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    - ENVIRONMENTAL STUDIES (702 journals)
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ENVIRONMENTAL STUDIES (702 journals)            First | 1 2 3 4 5 6 7 8     

Mathematical and Computational Forestry & Natural-Resource Sciences     Free  
Mathematical Population Studies: An International Journal of Mathematical Demography     Hybrid Journal   (Followers: 2)
Medieval Sermon Studies     Hybrid Journal   (Followers: 5)
Medio Ambiente y Urbanizacion     Full-text available via subscription  
Membranes     Open Access   (Followers: 4)
Michigan Journal of Sustainability     Open Access  
Midwest Studies In Philosophy     Hybrid Journal   (Followers: 10)
Mine Water and the Environment     Hybrid Journal   (Followers: 6)
Mitigation and Adaptation Strategies for Global Change     Hybrid Journal   (Followers: 12)
Modern Asian Studies     Hybrid Journal   (Followers: 4)
Modern Cartography Series     Full-text available via subscription   (Followers: 6)
Mountain Research and Development     Open Access   (Followers: 3)
Multequina     Open Access  
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis     Hybrid Journal   (Followers: 2)
Mutation Research/Genetic Toxicology and Environmental Mutagenesis     Hybrid Journal   (Followers: 8)
Nativa     Open Access  
Natur und Recht     Hybrid Journal   (Followers: 5)
Natural Areas Journal     Full-text available via subscription   (Followers: 7)
Natural Hazards     Hybrid Journal   (Followers: 176)
Natural Resources     Open Access  
Natural Resources and Environmental Issues     Open Access   (Followers: 5)
Nature and Culture     Full-text available via subscription   (Followers: 9)
NeuroToxicology     Hybrid Journal   (Followers: 1)
Neurotoxicology and Teratology     Hybrid Journal   (Followers: 2)
NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy     Full-text available via subscription   (Followers: 6)
New Zealand Journal of Environmental Law     Full-text available via subscription   (Followers: 3)
NJAS - Wageningen Journal of Life Sciences     Full-text available via subscription   (Followers: 1)
Noise Notes     Full-text available via subscription   (Followers: 3)
Novos Cadernos NAEA     Open Access  
Observatorio Medioambiental     Open Access  
Occupational and Environmental Medicine     Full-text available via subscription   (Followers: 8)
Ocean Acidification     Open Access  
Oecologia     Hybrid Journal   (Followers: 24)
Oikos     Hybrid Journal   (Followers: 29)
Open Journal of Ecology     Open Access   (Followers: 10)
Open Journal of Marine Science     Open Access   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 1)
Our Nature     Open Access   (Followers: 2)
Oxford Journal of Legal Studies     Hybrid Journal   (Followers: 16)
Pace Environmental Law Review     Open Access   (Followers: 4)
Packaging, Transport, Storage and Security of Radioactive Material     Hybrid Journal   (Followers: 2)
Palaeobiodiversity and Palaeoenvironments     Hybrid Journal   (Followers: 3)
Papers on Global Change IGBP     Open Access   (Followers: 1)
Particle and Fibre Toxicology     Open Access   (Followers: 3)
Pastos y Forrajes     Open Access  
Pesquisa em Educação Ambiental     Open Access  
Pharmacology & Therapeutics     Hybrid Journal   (Followers: 5)
Pharmacology Biochemistry and Behavior     Hybrid Journal   (Followers: 1)
Philosophical Studies     Hybrid Journal   (Followers: 7)
Physio-Géo     Open Access   (Followers: 2)
Pittsburgh Journal of Environmental and Public Health Law     Open Access   (Followers: 1)
Planet     Open Access  
Planning & Environmental Law: Issues and decisions that impact the built and natural environments     Hybrid Journal   (Followers: 6)
Plant Ecology & Diversity     Partially Free   (Followers: 9)
Plant Knowledge Journal     Open Access   (Followers: 2)
Plant, Cell & Environment     Hybrid Journal   (Followers: 4)
Polar Journal     Hybrid Journal   (Followers: 1)
Policy Studies     Hybrid Journal   (Followers: 7)
Policy Studies Journal     Hybrid Journal   (Followers: 5)
Polish Polar Research     Open Access   (Followers: 4)
Political Studies     Hybrid Journal   (Followers: 22)
Political Studies Review     Hybrid Journal   (Followers: 14)
Population and Environment     Hybrid Journal   (Followers: 6)
Population Ecology     Hybrid Journal   (Followers: 9)
Population Studies: A Journal of Demography     Hybrid Journal   (Followers: 4)
Postcolonial Studies     Hybrid Journal   (Followers: 5)
Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management     Full-text available via subscription   (Followers: 3)
Presence Teleoperators & Virtual Environments     Hybrid Journal   (Followers: 1)
Presidential Studies Quarterly     Hybrid Journal   (Followers: 3)
Procedia Environmental Sciences     Open Access   (Followers: 2)
Proceedings of ICE, Waste and Resource Management     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment     Hybrid Journal   (Followers: 1)
Proceedings of the International Academy of Ecology and Environmental Sciences     Open Access   (Followers: 4)
Process Safety and Environmental Protection     Hybrid Journal   (Followers: 3)
Progress in Industrial Ecology, An International Journal     Hybrid Journal   (Followers: 4)
Psychological Assessment     Full-text available via subscription   (Followers: 5)
Public Money & Management     Hybrid Journal   (Followers: 4)
Public Works Management & Policy     Hybrid Journal   (Followers: 5)
Qatar Foundation Annual Research Forum Proceedings     Open Access   (Followers: 3)
Radioactivity in the Environment     Full-text available via subscription   (Followers: 4)
Regional Environmental Change     Hybrid Journal   (Followers: 3)
Regional Studies     Hybrid Journal   (Followers: 6)
Religious Studies     Hybrid Journal   (Followers: 10)
RELP - Renewable Energy Law and Policy     Full-text available via subscription   (Followers: 4)
Remediation Journal     Hybrid Journal   (Followers: 5)
Remote Sensing Letters     Hybrid Journal   (Followers: 8)
Renaissance Studies     Hybrid Journal   (Followers: 13)
Rendiconti Lincei     Hybrid Journal  
Renewable Energy Focus     Full-text available via subscription   (Followers: 7)
Research & Reviews : Journal of Ecology     Full-text available via subscription  
Research and Practice for Persons with Severe Disabilities     Full-text available via subscription   (Followers: 3)
Research Journal of Environmental Sciences     Open Access   (Followers: 1)
Research Journal of Environmental Toxicology     Open Access   (Followers: 2)
ReSource     Full-text available via subscription  
Resources     Open Access  
Resources, Conservation and Recycling     Hybrid Journal   (Followers: 9)
Reuse/Recycle Newsletter     Hybrid Journal   (Followers: 2)
Review of English Studies     Hybrid Journal   (Followers: 7)
Review of Environmental Economics and Policy     Hybrid Journal   (Followers: 7)
Revista AIDIS de Ingeniería y Ciencias Ambientales. Investigación, desarrollo y práctica     Open Access   (Followers: 2)

  First | 1 2 3 4 5 6 7 8     

Journal Cover Theoretical Ecology
   [11 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1874-1746 - ISSN (Online) 1874-1738
     Published by Springer-Verlag Homepage  [2209 journals]   [SJR: 1.37]   [H-I: 10]
  • Distinguishing intrinsic limit cycles from forced oscillations in
           ecological time series
    • Abstract: Abstract Ecological cycles are ubiquitous in nature and have triggered ecologists’ interests for decades. Deciding whether a cyclic ecological variable, such as population density, is part of an intrinsically emerging limit cycle or simply driven by a varying environment is still an unresolved issue, particularly when the only available information is in the form of a recorded time series. We investigate the possibility of discerning intrinsic limit cycles from oscillations forced by a cyclic environment based on a single time series. We argue that such a distinction is possible because of the fundamentally different effects that perturbations have on the focal system in these two cases. Using a set of generic mathematical models, we show that random perturbations leave characteristic signatures on the power spectrum and autocovariance that differ between limit cycles and forced oscillations. We quantify these differences through two summary variables and demonstrate their predictive power using numerical simulations. Our work demonstrates that random perturbations of ecological cycles can give valuable insight into the underlying deterministic dynamics.
      PubDate: 2014-05-10
  • Evolution of acuteness in pathogen metapopulations: conflicts between
           “classical” and invasion-persistence trade-offs
    • Abstract: Abstract Classical life-history theory predicts that acute, immunizing pathogens should maximize between-host transmission. When such pathogens induce violent epidemic outbreaks, however, a pathogen’s short-term advantage at invasion may come at the expense of its ability to persist in the population over the long term. Here, we seek to understand how the classical and invasion-persistence trade-offs interact to shape pathogen life-history evolution as a function of the size and structure of the host population. We develop an individual-based infection model at three distinct levels of organization: within an individual host, among hosts within a local population, and among local populations within a metapopulation. We find a continuum of evolutionarily stable pathogen strategies. At one end of the spectrum—in large well-mixed populations—pathogens evolve to greater acuteness to maximize between-host transmission: the classical trade-off theory applies in this regime. At the other end of the spectrum—when the host population is broken into many small patches—selection favors less acute pathogens, which persist longer within a patch and thereby achieve enhanced between-patch transmission: the invasion-persistence trade-off dominates in this regime. Between these extremes, we explore the effects of the size and structure of the host population in determining pathogen strategy. In general, pathogen strategies respond to evolutionary pressures arising at both scales.
      PubDate: 2014-04-29
  • Composite temporal strategies in pathogen evolution: balancing invasion
           and persistence
    • Abstract: Abstract There is ongoing interest in the conditions that favor the evolution of acute, highly transmissible infections in contrast to chronic ones. Earlier studies typically consider the evolution of a trait that is constant over the lifetime of an infection. However, for many pathogens, such traits can vary over this course. Here, we address the evolution of temporal patterns in limited host population sizes, where a trade-off between invasion and persistence can arise. This is of particular relevance to questions on the evolution of acuteness and chronicity. We ask whether population dynamics of transmission at the between-host level could lead pathogen adaptation to favor temporal strategies during the course of infection. To do this, we consider an infection to be composed of multiple stages, allowing each of these to evolve independently under a transmission–duration trade-off. We only consider selection taking place on the between-host level and examine the balance of invasion and persistence (i.e., maximizing replication vs. minimizing vulnerability to extinction), using several fitness-related measures. We find that a composite strategy that is ordered in time can confer higher fitness than any single, constant, strategy. We discuss the relevance of these results for the ordered expression of var genes in Plasmodium falciparum, as well as for infections that characteristically have several stages as in some bacterial pathogens.
      PubDate: 2014-04-25
  • Partitioning of trait variation among communities: measures of
           apportionment and differentiation based on binary sampling
    • Abstract: Abstract The notion that trait variation is partitioned among communities essentially rests on the supposition that the total variation in the metacommunity exceeds the variation within the communities due to differences between their trait distributions (the partitioning principle). Two elementary perspectives of partitioning can be distinguished: apportionment (members of the same community tend to hold the same trait state) and differentiation (members of different communities tend to hold different trait states). While the apportionment perspective reaches its extreme when each community is monomorphic (fixation), the differentiation perspective does so if communities share no trait states. Even though both perspectives can be shown to be involved in the analysis of community dynamics, their assessment is still almost completely limited to the apportionment perspective (chiefly G ST and its relatives). To overcome this limitation, methods of quantifying both partitioning perspectives are developed for qualitatively and quantitatively varying traits, where variation is represented by the differences in type resulting from sampling two individuals. It is shown that the validity of the partitioning principle and the design of corresponding measures crucially depend on proper specification of the modes of sampling and specification of differences between types that follow a concavity principle. This approach allows comparison between measures of apportionment and measures of differentiation. Such comparisons enable conclusions about the share that random (drift) and directional (selection, migration) processes have in the partitioning of variation among communities. One of the more far-reaching conclusions is that effects of forces apportioning variation outperform the effects of forces of differentiation, if the average similarity within communities exceeds the average difference between them.
      PubDate: 2014-04-11
  • Conflict between dynamical and evolutionary stability in simple ecosystems
    • Abstract: Abstract Here, we address the essential question of whether, in the context of evolving populations, ecosystems attain properties that enable persistence of the ecosystem itself. We use a simple ecosystem model describing resource, producer, and consumer dynamics to analyze how evolution affects dynamical stability properties of the ecosystem. In particular, we compare resilience of the entire system after allowing the producer and consumer populations to evolve to their evolutionarily stable strategy (ESS) to the maximum attainable resilience. We find a substantial reduction in ecosystem resilience when producers and consumers are allowed to evolve compared to the maximal attainable resilience. This study illustrates the inherent difference and possible conflict between maximizing individual-level fitness and maximizing resilience of entire ecosystems.
      PubDate: 2014-03-20
  • Phenologically explicit models for studying plant–pollinator
           interactions under climate change
    • Abstract: Abstract Climate change is significantly influencing phenology. One potential effect is that historically interacting partners will respond to climate change at different rates, creating the potential for a phenological mismatch among previously synchronized interacting species, or even sexes of the same species. Focusing on plant demographics in a plant–pollinator interaction, we develop a hybrid dynamical model that uses a “non-autonomous” differential equation system (Zonneveld model) for within-season dynamics and discrete equations for season-to-season dynamics. Our model outlines how and when changes in the relative phenologies of an interacting species pair will alter the demographic outcome of the interaction. For our plant–pollinator system, we find that plant population growth rates are particularly sensitive to phenology mismatch when flowers are short-lived, when pollinators are short-lived, or when flowers and pollinators exhibit high levels of within-population synchrony in emergence or arrival dates. More generally, our aim is to introduce the use of hybrid dynamical models as a framework through which researchers can directly explore the demographic consequences of climatically driven phenological change.
      PubDate: 2014-02-22
  • Individual variability and mortality required for constant final yield in
           simulated plant populations
    • Abstract: Abstract When plant monocultures are sown over a wide range of densities for a given period of time, the total biomass yield increases with density at low densities and then levels off at high densities, a phenomenon called constant final yield (CFY). There are several reported cases, however, where the total yield decreases at very high densities, but the reasons for such exceptions are not known. We used a spatially explicit, individual-based “field of neighborhood” simulation model to investigate the potential roles of spatial pattern, individual variation, and competitive stress tolerance for CFY. In the model, individual plants compete asymmetrically for light when their fields overlap, and this competition decreases growth and increases mortality. We varied (1) the initial size variation, (2) the spatial pattern, and (3) ability to survive intense competition and examined the effects on the density-biomass relationship. CFY was always observed when there was high variability among individuals, but not always when variability was low. This high size variation could be the result of high initial size variability or variation in the degree of local crowding. For very different reasons, very high and very low tolerance for competition resulted in decreasing total biomass at very high densities. Our results emphasize the importance of individual variation for population processes and suggest that we should look for exceptions to CFY in homogeneous, even-aged, regularly spaced populations such as plantations.
      PubDate: 2014-02-12
  • Nile perch (Lates niloticus,        class="a-plus-plus">L.) and cichlids (       class="a-plus-plus">Haplochromis spp.) in Lake Victoria:
           could prey mortality promote invasion of its predator'
    • Abstract: Abstract The invasion of Nile perch into Lake Victoria is one of the iconic examples of the destructive effect of an introduced species on an ecosystem but no convincing explanation exists of why Nile perch only increased dramatically after a 25 year lag. Here, we consider this problem using a mathematical model that takes into account interactions between Nile perch and its cichlid prey. We examined competing hypotheses to explain Nile perch invasion and show that suppression of juvenile Nile perch by cichlids may cause the system to have two alternative stable states: one with only cichlids and one with coexistence of cichlids and Nile perch. Without cichlid predation on Nile perch, alternative stable states did not occur. Our analysis indicates that cichlid mortality, for example fishing mortality, may have induced the observed shift between the states.
      PubDate: 2014-02-01
  • Taylor's law and abrupt biotic change in a smoothly changing environment
    • Abstract: Abstract Taylor's law (TL), widely verified in empirical ecology, states that the variance of population density approximates a power function of the mean population density, with exponent denoted b. A model of multiplicative increments in population density, where the increments are determined by a Markovian environment, predicts TL with an explicit formula for b. We give a simple theoretical example where, unexpectedly, smooth changes in environmental autocorrelation lead to an abrupt, infinite discontinuity in b. As the daily probability of change in environmental state increases from 0 to 1, b rises from 2 slowly at first, then explodes to +∞ when the population becomes critical, drops to -∞, and rises again to 2. In this model, an exponent b of large magnitude (positive or negative) signals the proximity of a population's criticality and of a singularity in b. A comparable real-world singularity in b could adversely affect fisheries, forestry, agriculture, conservation, and public health.
      PubDate: 2014-02-01
  • Message from the editor
    • PubDate: 2014-01-23
  • Dynamics of herbivores and resources on a landscape with interspersed
           resources and refuges
    • Abstract: Abstract A tradeoff between energy gain from foraging and safety from predation in refuges is a common situation for many herbivores that are vulnerable to predation while foraging. This tradeoff affects the population dynamics of the plant–herbivore–predator interaction. A new functional response is derived based on the Holling type 2 functional response and the assumption that the herbivore can forage at a rate that maximizes its fitness. The predation rate on the herbivore is assumed to be proportional to the product of the time that the herbivore spends foraging and a risk factor that reflects the habitat complexity; where greater complexity means greater interspersion of high food quality habitat and refuge habitat, which increases the amount of the edge zone between refuge and foraging areas, making foraging safer. The snowshoe hare is chosen as an example to demonstrate the resulting dynamics of an herbivore that has been intensely studied and that undergoes well-known cycling. Two models are studied in which the optimal foraging by hares is assumed, a vegetation–hare–generalist predator model and a vegetation–hare–specialist predator model. In both cases, the results suggest that the cycling of the snowshoe hare population will be greatly moderated by optimal foraging in a habitat consisting of interspersed high quality foraging habitat and refuge habitat. However, there are also large differences in the dynamics produced by the two models as a function of predation pressure.
      PubDate: 2014-01-18
  • Infectious disease in consumer populations: dynamic consequences of
           resource-mediated transmission and infectiousness
    • Abstract: Abstract Nonhost species can strongly affect the timing and progression of epidemics. One central interaction—between hosts, their resources, and parasites—remains surprisingly underdeveloped from a theoretical perspective. Furthermore, key epidemiological traits that govern disease spread are known to depend on resource density. We tackle both issues here using models that fuse consumer–resource and epidemiological theory. Motivated by recent studies of a phytoplankton–zooplankton–fungus system, we derive and analyze a family of dynamic models for parasite spread among consumers in which transmission depends on consumer (host) and resource densities. These models yield four key insights. First, host–resource cycling can lower mean host density and inhibit parasite invasion. Second, host–resource cycling can create Allee effects (bistability) if parasites increase mean host density by reducing the amplitude of host–resource cycles. Third, parasites can stabilize host–resource cycles; however, host–resource cycling can also cause disease cycling. Fourth, resource dependence of epidemiological traits helps to govern the relative dominance of these different behaviors. However, these resource dependencies largely have quantitative rather than qualitative effects on these three-species dynamics. Given the extent of these results, host–resource–parasite interactions should become more fundamental components of the burgeoning theory for the community ecology of infectious diseases.
      PubDate: 2014-01-17
  • Restoration of plant–pollinator interaction networks via species
    • Abstract: Abstract The recent decline in pollinator biodiversity, notably in the case of wild bee populations, puts both wild and agricultural ecosystems at risk of ecological community collapse. This has triggered calls for further study of these mutualistic communities in order to more effectively inform restoration of disturbed plant–pollinator communities. Here, we use a dynamic network model to test a variety of translocation strategies for restoring a community after it experiences the loss of some of its species. We consider the reintroduction of extirpated species, both immediately after the original loss and after the community has reequilibrated, as well as the introduction of other native species that were originally absent from the community. We find that reintroducing multiple highly interacting generalist species best restores species richness for lightly disturbed communities. However, for communities that experience significant losses in biodiversity, introducing generalist species that are not originally present in the community may most effectively restore species richness, although in these cases the resultant community often shares few species with the original community. We also demonstrate that the translocation of a single species has a minimal impact on both species richness and the frequency of community collapse. These results have important implications for restoration practices in the face of varying degrees of community perturbations, the refinement of which is crucial for community management.
      PubDate: 2014-01-07
  • (A bit) Earlier or later is always better: Phenological shifts in
           consumer–resource interactions
    • Abstract: Abstract Phenology is a crucial life history trait for species interactions and it can have great repercussions on the persistence of communities and ecosystems. Changes in phenology caused by climate change can disrupt species interactions causing decreases in consumer growth rates, as suggested by the match–mismatch hypothesis (MMH). However, it is still not clear what the long-term consequences of such phenological changes are. In this paper, we present models in which phenology and consumer–resource feedbacks determine long-term community dynamics. Our results show that consumer viability is constrained by limits in the amount of phenological mismatch with their resources, in accordance with the MMH, but the effects of phenological shifts are often nonmonotonic. Consumers generally have higher abundances when they recruit some time before or after their resources because this reduces the long-term effects of overexploitation that would otherwise occur under closer synchrony. Changes in the duration of recruitment phenologies also have important impacts on community stability, with shorter phenologies promoting oscillations and cycles. For small community modules, the effects of phenological shifts on populations can be explained, to a great extent, as superpositions of their effects on consumer–resource pairs. We highlight that consumer–resource feedbacks and overexploitation, which are not typically considered in phenological models, are important factors shaping the long-term responses to phenological changes caused by climate change.
      PubDate: 2013-12-21
  • Dual invasion analysis: a general model of novel ecological dynamics due
           to Bt product and resistant pests in wild settings
    • Abstract: Abstract Transgenic Bt crops have been integrated as a central component of the agricultural policies of many nations across the globe due to their insecticidal properties. While focus on increased yield resulting from the use of Bt crops has overshadowed the concerns of pest populations developing resistance, resistance has been recently discovered in even highly managed fields. One issue that has received less attention is the resulting set of ecological dynamics from escaped Bt products into wild settings. I present a differential equation model of the ecological interaction between a wild plant–pest community and an invading Bt toxin-producing plant and the ensuing evolution of pest resistance. Key to this model investigation is the assumption of energy costs with both the production of Bt toxin by Bt plants and the resistance to Bt toxin exhibited by resistant pest individuals. Results show that persistence of the initial invading Bt plant population is possible through an intransitive loop dynamic. Furthermore, coexistence of wild-type plants and pests as well as Bt-producing plants and resistant pests is possible through the dynamics resultant from energy trade-offs.
      PubDate: 2013-12-12
  • A quantitative genetic approach for predicting ecological change in
           biological communities
    • Abstract: Abstract Ecological studies of communities have become increasingly focused on the role of genetics. These studies often conclude that genetics and evolution play an important role in community structure and function. For instance, studies have shown that the structure of insect communities associated with a host plant is heritable and therefore can potentially evolve. However, when studying communities of interacting species two problems are faced: (1) the traits that determine the outcomes of these interactions are often unknown, and (2) communities are normally highly multidimensional (n-dimensional for n species). In order to surmount these problems, we adapt a commonly used approach for studying the evolution of multivariate quantitative traits to the study of biological communities. Specifically, we propose utilizing a community-based genetic covariance matrix (G-matrix) and an associated vector of community selection gradients for predicting changes in community composition, where the “traits” under study are the abundances, or other properties, of various interacting species. This approach capitalizes on the relative ease with which data on the abundance of individuals interacting with individuals of a focal species (e.g., abundances of various herbivorous insects on a plant) can be collected and on the utility of the quantitative genetic approach for predicting multidimensional evolution. In order to evaluate the utility and accuracy of the G-matrix approach for predicting the evolution of communities, we develop and analyze numerical simulations of evolving communities. Results of these simulations show that an approach based on community G-matrices and selection gradients provides a rich understanding of how underlying genetics shape community structure and, in many cases, accurately predicts how community structure changes over time.
      PubDate: 2013-12-04
  • Resource competition and community response to fertilization: the outcome
           depends on spatial strategies
    • Abstract: Abstract Decreases in plant species richness and shifts in community structure following fertilization are usually attributed to increasing light limitation. However, there is increasing evidence that light limitation alone does not account for all of the observed effects of fertilization on plant communities. We present a model of competition for a single, spatially heterogeneous resource that shows fertility-mediated changes in community structure without light competition. This model predicts that in a low-productivity spatially heterogeneous habitat, species that interact with the resource environment over small spatial scales may exclude species that experience the environment at larger spatial scales, even when the latter species are better resource competitors in a uniform environment (have a lower R*). Increasing overall habitat fertility under these conditions minimizes the effects of spatial heterogeneity on the species that forage at a larger spatial scale, resulting in changes in species dominance and the potential for species coexistence. This analysis suggests that considering differences in the spatial scales at which species interact with environmental heterogeneity may help explain observed changes in community structure following fertilization.
      PubDate: 2013-11-21
  • The effect of predator limitation on the dynamicsof simple food chains
    • Abstract: Abstract We investigate the influence of competition between predators on the dynamics of bitrophic predator–prey systems and of tritrophic food chains. Competition between predators is implemented either as interference competition, or as a density-dependent mortality rate. With interference competition, the paradox of enrichment is reduced or completely suppressed, but otherwise, the dynamical behavior of the systems is not fundamentally different from that of the Rosenzweig–MacArthur model, which contains no predator competition and shows only continuous transitions between fixed points or periodic oscillations. In contrast, with density-dependent predator mortality, the system shows a surprisingly rich dynamical behavior. In particular, decreasing the density regulation of the predator can induce catastrophic shifts from a stable fixed point to a large oscillation where the predator chases the prey through a cycle that brings both species close to the threshold of extinction. Other catastrophic bifurcations, such as subcritical Hopf bifurcations and saddle-node bifurcations of limit cycles, do also occur. In tritrophic food chains, we find again that fixed points in the model with predator interference become unstable only through Hopf bifurcations, which can also be subcritical, in contrast to the bitrophic situation. The model with a density limitation shows again catastrophic destabilization of fixed points and various nonlocal bifurcations. In addition, chaos occurs for both models in appropriate parameter ranges.
      PubDate: 2013-11-13
  • Improving communications between theoretical ecologists, mathematical
           ecologists, and ecological modelers: response to the critique of our book
           How species
    • PubDate: 2013-10-24
  • A general mathematical framework for the analysis of spatiotemporal point
    • Abstract: Abstract Spatial and stochastic models are often straightforward to simulate but difficult to analyze mathematically. Most of the mathematical methods available for nonlinear stochastic and spatial models are based on heuristic rather than mathematically justified assumptions, so that, e.g., the choice of the moment closure can be considered more of an art than a science. In this paper, we build on recent developments in specific branch of probability theory, Markov evolutions in the space of locally finite configurations, to develop a mathematically rigorous and practical framework that we expect to be widely applicable for theoretical ecology. In particular, we show how spatial moment equations of all orders can be systematically derived from the underlying individual-based assumptions. Further, as a new mathematical development, we go beyond mean-field theory by discussing how spatial moment equations can be perturbatively expanded around the mean-field model. While we have suggested such a perturbation expansion in our previous research, the present paper gives a rigorous mathematical justification. In addition to bringing mathematical rigor, the application of the mathematically well-established framework of Markov evolutions allows one to derive perturbation expansions in a transparent and systematic manner, which we hope will facilitate the application of the methods in theoretical ecology.
      PubDate: 2013-10-22
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