Robust Coexistence Research Articles

The social landscape of wolves in Canada - preliminary findings

ABSTRACT Despite the long-standing presence of wolves (Canis lupus) in Canada, attitudes toward wolves have been understudied at the national scale. However, such data can inform wildlife management policies and robust coexistence strategies. We developed an 11-question survey to assess “the social landscape” of wolves in Canada. We explored the following research questions: 1) Are attitudes toward wolves generally positive? 2) What is the role of proximity on attitudes toward and tolerance for wolves? 3) What demographic characteristics matter most? Preliminary results indicate that Canadians have positive attitudes toward wolves regardless of age, gender, province, and vote in the last federal election; only ethnicity had a statistically significant effect. We also found that positive attitude is related to proximity and tolerance. More research with larger sample sizes and more focused surveys are needed to delve deeper into these preliminary results.

When can higher-order interactions produce stable coexistence?

Most ecological models are based on the assumption that species interact in pairs. Diverse communities, however, can have higher-order interactions, in which two or more species jointly impact the growth of a third species. A pitfall of the common pairwise approach is that it misses the higher-order interactions potentially responsible for maintaining natural diversity. Here, we explore the stability properties of systems where higher-order interactions guarantee that a specified set of abundances is a feasible equilibrium of the dynamics. Even these higher-order interactions which lead to equilibria do not necessarily produce stable coexistence. Instead, these systems are more likely to be stable when the pairwise interactions are weak or facilitative. Correlations between the pairwise and higher-order interactions, however, do permit robust coexistence even in diverse systems. Our work not only reveals the challenges in generating stable coexistence through higher-order interactions but also uncovers interaction patterns that can enable diversity.

Population regulation and adaptive dynamics of cross-feeding.

The particular importance of evolutionary studies in microbial experimental systems is that starting from the level of the metabolism of individual cells, the adaptive dynamics can be followed step by step by biochemical, genetic, and population dynamical tools. Moreover, the coincidence of evolutionary and ecological time scales helps to clarify the mutual role of ecological and evolutionary principles in predicting adaptive dynamics in general. Ecological principles define the ecological conditions under which adaptive branching can occur. This paper overviews and interprets the results of empirical and modeling studies of the evolution of metabolic cross-feeding in glucose-limited E.coli chemostats and batch cultures in the context of theories of robust coexistence and adaptive dynamics. Empirical results consistently demonstrate that the interactions between cells are mediated by the changing metabolite concentrations in the cultures and modeling confirms that these changes may control the adaptive dynamics of the clones. In consequence, the potential results of evolution can be predicted at the functional level by evolutionary flux balance analysis (evoFBA), while the genetic changes are more contingent. evoFBA follows the scheme of adaptive dynamics theory by calculating the feedback environment that changes during the evolutionary process and provides a promising tool to further investigate adaptive divergence in small microbial communities. Three general conclusions close the paper.

Plant-frugivore networks are robust to species loss even in highly built-up urban ecosystems.

Animal seed dispersal processes are an important aspect of ecosystem services, as they shape the survival of seed dispersers and the balanced distribution of propagules for many plant communities. Several studies within tropical wild ecosystems have generally shown that seed dispersal processes are highly generalised and robust to extinction. Studies examining seed dispersal networks in highly built-up urban ecosystems and their robustness to species loss or extinction are rare. We examined avian seed dispersal networks across an urban ecosystem characterised by a high human settlement and infrastructure of the built environment in Zambia to determine their network specialisation, interaction evenness and interaction diversity, as these three parameters are critical in driving the resilience of these mutualisms' interactions against extinction. A total of 405 individuals representing 11 species of birds were observed and recorded feeding on a total of 11 focal fleshy-fruiting plant species. Network specialisation was generally low and remained similar across study areas. Interaction evenness and interaction diversity were not only high but also remained similar across study areas. Low specialisation and high interaction evenness and diversity show that mutualistic interactions in these networks are equally highly generalised, suggesting a stable and robust coexistence of species in plant-frugivore communities within urban ecosystems. Generally, our results seem to broadly suggest that opportunities for conservation still exist in these ecosystems provided urbanisation is accompanied by promoting either the management of remnant fruiting plants or the cultivation of new ones to support the avian communities existing in these areas.

Multidimensional niche differentiation might buffer invasion impacts: the case of oligohaline corophiids (Crustacea: Amphipoda) in the Baltic Sea

Multidimensional niche differentiation might increase the stability of coexistence by reducing overall niche overlap which might have implications on the dynamics of biological invasions. The oligohaline Baltic Seais inhabited by three native and one invasive corophiid amphipod species. These filter feeding crustaceans differ in their substrate preferences and salinity optima which could potentially allow their robust coexistence. However, recent theory predicts that competing species must diverge across all non-substitutable resources (e.g., food and space). We have measured the filter mesh size in the four species (i.e., the distance between bristles on the filtering setae), revealing considerable differences among the three natives (Apocorophium lacustre, Corophium multisetosum and C. volutator), whereas the invasive Chelicorophium curvispinum showed strong overlap with A. lacustre. Theory suggests that the four species cannot coexist robustly due to their overlap in food particle size irrespective of differences in their salinity optima and substrate preferences which is in accordance with observations of local extinctions of A. lacustre. Nevertheless, the stability ensuing from the multidimensional niche differentiation might delay competitive exclusion; i.e., the spatial separation by salinity and substrate types might decrease the intensity of competition for food. Our data for co-occurring populations indicate that A. lacustre might be able to decrease its filter mesh size overlap with C. curvispinum by character displacement and its broader salinity tolerance also might help the native species to persist in the region. However, the niche shift of the species might increase its overlap with C. multisetosum.

Structural stability of coexistence in evolutionary dynamics of cyclic competition

One of the common assumptions in previous spatial dynamics of cyclic competition is that, regardless of competing structure and strength among species, the spatial size of a network is considered as large as possible to avoid finite size effect for species biodiversity. In real ecosystems, however, species richness, which can be defined by spatial size and competition strength, can sensitively affect species coexistence as a competition among individuals becomes complicated. In this paper, we investigate the structural stability of coexistence of mobile species in three cyclic competition games due to network complexity in which imposes a size of a square lattice and competition strength among species. By exploiting the coexistence probability, our computations quantitatively reveal that the network complexity due to changes in the competition rate and lattice size can strongly affect the structural stability of coexistence in each model. In particular, intense intraspecific competition can yield the robust coexistence at small-sized lattices regardless of mobility, and strengthening interspecific competition simultaneously induces changes in critical mobility that hampers coexistence and in spatial size for stable coexistence. Qualitatively, we find that such structural stability of coexistence relates to the degree of stability of fixed points in deterministic systems. Our finding can be useful to gain insights into species coexistence on spatially extended systems with respect to network complexity.

Two Qualitatively Different Superconducting Phases under High Pressure in Single-Crystalline CeNiGe3

We have measured the temperature dependence of resistivity in single-crystalline CeNiGe$_{3}$ under hydrostatic pressure in order to establish the characteristic pressure-temperature phase diagram. The transition temperature to AFM-I phase $T_{\rm N1}$ = 5.5 K at ambient pressure initially increases with increasing pressure and has a maximum at $\sim$ 3.0 GPa. Above 2.3 GPa, a clear zero-resistivity is observed (SC-I phase) and this superconducting (SC) state coexists with AFM-I phase. The SC-I phase suddenly disappears at 3.7 GPa simultaneously with the appearance of an additional kink anomaly corresponding to the phase transition to AFM-II phase. The AFM-II phase is continuously suppressed with further increasing pressure and disappears at $\sim$ 6.5 GPa. In the narrow range near the critical pressure, an SC phase reappears (SC-II phase). A large initial slope of upper critical field $\mu_0H_{\rm c2}$ and non-Fermi liquid behavior indicate that the SC-II phase is mediated by antiferromagnetic fluctuations. On the other hand, the robust coexistence of the SC-I phase and AFM-I phase is unusual on the contrary to superconductivity near a quantum critical point on most of heavy-fermion compounds.

A closer look at turbulence spreading: How bistability admits intermittent, propagating turbulence fronts

In magnetic fusion plasmas, mounting evidence suggests the possibility of sustained turbulence below the linear stability threshold or more generally global turbulence bistability. The usual reduced models for turbulence spreading are unistable/supercritical and incompatible with this result. The older models also cannot realistically support fronts connecting laminar and turbulent domains. In this work, a minimal model for “subcritical” turbulence spreading is introduced and analyzed. The model may be viewed as phenomenological or derived directly by considering the effect of profile corrugations in an E × B staircase. The model, which is related to the FitzHugh–Nagumo system, supports the robust coexistence of multiple turbulence levels via bistability. We show that this model predicts stronger penetration of turbulence into a linearly stable region as well as the formation of intermittent turbulence fronts that resemble avalanches. We derive the critical size that a localized slug of turbulence must exceed in order to spread. Finally, we make a prediction of global hysteretic behavior associated with the bistability, which should be testable via experiment.

An energy landscape approach to understanding variety and robustness in tissue morphogenesis

During morphogenesis in development, multicellular tissues deform by mechanical forces induced by spatiotemporally regulated cellular activities, such as cell proliferation and constriction. Various morphologies are formed because of various spatiotemporal combinations and sequences of multicellular activities. Despite its potential to variations, morphogenesis is a surprisingly robust process, in which qualitatively similar morphologies are reproducibly formed even under spatiotemporal fluctuation of multicellular activities. To understand these essential characteristics of tissue morphogenesis, which involves the coexistence of various morphologies and robustness of the morphogenetic process, in this study, we propose a novel approach to capture the overall view of morphogenesis from mechanical viewpoints. This approach will enable visualization of the energy landscape, which includes morphogenetic processes induced by admissible histories of cellular activities. This approach was applied to investigate the morphogenesis of a sheet-like tissue with curvature, where it deformed to a concave or convex morphology depending on the history of growth and constriction. Qualitatively different morphologies were produced by bifurcation of the valley in the energy landscape. The depth and steepness of the valley near the stable states represented the degree of robustness to fluctuations of multicellular activities. Furthermore, as a realistic example, we showed an application of this approach to luminal folding observed in the initial stage of intestinal villus formation. This approach will be helpful to understand the mechanism of how various morphologies are formed and how tissues reproducibly achieve specific morphologies.

Robust coexistence with alternative competition strategy in the spatial cyclic game of five species.

Alternative strategy is common in animal populations to promote reproductive fitness by obtaining resources. In spatial dynamics of cyclic competition, reproduction can occur when individuals obtain vacant rooms and, in this regard, empty sites should be resources for reproduction which can be induced by interspecific competition. In this paper, we study the role of alternative competition in the spatial system of cyclically competing five species by utilizing rock-paper-scissors-lizard-spock game. From Monte-Carlo simulations, we found that strong alternative competition can lead to the reemergence of coexistence of five species regardless of mobility, which is never reported in previous works under the symmetric competition structure. By investigating the coexistence probability, we also found that coexistence alternates by passing certain degrees of alternative competition in combination with mobility. In addition, we provided evidences in the opposite scenario by strengthening spontaneous competition, which exhibits the reemergence of coexistence similarly. Our findings may suggest more comprehensive perspectives to interpret mechanisms for biodiversity by alternative strategies in spatially extended systems than previously reported.

Asymmetric interplay leads to robust coexistence by means of a global attractor in the spatial dynamics of cyclic competition.

In the past decade, there have been many efforts to understand the species interplay with biodiversity in cyclic games within the macro and microscopic levels. In this direction, mobility and intraspecific competition have been found to be the main factors promoting coexistence in spatially extended systems. In this paper, we explore the relevant effect of asymmetric competitions coupled with mobility on the coexistence of cyclically competing species. By examining the coexistence probability, we have found that mobility can facilitate coexistence in the limited cases of asymmetric competition and can be well predicted by the basin structure of the deterministic system. In addition, it is found that mobility can have beneficial and harmful effects on coexistence when all competitions occur asymmetrically. We also found that the coexistence in the spatial dynamics ultimately becomes a global attractor. We hope to provide insights into the associated effects of asymmetric interplays on species coexistence in a spatially extended system and understand the biodiversity of asymmetrically competitive species under more complex competition structures.

Deciphering microbial interactions in synthetic human gut microbiome communities

The ecological forces that govern the assembly and stability of the human gut microbiota remain unresolved. We developed a generalizable model‐guided framework to predict higher‐dimensional consortia from time‐resolved measurements of lower‐order assemblages. This method was employed to decipher microbial interactions in a diverse human gut microbiome synthetic community. We show that pairwise interactions are major drivers of multi‐species community dynamics, as opposed to higher‐order interactions. The inferred ecological network exhibits a high proportion of negative and frequent positive interactions. Ecological drivers and responsive recipient species were discovered in the network. Our model demonstrated that a prevalent positive and negative interaction topology enables robust coexistence by implementing a negative feedback loop that balances disparities in monospecies fitness levels. We show that negative interactions could generate history‐dependent responses of initial species proportions that frequently do not originate from bistability. Measurements of extracellular metabolites illuminated the metabolic capabilities of monospecies and potential molecular basis of microbial interactions. In sum, these methods defined the ecological roles of major human‐associated intestinal species and illuminated design principles of microbial communities.

Phenotypes can be robust and evolvable if mutations have non-local effects on sequence constraints.

The mapping between biological genotypes and phenotypes plays an important role in evolution, and understanding the properties of this mapping is crucial to determine the outcome of evolutionary processes. One of the most striking properties observed in several genotype-phenotype (GP) maps is the positive correlation between the robustness and evolvability of phenotypes. This implies that a phenotype can be strongly robust against mutations and at the same time evolvable to a diverse range of alternative phenotypes. Here, we examine the causes for this positive correlation by introducing two analytically tractable GP map models that follow the principles of real biological GP maps. The first model is based on gene-like GP maps, reflecting the way in which genetic sequences are organized into protein-coding genes, and the second one is based on the GP map of RNA secondary structure. For both models, we find that a positive correlation between phenotype robustness and evolvability only emerges if mutations at one sequence position can have non-local effects on the sequence constraints at another position. This highlights that non-local effects of mutations are closely related to the coexistence of robustness and evolvability in phenotypes, and are likely to be an important feature of many biological GP maps.

Smart Bandwidth Assignation in an Underlay Cellular Network for Internet of Vehicles.

The evolution of the IoT (Internet of Things) paradigm applied to new scenarios as VANETs (Vehicular Ad Hoc Networks) has gained momentum in recent years. Both academia and industry have triggered advanced studies in the IoV (Internet of Vehicles), which is understood as an ecosystem where different types of users (vehicles, elements of the infrastructure, pedestrians) are connected. How to efficiently share the available radio resources among the different types of eligible users is one of the important issues to be addressed. This paper briefly analyzes various concepts presented hitherto in the literature and it proposes an enhanced algorithm for ensuring a robust co-existence of the aforementioned system users. Therefore, this paper introduces an underlay RRM (Radio Resource Management) methodology which is capable of (1) improving cellular spectral efficiency while making a minimal impact on cellular communications and (2) ensuring the different QoS (Quality of Service) requirements of ITS (Intelligent Transportation Systems) applications. Simulation results, where we compare the proposed algorithm to the other two RRM, show the promising spectral efficiency performance of the proposed RRM methodology.

Evolution of antibiotic resistance is linked to any genetic mechanism affecting bacterial duration of carriage

Understanding how changes in antibiotic consumption affect the prevalence of antibiotic resistance in bacterial pathogens is important for public health. In a number of bacterial species, including Streptococcus pneumoniae, the prevalence of resistance has remained relatively stable despite prolonged selection pressure from antibiotics. The evolutionary processes allowing the robust coexistence of antibiotic sensitive and resistant strains are not fully understood. While allelic diversity can be maintained at a locus by direct balancing selection, there is no evidence for such selection acting in the case of resistance. In this work, we propose a mechanism for maintaining coexistence at the resistance locus: linkage to a second locus that is under balancing selection and that modulates the fitness effect of resistance. We show that duration of carriage plays such a role, with long duration of carriage increasing the fitness advantage gained from resistance. We therefore predict that resistance will be more common in strains with a long duration of carriage and that mechanisms maintaining diversity in duration of carriage will also maintain diversity in antibiotic resistance. We test these predictions in S. pneumoniae and find that the duration of carriage of a serotype is indeed positively correlated with the prevalence of resistance in that serotype. These findings suggest heterogeneity in duration of carriage is a partial explanation for the coexistence of sensitive and resistant strains and that factors determining bacterial duration of carriage will also affect the prevalence of resistance.

Right tech, wrong time

Why do some transformative technologies dominate the market quickly, while others take decades to catch on? It’s a function not just of the technologies themselves, say the authors, but also of their broader ecosystems (electric cars, for example, need a network of charging stations). The ecosystems of the legacy technologies matter too—they can sometimes be improved enough to prolong the life of the old technology. Analyzing the ecosystem dynamics in your industry can help you predict how quickly technological change will occur. For example, if the new technology is surrounded by viable complements and there’s little room to improve the old technology’s ecosystem, substitution is rapid (creative destruction). When the opposite conditions hold—the new technology’s ecosystem needs work and the old technology can capitalize on improvements in the established ecosystem—the pace of substitution is very slow (robust resilience). The authors describe two other possible scenarios: robust coexistence of the two technologies, and the illusion of resistance (the old technology seems competitive for some time but quickly succumbs once the new technology’s ecosystem is ready to roll). If you understand which scenario applies to you, you can better assess the threat of disruptive change—and use the authors’ insights to respond effectively. [ABSTRACT FROM AUTHOR]

A resource-based game theoretical approach for the paradox of the plankton.

The maintenance of species diversity is a central focus in ecology. It is not rare to observe more species than the number of limiting resources, especially in plankton communities. However, such high species diversity is hard to achieve in theory under the competitive exclusion principles, known as the plankton paradox. Previous studies often focus on the coexistence of predefined species and ignore the fact that species can evolve. We model multi-resource competitions using evolutionary games, where the number of species fluctuates under extinction and the appearance of new species. The interspecific and intraspecific competitions are captured by a dynamical payoff matrix, which has a size of the number of species. The competition strength (payoff entries) is obtained from comparing the capability of species in consuming resources, which can change over time. This allows for the robust coexistence of a large number of species, providing a possible solution to the plankton paradox.

A new ferromagnetic superconductor: CsEuFe4As4

Superconductivity (SC) and ferromagnetism (FM) are in general antagonistic, which makes their coexistence very rare. Following our recent discovery of robust coexistence of SC and FM in RbEuFe4As4 (Liu et al. in Phys Rev B 93:214503, 2016), here we report another example of such a coexistence in its sister compound CsEuFe4As4, synthesized for the first time. The new material exhibits bulk SC at 35.2K and Eu2+-spin ferromagnetic ordering at 15.5K, demonstrating that it is a new robust ferromagnetic superconductor.

Host Gut Motility Promotes Competitive Exclusion within a Model Intestinal Microbiota.

The gut microbiota is a complex consortium of microorganisms with the ability to influence important aspects of host health and development. Harnessing this “microbial organ” for biomedical applications requires clarifying the degree to which host and bacterial factors act alone or in combination to govern the stability of specific lineages. To address this issue, we combined bacteriological manipulation and light sheet fluorescence microscopy to monitor the dynamics of a defined two-species microbiota within a vertebrate gut. We observed that the interplay between each population and the gut environment produces distinct spatiotemporal patterns. As a consequence, one species dominates while the other experiences sudden drops in abundance that are well fit by a stochastic mathematical model. Modeling revealed that direct bacterial competition could only partially explain the observed phenomena, suggesting that a host factor is also important in shaping the community. We hypothesized the host determinant to be gut motility, and tested this mechanism by measuring colonization in hosts with enteric nervous system dysfunction due to a mutation in the ret locus, which in humans is associated with the intestinal motility disorder known as Hirschsprung disease. In mutant hosts we found reduced gut motility and, confirming our hypothesis, robust coexistence of both bacterial species. This study provides evidence that host-mediated spatial structuring and stochastic perturbation of communities can drive bacterial population dynamics within the gut, and it reveals a new facet of the intestinal host–microbe interface by demonstrating the capacity of the enteric nervous system to influence the microbiota. Ultimately, these findings suggest that therapeutic strategies targeting the intestinal ecosystem should consider the dynamic physical nature of the gut environment.

Superconductivity and ferromagnetism in hole-dopedRbEuFe4As4

We discover a robust coexistence of superconductivity and ferromagnetism in an iron arsenide RbEuFe$_4$As$_4$. The new material crystallizes in an intergrowth structure of RbFe$_2$As$_2$ and EuFe$_2$As$_2$, such that the Eu sublattice turns out to be primitive instead of being body-centered in EuFe$_2$As$_2$. The FeAs layers, featured by asymmetric As coordinations, are hole doped due to charge homogenization. Our combined measurements of electrical transport, magnetization and heat capacity unambiguously and consistently indicate bulk superconductivity at 36.5 K in the FeAs layers and ferromagnetism at 15 K in the Eu sublattice. Interestingly, the Eu-spin ferromagnetic ordering belongs to a rare third-order transition, according to the Ehrenfest classification of phase transition. We also identify an additional anomaly at $\sim$ 5 K, which is possibly associated with the interplay between superconductivity and ferromagnetism.