Arthur G. Tansley writes
this article as a response to John Phillips’ papers in the Journal of Ecology, of which Tansley is the editor. Phillips’
papers are about how correct Frederic Clements is about the complex organism
and progression to the climax. This article is Tansley’s dissent on Phillips’
and Clements’ uses and the restrictive nature of their vocabulary.
Succession: According to Tansley, succession is not an
entirely progressive and developmental process of the complex organism towards
climax. Here, Tansley makes the case with retrogressive succession that keeps a
heath or grassland from becoming a forest. Heath, by the way, is a type of
shrubland. Disturbance is an important aspect in ecology, and Tansley is
talking about how destruction is an integral part of some systems.
Quasi-Organism: Tansley speaks often of how he disapproves
of the characterization of a community of plants as a “complex organism.” He
provides quasi-organism as an alternative, which, apparently, Clements does not
budge in compromise with using quasi-organism.
Ecosystem: One of the foundational words we use today is
coined in this article: ecosystem. Tansley considered Clements’ initial usage
of the word “biome” as much more appropriate than complex organism. Tansley preferred
to include the physical factors and the community together as a system. He
derives this sense of systems from physics. Tansley focuses on the climate,
soil type, and organisms of the system.
The different factors that can affect an ecosystem are the
auto- and allogenic factors. Autogenic factors are the processes of the plants
themselves; the community of plants drive the change into the different series
of succession. Allogenic factors are the abiotic factors of a system, such as soil
type and animals within the system.
This is a bit of a long read as far as articles go, but I
thoroughly enjoyed reading Tansley’s retort to Frederic Clements and John
Phillips. However, Tansley does not completely disagree with Clements and
Phillips. He disagrees mainly with their restrictive word usage and definitions.
Tansley equates the holistic nature of Clements’ beliefs on
the complex organism with religious fever and dogma. The running commentary on
Clements’ position as “prophet” and Phillips’ as “apostle” to the “holistic faith”
of succession as a progressive and developmental process for the complex
organism towards climax is rather hilarious to me.
Hey everyone... for some reason I can't post the other two summaries to the blog... help?
ReplyDeletehttps://www.blogger.com/blogger.g?blogID=2751578213059516331#allposts/src=dashboard
DeleteTry using this link and look at the top left for an orange box that says new post. :)
Yeah tried that... it just tells me I don't have any blogs.
DeleteUntil I figure it out... here's the summaries in comment form...
ReplyDeleteHomage to Santa Rosalia or Why are There So Many Kinds of Animals?
G.E. Hutchinson
This is a pleasant little tome by the master of the niche, G.E. Hutchinson. Having recently been named the president of Yale’s department of Zoology, his address at the annual meeting of The American Society of Naturalists begins with a recalling of a trip to Sicily, and observing two species of beetle in a small pond below the sanctuary of Santa Rosalita, whom Hutchinson proposes could be considered “the patroness of evolutionary studies” for the duration of the tale. The beetles are of the family Corixidae, C. punctata (the larger) and C. affinis (the smaller), and Hutchinson takes note that all of the observed C. punctata are female, and hence must be at the end of their breeding season, while there is an equal mix of sexes of the smaller beetle, which must be just beginning theirs. A series of questions – why are the breeding periods offset, why are there two beetles and not 200, finally leads us to the point of the story, an exploration on why there are so many kinds of animals. Rather than attempt to explain the existence of the magnitude of animals on the planet mathematically, Hutchinson decides to focus on some of the factors which control the number of kinds of animals.
Food Chains
Noting Elton’s work on predator chains and using as example what he terms the “Eltonian” food chain, in which each predator is successively bigger than its prey, Hutchinson theorizes on the number of links possible in a food chain. Generously assuming that 20% of the energy of one organism might be passed on to the next link in the chain, and that predators should reasonably be about twice the mass of their prey, Hutchinson proposes that 5 links is the maximum allowable by the Eltonian predator chain.
Natural Selection
Natural selection, Hutchinson states, is the abbreviator of food chains, noting that any increase of efficiency of a predator at the nth link in the chain may well cause the extinction of the (n-1)th link; and that this extinction would thereby force the nth link predator to adapt to eating the (n-2)th link or itself go extinct. He notes that it would be unlikely for a new terminal predator to form an (n+1)th link.
Effect of Size
Hutchinson briefly states his view on sympatric niche development in the beginning of his address, and from that understanding he expresses the limitation on the number of links in a food chain that might be filled by organisms that change drastically in size over the course of their lives. Should an organism normally occupying the nth link in the chain at adulthood inhabit the niche of a smaller animal in its youth, the number of different kinds of animals in that chain would be severely reduced due to competition.
Effects of terrestrial plants
Here Hutchinson simply points out the incredible variety of terrestrial plants, and the subsequently incredible variation of the insects that feed thereupon. However, while this increases the overall variety of organisms, this does not much increase the number of links in the Eltonian chain.
(continued next)
Interrelations of Food Chains
ReplyDeleteHere we step away from the direct contemplation of food chains and into food webs. Since realistically, any predator at the nth level would have more than one prey item at the (n-1)th level, they will not eat themselves into extinction, nor fully exterminate a single prey, as once the first prey item became scarce, it would be more feasible to hunt the other. As food webs do not represent a 1:1 interaction between predator and prey, there leaves room to examine how new organisms might join the web, and its effect upon the web. Hutchinson sites MacArthur (1955), which states that the stability of a community is directly related to the number of links in the food web, that efficient organisms will displace inefficient ones, and that stable communities will outlast the unstable. He further sites that there are three ways to add an organism to a community; by displacing an existing organism, by filling an empty niche, or it may partition a pre-existing niche. The first might increase the stability of the community if it itself is a more stable organism. The second and third could provide new links in the chain, thereby increasing stability. Siting Elton again, Hutchinson adds that the most stable communities are the oldest; those which have had ample time to replace inefficient organisms and add new links, and that as time goes on, it would be progressively more difficult to add new organisms because of this stability. This, he notes, explains a bit of the overall question of diversity- organisms are diverse because assemblages of diverse organisms increase the links in food webs and make communities more stable.
Limitation of Diversity
As we now have some answer for why there are so many kinds of animals, Hutchinson goes on to ask why there are not more kinds of animals. Using arctic species as example, Hutchinson notes that overall biomass is likely a limiting factor on diversity; if the basal members of the web can only support half of the predators that a more productive area might, there will obviously be fewer links in the web. Age of the community might also play a role, as communities become more stable over time, Hutchinson suggests the arctic communities may have simply not had enough time to evolve the diversity seen elsewhere. He also notes that competition for space might limit diversity in an area, as is reasonably the case for voles in the British Isles.
Niche Requirements
Here we examine the result of formerly allopatric species of similar size and niche becoming sympatric. Hutchinson provides a relatively famous metric for niche partitioning based on size and features of the “trophic apparatus”, now referred to as “Hutchinson’s ratio”. It simply states that for organisms to exist in the same niche space, they must be separated in size by at least 1:1.3. Remembering his beetles, Hutchinson explains that in their case the size difference is not enough, and C. punctata and C. affinismust therefore separate themselves by breeding season.
Mosiac Nature of Environment
Hutchinson takes a moment here to explore the nature of sympatry in various terrestrial fauna. I think it might be worthwhile to discuss why the interactions seen in various classes are such.
Hutchinson’s closing remarks are largely a re-hash of the points stated above, but in his last paragraph he raises an interesting question- if his assumptions on diversity and community structure are correct, it would mean that great diversity is more obtainable by small species than large; which would in turn mean that the evolutionary effects on each type are different.
Community Structure, Population Control, and Competition
ReplyDeleteNelson G. Hairston, Frederick E. Smith, and Lawrence B. Slobodkin
This paper concerns itself with population control. The authors begin at the bottom, so to speak, looking at the accumulation of fossil fuels vs the rate of energy fixation by photosynthesis. They conclude that the rate of photosynthesis far exceeds the build-up of fossil fuels and that the vast majority of energy fixed by autotrophs must therefore pass through the biosphere. Next we look at the decomposers, which the authors conclude, must be food limited, as by definition they exist to degrade organic debris. Even if some decomposers are instead limited by predation, population density etc, the remaining decomposers must consume whatever is left by those non-food-limited decomposers, and as such, as a group, the decomposers are food-limited. Furthermore, any population that is not food-limited must be limited by the limitations of the level below them.
Looking next to the primary producers. Since large herbivores are not decimating populations of plants, nor are plants controlled by natural catastrophe, they must be limited by abiotic factors in the environment. Light would be the most obvious, but in arid environments, the authors note, water would likely be a limiting factor. In connection, herbivore populations clearly cannot be food limited, as they will continue to grow out of control when protected by man, decimating the plant population of the area. Furthermore, weather does not seem to be a limiting factor, unless one supposes that populations of herbivores are not capable of removing themselves from an area that has been badly effected by weather. These assumptions leave the control of herbivore populations to predation, up to and including parasitism.
Interestingly, as predators would likely be immune to the limitations by weather and other abiotic factors that herbivores and producers are immune to, we must again assume that predators are food-limited as a group. The authors note that some predators are arguably territory-limited (although that in itself is limited by food availability).
The authors thereby reach the conclusion that terrestrial communities are resource-limited. We see the reasoning behind this by examining plant/herbivore interactions. Plants, being in competition for space, must exist in such an area where they are not regularly depleted by herbivores. Herbivores in turn, must be limited by predation in order to not deplete their food source. Interspecific competition is also a consideration, as any link in the web occupied by multiple organisms reduces the effects of predation on either.
Paper 15: A.G. Tansley
ReplyDeleteThis paper was an enjoyable read. Tansley basically sums up the most foundational principles of ecology, particularly vegetation ecology. He discusses the terminology and corresponding definitions while offering his own opinions and insights. I thought it kind of silly how Tansley and others of his time and maybe even scientists still today argue about the usage of a given term. With respect to Clement’s usage of the term “organism” or “superorganism” to a plant community, Tansley agrees for the most part with the arguments Clement’s makes and agrees that there are similarities and some parallels between the functioning of an organism and the functioning of a plant community but his contention is with the term itself. Tansley argues that the term “quasi-organism” is much more fitting because the term “organism” or “superorganism” is much too misleading. So it’s not that Tansley completely disagrees with Clement’s idea it’s just that he disagrees with his choice of term. In some sense I find that this could be counterproductive but I do suppose there is a need for standardizing definitions at the same time. But I’m not sure that Clements ever meant for that description to be taken literally, I thought it was more of an analogy or metaphor for illustrating the functioning of a community. Did he mean it literally? Something else that was interesting to me was Tansley’s rejection of the concept “biotic community.” He defines a community as a unit composed of members that are all equal in some way – “A community implies members and it seems to me that to lump animals and plants together as members of a community is to put on an equal footing things which in their whole nature and behavior are too different.” I definitely disagree here, I think “biotic community” makes sense because even though plants and animals are so different the two have an interdependence on each other which keeps the functioning of the whole system intact therefore creating a community. Of course they wouldn’t play the same roles but they don’t need to. Again, his contention is with the use of the term where here he prefers to use the term “system” which also works. So in his view it seems communities have to be limited to an association of a single life form rather than an association of multiple life forms. And if there are multiple life forms then we would refer to it as an ecosystem or a system but not a community. Is this strict use of terms necessary? In terms of function I don’t really see how a community is different from a system. Plus I just think that his idea of what a community is, in the first place, is flawed. The members of a human community are not all exactly equal for example in terms of influence and role.
I am really glad I finally had a reason to read this seminal work. That said I don’t know that he deserves his unofficial title as the “father of ecology.” No doubt that his definition of an ecosystem and integration of abiotic and biotic factors into this concept was field changing, but I don’t really see that this work had much more than lots of modifications of previously introduced terms., written much in the style of a modern review. I like how he moved the field away from Clements incredibly confusing pro-pre-post-sub climax jargon. To me Tansley was a better writer and salesman than those before him (and better than many after) hence he earned the title and showed us all how important it is to be a good writer.
ReplyDeleteI agree Tansley’s writing style makes following his this manuscript much easier. He redefines concepts such as succession, showing an importance to distinguish internal (autogentic) and external (allogenic) influences. He also suggests the term Quasi-organism for vegetative stands in a climax state instead of simply an organism or complex-organism. This is to avoid confusion as the latter is used to describe “higher animals” and organism refers to a single individual animal or plant. However he points out the dynamic interactions and development of these systems justifies the term quasi-organism. He also redefines climax including factors beyond climate to a climax that may be found. Finally he rejects the concept of a biotic community of plants and animals because “to lump animals and plants together as members of a community is to put equal footing things which their whole nature and behavior are too different.” Pg. 330(296). Instead he introduces the Biome to encompass plants and animals. He again rejects their interactions to that of a “complex organism” for the sample reasons as above and instead prefers the term ecosystem, a dynamic and stable equilibrium that systems tend toward through succession and development. This was a good paper that defines terms and concepts well. While the introduction talks of Tansley systematically tearing Clements point by point, I feel he was simply using new terminology and better defining many concepts Clements had introduced.
ReplyDeleteTansley 1935:
ReplyDeleteI agree with Tansley’s critique of Clements’ Procrustean adherence to the concept of a complex organism. Clements’ approach follows a long tradition of philosophers (Kant, Whitehead, etc.) who sacrifice continued careful observation of the messy natural world for the beauty of their own neat and tidy abstract systems. It is admirable that Tansley does not merely dismiss Clements’ system, but retains as much as he feels is sound, as in his statement that communities of ants, bees, and termites do exhibit many of the qualities of organisms. His discussion of the term “development” is especially helpful, and foreshadows the later definition of homology as shared derived characters.
He is a little dogmatic in his insistence that plants and animals must be treated as separate communities, but this is understandable, since he couldn’t have known about the later discovery that plants and animals are phylogenetically very closely related on the modern tree of life.
I respectfully disagree with Martina’s comment that arguing about usage of terms is silly. In my view, clarification of terms can be much more than just semantics—it can provide clarification of the ideas underlying the terms. For example, in his discussion of climax, he points out that soil composition is perhaps just as legitimate a consideration climate. By carefully defining “succession,” “climax,” “development,” “quasi-organism,” and “ecosystem,” Tansley clears the way for some of the groundbreaking progress in ecology in the 20th century.
As has been mentioned in a few previous comments, this article comes across as trying to elaborate upon the contention existing within the ecological term world. While I think that "terms" themselves are important to be able to define and agree upon, to me this article represents the gateway into how we view the ecological world. Up until this point, nobody had collated all of the ideas we think of today when we think of an ecosystem, and those that had attempted (Clements, Phillips) don't seem as inclusive as Tansley's article. I agree with many of the points that Tansley clarifies, but also agree with what Martina said about his definition of a "biotic community". I think using the term "community" is quite an apt description for many of the systems we study. Although the plants and animals obviously have different roles and effects on the system, I think they act together and do form a community. Some may have larger roles than others, but they are so interdependent it is hard to define where one causation stops and the effect begins. That being said, I appreciate Tansley's consideration of the anthropogenic effects on ecosystems, and how much or how little we should include humans in our idea of the community or total ecosystem.
ReplyDeleteI really agree with Ali here. This paper helped me understand what the title of the section meant by "Theses, Antitheses, and Syntheses" as it does a good job of showing multiple viewpoints and kind of mashing them together. As it said in the intro, he is the first to use and coin the term "ecosystem" and the paper represents that really well. He explains concisely and clearly his problems with the other kinds of super-organizational terms that were being used in ecology at the time and then goes and makes up a new term which is still widely used (and debated) today. One of the parts that I really like is his interpretation of H. Levy's work talking about how isolates are objects in a larger system and overlap with other isolates. He really puts into words the whole idea of "its more complicated than that" very well.
DeleteI really agree with Ali here. This paper helped me understand what the title of the section meant by "Theses, Antitheses, and Syntheses" as it does a good job of showing multiple viewpoints and kind of mashing them together. As it said in the intro, he is the first to use and coin the term "ecosystem" and the paper represents that really well. He explains concisely and clearly his problems with the other kinds of super-organizational terms that were being used in ecology at the time and then goes and makes up a new term which is still widely used (and debated) today. One of the parts that I really like is his interpretation of H. Levy's work talking about how isolates are objects in a larger system and overlap with other isolates. He really puts into words the whole idea of "its more complicated than that" very well.
DeleteI agree with others that this paper fits within the "Theses, Antitheses, and Syntheses" section. As per the introduction, it highlights critical issues of ecology that are under debate. Tansley thoroughly picks apart the viewpoints of Clements and Phillips and explains why they are inadequate in terms of explaining the entirety of the "physical system".
ReplyDeleteIt is Tansley's discussion of the "ecosystem" that I enjoyed most about this paper. Emphasizing the importance of both organic and inorganic aspects of the environment. Whether studying ecology (or even archaeology) it is important to understand all of the processes that affect the structure of the environment (site) in order to gain insight into what is actually going on with even an individual unit.
I pretty much just have to agree with most of what everyone else has already expressed about this paper. I really enjoyed his writing style. This was one of the least tedious and most accessible papers we have read yet I think. I envision the epitome of an erudite British academic sitting in his office with a pipe contemplating just how wrong the Americans are in their approach to ecology. I was so not disappointed when I google image searched Tansley. Aside from his writing style I also agree with his arguments about the misuse of terms up to this point. It is probably due to a lack of imagination, or my bias as an organismal biologist, that I had a really hard time getting behind the concept of communities being organisms. I also found all of the different kinds of climaxes being defined as overly complicated and sort of disconnected from reality. I probably just agree with Tansley because he was the most concise and simple in defining his terms and concepts, and he also acknowledge that mammals are the highest form of life.
ReplyDeleteThe analysis made by Tansley in this paper is focus on criticizing some of the definitions and usages of those terms used in ecology during those days. In the first part of the paper he acknowledged the contribution made by both of them to the study of plant communities, but at the same he is interested in redefining most of the concepts that were proposed by Clements and Phillips. I like the discussion about climax and succession. Succesion was made of different phases, an each one them has it own development until it reached the climax. Clements and Phillips believed in one type of climax, while Tansley introduced the policlimax theory, which divided them into different type of climax (e.g edaphic climax, fire climax). With regard to complex organisms or biotic communities for biome, he rather preferred the word systems. Once he introduced this concept, he coined the word ecosystem, that takes into account physical factors or abiotic factors in the biome Climax is defined as highest stage of integration, being close to what he called the dynamic equilibrium.
ReplyDeleteThis was a very enjoyable read, a nice combination of (mostly polite) snark and useful, novel insight. Tansley’s synopsis of the climax, in which he discusses the idea of multiple climaxes within a climatic region and climax-limiting factors makes a lot of sense and seems to be a good compliment/amendment to the formerly rigid definition of climax. On a side note, I am surprised that Clements or Phillips had not considered soil type among the factors that limit succession, it seems so obvious. Regarding the idea of super organisms or communities as organisms, I had the same issues expresses by Schuyler. With a background in systematics, I find it difficult to really accept a community as an organism and I was kind of hoping for something equivalent to the N-dimensional hypervolume to address this. Perhaps, Panddimensional-Polyspecific-Hyperorganism? Oh well, I guess I’ll have to settle for biome and ecosystem.
ReplyDeleteGiven recent insights, I think we can agree that the concept of Panddimensional-Polyspefic-Hyperorganisms in the Nth dimension is quite frankly absurd.
DeleteIn the first couple of paragraphs, Tansley emphasizes the importance of being blunt, but also seems very gentlemanly in making sure that he does not overstep his bluntness and seem rude. he praises Clements for his work and then goes into the points about why he does not agree. This kind of follows the paper on how to give a good literary review. How do we do it? Act like Tansley. My favorite part of the paper was thinking of communities as complex systems- or organisms. This seems to be a new way in thinking in ecology and once again its a physicist who comes up with this novel idea .
ReplyDeleteA few thoughts to add to insightful comments above:
ReplyDelete- In a lot of ways this piece was largely rhetorical, parsing definitions, language, and conceptual abstractions without data or even a lot of reference to observations made in the natural world (a few examples notwithstanding). Nonetheless, it seems like a really important conversation for ecologists to be having at that time - the argument over holism v. reductionism and the use of conceptual abstractions and metaphors as methodological tools for understanding versus philosophical positions seems really useful.
- Tansley seemed to be very accommodating and respectful of the position held by those in the Clementsian school (perhaps too much), while at the same time disagreeing strongly on several points. Calling Clements a prophet and Phillips his apostle for the religion of the organismal concept seemed a sharp jab, but may it would've been interpreted differently at the time.
- Interesting that the Clements piece we read was published a year after this came out. Didn't seem to change his position, but I wonder if it forced Clements to try to be more convincing and have better reasoning.
- Two things that Tansley's characterization of the organismal concept made me think of: 1) complexity theory and especially the concept of emergence, and 2) Lovelock's Gaia theory that the earth itself is like a living organism.
- I can see why Tansely wants to separate plant and animal communities - it certainly makes sense in some cases to distinguish stationaey primary producers from mobile consumers - but in other cases I agree with others that it can be very helpful to consider the entire biotic community. Tansley himself talks about the importance of grazers in determining successional patterns, and when you consider all the mutualisms that occur in ecosystems, like plant-fungal interactions and animal seed dispersal, it's hard to keep the plant and animal communities completely separate if you really want to understand an ecosystem.
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ReplyDelete