Predator-prey models: an application for the plankton dynamics of lake Geneva

In this paper we present a hierarchical Bayesian analysis for a predator-prey model applied to ecology considering the use of Markov Chain Monte Carlo methods. We consider the introduction of a random effect in the model and the presence of a covariate vector. An application to ecology is considered using a data set related to the plankton dynamics of lake Geneva for the year 1990. We also discuss some aspects of discrimination of the proposed models.

The role of predator overlap in the robustness and extinction of a four species predator-prey network

Predators and preys often form species networks with asymmetric patterns of interaction. We study the dynamics of a four species network consisting of two weakly connected predator-prey pairs. We focus our analysis on the effects of the cross interaction between the predator of the first pair and the prey of the second pair. This is an example where the predator overlap, which is the proportion of predators that a given prey shares with other preys, is not uniform across the network due to asymmetries in patterns of interaction. We explore the behavior of the system under different interaction strengths and study the dynamics of survival and extinction. In particular, we consider situations in which the four species have initial populations lower than their long-term equilibrium, simulating catastrophic situations in which their abundances are reduced due to human action or environmental change. We show that, under these reduced initial conditions, and depending on the strength of the cross interaction, the populations tend to oscillate before re-equilibrating, disturbing the community equilibrium and sometimes reaching values that are only a small fraction of the equilibrium population, potentially leading to their extinction. We predict that, contrary to one`s intuition, the most likely scenario is the extinction of the less predated preys. (C) 2010 Elsevier B.V. All rights reserved.

Reaction-diffusion stochastic lattice model for a predator-prey system

We have the purpose of analyzing the effect of explicit diffusion processes in a predator-prey stochastic lattice model. More precisely we wish to investigate the possible effects due to diffusion upon the thresholds of coexistence of species, i. e., the possible changes in the transition between the active state and the absorbing state devoid of predators. To accomplish this task we have performed time dependent simulations and dynamic mean-field approximations. Our results indicate that the diffusive process can enhance the species coexistence.

Can we disentangle predator-prey interactions from species distributions at a macro-scale? A case study with a raptor species.

There is a debate on whether an influence of biotic interactions on species distributions can be reflected at macro-scale levels. Whereas the influence of biotic interactions on spatial arrangements is beginning to be studied at local scales, similar studies at macro-scale levels are scarce. There is no example disentangling, from other similarities with related species, the influence of predator-prey interactions on species distributions at macro-scale levels. In this study we aimed to disentangle predator-prey interactions from species distribution data following an experimental approach including a factorial design. As a case of study we selected the short-toed eagle because of its known specialization on certain prey reptiles. We used presence-absence data at a 100 Km2 spatial resolution to extract the explanatory capacity of different environmental predictors (five abiotic and two biotic predictors) on the short-toed eagle species distribution in Peninsular Spain. Abiotic predictors were relevant climatic and topographic variables, and relevant biotic predictors were prey richness and forest density. In addition to the short-toed eagle, we also obtained the predictor's explanatory capacities for i) species of the same family Accipitridae (as a reference), ii) for other birds of different families (as controls) and iii) species with randomly selected presences (as null models). We run 650 models to test for similarities of the short-toed eagle, controls and null models with reference species, assessed by regressions of explanatory capacities. We found higher similarities between the short-toed eagle and other species of the family Accipitridae than for the other two groups. Once corrected by the family effect, our analyses revealed a signal of predator-prey interaction embedded in species distribution data. This result was corroborated with additional analyses testing for differences in the concordance between the distributions of different bird categories and the distributions of either prey or non-prey species of the short-toed eagle. Our analyses were useful to disentangle a signal of predator-prey interactions from species distribution data at a macro-scale. This study highlights the importance of disentangling specific features from the variation shared with a given taxonomic level.

On certain new exact solutions of a diffusive predator-prey system

We construct exact solutions for a system of two coupled nonlinear partial differential equations describing the spatio-temporal dynamics of a predator-prey system where the prey per capita growth rate is subject to the Allee effect. Using the G'/G expansion method, we derive exact solutions to this model for two different wave speeds. For each wave velocity we report three different forms of solutions. We also discuss the biological relevance of the solutions obtained. © 2012 Elsevier B.V.

Solving Ratio-Dependent Predator-Prey System with Constant Effort Harvesting using Variational Iteration Method

Due to wide range of interest in use of bio-economic models to gain insight into the scientific management of renewable resources like fisheries and forestry,variational iteration method (VIM) is employed to approximate the solution of the ratio-dependent predator-prey system with constant effort prey harvesting.The results are compared with the results obtained by Adomian decomposition method and reveal that VIM is very effective and convenient for solving nonlinear differential equations.

Predator-prey chemical warfare determines the expression of biocontrol genes by rhizosphere-associated Pseudomonas fluorescens.

Soil bacteria are heavily consumed by protozoan predators, and many bacteria have evolved defense strategies such as the production of toxic exometabolites. However, the production of toxins is energetically costly and therefore is likely to be adjusted according to the predation risk to balance the costs and benefits of predator defense. We investigated the response of the biocontrol bacterium Pseudomonas fluorescens CHA0 to a common predator, the free-living amoeba Acanthamoeba castellanii. We monitored the effect of the exposure to predator cues or direct contact with the predators on the expression of the phlA, prnA, hcnA, and pltA genes, which are involved in the synthesis of the toxins, 2,4-diacetylphloroglucinol (DAPG), pyrrolnitrin, hydrogen cyanide, and pyoluteorin, respectively. Predator chemical cues led to 2.2-, 2.0-, and 1.2-fold increases in prnA, phlA, and hcnA expression, respectively, and to a 25% increase in bacterial toxicity. The upregulation of the tested genes was related to the antiprotozoan toxicity of the corresponding toxins. Pyrrolnitrin and DAPG had the highest toxicity, suggesting that bacteria secrete a predator-specific toxin cocktail. The response of the bacteria was elicited by supernatants of amoeba cultures, indicating that water-soluble chemical compounds were responsible for induction of the bacterial defense response. In contrast, direct contact of bacteria with living amoebae reduced the expression of the four bacterial toxin genes by up to 50%, suggesting that protozoa can repress bacterial toxicity. The results indicate that predator-prey interactions are a determinant of toxin production by rhizosphere P. fluorescens and may have an impact on its biocontrol potential.

CRITICAL BEHAVIOR AND THRESHOLD OF COEXISTENCE OF A PREDATOR-PREY STOCHASTIC MODEL IN A 2D LATTICE

We investigate the critical behavior of a stochastic lattice model describing a predator-prey system. By means of Monte Carlo procedure we simulate the model defined on a regular square lattice and determine the threshold of species coexistence, that is, the critical phase boundaries related to the transition between an active state, where both species coexist and an absorbing state where one of the species is extinct. A finite size scaling analysis is employed to determine the order parameter, order parameter fluctuations, correlation length and the critical exponents. Our numerical results for the critical exponents agree with those of the directed percolation universality class. We also check the validity of the hyperscaling relation and present the data collapse curves.

The stochastic nature of predator-prey cycles

We study by numerical simulations the time correlation function of a stochastic lattice model describing the dynamics of coexistence of two interacting biological species that present time cycles in the number of species individuals. Its asymptotic behavior is shown to decrease in time as a sinusoidal exponential function from which we extract the dominant eigenvalue of the evolution operator related to the stochastic dynamics showing that it is complex with the imaginary part being the frequency of the population cycles. The transition from the oscillatory to the nonoscillatory behavior occurs when the asymptotic behavior of the time correlation function becomes a pure exponential, that is, when the real part of the complex eigenvalue equals a real eigenvalue. We also show that the amplitude of the undamped oscillations increases with the square root of the area of the habitat as ordinary random fluctuations. (C) 2009 Elsevier B.V. All rights reserved.

How population loss through habitat boundaries determines the dynamics of a predator-prey system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Multiobjective Biogeography-Based Optimization Based on Predator-Prey Approach

Biogeography is the science that studies the geographical distribution and the migration of species in an ecosystem. Biogeography-based optimization (BBO) is a recently developed global optimization algorithm as a generalization of biogeography to evolutionary algorithm and has shown its ability to solve complex optimization problems. BBO employs a migration operator to share information between the problem solutions. The problem solutions are identified as habitat, and the sharing of features is called migration. In this paper, a multiobjective BBO, combined with a predator-prey (PPBBO) approach, is proposed and validated in the constrained design of a brushless dc wheel motor. The results demonstrated that the proposed PPBBO approach converged to promising solutions in terms of quality and dominance when compared with the classical BBO in a multiobjective version.

Predator-prey interactions: jaguar predation on caiman in a floodplain forest

Advances in the understanding of ecological factors determining predatorprey interactions have provided a strong theoretical background on diet preferences of predators. We examined patterns of jaguar predation on caiman in southern Pantanal, Brazil. We investigated factors affecting predation rates and vulnerability of caiman to predation by jaguars. We recorded 114 caiman mortality incidents. Predation accounted for 62.3% (n = 71) of all caiman found dead, while other causes of mortality (nonpredation) accounted for 37.7% (n = 43). We found that jaguars prey on a broad size range of caiman body and caiman predation was influenced by distance to forests. During dry seasons, 70% (n = 49) of deaths were due to predation, while 30% (n = 21) were due to nonpredation causes. However, we found no significant relationship between annual and monthly killings of caiman and rainfall totals by year and month (r = 0.130, r = -0.316). The annual flooding regime may be a more important factor influencing prey selection by jaguars. Although neotropical crocodilians are relatively well studied, their interactions with jaguars have been mostly ignored and should be prioritized in future studies.

Predator-prey: interactions between the spiny waterflea (Bythotrephes longimanus) and pumpkinseed sunfish (Lepomis gibbosus)

Small pumpkinseed sunfish ( Lepomis gibbosus), were found to be capable of removing the spine of Bythotrephes longimanus, an invasive cladoceran. Because fish consumption may be important in the dispersal or control of Bythotrephes, aquarium feeding experiments were conducted to 1) establish if the spine removal behavior of the pumpkinseeds was locally unique; 2) quantify how frequently pumpkinseeds exhibit the behavior; 3) determine if pumpkinseed handle Bythotrephes more quickly than other species of fish; and 4) verify if Bythotrephes' resting eggs pass through the digestive systems of pumpkinseeds in viable condition. The experiments revealed that pumpkinseeds (45-70 mm TL) from two geographic regions were more successful (100%) at removing Bythotrephes' spine, and handled Bythotrephes more quickly than yellow perch (Perca flavescens) (49-57 mm TL) and smallmouth bass (Micropterus dolomieu) (50-57mm TL) used in the study. Of 244 live Bythotrephes' resting eggs fed to the pumpkinseeds, 104 (42.6%) passed through their digestive systems. From those eggs, only 10 successfully hatched. Preliminary enclosure experiments were carried out and indicated that pumpkinseeds will consume Bythotrephes in natural settings. These findings provide new evidence that certain fish, with specialized morphology for prey manipulation, have the ability to influence the distribution and establishment of Bythotrephes.

Putting prey and predator into the CO2 equation-qualitative and quantitative effects of ocean acidification on predator-prey interactions

Little is known about the impact of ocean acidification on predator-prey dynamics. Herein, we examined the effect of carbon dioxide (CO(2)) on both prey and predator by letting one predatory reef fish interact for 24 h with eight small or large juvenile damselfishes from four congeneric species. Both prey and predator were exposed to control or elevated levels of CO(2). Mortality rate and predator selectivity were compared across CO(2) treatments, prey size and species. Small juveniles of all species sustained greater mortality at high CO(2) levels, while large recruits were not affected. For large prey, the pattern of prey selectivity by predators was reversed under elevated CO(2). Our results demonstrate both quantitative and qualitative consumptive effects of CO(2) on small and larger damselfish recruits respectively, resulting from CO(2)-induced behavioural changes likely mediated by impaired neurological function. This study highlights the complexity of predicting the effects of climate change on coral reef ecosystems.