity–dispersal relationship through extinction and colonization dynamics in meta‐community models. I find that a wide range of beta diversity–dispersal relationships (e.g. negative, positive, hump‐shaped) can be generated by changes in species‐level occurrence probabilities when meta‐population dispersal (rather than mainland–island dispersal), disturbance and strong biotic interactions are at play. Specifically, reducing the variance of species‐level occurrence probabilities leads to community divergence and increasing the mean occurrence probability leads to community homogenization; a positive or hump‐shaped beta diversity–dispersal relationship emerges when the effect of the decreasing variance is stronger than the effect of increasing mean. These findings highlight the intrinsic constraint of occupancy stochasticity on beta diversity changes and echo the call for more realistic manipulations of stochastic dispersal and a detailed understanding of the interaction networks to test various beta diversity–dispersal relationships in future empirical studies.

Influence of factors of electroplating production on the immunoreactivity of the body of workers

Introduction. Modern electroplating production is the leader in air pollution of the working area with substances containing highly toxic compounds. Therefore, early detection of the negative impact of harmful factors on the body of workers is of paramount importance. The purpose of the study: to evaluate changes in individual parts of the immune system under prolonged exposure to chemical factors of the production environment. Materials and methods. 195 employees of electroplating production (the leading group) and 67 employees who are not in contact with harmful factors of the production environment (the control group) were examined. Cytochemical and immunological studies were performed according to standard and unified methods. The nickel content in the urine was determined by the voltammetric method. Results. With an increase in the work experience of workers, there is a decrease in the activity of myeloperoxidase of neutrophils MPn (r = -0.89) and an increase in the activity of acid phosphatase of neutrophils AcPN, alkaline phosphatase of neutrophils AlPN (r = 0,88-0,91). There was a destabilization of the cellular component of the immune response, characterized by a decrease in the immunoregulatory index by 2.0 times, and activation of the humoral component with an increase in the levels of IgM, IgE and circulating immune complexes by 1.4-1.8 times relative to the control. An imbalance of cytokine regulation was established, where proinflammatory responses with increased cytokine production by 1.5-3.5 times (IL-1β, TNF-α, IL-4) prevail. The relationship between the concentration of nickel in the urine and changes in the parameters of AcPN (r = 0.87), MPn (r = -0.84), IgA (r = -0.72); IL-1β, IL-4, IgE, (r = 0.62-0.71), confirming the priority effect of nickel compounds on the established changes. Conclusion. The identified violations of the immunoreactivity of the workers ‘ body can contribute to the development of immunodeficiency, allergic and autoimmune conditions that underlie occupational and industrial-related diseases. The proposed biomarkers are recommended to be used for early diagnosis of health disorders in workers of electroplating production, formation of “risk groups”, evaluation of the effectiveness of timely preventive and rehabilitation measures.

Microbiome‐mediated response to pulse fire disturbance outweighs the effects of fire legacy on plant performance

Fire plays a major role in structuring plant communities across the globe. Interactions with soil microbes impact plant fitness, scaling up to influence plant populations and distributions. Here we present the first factorial manipulation of both fire and soil microbiome presence to investigate their interactive effects on plant performance across a suite of plant species with varying life history traits. We conducted fully factorial experiments on 11 species from the Florida scrub ecosystem to test plant performance responses to soils with varying fire histories (36 soil sources), the presence/absence of a microbiome, and exposure to an experimental burn. Results revealed interactive 'pulse' effects between fire and the soil microbiome on plant performance. On average, post-fire soil microbiomes strongly reduced plant productivity compared to unburned or sterilized soils. Interestingly, longer-term fire 'legacy' effects had minor impacts on plant performance and were unrelated to soil microbiomes. While pulse fire effects on plant-microbiome interactions are short-term, they could have long-term consequences for plant communities by establishing differential microbiome-mediated priority effects during post-disturbance succession. The prominence of pulse fire effects on plant-microbe interactions has even greater import due to expected increases in fire disturbances resulting from anthropogenic climate change.

When Do Hedonic and Eudaimonic Orientations Lead to Happiness? Moderating Effects of Orientation Priority.

The effects of hedonic and eudaimonic orientations on individual well-being have received much scholarly attention. However, the empirical findings from previous research are not consistent, raising the question of when the pursuit of hedonia and eudaimonia lead to actual improvements in individual well-being. We argue that the relationship between orientations to happiness and well-being outcomes are moderated by orientation priorities, which reflect the relative level of importance individuals place on eudaimonic motives compared to hedonic motives. A total of 312 Chinese undergraduate students completed surveys assessing hedonic and eudaimonic orientations, orientation priorities, and well-being outcomes, including psychological well-being, positive affect, and negative affect. The results revealed that a eudaimonic orientation was positively related to psychological well-being, a hedonic orientation was positively related to positive affect, and both relationships were moderated by orientation priorities. For individuals who prioritized eudaimonia over hedonia, both orientations improved well-being. For individuals who prioritized hedonia over eudaimonia, the benefits related to well-being from both orientations decreased or disappeared. These findings suggest that orientation priorities are of equal importance in regard to hedonic and eudaimonic orientations.

Safety priority, safety rules, safety participation and safety behaviour: the mediating role of safety training

Objectives. This study explores the effects of employee perception of the management’s safety priority, safety rules and safety training on safety participation and safety behaviour decided by management, as well as the mediating role of safety training on the other four dimensions. Methods. The study covers employees working in 27 metal companies classed as hazardous/very hazardous in Turkey. The research data were collected by surveying 822 employees in the metal sector. Collected data were tested through explanatory and confirmatory factor analyses, in that order. Results. The findings of this analysis indicated statistically direct, positive effects of safety priority on safety rules and safety training, such an effect of safety rules on safety training, and again such effects of safety training on safety participation and safety behaviour. Besides, indirect relationships were detected between safety priority and safety rules and safety participation, and safety behaviour through the mediating role of safety training. Conclusion. Employee participation in health and safety issues as well as safe behaviour in the workplace depend on management prioritizing health and safety issues as much as production, formulating safe working rules, procedures and practices using comprehensive and regular training programmes.

A new approach for risk assessment of failure modes considering risk interaction and propagation effects

Failure Mode and Effect Analysis (FMEA) is an efficient method for risk prevention and control, which has been applied to identify the potential risks and improve system reliability in various fields. Nevertheless, few attempts in previous research have been made to examine the impacts of the interactions among the failure modes on risk priority, which will influence the risk priority accuracy. To solve this problem, we propose a novel method to improve the conventional FMEA approaches. The proposed method not only considers the positive and negative influences of failure modes, but also the attenuation effect of such influences in the system. In addition, different from the previous FMEA approaches assuming that all failure modes play equally important roles in risk propagation, the new FMEA method considers the initial strength effect of failure mode on the risk propagation to ensure the accuracy of the risk priority. The final risk priority of a failure mode is computed recursively by the PageRank algorithm, which considers the effect of risk priority of other failure modes associated with this failure mode. Finally, to verify the effectiveness of the proposed method, we apply it to a case study of failure mode effect analysis for smart bracelets.

Effects of proximal priority and distal priority robotic priming techniques with impairment-oriented training of upper limb functions in patients with chronic stroke: study protocol for a single-blind, randomized controlled trial

BackgroundThe sequence of establishing a proximal stability or function before facilitation of the distal body part has long been recognized in stroke rehabilitation practice but lacks scientific evidence. This study plans to examine the effects of proximal priority robotic priming and impairment-oriented training (PRI) and distal priority robotic priming and impairment-oriented training (DRI).MethodsThis single-blind, randomized, comparative efficacy study will involve 40 participants with chronic stroke. Participants will be randomized into the PRI or DRI groups and receive 18 intervention sessions (90 min/day, 3 days/weeks for 6 weeks). The Fugl-Meyer Assessment Upper Extremity subscale, Medical Research Council Scale, Revised Nottingham Sensory Assessment, and Wolf Motor Function Test will be administered at baseline, after treatment, and at the 3-month follow-up. Two-way repeated-measures analysis of variance and the chi-square automatic interaction detector method will be used to examine the comparative efficacy and predictors of outcome, respectively, after PRI and DRI.DiscussionThrough manipulating the sequence of applying wrist and forearm robots in therapy, this study will attempt to examine empirically the priming effect of proximal or distal priority robotic therapy in upper extremity impairment-oriented training for people with stroke. The findings will provide directions for further studies and empirical implications for clinical practice in upper extremity rehabilitation after stroke.Trial RegistrationClinicalTrials.gov NCT04446273. Registered on June 23, 2020.

Untangling the complexity of priority effects in multispecies communities.

The history of species immigration can dictate how species interact in local communities, thereby causing historical contingency in community assembly. Since immigration history is rarely known, these historical influences, or priority effects, pose a major challenge in predicting community assembly. Here, we provide a graph-based, non-parametric, theoretical framework for understanding the predictability of community assembly as affected by priority effects. To develop this framework, we first show that the diversity of possible priority effects increases super-exponentially with the number of species. We then point out that, despite this diversity, the consequences of priority effects for multispecies communities can be classified into four basic types, each of which reduces community predictability: alternative stable states, alternative transient paths, compositional cycles and the lack of escapes from compositional cycles to stable states. Using a neural network, we show that this classification of priority effects enables accurate explanation of community predictability, particularly when each species immigrates repeatedly. We also demonstrate the empirical utility of our theoretical framework by applying it to two experimentally derived assembly graphs of algal and ciliate communities. Based on these analyses, we discuss how the framework proposed here can help guide experimental investigation of the predictability of history-dependent community assembly.

Validating the Strategic Task Overload Management (STOM) Model Using MATB II and Eye-tracking

Operators can be overloaded and struggle to make sense of and prioritize multiple tasks. Task selection in these cases is of utmost importance. We replicated an experiment using the Multi Attribute Task Battery II (MATB II) for validating a model of strategic task switching (STOM), adding eye tracking measurement, resulting in a new assessment. Task difficulty affected how operators switched tasks, while priority had little to no effect. Newly measured for STOM, eye tracking revealed a link between task difficulty and time spent performing a task but failed to meet predictions for interest and priority effects. The outcome of the validation effort as it relates to the STOM model, as well as eye tracking implications, are discussed.

Late Development of Early Visual Perception: No Topology-Priority in Peripheral Vision Until Age 10.

Topological property (TP) is a basic geometric attribute of objects, which is preserved over continuous and one‐to‐one transformations and considered to be processed in early vision. This study investigated the global TP perception of 773 children aged 6–14, as compared to 179 adults. The results revealed that adults and children aged 10 or over show a TP priority trend in both central and peripheral vision, that is, less time is required to discriminate TP differences than non‐TP differences. Children aged 6–8 show a TP priority trend for central stimuli, but not in their peripheral vision. The TP priority effect in peripheral vision does not emerge until age ˜10 years, and the development of central and peripheral vision seems to be different.

Early successional colonizers both facilitate and inhibit the late successional colonizers in communities of dung-inhabiting insects

The influence of early arriving species on the establishment and activity of later ones (the priority effect) is a key issue in ecological succession. Priority effects have been extensively studied in communities subject to autotrophic succession (plants, sessile animals), but only sporadically studied in communities subject to heterotrophic succession (e.g. dung or carrion inhabiting communities). We studied the influence of early successional colonizers on late successional colonizers by manipulating the successional processes in cow dung pats via delaying, and thus lowering, colonization by early successional insects. The decreased activity of early successional insects did not affect the species richness of late successional insects, but it did lead to increased abundance of colonizers. Late successional coprophagous beetles were facilitated by early successional species while larvae of late successional coprophagous flies were inhibited, presumably, by the larvae of early successional flies. We therefore propose that both facilitation and inhibition have a role to play in the heterotrophic succession of coprophilous insects. In addition, facilitation and inhibition among taxa seems to reflect their evolutionary relationships, with facilitation being prominent between phylogenetically distant lineages (early successional Diptera and late successional Coleoptera), and inhibition being more common between closely related lineages (early vs. late successional Diptera). These patterns are strikingly reminiscent of the situation in the autotrophic succession of plants.

Priority effects in microbiome assembly.

Advances in next-generation sequencing have enabled the widespread measurement of microbiome composition across systems and over the course of microbiome assembly. Despite substantial progress in understanding the deterministic drivers of community composition, the role of historical contingency remains poorly understood. The establishment of new species in a community can depend on the order and/or timing of their arrival, a phenomenon known as a priority effect. Here, we review the mechanisms of priority effects and evidence for their importance in microbial communities inhabiting a range of environments, including the mammalian gut, the plant phyllosphere and rhizosphere, soil, freshwaters and oceans. We describe approaches for the direct testing and prediction of priority effects in complex microbial communities and illustrate these with re-analysis of publicly available plant and animal microbiome datasets. Finally, we discuss the shared principles that emerge across study systems, focusing on eco-evolutionary dynamics and the importance of scale. Overall, we argue that predicting when and how current community state impacts the success of newly arriving microbial taxa is crucial for the management of microbiomes to sustain ecological function and host health. We conclude by discussing outstanding conceptual and practical challenges that are faced when measuring priority effects in microbiomes.

Air-dispersed aquatic microorganisms show establishment and growth preferences in different freshwater colonisation habitats.

We attempted to mimic aeolian ecosystems to examine how filters posed by regional characteristics can influence the establishment and growth of airborne microcolonisers of a common air source. Using a natural single source of aerosols we applied a combined microscopy and high-throughput sequencing approach to examine the diversity, settling and growth potential of air-dispersed microbes in water containers representing newly formed aquatic colonisation habitats of different trophic states and salinity. Heterotrophic microeukaryotes were favoured as initial settlers when nutrients were low, while autotrophs rapidly proliferated in the high-nutrient containers, possibly due to favourable germinating conditions for their preferred mode of dispersal with resting spores. Following settling of colonisers, we investigated two contrasting hypotheses: if the different water colonisation habitats harboured the same microbial communities after establishment and growth periods, this would point towards a selection of best-fit cosmopolitan colonisers, regardless of habitat-specific characteristics. Alternatively, community dissimilarities after the growth period would suggest a selection of settlers due to bottom-up controls combined with priority effects. Both analyses suggested that the structure of the microbial communities in the different colonisation habitats were driven by nutrient content and salinity, showing clustering to similar bottom-up forces and dissimilarities in significantly different colonisation habitats.