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  Subjects -> ENVIRONMENTAL STUDIES (Total: 793 journals)
    - ENVIRONMENTAL STUDIES (726 journals)
    - POLLUTION (21 journals)
    - WASTE MANAGEMENT (8 journals)

ENVIRONMENTAL STUDIES (726 journals)            First | 1 2 3 4 5 6 7 8     

Latin American Journal of Management for Sustainable Development     Hybrid Journal  
Legal Studies     Hybrid Journal   (Followers: 3)
Leviathan : A Journal of Melville Studies     Full-text available via subscription   (Followers: 2)
Limnological Review     Open Access   (Followers: 6)
Living Reviews in Landscape Research     Open Access   (Followers: 2)
Local Environment: The International Journal of Justice and Sustainability     Hybrid Journal   (Followers: 7)
Low Carbon Economy     Open Access   (Followers: 4)
Luna Azul     Open Access  
M+A. Revista Electrónica de Medioambiente     Open Access  
Macquarie Journal of International and Comparative Environmental Law     Full-text available via subscription   (Followers: 8)
Madagascar Conservation & Development     Open Access  
Management International Review     Hybrid Journal   (Followers: 5)
Management of Environmental Quality: An International Journal     Hybrid Journal   (Followers: 5)
Management of Sustainable Development     Open Access   (Followers: 2)
Marine Ecology     Hybrid Journal   (Followers: 13)
Marine Environmental Research     Hybrid Journal   (Followers: 12)
Marine Pollution Bulletin     Hybrid Journal   (Followers: 12)
Materials for Renewable and Sustainable Energy     Open Access   (Followers: 9)
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: 4)
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: 7)
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: 7)
Nativa     Open Access  
Natur und Recht     Hybrid Journal   (Followers: 7)
Natural Areas Journal     Full-text available via subscription   (Followers: 7)
Natural Hazards     Hybrid Journal   (Followers: 310)
Natural Resources     Open Access  
Natural Resources and Environmental Issues     Open Access   (Followers: 5)
Nature and Culture     Full-text available via subscription   (Followers: 10)
NeuroToxicology     Hybrid Journal  
Neurotoxicology and Teratology     Hybrid Journal   (Followers: 1)
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   (Followers: 1)
Observatorio Medioambiental     Open Access  
Occupational and Environmental Medicine     Full-text available via subscription   (Followers: 7)
Ocean Acidification     Open Access  
Ochrona Srodowiska i Zasobów Naturalnych     Open Access  
Oecologia     Hybrid Journal   (Followers: 29)
Oikos     Hybrid Journal   (Followers: 33)
Open Journal of Ecology     Open Access   (Followers: 11)
Open Journal of Marine Science     Open Access   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 3)
Our Nature     Open Access   (Followers: 2)
Oxford Journal of Legal Studies     Hybrid Journal   (Followers: 18)
Pace Environmental Law Review     Open Access   (Followers: 4)
Packaging, Transport, Storage and Security of Radioactive Material     Hybrid Journal   (Followers: 1)
Palaeobiodiversity and Palaeoenvironments     Hybrid Journal   (Followers: 3)
Particle and Fibre Toxicology     Open Access   (Followers: 2)
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: 9)
Physio-Géo     Open Access   (Followers: 2)
Pittsburgh Journal of Environmental and Public Health Law     Open Access   (Followers: 1)
Planet     Open Access   (Followers: 1)
Planning & Environmental Law: Issues and decisions that impact the built and natural environments     Hybrid Journal   (Followers: 7)
Plant Ecology & Diversity     Partially Free   (Followers: 11)
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: 8)
Policy Studies Journal     Hybrid Journal   (Followers: 5)
Polish Polar Research     Open Access   (Followers: 4)
Political Studies     Hybrid Journal   (Followers: 24)
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: 8)
Postcolonial Studies     Hybrid Journal   (Followers: 10)
Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management     Full-text available via subscription   (Followers: 2)
Presence Teleoperators & Virtual Environments     Hybrid Journal   (Followers: 1)
Presidential Studies Quarterly     Hybrid Journal   (Followers: 4)
Procedia Environmental Sciences     Open Access   (Followers: 2)
Proceedings of ICE, Waste and Resource Management     Hybrid Journal   (Followers: 2)
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: 5)
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: 5)
Public Works Management & Policy     Hybrid Journal   (Followers: 6)
Qatar Foundation Annual Research Forum Proceedings     Open Access   (Followers: 3)
Radioactivity in the Environment     Full-text available via subscription   (Followers: 3)
Regional Environmental Change     Hybrid Journal   (Followers: 4)
Regional Studies     Hybrid Journal   (Followers: 6)

  First | 1 2 3 4 5 6 7 8     

Journal Cover   Theoretical Ecology
  [SJR: 1.456]   [H-I: 13]   [12 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  [2302 journals]
  • Landmarking and strong Allee thresholds
    • Abstract: Abstract Mate-finding difficulties in small populations are often postulated to create strong demographic Allee effects that increase the probability of extinction of native species or, similarly, decrease the probability that non-native species will successfully invade. Many species make use of a restricted number of mating locations, detectable from long-distance, that are not selected for habitat reasons (e.g., hilltopping in butterflies). This ‘landmarking’ strategy may specifically address the problem of overcoming mate-finding difficulties. Using a variant of the birthday problem, we demonstrate that populations which locate a restricted number of mate-finding sites using landmark features may have high probability of successful mating even at very low population densities. Therefore, a strong Allee threshold, if it exists, may be very small, and non-native species that make use of this strategy may have a very good chance of population establishment at low density.
      PubDate: 2015-03-11
  • Coevolution-driven predator-prey cycles: predicting the characteristics of
           eco-coevolutionary cycles using fast-slow dynamical systems theory
    • Abstract: Abstract Eco-coevolutionary theory predicts that predator-prey coevolution occurring on the time scale of ecological dynamics (e.g., changes in population abundances) can drive novel kinds of predator-prey cycles, e.g., cryptic cycles where one species cycles while the other remains effectively constant and clockwise cycles where peaks in predator density precede peaks in prey density. However, because this body of theory has focused on particular models and studied the different cycle types in isolation, it is unclear what biological characteristics (e.g., costs for offense or defense) determine when a particular cycle type will arise. In this study, I explore the kinds of predator-prey cycles that arise in a general eco-coevolutionary model where there is disruptive selection and the coevolutionary dynamics are fast relative to the ecological dynamics of the system. With a graphical tool created using the theory of fast-slow dynamical systems, I predict what kinds of cycles can arise in the model and how cycle type depends on the costs for prey defense and predator offense. Fast-slow dynamical systems theory requires a separation of time scales between the ecological and evolutionary processes; however, numerical simulations show that this tool can help predict how coevolution drives populations cycles in systems where the speeds of ecological and evolutionary dynamics are comparable. Thus, this work is a step forward in building a general eco-coevolutionary theory.
      PubDate: 2015-03-08
  • Combining mechanism and drift in community ecology: a novel statistical
           mechanics approach
    • Abstract: Abstract A key challenge for models of community ecology is to combine deterministic mechanism and stochastic drift in a systematic, transparent and tractable manner. Another challenge is to explain and unify different ecological patterns, hitherto modelled in isolation, within a single modelling framework. Here, we show that statistical mechanics provides an effective way to meet both challenges. We apply the statistical principle of maximum entropy (MaxEnt) to a simple resource-based, non-neutral model of a plant community. In contrast to previous ecological applications of MaxEnt, our use of MaxEnt emphasises its theoretical basis in the combinatorics of sampling frequencies, an approach that clarifies its ecological interpretation. In this approach, mechanism and drift are identified, respectively, with ecological resource constraints and entropy maximization. We obtain realistic predictions for species abundance distributions as well as contrasting stability-diversity relationships at community and population levels. The model also predicts critical behaviour that may provide a basis for understanding desertification and other ecological tipping points. Our results complement and extend previous ecological applications of MaxEnt to new areas of community ecology, and further illustrate MaxEnt as a powerful yet simple modelling tool for combining mechanism and drift in a way that unifies disparate ecological patterns.
      PubDate: 2015-03-06
  • The potential for alternative stable states in nutrient-enriched invaded
    • Abstract: Abstract Nutrient enrichment of native grasslands can promote invasion by exotic plant species, leading to reduced biodiversity and altered ecosystem function. Empirical evidence suggests that positive feedbacks may make such transitions difficult to reverse. We developed a mathematical model of grassland dynamics in which one group of species (native) is a better competitor for nitrogen (N) and another group (exotic) is a better competitor for light. We parameterized the model for a grassland community and reproduced observed transitions from a native- to an exotic-dominated state under N loading. Within known bounds of parameter values, both smooth and hysteretic transitions are plausible. The model also predicts that N loading alone is insufficient to achieve a transition to an exotic-dominated state on a timescale relevant to grassland management (a few decades), and that therefore some other disturbance (e.g., fire suppression or heaving grazing) must be present to accelerate it. The model predicts that to restore a grassland to a native-dominated state after N inputs have been reduced, fire and carbon supplements would be most effective. Further field research in N-enriched invaded grasslands is required to establish the strengths of positive feedbacks and, in turn, the consequences of anthropogenic modification of grasslands worldwide.
      PubDate: 2015-02-18
  • The effect of dispersal between patches on the stability of large trophic
           food webs
    • Abstract: Abstract Using computer simulations for the population dynamics of systems with many species, we investigate the stability of food webs distributed over several patches that are connected by migration. We evaluate the proportion of persisting species (robustness) and the probability that dynamics reach a fixed point in dependence of food-web complexity, patch arrangement, and migration rule. We find that migration in general increases robustness. This increase is strongest for intermediate migration rates and for star-like patch arrangements. The probability of reaching a fixed point decreases for intermediate migration rate, and has a large peak at larger migration rate for the star topology. We explain these various observations by the rescue effect, by dynamical coexistence of species, and by the buildup of biomass reservoirs in highly connected patches. As the species number becomes larger, differences between different patch arrangements become smaller, and the decrease in the probability of reaching a fixed point vanishes. This means that complex food webs are in some sense dynamically simpler than food webs consisting of less species.
      PubDate: 2015-02-13
  • How do generalist consumers coexist over evolutionary time? An
           explanation with nutrition and tradeoffs
    • Abstract: Abstract Generalist consumers commonly coexist in many ecosystems. Yet, eco-evolutionary theory poses a problem with this observation: generalist consumers (usually) cannot coexist stably. To provide a solution to this theory-observation dissonance, we analyzed a simple eco-evolutionary consumer resource model. We modeled consumption of two nutritionally interactive resources by species which evolve their resource encounter rates subject to a tradeoff. As shown previously, consumers can ecologically coexist through tradeoffs in resource encounter rates; however, this coexistence is evolutionary unstable. Here, we find that nutritional interactions between resources and the shape of acquisition tradeoffs produce very similar evolutionary outcomes in isolation. Specifically, they produce evolutionarily stable communities composed either of two specialists (concave acquisition tradeoff or antagonistic nutrition) or a single generalist (convex acquisition tradeoff or complementary nutrition). Thus, the generalist-coexistence problem remains. However, the combination of nonlinear resource acquisition tradeoffs with nonlinear resource nutritional relationships creates selection forces that can push and pull against each other. Ultimately, this push-pull dynamic can stabilize the coexistence of two competing generalist consumers—but only when we coupled a convex acquisition tradeoff with antagonistic nutrition. Thus, our model here offers some resolution to the generalist-coexistence problem in eco-evolutionary, consumer-resource theory.
      PubDate: 2015-02-11
  • How nested and monogamous infection networks in host-phage communities
           come to be
    • Abstract: Abstract We show that a chemostat community of bacteria and bacteriophage in which bacteria compete for a single nutrient and for which the bipartite infection network is perfectly nested is permanent, a.k.a. uniformly persistent, provided that bacteria that are superior competitors for nutrient devote the least effort to defence against infection and the virus that are the most efficient at infecting host have the smallest host range. This confirms an earlier work of Jover et al. (J. Theor. Biol. 332:65–77, 2013) who raised the issue of whether nested infection networks are permanent. In addition, we provide sufficient conditions that a bacteria-phage community of arbitrary size with nested infection network can arise through a succession of permanent subcommunties each with a nested infection network by the successive addition of one new population. The same permanence results hold for the monogamous infection network considered by Thingstad (Limnol Oceanogr 45:1320–1328, 2000) but without the trade-offs.
      PubDate: 2015-02-01
  • A two-strain ecoepidemic competition model
    • Abstract: Abstract In this paper, we consider a competition system in which two diseases spread by contact. We characterize the system behavior, establishing that only some configurations are possible. In particular, we discover that coexistence of the two strains is not possible, under the assumptions of the model. A number of transcritical bifurcations relates the more relevant system’s equilibria. Coexistence via persistent oscillations is shown. Bistability is shown between a situation in which only the disease-unaffected population thrives and another one containing only the second population with endemic disease. An accurate computation of the separating surface of the basins of attraction of these two mutually exclusive equilibria is obtained via novel results in approximation theory. The behavior of the ecosystem in some of the parameter spaces is investigated.
      PubDate: 2015-02-01
  • Modeling the dynamics of soil erosion and vegetative control —
           catastrophe and hysteresis
    • Abstract: Abstract Wildfire events and anthropogenic activities such as agriculture and livestock grazing may denude the landscape from vegetation cover, resulting in systems prone to soil loss and degradation. Soil dynamics is an intricate process balanced between pedogenesis, which is a relatively slow process, and erosion which depends on many inert (e.g., soil texture, slope, precipitation, and wind) and biological factors such as vegetation properties, grazing intensity, and human disturbance. We develop here a theoretical model of the global dynamics of the interactions between vegetation and soil. Assuming a double feedback between them—plants control erosion, and soil availability facilitates plants growth—a system of nonlinear differential equations is derived, and the outcomes are investigated. The range of realistic parameter values were taken from the literature. Complex properties emerge from this model. For some ranges of parameter values, the model predicts one of two types of steady states—full recovery of vegetation cover or a degraded barren system. For another range of parameter values, bistability appears. We identify the parameter combinations which determine the qualitative behavior of the system and the threshold values beyond which the system becomes bistable. The model predicts that certain ecosystems are highly stable. Others might be bistable transitioning between these two states through perturbations. Therefore, the possibly of hysteresis as parameters vary arises, as well as the ability of the system to shift between steady states, possibly leading to sudden and dramatic changes.
      PubDate: 2015-02-01
  • Assessing the efficacy of population-level models of mast seeding
    • Abstract: Abstract We compare five models of mast seeding: the well-established resource-based model of Isagi et al. (J Theor Biol 187:231–239, 1997) and Satake and Iwasa (J Theor Biol 203:63–84, 2000), the regression based model of Masaka and Maguchi (Ann Bot 88:1049–1055, 2001), the more recent Delta temperature (ΔT) model of Kelly et al. (Ecol Lett 16:90–98, 2013), the resource model of Pearse et al. (Oikos 123:179–184, 2014) and the long-used temperature model. We discuss fitting methods for each model and compare the theoretical overlap between the models. Population level data from 28 seed sets and corresponding mean summer temperature are used and the error of each model is compared. On average, the ΔT model provides a better fit than the other models tested.
      PubDate: 2015-02-01
  • Heterogeneity in symbiotic effects facilitates Wolbachia establishment in
           insect populations
    • Abstract: Abstract Facultative vertically transmitted bacterial symbionts often manipulate its host’s reproductive biology and thus facilitate their persistence. Wolbachia is one such symbiont where frequency-dependent reproductive benefits are opposed by frequency-independent fitness costs leading to bistable dynamics. Introduction of carriers does not assure invasion unless the initial frequency is above a threshold determined by the balance of costs and benefits. Recent laboratory experiments have uncovered that Wolbachia also protects their hosts from pathogens. The expected consequence of this phenotype in natural environments is to lower the invasion threshold by a factor that increases with the extent of pathogen exposure. Here, we introduce a series of mathematical models to address how pathogen protection affects Wolbachia invasion. First, under homogeneous symbiotic effects, we obtain an analytical expression for the invasion threshold in terms of pathogen exposure, and find a regime where symbiont releases may result in elimination of the entire host population provided that abundance of virulent pathogens is high. Second, we distribute Wolbachia effects such that some carriers are totally protected and others not at all, and explore how this interplays with different pathogen intensities, to conclude that heterogeneity further lowers the threshold for Wolbachia invasion. Third, we replicate the analysis using a realistic distribution of protective effects and confirm that heterogeneity increases system resilience by reducing the odds of population collapse.
      PubDate: 2015-02-01
  • Resource availability determines stability for
           mutualist–pathogen–host interactions
    • Abstract: Abstract Traditional explorations of interspecific interactions have generated extensive bodies of theory on mutualism and disease independently, but few studies have considered the interaction between them. We developed a model exploring the interactions among a fungal mutualist, a viral pathogen, and their shared plant host. Both microbes were assumed to alter the uptake and use of nutrients by the plant. We found that the productivity of the system and the strength of the plant–fungal mutualism influenced community dynamics. In particular, at low productivity, the pathogen may depend on the presence of the fungal mutualist for persistence. Furthermore, under some conditions, both the productivity of the system and the strength of the plant–fungal mutualism may simultaneously cause the mutualist to go extinct. We note the presence of cyclic plant–pathogen population dynamics only in the presence of the mutualist. As found in other models of consumer–resource interactions, cyclic dynamics were driven by high productivity, but, in contrast to simpler systems, high pathogen effectiveness did not consistently lead to cyclic dynamics. In total, association with mutualists can alter host–pathogen interactions, and the reverse is also true in that pathogens may alter host–mutualist interactions.
      PubDate: 2015-02-01
  • Inferring topology from dynamics in spatial networks
    • Abstract: Abstract We examine the dynamics of oscillating populations in habitats described as networks of connected patches where the connections are not regular. This system would be typically analysed focusing either on the population dynamics, or measuring dispersal directly or indirectly. We focus on the question of the degree to which the dynamical patterns, as reflected in synchrony, reveal the underlying dispersal pathways. This would represent a bridge between two major spatial approaches: topological and dynamical. We show how local populations can be synchronized even if there is no direct dispersal route between them, while the stepping-stone populations are not synchronized. This leads to the surprising result that the topological structure of the underlying network is not reflected simply in patterns of synchrony across space in population dynamics. This shows that, with our current tools, the complex relationship between the underlying dispersal patterns and population dynamics prevent us from determining network structure through the observation of population dynamics.
      PubDate: 2015-02-01
  • Role of trade-off between sexual and vertical routes for evolution of
           pathogen transmission
    • Abstract: Abstract Many pathogens that are predominantly sexually transmitted can also be transmitted vertically. On the other hand, nonbeneficial pathogens that are predominantly vertically transmitted appear to be rare to absent. Many infections also exist that are only transmitted sexually. Using an empirically suggested trade-off between the horizontal and vertical transmission modes, we develop and analyze a model to study evolutionary dynamics of sterilizing, sexually transmitted infections which can also be transmitted vertically. We assume several flexible forms of the trade-off and ask under which conditions evolution in nonbeneficial pathogens favors vertical transmission, sexual transmission, or a mixture of the two. The evolutionary analysis of our model reveals a rich spectrum of evolutionary outcomes. In particular, evolution of pure sexual, pure vertical, and mixed transmission is possible, in addition to a frequent occurrence of evolutionary suicide. These outcomes can also arise via evolutionary branching and be combined in several evolutionary bistability regimes. We show that the shape of the trade-off between the two transmission modes significantly affects pathogen evolution. In particular, while vertical transmission dominates for concave and sigmoid trade-offs, sexual transmission is most commonly observed under convex trade-offs. Our analysis can shed more light on when an infection adopts a particular evolutionary behavior, and which region of the parameter space is realistic, so something about the evolutionary process itself.
      PubDate: 2015-02-01
  • A stochastic biodiversity model with overlapping niche structure
    • Abstract: Abstract The niche is a fundamental ecological concept that underpins many explanations of patterns of biodiversity. The complexity of niche processes in ecological systems, however, means that it is difficult to capture them accurately in theoretical models of community assembly. In this study, we build upon simple neutral biodiversity models by adding the important ingredient of overlapping niche structure. Our model is spatially implicit and contains a fixed number of equal-sized habitats. Each species in the metacommunity arises through a speciation event; at which time, it is randomly assigned a fundamental niche or set of environments/habitats in which it can persist. Within each habitat, species compete with other species that have different but overlapping fundamental niches. Species abundances then change through ecological drift; each, however, is constrained by its maximum niche breadth and by the presence of other species in its habitats. Using our model, we derive analytical expressions for steady-state species abundance distributions, steady-state distributions of niche breadth across individuals and across species, and dynamic distributions of niche breadth across species. With this framework, we identify the conditions that produce the log-series species abundance distribution familiar from neutral models. We then identify how overlapping niche structure can lead to other species abundance distributions and, in particular, ask whether these new distributions differ significantly from species abundance distributions predicted by non-overlapping niche models. Finally, we extend our analysis to consider additional distributions associated with realized niche breadths. Overall, our results show that models with overlapping niches can exhibit behavior similar to neutral models, with the caveat that species with narrow fundamental niche breadths will be very rare. If narrow-niche species are common, it must be because they are in a non-overlapping niche or have countervailing advantages over broad-niche species. This result highlights the role that niches can play in establishing demographic neutrality.
      PubDate: 2015-02-01
  • A generalized perturbation approach for exploring stock recruitment
    • Abstract: Abstract Models of stock-recruitment relationships (SRRs) are often used to predict fish population dynamics. Commonly used SRRs include the Ricker, Beverton-Holt, and Cushing functional forms, which differ primarily by the degree of density-dependent effects (compensation). The degree of compensation determines whether recruitment respectively decreases, saturates, or increases at high levels of spawning stock biomass. In 1982, J.G. Shepherd united these dynamics into a single model, where the degree of compensation is determined by a single parameter. However, the difficulty in relating this parameter to biological data has limited its usefulness. Here, we use a generalized modeling framework to show that the degree of compensation can be related directly to the functional elasticity of growth, which is a general quantity that measures the change in recruitment relative to a change in biomass. We show that the elasticity of growth can be calculated from perturbations in fish biomass, is robust to observation error, and can be used to determine general attributes of the SRR in both continuous time production models, as well as discrete time age-structured models.
      PubDate: 2015-02-01
  • Homing fidelity and reproductive rate for migratory populations
    • Abstract: Abstract Short-term and long-term population growth rates can differ considerably. While changes in growth rates can be driven by external factors, we consider another source for changes in growth rate. That is, changes are generated internally by gradual modification of population structure. Such a modification of population structure may take many generations, particularly when the populations are distributed spatially in heterogeneous environments. Here, the net reproductive rate R 0 is not sufficient to characterize short-term growth. Indeed, a population with net reproductive rate greater than one could initially decline precipitously, or a population with net reproductive rate less than one could initially grow substantially. Thus, we augment the net reproductive rate with lower and upper bounds for the transient reproductive rate, R l and R u . We apply these measures to the study of spatially structured salmon populations and show the effect of variable homing fidelity on short-term and long-term generational growth rates.
      PubDate: 2015-01-28
  • Egg limitation in host-parasitoid dynamics: an individual-based
    • Abstract: Abstract Theoretical models of parasitoid-host dynamics predict that egg limitation in parasitoids destabilizes community dynamics. However, although egg limitation is experienced by individual parasitoids with variable success of encountering hosts, such details were neglected in previous models. This study developed an individual-based parasitoid-host model that explicitly incorporates egg limitation and host encounters of individual parasitoids. The model indicates that the combination of egg limitation and variation in the success of encountering hosts stabilizes parasitoid-host dynamics. The stabilizing mechanism emerges from Jensen’s inequality because egg limitation makes the number of offspring inherently concave down in the number of encountered hosts. Reasons for the inconsistent predictions of the effect of egg limitation between the current model and previous models are discussed.
      PubDate: 2015-01-27
  • The effects of maternal immunity and age structure on population immunity
           to measles
    • Abstract: Abstract Measles was successfully eradicated in the Pan-American Health Region in 2002. However, maintenance of elimination in parts of Africa, Europe, the USA, and other regions is proving difficult, despite apparently high vaccine coverage. This may be due to the different age structure in developed and developing populations, as well as to differences in the duration of maternal immunity. We explore the interaction between maternal immunity and age structure and quantify the resulting immunity gap between vaccine coverage and population immunity; we use this immunity gap as a novel metric of vaccine program success as it highlights the difference between actual and estimated immunity. We find that, for some combinations of maternal immunity and age structure, the accepted herd immunity threshold is not maintainable with a single-dose vaccine strategy for any combination of target age and coverage. In all cases, the herd immunity threshold is more difficult to maintain in a population with developing age structure. True population immunity is always improved if the target age at vaccination is chosen for the specific combination of maternal immunity and age structure.
      PubDate: 2015-01-25
  • A niche remedy for the dynamical problems of neutral theory
    • Abstract: Abstract We demonstrate how niche theory and Hubbell’s original formulation of neutral theory can be blended together into a general framework modeling the combined effects of selection, drift, speciation, and dispersal on community dynamics. This framework connects many seemingly unrelated ecological population models and allows for quantitative predictions to be made about the impact of niche stabilizing and destabilizing forces on population extinction times and abundance distributions. In particular, the existence of niche stabilizing forces in our blended framework can simultaneously resolve two major problems with the dynamics of neutral theory, namely predictions of species lifetimes that are too short and species ages that are too long.
      PubDate: 2014-11-13
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