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 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 Some Discrete Competition Models and the Competitive Exclusion Principle†

2004 ◽  
Vol 10 (13-15) ◽  
pp. 1139-1151 ◽  
Author(s):  
J.M. Cushing ◽  
Sheree Levarge ◽  
Nakul Chitnis ◽  
Shandelle M. Henson
Keyword(s):  
Competitive Exclusion ◽  
Exclusion Principle ◽  
Competitive Exclusion Principle ◽  
Competition Models

scholarly journals On a solution of the biodiversity paradox and a competitive coexistence principle

2014 ◽  
Author(s):  
Lev V. Kalmykov ◽  
Vyacheslav L. Kalmykov
Keyword(s):  
Sustainable Development ◽  
Biodiversity Conservation ◽  
Theoretical Basis ◽  
Competitive Exclusion ◽  
Exclusion Principle ◽  
Central Problem ◽  
Competitive Exclusion Principle ◽  
Theoretical Ecology ◽  
Competitive Coexistence ◽  
Trade Offs

The biodiversity paradox is the central problem in theoretical ecology. The paradox consists in the contradiction between the competitive exclusion principle and the observed biodiversity. This contradiction is the key subject of the long-standing and continuing biodiversity debates. The paradox impedes our insights into biodiversity conservation. Previously we proved that due to a soliton-like behaviour of population waves complete competitors can indefinitely coexist in one closed homogeneous habitat on one and the same limiting resource under constant conditions of environment, without any trade-offs and cooperations. As this fact violates the known formulations of the competitive exclusion principle we have reformulated the principle. Here we explain why this reformulation of the principle results in a solution of the biodiversity paradox. In addition, we generalize the competitive exclusion principle. Reasoning by contradiction, we formulate a generalized principle of competitive coexistence. These principles expand theoretical basis for biodiversity conservation and sustainable development.

scholarly journals Coexistence of complete competitors with fitness inequality

2017 ◽  
Author(s):  
Lev Kalmykov ◽  
Vyacheslav Kalmykov
Keyword(s):  
Competitive Exclusion ◽  
Initial Conditions ◽  
Exclusion Principle ◽  
Single Individual ◽  
Competing Species ◽  
Competitive Exclusion Principle ◽  
Trade Offs ◽  
Initial Stage ◽  
Initial Location ◽  
Rigorous Model

There was a long standing contradiction between formulations of the competitive exclusion principle and natural species richness, which is known as the biodiversity paradox. Here we investigate a role of fitness differences in coexistence of two completely competing species using individual-based cellular automata. According to the classical formulations of the competitive exclusion principle such coexistence is impossible. Earlier we found that coexistence of complete competitors is possible with a 100% difference in fitness, but only under certain initial conditions. Here we verify a hypothesis that completely competing species may coexist with less than 100% difference in fitness regardless of different initial location of competing individuals in the ecosystem. We have found a new fact that two aggressively propagating complete competitors can stably coexist in one limited, stable and homogeneous habitat, when one species has some advantage in fitness over the other and all other characteristics of the species are equal, in particular any trade-offs and cooperations are absent. This fact is established theoretically on the rigorous model. The found competitive coexistence occurred regardless of the initial location of individuals in the ecosystem. When colonization of free habitat started from a single individual of each species, then the complete competitors coexisted up to 31% of their difference in fitness. And when on initial stage half of the territory was probabilistically occupied, the complete competitors coexisted up to 22% of their difference in fitness. These results additionally support our reformulation of the competitive exclusion principle, which we consider as resolving of the biodiversity paradox.

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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