Coexistence Theory Research Articles

Predicting pathogen mutual invasibility and co-circulation.

Observations of pathogen community structure provide evidence for both the coexistence and replacement of related strains. Despite many studies of specific host-pathogen systems, a unifying framework for predicting the outcomes of interactions among pathogens has remained elusive. We address this gap by developing a pathogen invasion theory (PIT) based on modern ecological coexistence theory and testing the resulting framework against empirical systems. Across major human pathogens, PIT predicts near-universal mutual susceptibility of one strain to invasion by another strain. However, predicting co-circulation from mutual invasion also depends on the degree to which susceptible abundance is reduced below the invasion threshold by overcompensatory epidemic dynamics, and the time it takes for susceptibles to replenish. The transmission advantage of an invading strain and the strength and duration of immunity are key determinants of susceptible dynamics. PIT unifies existing ideas about pathogen co-circulation, offering a quantitative framework for predicting the emergence of novel pathogen strains.

It's about (taking up) space: Discreteness of individuals and the strength of spatial coexistence mechanisms.

One strand of modern coexistence theory (MCT) partitions invader growth rates (IGR) to quantify how different mechanisms contribute to species coexistence, highlighting fluctuation-dependent mechanisms. A general conclusion from the classical analytic MCT theory is that coexistence mechanisms relying on temporal variation (such as the temporal storage effect) are generally less effective at promoting coexistence than mechanisms relying on spatial or spatiotemporal variation (primarily growth-density covariance). However, the analytic theory assumes continuous population density, and IGRs are calculated for infinitesimally rare invaders that have infinite time to find their preferred habitat and regrow, without ever experiencing intraspecific competition. Here we ask if the disparity between spatial and temporal mechanisms persists when individuals are, instead, discrete and occupy finite amounts of space. We present a simulation-based approach to quantifying IGRs in this situation, building on our previous approach for spatially non-varying habitats. As expected, we found that spatial mechanisms are weakened; unexpectedly, the contribution to IGR from growth-density covariance could even become negative, opposing coexistence. We also found shifts in which demographic parameters had the largest effect on the strength of spatial coexistence mechanisms. Our substantive conclusions are statements about one model, across parameter ranges that we subjectively considered realistic. Using the methods developed here, effects of individual discreteness should be explored theoretically across a broader range of conditions, and in models parameterized from empirical data on real communities.

A Parasite Plant Promotes the Coexistence of Two Annual Plants.

Consumers can influence the competitive outcomes of prey species in various ways. Modern coexistence theory predicts that consumers can promote prey coexistence by preferably targeting a competitively superior one, thereby reducing fitness differences. However, previous studies yielded mixed conclusions. In this study, we tested the hypothesis that a parasitic annual plant, Cuscuta campestris, facilitates the coexistence of two common annual plants. We performed field surveys and parasitism experiments to parameterize a plant competition dynamics model. The model suggested a competition-defence tradeoff: the legume Lespedeza striata was a better competitor than the grass Setaria faberi, while it was more susceptible to the parasite. Moreover, an empirical host-parasite dynamics model, extended from the plant competition model, predicted their coexistence within broad, biologically reasonable ranges of parameters. This work provides field evidence of the coexisting-promoting role of a parasitic plant, as caused by stabilising feedback between host and parasite densities.

Soil mycobiome dissimilarity, independent of fungal guild, is associated with increased probability of plant coexistence

Abstract Major theories regarding microbe‐mediated plant community dynamics assume that plant species cultivate distinct microbial communities. However, few studies empirically assess the role of species‐associated microbial community dissimilarity in plant competitive dynamics. In this study, we paired a competition experiment between eight annual forbs with characterisation of species‐associated fungal communities to assess whether mycobiome dissimilarity is associated with pairwise competitive dynamics. Using a quantitative approach informed by modern coexistence theory, we found that fungal dissimilarity was correlated with both increased stabilising niche differences and fitness inequalities. Additionally, we found that the probability of coexistence increased with mycobiome dissimilarity. When subsetting the community into different fungal functional groups (pathotrophs, saprotrophs, symbiotrophs), overall relationships between dissimilarity and competitive dynamics were independent of these functional groups. Synthesis. These results suggest that fungal community divergence may play an important role in mediating plant competitive dynamics. Although fungal community dissimilarity is associated with both niche and fitness differences, complex biotic and/or abiotic interactions below‐ground may result in an observed correlation between fungal community dissimilarity and plant coexistence. Ultimately, this study suggests a novel approach to better understanding how microbiome dissimilarity may impact host community dynamics.

Germination phenology alters species coexistence outcomes

Abstract Species‐specific phenological responses to changing climate are reshuffling the timing of species interactions, however we do not fully understand the consequences of these changes for species' population dynamics and community composition. In this study, we experimentally manipulated the timing of germination for five annual plant species from southern California and used pairwise competition experiments and coexistence theory to quantify how phenological shifts may impact species interactions and coexistence. We found that phenological shifts may help promote coexistence when they confer an advantage for competitively inferior species, but in other cases promote dominance by competitively superior species. Earlier germination generally increased species' performance relative to competitors, but the relative changes in intra‐and inter‐specific interactions caused more complex effects on niche and fitness differences. Phenological differences tended to reduce stabilising niche differences for many species pairs and reduced overall coexistence probabilities. Synthesis. While phenological differences among species have typically been considered a form of niche partitioning, it seems increasingly likely that phenological offsets could destabilise species coexistence. The net effects of changing phenology on species coexistence will depend on the complex combinations of effects on intra‐ and inter‐specific interactions, which remain challenging to predict.

Influence of Top Slag Containing TiO2 and VOx on Hot Metal Pre-Desulfurization

The desulfurization capacity of top slag in the process of pre-desulfurization of hot metal containing vanadium and titanium was researched. The top slag system of CaO-SiO2-MgO-Al2O3-TiO2-VOx that was formed by blast furnace slag and a CaO desulfurization agent reduced the sulfur in hot metal from 0.08 wt.% to 0.02 wt.%. It was found that the resulfurization of the slag happened in the later periods of the desulfurization process. The vanadium–titanium oxides were both acidic in the desulfurization slag. TiO2 and VOx reacted with the basic oxides to form CaTiO3 and MgV2O4 at 1623 K, which reduced free CaO and was not conducive to top slag desulfurization. The results of calculation showed that the top slag desulfurization accounted for 15% of the total desulfurization. Using the ionic and molecule coexistence theory of slag structure, it is shown that the desulfurization efficiency could be enhanced by adjusting both the amount of desulfurization agent and the composition of the blast furnace slag before pre-desulfurization.

Thermodynamic modelling on the reaction between steel and slag

An integrated thermodynamic model was developed to determine the equilibrium between the slag and the steel at high temperatures, employing the Unified Interaction Parameter Formalism (UIPF) and the Associate Model (AM) for a twelve-element molten steel system (Fe–Al–C–Ca–Cr–Mg–Mn–N–O–S–Si–Ti). A model for slag activity was based on the Ion and Molecular Coexistence Theory (IMCT) and applied to a refining slag system (CaO–MgO–FeO–MnO–CaF2–SiO2–Al2O3–Fe2O3). Comparative analyses were conducted using FactSage software and experimental data, validating the accuracy of the established model. The impact of slag modifiers, specifically aluminum granules, on slag oxidability, and the role of CaO/Al2O3 ratio in slag desulfurization were investigated. The effect of slag modifier on the oxidability and the influence of CaO/Al2O3 on the desulfurization of the slag were determined using the current model. Aluminum in the slag modifier reacted with MnO and FeO in the slag, thereby reducing the oxidability of the slag. With a 30 wt% slag modifier, the MnO content in the slag (initially 15 wt%) stabilized and showed minimal change, dropping below 1 wt%. An increase in CaO content above 80 wt% in the slag led to a reduction of equilibrium sulfur in the steel to below 10 ppm. Little amount of calcium transferred from the slag into the steel with the increase in CaO content, but the [Ca] content remained below 0.5 ppm even though the content of CaO in the slag was greater than 80 wt%. The developed model offered a versatile tool for designing slag compositions tailored to various purposes.

Soil Microbial Community in 47 Chinese Forest Sites: Biogeographic Patterns and Links With Soil Dissolved Organic Matter

AbstractSoils in forested ecosystems are extremely heterogeneous and represent a critical component of terrestrial ecosystems. Despite their substantial ecological value, the geographic characteristics, ecological processes, and coexistence of microbial communities in forest soils remain poorly understood. Here, we investigated the biodiversity dynamics, environmental influences, community assembly, and co‐occurrence patterns of bacterial and fungal communities in surface and subsurface soils across 47 Chinese forest sites. The biogeographic characteristics determined using high‐throughput sequencing data sets revealed evident spatial patterns of bacterial and fungal α and β diversity, assembly processes, and co‐occurrence relationship, with greater variation in the bacterial than in fungal communities. Both fungal and bacterial communities showed significant spatial separations regulated by community assembly processes, co‐occurrence patterns, and soil variables. The microbial dissimilarity was lower in high latitudes than in low latitudes, which was consistent with the lower deterministic processes and relatively higher co‐occurrence associations in high latitudes than in low latitudes. Additionally, there were significant associations of soil dissolved organic matter (DOM) characteristics (e.g., its content, aromaticity, and molecular weight) with biodiversity dissimilarities, microbial assembly process balances, and microbial co‐occurrence relationships in bacterial and fungal communities; they clearly indicate the key role of DOM in regulating microbial biogeographic patterns in forest soil ecosystems. Collectively, our study enhances the understanding of biogeographic patterns and coexistence theories in forest soil microbial ecosystems.

Prediction of titanium burn-off and untimate titanium content in electroslag process

In this study, we investigate the burning behavior of titanium during the electroslag remelting (ESR) process and its impact on the titanium content at the endpoint using machine learning. Initially, a comprehensive database was established by collecting data from literature and experiments, encompassing slag system composition, smelting temperature, and material composition content. Subsequently, six machine learning algorithms, including random forest and Bayesian regression, were employed to model the burning loss behavior of titanium. The random forest model, which exhibited optimal mean square error (MSE) performance, was utilized to generate partial dependence plots. These plots, in conjunction with experimental observations and existing studies, facilitated the analysis of key factors influencing titanium burn loss. Furthermore, the same six machine learning models were applied to predict the endpoint titanium content. The Bayesian regression model demonstrated superior performance in terms of R2 and MSE, leading to the derivation of an empirical formula for predicting endpoint titanium content. This empirical formula was subsequently validated, refined, and optimized using a thermodynamic model based on the theory of molecular ion coexistence. The final prediction formula achieved an error margin of 0.123%.

Aligning spatial ecological theory with the study of clonal organisms: the case of fungal coexistence.

Established ecological theory has focused on unitary organisms, and thus its concepts have matured into a form that often hinders rather than facilitates the ecological study of modular organisms. Here, we use the example of filamentous fungi to develop concepts that enable integration of non-unitary (modular) organisms into the established community ecology theory, with particular focus on its spatial aspects. In doing so, we provide a link between fungal community ecology and modern coexistence theory (MCT). We first show how community processes and predictions made by MCT can be used to define meaningful scales in fungal ecology. This leads to the novel concept of the unit of community interactions (UCI), a promising conceptual tool for applying MCT to communities of modular organisms with indeterminate clonal growth and hierarchical individuality. We outline plausible coexistence mechanisms structuring fungal communities, and show at what spatial scales and in what habitats they are most likely to act. We end by describing challenges and opportunities for empirical and theoretical research in fungal competitive coexistence.

Temperature-driven dynamics: unraveling the impact of climate change on cryptic species interactions within the Litoditis marina complex.

Anthropogenic climate change and the associated increase in sea temperatures are projected to greatly impact marine ecosystems. Temperature variation can influence the interactions between species, leading to cascading effects on the abundance, diversity and composition of communities. Such changes in community structure can have consequences on ecosystem stability, processes and the services it provides. Therefore, it is important to better understand the role of species interactions in the development of communities and how they are influenced by environmental factors like temperature. The coexistence of closely related cryptic species, with significant biological and ecological differences, makes this even more complex. This study investigated the effect of temperature on species growth and both intra- and interspecific interactions of three species within the free-living nematode Litoditis marina complex. To achieve this, closed microcosm experiments were conducted on the L. marina species Pm I, Pm III and Pm IV in monoculture and combined cultures at two temperature treatments of 15 °C and 20 °C. A population model was constructed to elucidate and quantify the effects of intra- and interspecific interactions on nematode populations. The relative competitive abilities of the investigated species were quantified using the Modern Coexistence Theory (MCT) framework. Temperature had strong and disparate effects on the population growth of the distinct L. marina species. This indicates temperature could play an important role in the distribution of these cryptic species. Both competitive and facilitative interactions were observed in the experiments. Temperature affected both the type and the strength of the species interactions, suggesting a change in temperature could impact the coexistence of these closely related species, alter community dynamics and consequently affect ecosystem processes and services.

Mechanisms of microbial coexistence in a patchy ecosystem: Differences in ecological niche overlap and species fitness between rhythmic and non-rhythmic species

Resource patchiness caused by external events breaks the continuity and homogeneity of resource distribution in the original ecosystem. For local organisms, this leads to drastic changes in the availability of resources, breaks down the co-existence of species, and reshuffles the local ecosystem. West Lake is a freshwater lake with resource patchiness caused by multiple exogenous disturbances that has strong environmental heterogeneity that prevents clear observation of seasonal changes in the microbial communities. Despite this, the emergence of rhythmic species in response to irregular changes in the environment has been helpful for observing microbial communities dynamics in patchy ecosystems. We investigated the ecological mechanisms of seasonal changes in microbial communities in West Lake by screening rhythmic species based on the ecological niche and modern coexistence theories. The results showed that rhythmic species were the dominant factors in microbial community changes and the effects of most environmental factors on the microbial community were indirectly realised through the rhythmic species. Random forest analyses showed that seasonal changes in the microbial community were similarly predicted by the rhythmic species. In addition, we incorporated species interactions and community phylogenetic patterns into stepwise multiple regression analyses, the results of which indicate that ecological niches and species fitness may drive the coexistence of these subcommunities. Thus, this study extends our understanding of seasonal changes in microbial communities and provides new ways for observing seasonal changes in microbial communities, especially in ecosystems with resource patches. Our study also show that combining community phylogenies with co-occurrence networks based on ecological niches and modern coexistence theory can further help us understand the ecological mechanisms of interspecies coexistence.

Beyond Tolerance: Mitigating Human-Wildlife Conflict with Hospitality.

Tolerance has become a central position in wildlife conservation thought, and a goal in and of itself. Appeals to tolerance are expected to grow as the planet becomes more crowded, species are lost, and habitat is degraded. The concept has been uncritically adopted in wildlife conservation to mitigate human-wildlife conflicts (HWCs). However, scholars have demonstrated that tolerance is burdened with limitations, paradoxes, and shortcomings. Thus, blind adherence to it is not expected to produce a coexistence design necessary to sustain wildlife populations in the long term. This paper is a conceptual scoping project that engages a summary and critique of tolerance as a design principle within wildlife conservation governance. After introducing a resultant theory of dysfunctional human-wildlife coexistence, a pathway toward hospitality as a social institution is outlined via several commitments societies can make to transition to an era of normalizing a process of sincere welcoming, care, and support. The transition from tolerance to hospitality will entail shifting responsibility to humans to modify their behavior to help keep wildlife invisible where it is essential, learning about what wildlife want and need, and ensuring wildlife is not injured for being themselves.

Influence of the Basicity on Phosphorus Enrichment Properties of Decarbonization Slag in Low‐Carbon Double Slag Converter Steelmaking Process with Industrial Experiments, Mineralogy, and Ion–molecule Coexistence Theory

To achieve low‐cost clean production in steelmaking plants, a low‐carbon double slag converter steelmaking process (LCDSP) with high dephosphorization efficiency, low lime consumption, and low CO2 emissions is focused on. The average lime consumption in LCDSP has decreased about 25.8%, which can reduce at least about 10.3 million m3 CO2 emissions per converter per year in the current steelmaking plant. The phosphorus enrichment properties of decarbonization slag with different basicities are comprehensively evaluated through LCDSP industrial experiments, mineralogy, and ion–molecule coexistence theory (IMCT). The increase of decarburization slag basicity (DSB) significantly improves the dephosphorization efficiency of molten steel. With increasing the DSB from 2.93 to 3.52, the typical morphology of the P‐rich phase extends from small pieces to long strips and then changes to block shapes with smooth edges. Finally, it forms a massive P‐rich phase with an area of more than 10 000 μm2 with a DSB of 3.80. The phosphorus enrichment properties of decarbonization slag with different DSBs evaluated using multiple perspectives show a consistent change trend. IMCT provides an accurate thermodynamic method for quantitatively predicting the phosphorus enrichment capacity in slag in two stages of LCDSP.

The three-species problem: Incorporating competitive asymmetry and intransitivity in modern coexistence theory.

While natural communities can contain hundreds of species, modern coexistence theory focuses primarily on species pairs. Alternatively, the structural stability approach considers the feasibility of equilibria, gaining scalability to larger communities but sacrificing information about dynamic stability. Three-species competitive communities are a bridge to more-diverse communities. They display novel phenomena while remaining amenable to mathematical analysis, but remain incompletely understood. Here, we combine these approaches to identify the key quantities that determine three-species competition outcomes. We show that pairwise niche overlap and fitness differences are insufficient to completely characterize competitive outcomes, which requires a strictly triplet-wise quantity: cyclic asymmetry, which underlies intransitivity. Low pairwise niche overlap stabilizes the triplet, while high fitness differences promote competitive exclusion. The effect of cyclic asymmetry on stability is complex and depends on pairwise niche overlap. In summary, we elucidate how pairwise niche overlap, fitness differences and cyclic asymmetry determine three-species competition outcomes.

Phosphorus Removal Properties of the Fe–C–Si–Mn–P–S Metallic Melts Based on the Atom–Molecule Coexistence Theory: Mutual Verification by Industrial and Laboratorial Experiments

Phosphorus Removal Properties of the Fe–C–Si–Mn–P–S Metallic Melts Based on the Atom–Molecule Coexistence Theory: Mutual Verification by Industrial and Laboratorial Experiments

Temporal development in the impacts of plant invasions: search for the underlying mechanisms.

Many invasive plants have negative impacts on native populations and communities, but there remains much uncertainty about how these impacts develop over time. In this review, I describe the mechanisms that promote the initial dominance of invaders, the characteristic associated with large negative impacts, and present the processes that contribute to changes in invader abundance and impacts over time. Together with ecological processes such as ecosystem engineering or enemy accumulation, I show that temporal variation in impacts can be linked to evolution in both native and invasive species. I also show that multiple processes operating in the same invasion system can jointly shape long-term impacts. Finally, I present the framework of modern of coexistence theory as a tool for predicting the effects of invaders on native populations, and how these effects change with processes ongoing within invaded communities.

Control of Aluminum and Titanium Contents in the Electroslag Remelting of ATI 718PlusTM Alloy.

The burning loss of Al and Ti elements in superalloys during electroslag remelting has become a prevalent issue. And the existing slag system is not suitable for smelting the ATI 718PlusTM alloy. Therefore, it is imperative to develop a new slag system for smelting the ATI 718PlusTM alloy. To mitigate this issue, a thermodynamic model of the oxidation reaction of Al and Ti at the slag and alloy interface was established based on the ion and molecule coexistence theory (IMCT). The thermodynamic model was used to investigate the correlation between the equilibrium content of Al and Ti, slag composition, smelting temperature, and initial Al and Ti content of the electrode. The results indicate that while increasing the smelting temperature can effectively inhibit the burning loss of Al, it will exacerbate the burning loss of Ti. Increasing CaO and Al2O3 contents can inhibit the Al burning loss, while an increase in the TiO2 content can inhibit the Ti burning loss. Although an increase in the MgO content results in the burning loss of Al, its impact on the Al is minimal. The burning loss of Al and Ti was not affected by the change in the CaF2 content. The high Al content in ATI 718PlusTM makes it prone to burning loss of Al during the electroslag remelting. The combustion loss of Al can be reduced by increasing the Ti content in the electrode or adding a suitable amount of aluminum powder to the slag system. The accuracy of the model had been validated through experimental verification.

Widespread analytical pitfalls in empirical coexistence studies and a checklist for improving their statistical robustness

Abstract Modern coexistence theory (MCT) offers a conceptually straightforward approach for connecting empirical observations with an elegant theoretical framework, gaining popularity rapidly over the past decade. However, beneath this surface‐level simplicity lie various assumptions and subjective choices made during data analysis. These can lead researchers to draw qualitatively different conclusions from the same set of experiments. As the predictions of MCT studies are often treated as outcomes, and many readers and reviewers may not be familiar with the framework's assumptions, there is a particular risk of ‘researcher degrees of freedom’ inflating the confidence in results, thereby affecting reproducibility and predictive power. To tackle these concerns, we introduce a checklist consisting of statistical best practices to promote more robust empirical applications of MCT. Our recommendations are organised into four categories: presentation and sharing of raw data, testing model assumptions and fits, managing uncertainty associated with model coefficients and incorporating this uncertainty into coexistence predictions. We surveyed empirical MCT studies published over the past 15 years and discovered a high degree of variation in the level of statistical rigour and adherence to best practices. We present case studies to illustrate the dependence of results on seemingly innocuous choices among competition model structure and error distributions, which in some cases reversed the predicted coexistence outcomes. These results demonstrate how different analytical approaches can profoundly alter the interpretation of experimental results, underscoring the importance of carefully considering and thoroughly justifying each step taken in the analysis pathway. Our checklist serves as a resource for authors and reviewers alike, providing guidance to strengthen the empirical foundation of empirical coexistence analyses. As the field of empirical MCT shifts from a descriptive, trailblazing phase to a stage of consolidation, we emphasise the need for caution when building upon the findings of earlier studies. To ensure that progress made in the field of ecological coexistence is based on robust and reliable evidence, it is crucial to subject our predictions, conclusions and generalisability to a more rigorous assessment than is currently the trend.

The role of plasticity and stochasticity in coexistence.

Species coexistence in ecological communities is a central feature of biodiversity. Different concepts, i.e., contemporary niche theory, modern coexistence theory, and the unified neutral theory, have identified many building blocks of such ecological assemblies. However, other factors, such as phenotypic plasticity and stochastic inter-individual variation, have received little attention, in particular in animals. For example, how resource polyphenisms resulting in predator-prey interactions affect coexistence is currently unknown. Here, we present an integrative theoretical-experimental framework using the nematode plasticity model Pristionchus pacificus with its well-studied mouth-form dimorphism resulting in cannibalism. We develop an individual-based model that relies upon synthetic data based on our empirical measurements of fecundity and polyphenism to preserve demographic heterogeneity. We demonstrate how the interplay between plasticity and individual stochasticity result in all-or-nothing outcomes at the local level. Coexistence is made possible when spatial structure is introduced.