scholarly journals Local Interactions Affect Spread of Resource in a Consumer-resource System With Group Defense

2021 ◽  
Author(s):  
Jorge Arroyo-Esqu ◽  
Alan Hastings ◽  
Marissa L. Baskett
Keyword(s):  
Defense Mechanisms ◽  
Life Cycle Stage ◽  
Ecological Interactions ◽  
Resource Population ◽  
High Resource ◽  
Type Iv ◽  
Spread Dynamics ◽  
Group Defense ◽  
Resource System ◽  
Consumer Resource

Abstract Integrodifference equations are a discrete time spatially explicit model that describes dispersal of ecological populations through space. This framework is useful to study spread dynamics of organisms and how ecological interactions can affect their spread. When studying interactions such as consumption, dispersal rates might vary with life cycle stage, such as cases with dispersive juveniles and sessile adults. In the non-dispersive stage, resources may engage in group defense to protect themselves from consumption. These local nondispersive interactions may limit the number of dispersing recruits that are produced and therefore affect how fast populations can spread. We present a spatial consumer-resource system using an integrodifference framework with limited movement of their adult stages and group defense mechanisms in the resource population. We model group defense using a Type IV Holling functional response, which limits survival of adult resource population and enhances juvenile consumers production. We find that high mortality levels for sessile adults can destabilize resource at carrying capacity. Furthermore, we find that at high resource densities, group defense leads to a slower local growth of resource in newly invaded regions due to intraspecific competition outweighing the effect of consumption on resource growth.

scholarly journals How superdiffusion gets arrested: ecological encounters explain shift from Lévy to Brownian movement

2014 ◽  
Vol 281 (1774) ◽  
pp. 20132605 ◽  
Author(s):  
Monique de Jager ◽  
Frederic Bartumeus ◽  
Andrea Kölzsch ◽  
Franz J. Weissing ◽  
Geerten M. Hengeveld ◽  
...  
Keyword(s):  
Brownian Motion ◽  
Empirical Studies ◽  
Movement Patterns ◽  
Movement Pattern ◽  
Mechanistic Explanation ◽  
Theoretical Argument ◽  
Ecological Interactions ◽  
High Resource ◽  
Dependent Change ◽  
Movement Strategy

Ecological theory uses Brownian motion as a default template for describing ecological movement, despite limited mechanistic underpinning. The generality of Brownian motion has recently been challenged by empirical studies that highlight alternative movement patterns of animals, especially when foraging in resource-poor environments. Yet, empirical studies reveal animals moving in a Brownian fashion when resources are abundant. We demonstrate that Einstein's original theory of collision-induced Brownian motion in physics provides a parsimonious, mechanistic explanation for these observations. Here, Brownian motion results from frequent encounters between organisms in dense environments. In density-controlled experiments, movement patterns of mussels shifted from Lévy towards Brownian motion with increasing density. When the analysis was restricted to moves not truncated by encounters, this shift did not occur. Using a theoretical argument, we explain that any movement pattern approximates Brownian motion at high-resource densities, provided that movement is interrupted upon encounters. Hence, the observed shift to Brownian motion does not indicate a density-dependent change in movement strategy but rather results from frequent collisions. Our results emphasize the need for a more mechanistic use of Brownian motion in ecology, highlighting that especially in rich environments, Brownian motion emerges from ecological interactions, rather than being a default movement pattern.

scholarly journals Mouse Macrophages Are Permissive to Motile Legionella Species That Fail To Trigger Pyroptosis

2009 ◽  
Vol 78 (1) ◽  
pp. 423-432 ◽  
Author(s):  
Natalie N. Whitfield ◽  
Brenda G. Byrne ◽  
Michele S. Swanson
Keyword(s):  
Cell Death ◽  
Legionella Pneumophila ◽  
Defense Mechanisms ◽  
Opportunistic Pathogen ◽  
Pathogenic Potential ◽  
Innate Defense ◽  
Transplant Patients ◽  
Type Iv ◽  
Mouse Macrophages ◽  
Motile Species

ABSTRACT Legionella pneumophila, a motile opportunistic pathogen of humans, is restricted from replicating in the lungs of C57BL/6 mice. Resistance of mouse macrophages to L. pneumophila depends on recognition of cytosolic flagellin. Once detected by the NOD-like receptors Naip5 and Ipaf (Nlrc4), flagellin triggers pyroptosis, a proinflammatory cell death. In contrast, motile strains of L. parisiensis and L. tucsonensis replicate profusely within C57BL/6 macrophages, similar to flagellin-deficient L. pneumophila. To gain insight into how motile species escape innate defense mechanisms of mice, we compared their impacts on macrophages. L. parisiensis and L. tucsonensis do not induce proinflammatory cell death, as measured by lactate dehydrogenase (LDH) release and interleukin-1β (IL-1β) secretion. However, flagellin isolated from L. parisiensis and L. tucsonensis triggers cell death and IL-1β secretion when transfected into the cytosol of macrophages. Neither strain displays three characteristics of the canonical L. pneumophila Dot/Icm type IV secretion system: sodium sensitivity, LAMP-1 evasion, and pore formation. Therefore, we postulate that when L. parisiensis and L. tucsonensis invade a mouse macrophage, flagellin is confined to the phagosome, protecting the bacteria from recognition by the cytosolic surveillance system and allowing Legionella to replicate. Despite their superior capacity to multiply in mouse macrophages, L. parisiensis and L. tucsonensis have been associated with only two cases of disease, both in renal transplant patients. These results point to the complexity of disease, a product of the pathogenic potential of the microbe, as defined in the laboratory, and the capacity of the host to mount a measured defense.

MODELING TOXIC STRESS BY ATRAZINE IN A MARINE CONSUMER-RESOURCE SYSTEM

2013 ◽  
Vol 32 (5) ◽  
pp. 1088-1095 ◽  
Author(s):  
Lisette De Hoop ◽  
Marleen De Troch ◽  
A. Jan Hendriks ◽  
Frederik De Laender
Keyword(s):  
Toxic Stress ◽  
Resource System ◽  
Consumer Resource

scholarly journals Xanthomonas citri subsp. citri Type IV Pilus Is Required for Twitching Motility, Biofilm Development, and Adherence

2014 ◽  
Vol 27 (10) ◽  
pp. 1132-1147 ◽  
Author(s):  
German Dunger ◽  
Cristiane R. Guzzo ◽  
Maxuel O. Andrade ◽  
Jeffrey B. Jones ◽  
Chuck S. Farah
Keyword(s):  
Biofilm Formation ◽  
Defense Mechanisms ◽  
Large Set ◽  
Twitching Motility ◽  
Xanthomonas Citri ◽  
Helical Polymers ◽  
Type Iv ◽  
Bacterial Migration ◽  
In The Wild ◽  
Biofilm Development

Bacterial type IV pili (T4P) are long, flexible surface filaments that consist of helical polymers of mostly pilin subunits. Cycles of polymerization, attachment, and depolymerization mediate several pilus-dependent bacterial behaviors, including twitching motility, surface adhesion, pathogenicity, natural transformation, escape from immune system defense mechanisms, and biofilm formation. The Xanthomonas citri subsp. citri strain 306 genome codes for a large set of genes involved in T4P biogenesis and regulation and includes several pilin homologs. We show that X. citri subsp. citri can exhibit twitching motility in a manner similar to that observed in other bacteria such as Pseudomonas aeruginosa and Xylella fastidiosa and that this motility is abolished in Xanthomonas citri subsp. citri knockout strains in the genes coding for the major pilin subunit PilAXAC3241, the ATPases PilBXAC3239 and PilTXAC2924, and the T4P biogenesis regulators PilZXAC1133 and FimXXAC2398. Microscopy analyses were performed to compare patterns of bacterial migration in the wild-type and knockout strains and we observed that the formation of mushroom-like structures in X. citri subsp. citri biofilm requires a functional T4P. Finally, infection of X. citri subsp. citri cells by the bacteriophage (ΦXacm4-11 is T4P dependent. The results of this study improve our understanding of how T4P influence Xanthomonas motility, biofilm formation, and susceptibility to phage infection.

scholarly journals Computational Study on the Dynamics of a Consumer-Resource Model: The Influence of the Growth Law in the Resource

Mathematics ◽  
2021 ◽  
Vol 9 (21) ◽  
pp. 2746
Author(s):  
Luis M. Abia ◽  
Óscar Angulo ◽  
Juan Carlos López-Marcos ◽  
Miguel Ángel López-Marcos
Keyword(s):  
Numerical Study ◽  
Computational Study ◽  
Point Of View ◽  
Global Dynamics ◽  
Resource Model ◽  
Resource Population ◽  
Consumer Population ◽  
Order Scheme ◽  
Growth Laws ◽  
Consumer Resource

The dynamics of a specific consumer-resource model for Daphnia magna is studied from a numerical point of view. In this study, Malthusian, chemostatic, and Gompertz growth laws for the evolution of the resource population are considered, and the resulting global dynamics of the model are compared as different parameters involved in the model change. In the case of Gompertz growth law, a new complex dynamic is found as the carrying capacity for the resource population increases. The numerical study is carried out with a second-order scheme that approximates the size-dependent density function for individuals in the consumer population. The numerical method is well adapted to the situation in which the growth rate for the consumer individuals is allowed to change the sign and, therefore, individuals in the consumer population can shrink in size as time evolves. The numerical simulations confirm that the shortage of the resource has, as a biological consequence, the effective shrink in size of individuals of the consumer population. Moreover, the choice of the growth law for the resource population can be selected by how the dynamics of the populations match with the qualitative behaviour of the data.

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