Ecological Complexity最新文献

Grassland degradation has been one of the major ecological concerns on the Qinghai-Tibet Plateau (QTP) in recent years, but the degradation of alpine shrub meadows, and in particular the changes in its surface landscape pattern, has been less well assessed. This study selected a warm-season pasture on the QTP as a study area, and used an unmanned aerial vehicle (UAV) to collect aerial photographs along the degradation gradient from late June to early July 2018. We then classified the surface landscape as alpine shrub, alpine meadow, bare soil and plateau pika hole and analyzed the landscape pattern changes at different degradation levels. The results showed that the alpine shrub and alpine meadow dominated landscape degraded to a pattern of alpine meadow and bare soil dominance and pika hole pervasiveness, during which vegetation cover declined and the overall landscape pattern tended to fragment. Landscape pattern characteristics related to the area, density, connectivity and boundaries respond more clearly to the shrub degradation, with moderate degradation being the key stage at which the surface landscape pattern changes dramatically. Our study demonstrates a potential application of UAV technology in the study of grassland degradation. Future research should focus on the status, mechanisms and ecological effects of alpine shrub meadows degradation and the quantitative relationships between surface landscape patterns and ecological functions.

The growing interest in ecosystem services is mainly related to land use changes. The aim of the study is to analyse spatial-temporal changes in the capacity to supply of ES in Lithuania based on land use changes in 1990–2018. The results show some balance between loss and gains of ecosystem services capacity due to land use changes. Decrease in heterogenous agricultural areas had negative impact on provision of ecosystem integrity and services. Considerable increase in scrubland and herbaceous vegetation areas significantly increased the ecosystem service potential. The conversion of former agricultural land to less intensively managed ecosystems enhance the potential of valuable habitats for biodiversity and ecosystem services associated with natural grasslands, moors and heathland, transitional woodland shrubs. The urbanization process along with increase in urban fabric areas had little effect on ESs potential since artificial vegetated areas had compensated the loss of ESs due to increased areas of urbanized ecosystems. Despite the area of open spaces slightly increased, this led to decrease of provision of ESs. Temporal changes in overall ESs capacity indicated an increase in Lithuania over the last two decades. Given the observed dynamic context of land cover, the structure of ecosystem services may face potential threats from land use change due to urban development and agricultural activities.

The patch-corridor-matrix is the most commonly used model when dealing with landscape characterization studies, but it shows relevant limitations to detect landscape heterogeneity. Other authors have used a functional approach, since it is well known that nutrient, mineral and energy flows exist among ecosystems. These flows can be perceived in boundaries between different landcovers, making possible the identification of spatial units sharing a common pattern of ecological interactions known as mosaics. While the influence of each mosaic over a certain species has been previously addressed, no attention has been given to the intra-mosaic variation. The aim of this research is to assess the influence of functional diversity and connectivity, on the habitat suitability of the Iberian lynx (Lynx pardinus). For this, we built two GLMs to test if these features show a differential effect on lynxes’ habitat suitability depending on the mosaic. Both GLMs built show that the influence of these landscape features on lynxes’ habitat suitability depends on the landscape spatial organization and landcover composition, suggesting that there is no unique response of a species to changes in landscape diversity and/or connectivity. Thus, we conclude that considering both landscape and species features would allow to a better integration of land management strategies and conservation actions, which could favor species adaptation to highly human-modified landscapes.

A novel coronavirus is a serious global issue and has a negative impact on the economy of Egypt. According to the publicly reported data, the first case of the novel corona virus in Egypt was reported on 14 February 2020. Total of 96753 cases were recorded in Egypt from the beginning of the pandemic until the eighteenth of August, where 96, 581 individuals were Egyptians and 172 were foreigners. Recently, many mathematical models have been considered to better understand coronavirus infection. Most of these models are based on classical integer-order derivatives which can not capture the fading memory and crossover behavior found in many biological phenomena. Therefore, we study the coronavirus disease in this paper by exploring the dynamics of COVID-19 infection using new variable-order fractional derivatives. This paper presents an optimal control problem of the hybrid variable-order fractional model of Coronavirus. The variable-order fractional operator is modified by an auxiliary parameter in order to satisfy the dimensional matching between the both sides of the resultant variable-order fractional equations. Existence, uniqueness, boundedness, positivity, local and global stability of the solutions are proved. Two control variables are considered to reduce the transmission of infection into healthy people. To approximate the new hybrid variable-order operator, Grünwald-Letnikov approximation is used. Finite difference method with a hybrid variable-order operator and generalized fourth order Runge-Kutta method are used to solve the optimality system. Numerical examples and comparative studies for testing the applicability of the utilized methods and to show the simplicity of these approximation approaches are presented. Moreover, by using the proposed methods we can concluded that, the model given in this paper describes well the confirmed real data given by WHO about Egypt.

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.