scholarly journals The Dynamics of a Tritrophic Leslie-Gower Food-Web System with the Effect of Fear

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Firas Hussean Maghool ◽  
Raid Kamel Naji
Keyword(s):  
Food Web ◽  
Evolutionary Biology ◽  
Basin Of Attraction ◽  
Growth Function ◽  
Generalist Predator ◽  
Specific Level ◽  
Predator Species ◽  
Web System ◽  
Group Defense ◽  
The Impact

The avoidance strategy of prey to predation and the predation strategy for predators are important topics in evolutionary biology. Both prey and predators adjust their behaviors in order to obtain the maximal benefits and to raise their biomass for each. Therefore, this paper is aimed at studying the impact of prey’s fear and group defense against predation on the dynamics of the food-web model. Consequently, in this paper, a mathematical model that describes a tritrophic Leslie-Gower food-web system is formulated. Sokol-Howell type of function response is adapted to describe the predation process due to the prey’s group defensive capability. The effects of fear due to the predation process are considered in the first two levels. It is assumed that the generalist predator grows logistically using the Leslie-Gower type of growth function. All the solution properties of the model are studied. Local dynamics behaviors are investigated. The basin of attraction for each equilibrium is determined using the Lyapunov function. The conditions of persistence of the model are specified. The study of local bifurcation in the model is done. Numerical simulations are implemented to show the obtained results. It is watched that the system is wealthy in its dynamics including chaos. The fear factor works as a stabilizing factor in the system up to a specific level; otherwise, it leads to the extinction of the predator. However, increasing the prey’s group defense leads to extinction in predator species.

Cursorial spiders retard initial aphid population growth at low densities in winter wheat

2008 ◽  
Vol 98 (3) ◽  
pp. 249-255 ◽  
Author(s):  
K. Birkhofer ◽  
E. Gavish-Regev ◽  
K. Endlweber ◽  
Y.D. Lubin ◽  
K. von Berg ◽  
...  
Keyword(s):  
Population Growth ◽  
Functional Groups ◽  
Arable Land ◽  
Aphid Population ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Molecular Technique ◽  
Predator Species ◽  
Web Building ◽  
The Impact

AbstractGeneralist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna in arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated the relative impact of these two functional groups on a common pest (Sitobion avenae, Aphididae) in wheat by combining a molecular technique that revealed species-specific aphid consumption rates with a factorial field experiment that analyzed the impact, separately and together, of equal densities of these two spider functional groups on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment, but this effect was limited to the initial aphid-population growth period and low-to-intermediate aphid densities. The molecular analysis, which used aphid-specific primers to detect aphid DNA in predator species, detected the highest proportion of aphid-consuming individuals in two cursorial spiders: the foliage-dwelling Xysticus cristatus (Thomisidae) and the ground-active Pardosa palustris (Lycosidae). The results suggest that manipulating the community composition in favour of pest-consuming functional groups may be more important for improving biological control than fostering predator biodiversity per se. Agricultural management practices that specifically foster effective species or functional groups (e.g. mulching for cursorial spiders) should receive more attention in low-pesticide farming systems.

scholarly journals On The Mathematical Model of Two- Prey and Two-Predator Species

2020 ◽  
pp. 608-619
Author(s):  
A. G. Frahan
Keyword(s):  
Mathematical Model ◽  
Local Stability ◽  
Equilibrium Points ◽  
Basin Of Attraction ◽  
Predator Species ◽  
Numerical Examples ◽  
Group Defense ◽  
The Mathematical Model ◽  
Interior Points ◽  
Theoretical Results

In this work, we study two species of predator with two species of prey model, where the two species of prey live in two diverse habitats and have the ability to group-defense. Only one of the two predators tends to switch between the habitats. The mathematical model has at most 13 possible equilibrium points, one of which is the point of origin, two are axial, tow are interior points and the others are boundary points. The model with , where n is the switching index, is discussed regarding the boundedness of its solutions and the local stability of its equilibrium points. In addition, a basin of attraction was created for the interior point. Finally, three numerical examples were given to support the theoretical results.

scholarly journals The effect of prey refuge on the dynamics of three species food web system

2021 ◽  
Vol 14 (2) ◽  
pp. 105-121
Author(s):  
Dawit Melese ◽  
Abraha Hailu
Keyword(s):  
Numerical Simulation ◽  
Food Web ◽  
Equilibrium Points ◽  
Existence Condition ◽  
Prey Refuge ◽  
Predator Species ◽  
Web System ◽  
Analytical Result ◽  
Type Ii Functional Response ◽  
Linearization Techniques

In this paper, a mathematical model is proposed to study the effect of prey refuge on the dynamics of three species food web system. The food web comprises of a single prey and two competing predators. The two predators predate their prey following Holling type II functional response. In this work we discussed boundedness of the system, existence condition of the equilibrium points and the Jacobean matrix is obtained by linearization techniques. The local stability of the equilibrium points was discussed by using Routh-Hurwitz criteria and the global stability of the equilibrium points by constructing suitable Lyapunov function. Numerical simulation is conducted to support the analytical result. Finally, the effect of prey refuge on the dynamics of one prey two predator was discussed based on the analytical and numerical simulation results. From the numerical simulations, it is found that the dynamical system is persistent for a small value of the refuge constant. However, an increase in the refuge constant leads to the extinction of one of the predator species.

scholarly journals Evidence for Ecosystem-Level Trophic Cascade Effects Involving Gulf Menhaden (Brevoortia patronus) Triggered by the Deepwater Horizon Blowout

2021 ◽  
Vol 9 (2) ◽  
pp. 190
Author(s):  
Jeffrey Short ◽  
Christine Voss ◽  
Maria Vozzo ◽  
Vincent Guillory ◽  
Harold Geiger ◽  
...  
Keyword(s):  
Food Web ◽  
Mississippi River ◽  
Trophic Cascade ◽  
Oil Spills ◽  
Net Primary Production ◽  
Spatial Scales ◽  
Dominant Role ◽  
Deepwater Horizon ◽  
Predator Species ◽  
Brevoortia Patronus

Unprecedented recruitment of Gulf menhaden (Brevoortia patronus) followed the 2010 Deepwater Horizon blowout (DWH). The foregone consumption of Gulf menhaden, after their many predator species were killed by oiling, increased competition among menhaden for food, resulting in poor physiological conditions and low lipid content during 2011 and 2012. Menhaden sampled for length and weight measurements, beginning in 2011, exhibited the poorest condition around Barataria Bay, west of the Mississippi River, where recruitment of the 2010 year class was highest. Trophodynamic comparisons indicate that ~20% of net primary production flowed through Gulf menhaden prior to the DWH, increasing to ~38% in 2011 and ~27% in 2012, confirming the dominant role of Gulf menhaden in their food web. Hyperabundant Gulf menhaden likely suppressed populations of their zooplankton prey, suggesting a trophic cascade triggered by increased menhaden recruitment. Additionally, low-lipid menhaden likely became “junk food” for predators, further propagating adverse effects. We posit that food web analyses based on inappropriate spatial scales for dominant species, or solely on biomass, provide insufficient indication of the ecosystem consequences of oiling injury. Including such cascading and associated indirect effects in damage assessment models will enhance the ability to anticipate and estimate ecosystem damage from, and provide recovery guidance for, major oil spills.

scholarly journals Enhanced Viral Activity in the Surface Microlayer of the Arctic and Antarctic Oceans

2021 ◽  
Vol 9 (2) ◽  
pp. 317
Author(s):  
Dolors Vaqué ◽  
Julia A. Boras ◽  
Jesús Maria Arrieta ◽  
Susana Agustí ◽  
Carlos M. Duarte ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Food Web ◽  
Physicochemical Characteristics ◽  
The Arctic ◽  
Microbial Food Web ◽  
Surface Microlayer ◽  
Polar Regions ◽  
Nutrient Inputs ◽  
Viral Activity ◽  
The Impact

The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column.

scholarly journals Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 321
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Studies ◽  
Generalist Predators ◽  
Predator Species ◽  
Potted Plants ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
Pest Outbreaks ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

scholarly journals Sensory-based niche partitioning in a multiple predator–multiple prey community

2015 ◽  
Vol 282 (1808) ◽  
pp. 20150520 ◽  
Author(s):  
Jay J. Falk ◽  
Hannah M. ter Hofstede ◽  
Patricia L. Jones ◽  
Marjorie M. Dixon ◽  
Paul A. Faure ◽  
...  
Keyword(s):  
Species Interactions ◽  
Prey Species ◽  
Niche Partitioning ◽  
Signal Evolution ◽  
Signal Design ◽  
Predator Species ◽  
Mate Attraction ◽  
Communication Signals ◽  
Signal Features ◽  
The Impact

Many predators and parasites eavesdrop on the communication signals of their prey. Eavesdropping is typically studied as dyadic predator–prey species interactions; yet in nature, most predators target multiple prey species and most prey must evade multiple predator species. The impact of predator communities on prey signal evolution is not well understood. Predators could converge in their preferences for conspicuous signal properties, generating competition among predators and natural selection on particular prey signal features. Alternatively, predator species could vary in their preferences for prey signal properties, resulting in sensory-based niche partitioning of prey resources. In the Neotropics, many substrate-gleaning bats use the mate-attraction songs of male katydids to locate them as prey. We studied mechanisms of niche partitioning in four substrate-gleaning bat species and found they are similar in morphology, echolocation signal design and prey-handling ability, but each species preferred different acoustic features of male song in 12 sympatric katydid species. This divergence in predator preference probably contributes to the coexistence of many substrate-gleaning bat species in the Neotropics, and the substantial diversity in the mate-attraction signals of katydids. Our results provide insight into how multiple eavesdropping predator species might influence prey signal evolution through sensory-based niche partitioning.

scholarly journals The impact of intraspecific variation on food web structure

Ecology ◽  
2018 ◽  
Vol 99 (12) ◽  
pp. 2712-2720 ◽  
Author(s):  
Tom Clegg ◽  
Mohammad Ali ◽  
Andrew P. Beckerman
Keyword(s):  
Food Web ◽  
Intraspecific Variation ◽  
Food Web Structure ◽  
Web Structure ◽  
The Impact

scholarly journals Evolution in the cold

2000 ◽  
Vol 12 (3) ◽  
pp. 257-257 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Evolutionary Biology ◽  
Antarctic Fish ◽  
The Arctic ◽  
Polar Regions ◽  
Evolutionary Studies ◽  
Adaptive Radiations ◽  
The Antarctic ◽  
The Impact ◽  
Insight Into

Theodosius Dobzhansky once remarked that nothing in biology makes sense other than in the light of evolution, thereby emphasising the central role of evolutionary studies in providing the theoretical context for all of biology. It is perhaps surprising then that evolutionary biology has played such a small role to date in Antarctic science. This is particularly so when it is recognised that the polar regions provide us with an unrivalled laboratory within which to undertake evolutionary studies. The Antarctic exhibits one of the classic examples of a resistance adaptation (antifreeze peptides and glycopeptides, first described from Antarctic fish), and provides textbook examples of adaptive radiations (for example amphipod crustaceans and notothenioid fish). The land is still largely in the grip of major glaciation, and the once rich terrestrial floras and faunas of Cenozoic Gondwana are now highly depauperate and confined to relatively small patches of habitat, often extremely isolated from other such patches. Unlike the Arctic, where organisms are returning to newly deglaciated land from refugia on the continental landmasses to the south, recolonization of Antarctica has had to take place by the dispersal of propagules over vast distances. Antarctica thus offers an insight into the evolutionary responses of terrestrial floras and faunas to extreme climatic change unrivalled in the world. The sea forms a strong contrast to the land in that here the impact of climate appears to have been less severe, at least in as much as few elements of the fauna show convincing signs of having been completely eradicated.

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