Ecological Complexity最新文献

This paper studies the dynamic behavior of a discrete-time prey-predator model. It is shown that this model undergoes codimension one and codimension two bifurcations such as transcritical, flip (period-doubling), Neimark-Sacker and strong resonances 1:2, 1:3 and 1:4. The bifurcation analysis is based on the numerical normal form method and the bifurcation scenario around the bifurcation point is determined by their critical normal form coefficients. The advantage of this method is that there is no need to calculate the center manifold and to convert the linear part of the map to a Jordan form. The bifurcation curves of fixed points under variation of one and two parameters are obtained, and the codimensions one and the two bifurcations on the corresponding curves are computed.

Like predation and competition, mutualism is recognized as a consumer-resource interaction, which includes bi-directional and uni-directional mutualisms. In this paper, we firstly propose a stochastic uni-directional consumer-resource system of two species in which the consumer has both positive and negative effects on the resource, while the resource has only a positive effect on the consumer. We then mathematically analyze the system, to demonstrate the existence, uniqueness, asymptotic pathwise behavior and stochastically ultimately boundedness of the global positive solution, and to establish sufficient conditions for the global attractivity and the existence of ergodic stationary distribution of the system. We also establish sufficient conditions for the extinction and persistence in mean of the resource, the consumer or the entire system. Numerical simulations are carried out to demonstrate the analytical results.

Ecological interactions between native species are often disturbed by invasive species. However, to understand their impact on wild native animal populations on a country scale it is necessary to develop a predictive model. Therefore, I followed the species density distribution modelling approach to explore how feral domestic cats (Felis catus) along with environmental predictors determined densities of two bird species, the Yellowhammer (Emberiza citrinella) and the Yellow Wagtail (Motacilla flava) on the whole area of Poland. As a modelling method, I used the Generalised Additive Model to develop two models for each of the two bird species: The first with the feral cat density as an additional predictor, and the second without it. As a result, I demonstrated the negative impact of cat density on native bird populations, illustrated by reduced density of the two studied species in their preferred habitats, in which cats reached a high density. Although it cannot be explicitly asserted that cats lead to a local extinction of the two bird species, these predators should not be underestimated. In many locations feral populations are fed with new individuals, and they do not follow the same internal mechanisms regulating their population as the native bird fauna. Thus, on a large spatial scale species density distribution models of birds should include cats’ population size as an additional predictor when this predator's environmental preferences overlap with preferences of the studied target groups.

Habitat fragmentation and connectivity loss pose significant threats to biodiversity at both local and landscape levels. Strategies to increase ecological connectivity and preserve strong connectivity are important for dealing with the potential threat of habitat degradation. Various metrics have been used to measure (i.e., quantify) landscape composition and configuration in landscape ecology. However, their relationship with ecological connectivity must be understood to interpret landscape patterns comprehensively. In the present study, correlations between ecological connectivity and land complexity are examined based on information-theory metrics. Two primary questions are explored: (1) to what extent are landscape mosaic measures of entropy correlated with ecological connectivity, with landscape gradient-based measures, and with each other? (2) are landscape gradient-based entropy measures correlated with ecological connectivity more than discrete entropy measures? Results show that all information theoretic metrics are statistically significant (p < 0.05) for modelling ecological connectivity. Among categorically-based indices, the relationship between ECI and joint entropy was the most significant, while a generalized additive model indicated that Boltzmann entropy could predict the ecological connectivity index, explaining ∼60% of the variance. Therefore, configurational entropy can be used for improving ecological connectivity models.

Cooperation is a mysterious evolutionary phenomenon and its mechanisms require elucidation. When cooperators can stop interactions with defectors, the evolution of cooperation becomes possible; this is one mechanism that facilitates the evolution of cooperation. Here, stopping interactions with defectors is beneficial not only for cooperators but also for defectors. The question then arises, for whom is stopping interactions with defectors more beneficial: cooperators or defectors? By utilizing evolutionary game theory, I addressed this question using a two-player game involving four strategies: (1) cooperators who stop the interaction if the current partner is a defector, (2) cooperators who attempt to maintain a relationship with anyone, (3) defectors who stop the interaction if the current partner is a defector, and (4) defectors who attempt to maintain a relationship with anyone. Our results show that, at equilibrium, the ratio of cooperators who stop the interaction if the current partner is a defector to cooperators who attempt to maintain a relationship with anyone is larger than the ratio of defectors who stop the interaction if the current partner is a defector to defectors who attempt to maintain a relationship with anyone. Thus, cooperators rather than defectors are more likely to stop interactions with defectors at equilibrium. This result is consistent with a previous experimental study in which a positive correlation was detected between the degree of individuals’ cooperativeness and how accurately the individuals recognize whether other individuals are cooperators or defectors. Thus, the theoretical work presented in this study provides relevant insights into the natural phenomena of cooperation and recognition.

Mitigating the poaching pressure on food webs under multiple constraints (including financial and ecological ones) remains an open problem within conservation. Within this field, mathematically modeling the effects of poaching threats on managerial decision-making is a novel approach. To fill this scientific gap, the present paper uses a security game approach to model the interactions between an environmental manager (defender) and a group of profit-seeking pursuit poachers (attackers) who target species which are nodes of the food web. Based upon the non-cooperative Stackelberg game, the objective of the defender (as leader) is to keep the food web at or near equilibrium through optimally manipulating the populations of an optimal subset of species. In contrast, each attacker strives to maximize monetary profit by hunting an optimal population size of the selected species. The model is validated by a numerical example examining the food web of the endangered Persian leopard (Panthera pardus saxicolor), which lives in Golestan National Park (GNP), Iran. The model provides an overarching biotic intervention strategy to keep the (1 predator-4 prey) food web near equilibrium, while only 2 prey species (the urial (Ovis vignei) and the red deer (Cervus elaphus)) are directly threatened by poachers. The examination revealed that both species population data and poaching data should be taken into account to set effective multi-species conservation prioritization levels. In a sensitivity analysis approach, it was found that, despite the fact that red deer is endangered and preferred by poachers, the deterrent penalty measure should be 1.5 times greater for poaching urial than red deer. The output analysis illustrated that, in order to bring the urial deterrent penalty measure closer to the red deer one, enforcement measures should be about 2.5 times stricter for poaching urial than red deer. The results specifically yield insight into how to optimally conserve a food web equilibrium under poaching pressure and within several constraints.

Tick-borne diseases have long been mainly associated with forests, the primary habitat for Ixodes ricinus, where they are mostly found. However, increasing evidence shows that humans also often get bitten in gardens, parks and other habitats generally associated with lower vegetation and tick density. Therefore, to understand the risk of infection from a tick bite and thus of potential subsequent infection, it is necessary to separate the factors of risk: hazard and vulnerability, here detailed as exposure and coping capacity, and to examine their spatial heterogeneity. This paper proposes a spatially explicit model for human movement through the entire landscape and forest visits to investigate the three components of risk. The population and its movements are set spatially in three study case landscapes extracted from Wallonia, south Belgium. Parameters that are challenging to estimate, such as the probability of a person getting bitten in various environments and the probability of inspecting one’s body to remove ticks, are analyzed in a wide range of combinations. Results show that, while bites are densest in the forest, they happen across the landscape at levels comparable when summed. When coping capacity is modified, as it could be through raising awareness and improving uptake of protective measures, the most at-risk group can change, and the riskier landscape can become the periurban or the rural landscape. This model offers a platform to investigate the respective contributions of hazard, exposure, and people’s capacity to cope with the hazard. It would benefit from empirical input parameters measured more specifically for its purpose.

In this paper, the dynamical behaviours and mathematics of the fractional order atmosphere-soil-land plant carbon cycle system involving the time dependent variable of carbon flux in atmosphere, the carbon flux of soil, and the carbon flux of animals and plants are qualitatively and numerically investigated. Explicit solutions in terms of the Mittag-Leffler functions to the terrestrial carbon cycle system around the equilibrium point are first time reported by applying Laplace transform of Caputo fractional derivative. The graphs of obtained solutions the time dependent variable of carbon flux in atmosphere, the carbon flux of soil and the carbon flux of animals and plants are plotted against each other. Explicit solutions to original system and stability of the fractional order linearized system around the equilibrium point are graphically compared as well.

Human activities severely impact the distribution and behaviour of apex predators in numerous terrestrial and aquatic ecosystems, with cascading effects on several species. Mesopredator outbreaks attributable to the removal of an apex predator have often been recorded and described in the literature as “mesopredator release”. During recent decades several examples of the phenomenon have been observed and studied in many different parts of the world. In this paper, we quantitatively reviewed the existing literature on mesopredator release using two software packages (VOSviewer and CiteSpace) to investigate patterns and trends in author keywords through occurrences and temporal analyses, and creating relative network maps. The results showed that even though the general scientific interest in mesopredator release has increased in recent decades, the vast majority of studies focus on canid species, leaving many other species or entire taxa (e.g., reptiles) understudied and under-described. The connection between invasive species and mesopredator release has only recently been more extensively explored and also the effects of apex predators declining in aquatic ecosystems are still only partially investigated. Due to the increasing effect of biological invasions, overfishing, and either the decline or the rise of apex predators in different parts of the world, we expect an even higher increase in interest and number of published documents on the subject. We also encourage widening the research focus beyond canids to include other important taxa.

Population aging has become a global phenomenon. Whereas, the ecological consequences of population aging are rarely addressed in current research. In this context, this study contributes to the existing literature by providing new empirical evidence on how population aging along with globalization, economic growth, energy consumption, natural resource rent, and human capital affect ecological footprint for selected 27 Organization for Economic Cooperation and Development (OECD) countries during 1970–2017. This study utilizes an advanced econometric approach, Pooled Mean Group (PMG) estimator for empirical estimation, that allows heterogeneity in the slope parameters and dependencies across countries. The long-term results disclose that globalization (overall) decreases the ecological footprint. On the other hand, financial and political globalization poses a favorable impact on environmental quality, while economic and social globalization is found to increase environmental degradation. Population aging has a statistically significant negative effect on the ecological footprint, but its non-linear term increases the ecological footprint. Additionally, economic growth, energy consumption, and natural resource rent exacerbate environmental deterioration. In contrast, human capital decreases ecological footprint. Based on the empirical results, important policy implications have been provided.