Talk:Competitive exclusion principle

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Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 18:12, 16 January 2022 (UTC)

Photos
The article needs some images. A graph showing population changes over time for two competing species grown together experimentally would be good, though anything appropriate would be better than nothing. Richard001 04:25, 6 July 2007 (UTC)

Diversity paradox
"(or the diversity paradox)"

Can someone provide citations for this alternate name? A quick googling found only sources derived from this article. Paradoctor (talk) 09:41, 28 June 2009 (UTC)

Why is this a paradox?
I am no biologist and I have some difficulty in understanding the use of the word "paradox" when comparing two experiments conducted in environmental conditions that seem to be very different. In Gause's experiment it seems that the system is closed and the two bacterial species do not only have to fight for food, but also for space. Just the simple fact that any organism occupies some volume in space should indicate that reproduction is constrained not only by the available nutritional resources but also by the available "free space". If saturation constrains chemical reactions, why should this not be true for biological ones? On the other hand, in the Ocean there is no space limitation. Could anybody please explain in detail the conditions of Gause's experiment? Thanks.--Marcellot (talk) 12:44, 19 July 2009 (UTC)


 * What makes you think the bacteria have to "fight ... for space"? And the oceans are space limited, with a hard upper limit at five billion km3. Regards, Paradoctor (talk) 14:39, 19 July 2009 (UTC)


 * Thank you for your quick reply. As I said before, I am no biologist but as far as I know the concept of saturation influences chemical reactions as well as cellular dynamics. Cellular reproduction slows down and even stops when given densities are reached (i.e. "saturation density"). Chemical reactions stop taking place when the density of their products exceeds the saturation level. I have just wondered if Gause simply kept feeding the bacterial colonies in an unnatural way (resources in nature are limited) to make them reproduce exponentially in a limited space, until they reached a given density. At that point, it would be logical to expect that either the colonies stop reproducing (saturation) or start fighting for space. Yes, open sea is actually limited, but not in the terms of Gause's experiment, because the whole ocean is not full of plankton at saturation levels. This brings me back to my original question, which has remained unanswered: which were exactly Gause' experimental conditions? One could try the following experiment: let one single bacterial species reproduce in Gause's experimental conditions. If the reproduction stops at a given point, this would mean that space is actually an issue... --Marcellot (talk) 13:46, 20 July 2009 (UTC)


 * YW. Finally got around to having a look at the 1934 Gause reference from the article, and while I'm no biologist either, I think I understand the source of your confusion. That talk of "places" is misleading. In the experiment, growth is primarily limited by the accumulation of waste products, chiefly alcohol, and later on by the increasing scarcity of food, i. e. sugar. Another example would be free-range chicken: as long as the amount of food per day stays constant, the population will never increase beyond a certain level, regardless of how big the range is made.
 * "feeding" ... "in an unnatural way (resources in nature are limited)": That depends on what your definition of "resource" is. For trees, sunlight is an unlimited resource. Ground providing access to sunlight (and nutrients) is not.
 * "Gause' experimental conditions": Gause's 1934 paper indicates that he conducted multiple experiments over varying time intervals up to those sufficiently long to reach saturation.
 * I hope the above answers your question. If not, maybe this will do the trick: Space around us is empty, so whatever living beings compete for, space is not the limiting factor. If that's too "far out", you might want to ponder the fact that there are no 500 m tall trees. ;)
 * Paradoctor (talk) 15:51, 20 July 2009 (UTC)


 * Well, you don't have 100 trees in 1 m2 either. That is actually my point. By the way, I found an interesting link: . It's about arelatively old article (1969), which claims the non reproducibility of Gause's experiment. But what matters more to me is the reference to "limited resources of space". I therefore guess that I was not wrong in my assumption.--Marcellot (talk) 07:33, 21 July 2009 (UTC)


 * [[image:Forest on San Juan Island.jpg|thumb|120px|right]] In my parent's garden is a very small spot where four trees have grown to a height of more than 10 m each. The reason that forests do not have such high population densities is that a mature tree requires a minimum of sunlight. If you look at the image to the right, you'll see that there is ample room for more trees, which makes it obvious that space is not the limiting factor.
 * "limited resources of" ... "space": I'll bet you a penny to a dollar that I can refute that. "Space" is practically always a metaphor for some resource correlated to the volume/area "controlled" by an individual. Think of a predator's territory. If the density of prey increases, the predator's territory will decrease. I recall reading about a pair of falcons which never left their tower, because there so many pigeons in it.
 * The Ayala paper is useful, you might want to add it in a Criticism section. The article could stand definitely more secondary sources, like reviews and text books. 08:36, 21 July 2009 (UTC) —Preceding unsigned comment added by Paradoctor (talk • contribs)


 * I gladly go along with your definition of space: I was the first to talk about population densities and saturation densities, now you say "density of prey". However you put it, space is an issue. Dimensionally, even your supposed "volume/area" ratio is a length, i.e. a measure of space. Regarding your forest example, as you pointed out, there are other limiting factors such as access to light and water. This doesn't rule out space as limiting factor. I accept your bet. Please devolve your dollar to the Wikipedia project. :-) —Preceding unsigned comment added by 192.109.190.88 (talk) 09:02, 21 July 2009 (UTC)


 * This discussion has gone off-topic, we'll continue at your user talk. Paradoctor (talk) 11:17, 21 July 2009 (UTC)

[Late-comer comments] I think space is probably just a confounding issue here. The availability of nutrients from which organisms are constructed ultimately limits the maximum biomass possible in the ocean. As it happens, these are sufficiently scarce that space is never going to be an issue there. And on top of that, nutrients are not the only things that limit phytoplankton in the ocean, so their concentrations will be lower even than that permitted by nutrients. It may well be the Gause experiments found limited space to be an issue (which wouldn't be too surprising since they dealt with laboratory cultures), but I don't think it applies to the oceans. Other factors come into play long before space does. Does this help? --P LUMBAGO 14:54, 21 July 2009 (UTC)


 * Thanks, this helps. And I definitely agree with you. In the open sea, the first limiting factor may well be the nutrients. Since they are limited in comparison to the available space, the latter never comes to be an issue. I agree. On the other hand, in Gause's experiment you have 1) an infinite quantity of nutrients (he kept feeding the colonies from outside); 2) a limited space. So space may have been an issue here, as you seem to concede. Now, my point was: if the conditions in Gause's experiment and in the open sea are that different, why call it a paradox? The two systems are not comparable to me in the first place. I don't understand why one should think that Gause's results should apply to the open sea. But I am an engineer, not a biologist... --Marcellot (talk) 17:52, 21 July 2009 (UTC)


 * That's what I've been saying all along. ;) Anyway, this discussion is now about Marcellot's solution to the paradox, which is OR, so please post any further replies on Marcellot's user page, ok? Regards, Paradoctor (talk) 17:20, 21 July 2009 (UTC)


 * Who are you to moderate even discussion boards? I am free to ask my questions about this topic here, as long as I do not offend anyone. The policy on "original research" only regards articles, not discussions. If you are not interested in the discussion you are free to leave. --Marcellot (talk) 17:52, 21 July 2009 (UTC)


 * I would agree with Paradoctor that article talk pages aren't really for general discussions about a topic, but I don't think it really does any harm on an infrequently visited talk page like this one. And sometimes general discussions do throw up things that might help improve an article.


 * Marcellot, regarding your point about there being no comparison between Gause's experiments and ocean systems, again, I think you're perhaps focussing too much on space. Although Gause's work focuses on competition in cultures for some very specific resources (substrate and/or space), his experiments can be, and are, interpreted for a much wider range of resources.  In the case of plankton systems, to a first approximation phytoplankton compete for a mere handful of resources, including light, nitrate, phosphate, silicic acid, dissolved iron, etc.  But in terms of number of species, or even numbers of higher taxonomic groupings, there are far more of these than there are different resources.  As such, there is clearly a lot of overlap between these groups for resources, and one might naively expect competition to have thinned this diversity down to a level more commensurate with the number of resources.  Hence the paradox.  However, as the article goes on to explain, the seeming paradox is resolved (or, at least, may be resolved) by considering other factors.  Among these is the idea that the planktonic environment, though it may appear homogeneous and dull, is constantly changing, such that no one species (or group of species) has the time to grind its opponents into extinction.


 * Anyway, Gause's work serves to illustrate how, when species are pitted against one another for shared resources in a relatively homogeneous environment, "complete competitors cannot coexist" (to quote Hardin). And since the ocean presents, to the untrained (or even trained!) eye, the appearance of homogeneity and a mere handful of resources, this is why the paradox of the plankton came to be formulated.  Although the paradox is obviously refuted by the evidence, it provides a framework for thinking about where plankton systems get their diversity from.  Again, I hope this helps.  Best regards, --P LUMBAGO  08:51, 22 July 2009 (UTC)

"Redefinition" Section
It was written by the author of the core source being cited. It also does not reflect any substantial consensus, nor novel principle on the subject. I think that it does not belong in this article, and should be removed. 141.214.17.228 (talk) 20:00, 10 July 2014 (UTC)

UNDUE question re WP:SELFCITE
In [https://en.wikipedia.org/w/index.php?title=Competitive_exclusion_principle&type=revision&diff=573818452&oldid=569559257 this dif, the author of the source added content based on the source. I have reverted and am copying here for others to review.

As the contradiction between the principle and natural species richness still remains, the principle was verified. A mechanism of competitive coexistence which violates all known formulations of the competitive exclusion principle was found. As a consequence, a fully mechanistic and most stringent formulation of the principle was proposed:

Implementation of this extremely strict formulation of the competitive exclusion principle is rather a very rare case in nature. Therefore, this new formulation eliminates old contradictions between the competitive exclusion principle and observed biodiversity.

Is this appropriate content and WP:WEIGHT? Thanks. Jytdog (talk) 13:52, 13 June 2015 (UTC)


 * No. the source is a minor article in a very controversial journal. This would be considered a fringe view in science and to seems to be based on a misinterpretation. Fzbristol (talk) 13:11, 18 September 2022 (UTC)

Some key points missing?
What is on the page is correct but some key insights that came from this principle are lost between the lines. The standard textbook version of the story comes in five steps I somehow find this flow of arguments is lost in the present text, thus that the bigger picture is lost. Fzbristol (talk) 13:07, 18 September 2022 (UTC)
 * 1) The competitive exclusion principle seems mathematically inevitable
 * 2) In the modern formulation (number of species does not exceed the number of niches) the principle is tautological and therefore guaranteed to be true.
 * 3) The principle is apparently violated almost everywhere in nature as near-identical are seen to coexists (MacArthur's Warblers) and some systems seem to harbor an abundance of species based on very limited resources (Hutchinson's Paradox of Plankton and more generally his Santa Rosalia paper)
 * 4) Gause's experiments became famous because the first demonstration of the principle, but were seen by many as a "laboratory curiosity" (Pearl, other sources reviewed by Gentleman)
 * 5) The modern understanding (building on MacArthur) is that the principle is valuable, precisely because it must be logically true but apparently violated in nature. It is to identify previously undetected niches.