scholarly journals Dynamical persistence in resource-consumer models

2020 ◽  
Author(s):  
Itay Dalmedigos ◽  
Guy Bunin
Keyword(s):  
Fixed Points ◽  
Competitive Exclusion ◽  
Resource Competition ◽  
Exclusion Principle ◽  
Ecological Communities ◽  
Competitive Exclusion Principle ◽  
Stable Equilibria ◽  
Species Being ◽  
Abundance Fluctuations ◽  
High Diversity

We show how highly-diverse ecological communities may display persistent abundance fluctuations, when interacting through resource competition and subjected to migration from a species pool. This turns out to be closely related to the ratio of realized species diversity to the number of resources. This ratio is set by competition, through the balance between species being pushed out and invading. When this ratio is smaller than one, dynamics will reach stable equilibria. When this ratio is larger than one, fixed-points are either unstable or marginally stable, as expected by the competitive exclusion principle. If they are unstable, the system is repelled from fixed points, and abundances forever fluctuate. While marginally-stable fixed points are in principle allowed and predicted by some models, they become structurally unstable at high diversity. This means that even small changes to the model, such as non-linearities in how resources combine to generate species’ growth, will result in persistent abundance fluctuations.

scholarly journals The Paradox of the Plankton: Coexistence of Structured Microbial Communities

2021 ◽  
Author(s):  
Alberto Scarampi
Keyword(s):  
Competitive Exclusion ◽  
Resource Competition ◽  
Exclusion Principle ◽  
Limited Resources ◽  
Shared Resources ◽  
Competitive Exclusion Principle ◽  
Biophysical Models ◽  
Competition Models ◽  
Model Match ◽  
Trade Offs

In the framework of resource-competition models, it has been argued that the number of species stably coexisting in an ecosystem cannot exceed the number of shared resources. However, plankton seems to be an exception of this so-called "competitive-exclusion principle". In planktic ecosystems, a large number of different species stably coexist in an environment with limited resources. This contradiction between theoretical expectations and empirical observations is often referred to as "The Paradox of the Plankton". This project aims to investigate biophysical models that can account for the large biodiversity observed in real ecosystems in order to resolve this paradox. A model is proposed that combines classical resource competition models, metabolic trade-offs and stochastic ecosystem assembly. Simulations of the model match empirical observations, while relaxing some unrealistic assumptions from previous models.

scholarly journals Cancer Community Ecology

2020 ◽  
Vol 27 (1) ◽  
pp. 107327482095177
Author(s):  
Burt P. Kotler ◽  
Joel S. Brown
Keyword(s):  
Community Ecology ◽  
Cancer Cells ◽  
Cancer Biology ◽  
Competitive Exclusion ◽  
Variance Partitioning ◽  
Exclusion Principle ◽  
Ecological Communities ◽  
Closely Related Species ◽  
Local Conditions ◽  
Competitive Exclusion Principle

Here we advocate Cancer Community Ecology as a valuable focus of study in Cancer Biology. We hypothesize that the heterogeneity and characteristics of cancer cells within tumors should vary systematically in space and time and that cancer cells form local ecological communities within tumors. These communities possess limited numbers of species determined by local conditions, with each species in a community possessing predictable traits that enable them to cope with their particular environment and coexist with each other. We start with a discussion of concepts and assumptions that ecologists use to study closely related species. We then discuss the competitive exclusion principle as a means for knowing when two species should not coexist, and as an opening towards understanding how they can. We present the five major categories of mechanisms of coexistence that operate in nature and suggest that the same mechanisms apply towards understanding the diversification and coexistence of cancer cell species. They are: Food-Safety Tradeoffs, Diet Choice, Habitat Selection, Variance Partitioning, and Competition-Colonization Tradeoffs. For each mechanism, we discuss how it works in nature, how it might work in cancers, and its implications for therapy.

Ecological Theory and the Superfluous Niche

2019 ◽  
Vol 47 (1) ◽  
pp. 105-123
Author(s):  
James Justus ◽  
Keyword(s):  
Competitive Exclusion ◽  
Ecological Theory ◽  
Character Displacement ◽  
Exclusion Principle ◽  
Limiting Similarity ◽  
Competitive Exclusion Principle ◽  
Ecological Equivalence

Perhaps no concept has been thought more important to ecological theorizing than the niche. Without it, technically sophisticated and well-regarded accounts of character displacement, ecological equivalence, limiting similarity, and others would seemingly never have been developed. The niche is also widely considered the centerpiece of the best candidate for a distinctively ecological law, the competitive exclusion principle. But the incongruous array and imprecise character of proposed definitions of the concept square poorly with its apparent scientific centrality. I argue this definitional diversity and imprecision reflects a problematic conceptual indeterminacy that challenges its putative indispensability in ecology.

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