Tag Archives: Critique

From Animalcules to an Ecosystem: Application of Ecological Concepts to the Human Microbiome (Fierer, et al. 2012)

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The two essays on microorganisms were concerned with very similar ideas with very different applications. While Martiny’s essay considered that the properties effecting macroorganisms may be helpful in understanding the dispersal of microorganisms globally, Fierer posits that perhaps those same properties may effect microorganisms on a much smaller scale, within each human being.

Fierer puts forth some interesting ideas such as succession among microbiome communities which could be initiated by disturbances such as treatment with antibiotics (Fig 3). I can’t quite figure out how to square that idea with any sort of climax, especially given the rapid and constant changes in the human microbiome. He also states that taxa of microorganisms may fit into biological niches within the body.

That having been said, I am hesitant to agree entirely with Fierer. As I mentioned in my discussion question last week, the conditions that determine behavior of one species or in one region don’t necessarily do the same to other populations. They may be useful as a guide as to what to study, though there can be no promise as to whether those studies would be fruitful. One particular hurdle facing this line of inquiry is the difficulty inherent in conducting studies given the diversity of microbiomes among individuals. How accurate is a control when abundances of taxa even within family members can vary by up to two orders of magnitude (Turnbaugh et al. 2009a)?

Experimental Zoogeography of Islands: The Colonization of Empty Islands. Daniel Simberloff and E.O. Wilson (1968)

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This study was of the events following a defaunation event on six islands of the coast of the Florida Keys, each island consisting of one or several mangroves. Simberloff and Wilson suggest that given time the population of species on each island will reach a predictable dynamic equilibrium consisting of a similar but constantly changing cast of species.

The issues I found with this research were several. The authors conducted only a single survey of each island plus two controls before the experiment began and used this is an assumed average species number on each island, a sample size far too small from which to draw any conclusions. Beginning from this survey, any information they glean about average species numbers may match up to an anomalous “average” and wrongfully confirm their theories. Throughout the experiment, the collection of data was too infrequent given the ephemeral nature of many of the species involved. The experiment also ended before any of the islands populations were found to have arrived at a dynamic equilibrium, so any similarity between the pre-defaunation survey and the final survey could be a case of a broken clock being “right” twice a day, in this case, right meaning supporting the theory put forward in the paper. Finally, there is no indication that the two control islands were surveyed more than once before and once after the experiment, which would have given a much clearer view of the properties and typical variance of a dynamic equilibrium.

Aside from the conduct of the experiment, I found the writing to be a bit lacking. I would have found technical details on how the surveys were conducted, and where each island was located relative to a source and each other to be helpful in filling out my understanding of the theory.

My feeling toward this essay isn’t that the authors’ theory is incorrect, it’s that the way the experiment was conducted left didn’t find conclusive enough evidence to confirm it.

Landscape Ecology: The Effect of Pattern on Process. Monica G Turner (1989)

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Landscape ecology differs from most other ecological theories we’ve read in class in the way it approaches seeing a region. Where Clements would see a climax, or succession toward a climax, or Gleason would see millions of individual organisms vying for space to spread their seeds and germinate, or where Paine, Connell, or MacArthur or others may be studying a single species or a narrow portion of an ecosystem, Turner is taking a wider view. When I imagine the map of a region a landscape ecologist would use, I imagine many overhead transparencies that were used in school when I was younger; one would have the type of vegetation growing in a region drawn on it, another would be a topographical map, another shows drainage, another soil nutrient content, and so on. Layering these transparencies atop one another, one would begin to see patterns emerge where certain types of vegetation always grew near a stream but only in regions where another type of vegetation grew upstream, or perhaps the probability of a hectacre of land succeeding from one phase to the next in a given number of years is increased in proximity to a certain type of soil nutrient.

One of the points I appreciated about the essay is that, while it didn’t address the topic directly, I saw it as something of an answer to Gleason’s issue with the definition of a plant association. I see landscape ecology, when employed on a mass scale, as able to show the overarching trends in vegetational growth that would satisfy Clements’ and other’s definition of an association, while also having the nuance to address smaller regions that were anomalous to the general trend.

A few of the issues I found with this theory were that the more data one collected, the more variables were involved. In order to account for those variables more data still would need to be collected and so on and so on. In addition, there is an issue of scale. Turner writes on page 175, “Landscape complexity has not been shown to be constant across a wide range of a spatial scales… Applying predictions made at one scale to other scales may be difficult if landscape structure varies with scale.” On page 180 she also says, “Elucidating the relationship between landscape pattern and ecological processes is a primary goal of ecological research on landscapes… achieving this goal may require the extrapolation of results obtained from small-scale experiments to broad scales.” The issue here is that at each scale the variables involved will fluctuate. The scales aren’t just small or broad scale either; every scale, while similar will have slightly different considerations. What this leaves one with are more unknown unknowns the more one extrapolates from data extracted from a different scale. However, this is unavoidable because a thorough survey of all variables at every scale in every region of the earth is impossible, a point the author also addresses.

Once I began to understand the process of landscape ecology the utility quickly became clear. Being able to predict the behavior of a plot of land based on how it can be expected to interact with surrounding plots of lands could be extremely useful and paint a more accurate image of the future. The author points out that this form of fortune telling could and should be used by conservationists in planning preserves among other uses. I largely agree with the theory and the author’s closing statement that through experimentation and testing of the theory it could develop to an even more powerful tool.

Metapopulation Dynamics. Illka Hanski (1998)

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Metapopulation Dynamics is different in both form and function from all the previous readings we’ve done in Ecological Thought and Practice. Rather than perform an experiment and explain the results, as Paine, Connell, Lubchenco and Menge, and MacArthur did, or speak to the ideas and terms used in ecological thought as Clements, Tansley, and Gleason did, Hanski instead provided arguments for a way of predicting the behavior and trends of species in a region.

While I was reading Metapopulation Dynamics I had to revise the way I thought about a metapopulation. Initially, I thought of fish in ponds; the same species may be in several ponds. While each pond has its own population, they could also be observed as a whole and studied as a metapopulation. This conceptualization fell apart when Hanski began speaking about colonization. A species of fish colonizing a pond that wasn’t already connected to their own pond wasn’t helpful to me. Hanski also mentions pathogens as an example. If I have the flu, I have a population of influenza virus cells in my body. Considered with others with the same virus, the virus could be studied as a metapopulation. Colonization would take place, for example, if I sneezed and the virus landed on a surface. The virus cells may get into a healthy person and infect them, thereby colonizing another suitable space, or it might die before it colonizes, a risk of migration. Ultimately, after working through both of these, it helped me understand the example Hanski used, the Glanville Fritillary butterfly.

Hanski spends a good deal of time explaining how metapopulation dynamics can be used to predict a species’ persistence. I can’t explain any of the equations used, but when factoring the area of separate “patches” of populations, distance of the patches from one another, time, population density of patches, total number of patches, and other factors, one ought to be able to predict the persistence or tendency toward extinction of a metapopulation.  In this essay, I take patch to be a region of what MacArthur would call “suitable space”

There are a few, perhaps pedantic, issues I had with this essay. I don’t understand why, as Hanski says on page 42, why “for long-term metapopulation persistence the expected number of new populations generated by one existing population during its lifetime in an otherwise empty patch network must be greater than one.” Would replacement not be persistence? I understand that stochasticity leads to unforeseen events which could lead to the destruction of a single population, but if that group has already replaced itself with another colony elsewhere, the species should persist.  This sort of made me think of Zeno’s arrow, but I’m not sure how useful of a tool that is, considering Zeno was a philosopher and Hanski was using math.

In the last few paragraphs of the article, Hanski advocates for conservation in what seemed to me to be an emotional appeal to others. I highlighted the sentences, “We do not know which fraction of currently endangered populations and species are already committed to metapopulation extinction in their present environments. A real worry is that such ‘living dead’ populations and species are numerous, especially because the delay in reaching the new equilibrium is particularly ling in just those cases that matter most, where the new equilibrium is metapopulation extinction.” This type of appeal is new to me in academic writing. I appreciate that he voiced it though. Studying and understanding the environment is interesting but ultimately useless if that information isn’t applied to the preservation of life on earth.

Ecology of Some Warblers of Northeastern Coniferous Forests. Robert H. MacArthur (1958)

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Ecology of Some Warblers of Northeastern Coniferous Forests asks one central question, how is it that five species of warblers with similar needs and similar capabilities are able to live in the same region without one species out-competing the others and all but the dominant one being eliminated. MacArthur hypothesized that the species were in balance with one another because the factor limiting each species growth was intraspecific competition rather than interspecific competition.

To determine which factors governed the competition among species and among individuals of a single species, MacArthur observed the behavior of the species to discover their feeding habits and zones, nesting, and territoriality.

Observations showed each of the five species had preferences in their feeding habits and nesting locations. The species-wide preference in feeding locations largely meant that when a particular species was hunting for food, it was more likely that another individual from its own species had been there than an individual of any other species. The preference in feeding zone directly correlated to preference in nesting zone and territoriality as well, given that each warbler tended to build their nest in their preferred feeding ground and defend just enough space as they needed to eat and provide for young.

Further evidence that most competition was intraspecific is that each species nested as slightly different times of the year, meaning that the need for food was greatest among a single species at a time rather than among all species at once. When considered along with the preference for a single feeding area, the likelihood of a particular zone being over-hunted, thereby leading to the mortality of fledglings, was due to the behavior of others of the same species. There were several times when new parents of fledglings would feed only one or two of their young.  This was shown to be the most common cause of mortality among fledglings.

To close the essay, MacArthur succinctly states that differences in feeding position, behavior, and nesting date reduce competition among species and instead focuses competition among individuals of each species.

Community Development and Persistence in a Low Rocky Intertidal Zone. Jane Lubchenco and Bruce Menge (1978)

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Though I had to read through Community Development in a Low Rocky Intertidal Zone, in part or in full, several times before I feel I came to approach understanding, I feel the central idea is one of the more useful ones I’ve yet to read about for Ecological Thought and Practice. In the essay’s introduction the authors state that while communities have several characteristics, it is a mistake to study them as separate phenomena when in reality they are interconnected. In my notes, I wrote the following in order to clarify for myself what I was reading about: “Succession depends on competition (Connell) but also predation (Paine), dispersal rates and reproductive output (Gleason), life histories and persistence (Clements).

I think that due to their more holistic approach Lubchenco and Menge were able to add to ecological thought of the day by confirming and documenting the interactions among the ideas that their predecessors had proven. Though their results stated that “the role of consumers in determining the pattern followed during community development, or succession, seemed of overriding importance” which primarily confirms Paine’s 1966 essay, but predation, they found was largely inversely proportional to wave energy. They also documented, through denudation of patched of the rocks, the importance of dispersal and growth rates in determining which species became dominant, but because their study took place over several years, they were able to show the persistence of the communities and how quickly those patches returned to the state at which they had been before the experiment. This persistence supports Clements theory of a tendency toward climactic climax.

Today in class we were asked whether or not Connell and Paine’s studies contradicted one another, here Lubchenco and Menge showed that at least in some communities, the two ideas are both valid. I thought the reading was helpful in understanding other ideas we’ve already covered in class. The use of so many variables and controls including not only the exclusion of predators but the enclosure of predators were useful in illuminating the authors’ points.

The Influence of Interspecific Competition and Other Factors on the Distribution of the Barnacle Chthamalus Stellatus. Joseph Connell (1961)

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Upon witnessing that two species of barnacles seemed to have the adults of their species segregated into horizontal bands on a rocky intertidal shore but that the youth of the higher species could be found in the lower band with the other species, Connell set out to study the primary reason for that segregation. His theory was that the completion for space between the two species bore at least some responsibility for the separation. This theory was supported by the following studies; two species will either compete for resources with one species becoming more dominant in an area (Beauchamp and Ullyott 1932) (Kenny and Stevenson 1956), equal distribution of one species is due to that species competing primarily with itself (Holme 1950) (Clark and Evans 1954), and if two species with similar needs are living in the same area it is because they are not competing for resources (Lack 1954) (MacArthur 1958).

The method Connell used to test this theory was to map the locations of the barnacle species Chthamalus Stellatus, hereafter referred to at C.S., in the period of the year before what he hypothesized to be C.S.’s competitor Balanus Balanoides, hereafter referred to as B.B.. After mapping the locations of C.S. it was possible to control the height above or below mean tide level so that the effects of competition could be seen in environments where both C.S. and B.B. were primarily observed. One half of all clusters of C.S.  growth were kept from being interfered with by B.B.. The growth and mortality rates in each case were recorded.

The results showed that C.S. was fully capable of growing to maturity at the levels on which B.B. was typically dominant, implying that the competition for space is what was preventing C.S.’s proliferation at the lower levels. In fact, while the hypothesis was that competition was at least somewhat responsible for the distribution of the two species, the study found that predation by carnivorous aquatic snails, battery by waves, and intraspecies crowding combined were not much more likely to be responsible for the death of an individual C.S. than was crowding of some sort by B.B..

I read this essay about two hours ago and have been idly trying to come up with an example of competitors coexisting. None come to mind except in the case of lions and tigers and bears coexisting in Oz. Given this, I can’t find fault in Connell’s reasoning. His experiment took into account as many variables as I could think of and the information gained fulfilled his hypothesis without assumption. In the case of this essay the limited resource in question was space, but it is easy to imagine that if the same experiment were performed on species competing for water or a nutrient source like meat the results would show that at least some of the reason for animal dispersion was due to interspecific competition. As a follow up to this study, I would be interested to see if there were more studies done on intraspecific competition and what its causes may be.

Linchpin: Are You Indispensable? (Pgs.1-27)Seth Godin (2010)

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Chapter 1

I don’t have anything particularly profound to say about Linchpin, but that’s partially because neither does Seth Godin. The central conceit of the first chapter is that the mode of the economy is changing and to be successful, one must change with it.

There was once a time when the better paid and most secure individuals among the working classes were artisans and craftspeople, these individuals had mastery over some necessary part of life, such as horseshoe making, or wool weaving. Then a tremendous shift took place and factories became commonplace. While machines were meant to become an extension of the individual working them, the opposite took place; human beings became the non-automated portions of machines.

This economic model gave rise to what Godin might call the recently deceased economic mode. If one were to show up and work as part of the machine for wages that were just barely acceptable, they would survive. If they were particularly polite or some small percentage more efficient, they might become a supervisor. Even white collar work is to be considered factory work because the person whose job it is to transcribe interviews is nothing more than a non-automated machine that takes sound waves and makes them into word documents. Where there is no creativity, there is no humanity in work. This mode of economy led to a race to the bottom regarding wages. If the skill was easy to teach, then the labor was easy to replace. If the labor was easy to replace, workers couldn’t go on strike if you didn’t pay them well.

The issue arose because everyone followed that model and now none of the products on the market have any heart or personality. Without some humanity to inspire loyalty in the consumer, they’re just as likely to buy your product as the next cheap option. A new force is required to inspire continued growth, and that power is linchpins.

Godin says formerly there were two types of people involved in labor, managers and laborers. Managers tell laborers what to do, laborers are non-automated machines. Linchpins are going to be the third piece in that puzzle. Situated between the manager and the laborer, the linchpin brings their creativity, their ability to come up with novel solutions to complex problems, their ability to create meaningful relationships to a business. In other words, they’re going to be Good Managers.

That’s it. Godin thinks people smart enough to read this book should be the ones who are successful in the future. Those people need to be creative and dynamic to be successful. Automation is going to grow in the future so before your job gets automated or outsourced, dazzle your boss or become your own boss and start using those skills, probably in a managerial position.

I cannot overstate my frustration with this reading. I believe that Seth Godin wants to help people, but I also believe that most of all he wants to help himself. Some of his pearls of wisdom are that the dying economic model grew because it promised people they wouldn’t have to think (rather than that if they didn’t sacrifice their humanity for wages they would starve), Karl Marx and Adam Smith agreed but neither ideology is prepared for the rise of a third piece of the manager vs. worker dichotomy, that each person with a laptop and an internet connection today has the same earning potential as a factory owner in the past, and many more.

I’ve only completed one chapter (as assigned in class) but rest assured, I’ll write more here about this gem as time goes on.

The Individualistic Concept of the Plant Association. Henry Gleason (1926)

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Throughout The Individualistic Concept of the Plant Association, Gleason makes several arguments as to what the particular issues are with a term as broad as “association”. The essay states that previous descriptions of plant associations are mistaken due to their attempts to fit within existing frameworks which were developed when less information was available, and that, instead, as new information becomes available, new frameworks should be developed. Due to the use of what Gleason might have called antiquated frameworks ecologists were making undue reaches as to the conclusions implied by their research. Gleason suggests a new model based upon the individual plant.

A plant association is defined by Gleason as “an area of vegetation, having a measurable extent, in which each of which there is a high degree of uniformity throughout, so that any two small portions of one of them look reasonably alike.” One of the main issues with this definition is that there may be a continuous stretch of grassland from Illinois to Nebraska, but the easternmost and westernmost portions have vast differences. Is it to be considered one association due to the continuous stretch of grassland, or two associations due to the multitude of smaller differences in species? If it is to be considered two associations, where should that “measurable extent” extend to if each square mile is almost indistinguishable from the next and it is only at great distances that a difference can be quantified? For another example, Gleason speaks of woodlands. Without human interaction, a woodland’s advance or retreat into or from a particular grassland would be so slow as to make it impossible to define clearly a time-boundary on when the association began or ended in a particular locale. Additionally, Gleason states, that, particularly in growth after a fire, an association may be so brief that there is never a period of equilibrium. Gleason then calls an association effectively a coincidence.

To back up this claim, Gleason explains, in simple terms, how plant life comes to be in an area; “if I viable seed migrates to a suitable environment, it germinates.” No matter how far it has traveled, whether on the wind, in an animal’s digestive system or on its fur, by stream, or any other manner, if a seed comes to rest someplace that can provide the right amount of sun, nutrients, and water, it will grow. The majority of seeds land relatively nearby the parent plant, and fewer and fewer do in concentric rings traveling outward from that plant. Thereby, Gleason contends, every plant germinates wherever it is able and grows in proximity to other vegetation with similar environmental needs. Plant associations as popularly defined by ecologists of the time were an attempt at ascribing monolithic order to a system containing billions and billions of free agents in the form of each individual plant attempting to grow and spread.

My personal thoughts on this writing are that it was an interesting idea and helped me to understand not only Gleason’s ideas but also other ecologists’ definition of a plant association. I largely agree with Gleason’s concept, however understand the utility of grouping vegetation into associations for the sake of study. Aside from all that, I thought Gleason’s clarity of voice made reading this essay easy and enjoyable.

The Use and Abuse of Vegetational Concepts and Terms. Arthur Tansley (1935)

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Throughout this essay, Tansley argues for the standardization of the definition of several temrs commonly used in the discussion of vegetation and ecology. I will herein define in my own words what those terms are as well as discuss several of Tansleys arguments for them and some of my own thoughts on the essay.

Succession: A series of changes in the life cycle of a plant, quasi-organism, or eco-system. Each change leading to the next. The change is continuous, but can be categorized into successional phases.
Autogenic Succession: A succession primarily brought on by the actions of the plant life on their environment. E.g. A reduction in soil quality due to leeching leading to less growth.
Allogenic Succession: A succession primarily brought on by factors other than those actions of the plant life on their environment. E.g. A forest fire.
Anthrogenic Succession: A succession primarily brought on by the actions of humans on the plant life and its environment. E.g. The clearing of forest for grazing land.
Retrogressive Succession: Tansley argues that retrogressive succession is an ill-suited, though others ( use it to mean “regression” from a “higher” to “lower” form of vegetation (No clarification is given as to what higher and lower here mean) Tansley seems to say that retrogressive isn’t the correct term because the plant life is still adapting in a forward direction given the conditions of its environment at any given time.
Quasi-Organism: A mature, well-integrated plant community having enough of the characteristics of an organism. A community of plants that reaches a dynamic balance. Others use the term “complex organism”, which Tansley objects to on the grounds that an individual plant or animal is a complex organism and a network of complex organisms ought to have another name. (I initially took quasi-organism to mean the same as my understanding of an eco-system until eco-system was defined later in the text)
Climax: Permanent of apparently permanent condition reached when vegetation is in equilibrium with all Incidental factors. (There are arguably many sub-types of climax e.g. “mowing climax” a climax wherein the plant life is in a state of balance with its frequent mowing, where it doesn’t over-grow, or die off as a result of this action)
Ecosystem: The exchange among a quasi-organism and its environment. Components of which are both organic (plants, animals) and inorganic (soil, climate).
Two terms which were not defined in the text but which I found useful to look up are
Edaphic: of or relating to soil
Sere: A series of ecological communities formed in succession

My first impression of Tansley is that a contemporary reader likely would have either found him very funny or very annoying. He refers to himself twice as someone who was a heretic or who did not keep the “faith” of popular belief among ecologists of the day, instead challenging their ideas and definitions. I was intrigued by his thought on “retrogressive succession” and whether all change was necessarily “forward”, as well as the times he referred to minute and constant change in an ecosystem or quasi-organism and whether those two beliefs are related. In my notes, I likened the constant minute changes to the movement by the driver of a steering wheel on a straight road; the direction of the vehicle is always forward but the steering wheel is always being slightly turned to maintain that status. There is also the question as to whether human action can be considered part of nature, Tansley doesn’t clearly give his opinion, though through the addition of the definition of anthrogenic succession, seems to imply that humans are too great a variable to count among allogenic successions. I agree with this descision, because unlike all other animals and plants, humans don’t have to be at balance with their local environment to survive. Humans are at liberty to radically change their environment because of their ability to transport resources from afar.

Overall, I found the reading itself interesting, though, as it was my first reading of this kind, it will take me some time to be able to more fully digest its meaning and implication.