MacArthur, R.H., “Population Ecology of Some Warblers of Northeastern Coniferous Forests.” Ecology, Vol. 39 No. 4 (Oct 1958), p. 599-618).
Remold, S.K., Brown, C.K., Farris, J.E., Hundley, T.C., Perpich, J.A., Purdy, M.E., “Differential Habitat Use and Niche Partitioning byPseudomonas Species in Human Homes.” Microbial Ecology, Vol 62 (2011), p. 505-517.
Robert H. MacArthur (1930-1972)was an American ecologist. In this course, we previously read MacArthur’s work “On optimal use of a patchy environment” (1966). MacArthur completed the work for the warbler paper for his Ph.D. thesis. Upon the time of the paper’s publication in 1958, MacArthur had just started as a professor at the University of Pennsylvania. MacArthur was later a professor at Princeton University.
Susanna Remold is an associate professor in the biology department at the University of Louisville. Her research focus is on the distribution and phenotypic variability of the Pseudomonasbacteria found in human homes.
MacArthur (1958)
MacArthur observed that there were five species of warblers with similar food sources (insects) living in the same habitat (mature boreal forests). The focus of MacArthur’s paper was to determine how these five species with seemingly overlapping niches were able to coexist. MacArthur also aimed to figure out the limiting factors on the five warbler populations.
MacArthur’s study was divided into four parts:
Part 1) Density dependent events that regulate warbler populations
Part 2) General ecology of warblers (feeding behaviors, nest positions, territoriality, clutch sizes)
Part 3) Seasonal ecology of warblers (habitat, feeding behaviors)
Part 4) Warbler abundance
Part 2) General ecology of warblers (feeding behaviors, nest positions, territoriality, clutch sizes)
Part 3) Seasonal ecology of warblers (habitat, feeding behaviors)
Part 4) Warbler abundance
MacArthur conducted his observations of the warbler species between 1956 and 1957. His methods were sometimes a bit questionable. The data about feeding zones was determined by counting seconds manually (“thousand and one, thousand and two,…”) or with a seemingly faulty stopwatch. He also relied heavily upon museum specimens for data about clutch sizes and provided a rationalization about how the “prized” warbler nests “do not reflect any bias,” which is claim that seems a bit dubious.
His observations and data collection led to the following conclusions for each of the four parts of his study:
Part 1) MacArthur determined that the warbler populations were primarily regulated by density dependent events. He drew this conclusion by examining data about changes in warbler populations. Each species tended to decrease following an increase and to increase following a decrease. This non-random pattern cannot be attributed to density-independent population regulation, so there must be density dependent factors regulating the warbler populations.
Part 2) MacArthur divided the arboreal warbler habitat into regions defined by the height and area of the branch and observed how many seconds warblers tended to spend in each region during feeding. Figures 2 – 6 show the feeding positions of the different warbler species. While there was some overlap in the feeding regions between species, each species tended to have distinct preferred feeding regions. MacArthur also observed the feeding behavior of the warblers and noted differences in the species behaviors. He also noted that the nest positions of the warbler species tended to reflect their preferred feeding zones. MacArthur observed territoriality in the warblers and determined that there was greater intraspecific territoriality within a species than interspecific territoriality between species. An examination of clutch sizes and data about the occurrence of budworm outbreaks led MacArthur to conclude that the bay breasted warbler had greater clutch sizes during the years with outbreaks.
Part 3) The distribution of warblers in winter was generally inconclusive. The five species show the amount of overlapping of winter range that would be expected on a random basis. The general aspects of observed warbler behavior are nearly the same in the summer and winter.
Part 4) The composition of the warbler populations in different plots is summarized in Figure 10. The Cape May warbler population is mostly dependent on volume of food, but the other species of warblers have populations that are relatively proportional to the volume of foliage in their feeding zones.
Remold (2011)
The Remold study was conducted to determine if the actual habitat use by Pseudomonas species was as broad as the fundamental niche. The habitat examined in the study was surfaces and structures in human homes. The paper also addressed the degree to which the realized niches of Pseudomonas species overlapped.
Twenty households were sampled in the study, and within each household, between 25 and 96 samples were collected. Sampled surfaces and structures included human skin, animal foot pads, garbage bins, shower drains, and the soil of houseplants (a more complete list in Table 1). The samples were plated on Pseudomonas-isolating agar and incubated. The species of Pseudomonas in each viable sample was recorded.
Pseudomonas species were recovered from and were categorized as being from a vertebrate (internal), vertebrate (skin), surfaces, water, drain, soil, or garbage. Some of the Pseudomonas species displayed specificity to certain environments. P. delhiensis showed specificity to the soil of house plants, while P. oryzihabitans was unique to outdoor soil. P. aeruginosa was most commonly in the drains in bathroom sinks, while P. plecoglossicida was more frequently isolated from the drains in tubs and showers. The different Pseudomonas species differed in their distribution among sites, which provides evidence that the realized niches of Pseudomonas are narrower than their fundamental niches.
Thoughts
The MacArthur study is the textbook example of niche partitioning, so it is fascinating to go back and see the original document. It is also a bit horrifying to think about how poorly this paper is interpreted in introductory biology classes. I remember seeing one iteration of the warbler diagram in which all five species of warbler were represented on one tree where each species had a very definitive feeding zone that excluded all the other birds. After seeing MacArthur’s original figures, the actual “partitioning” of the tree spaces is much less clear cut. For example, four of the five species use the T2 zone and three of the five use the M3 zone. I also thought that some of MacArthur’s methods were a bit fuzzy, but I do have to consider the technological limitations of the 1950s. It is also a bit amusing to consider that the main conclusions about the warbler feeding zones were based on just over 4 hours of recorded observation (though MacArthur did acknowledge that the warblers were often difficult to see in the densest areas of foliage). I liked the Remold paper because it covered the ecology of bacteria (which is something that we have not spent all too much time discussing in class yet). The paper was from 2011, so in the time since the original publication, given the fast rate at bacterial reproduction (and consequently evolution), I am curious to know if the houses in the study were re-sampled, would the same species be present in the same distributions and abundances?
I have heard a lot about this MacArthur (1968) paper so was excited to finally sit down and read it. Overall, I found the paper quite good. The format struck me as different than the typical science paper. MacArutur presented a general idea (niche partitioning based on limiting factors) and then followed this by dissecting the idea (looking at the different factors that impact the warblers realized niches such as feeding and territoriality). I enjoyed the way MacArthur looked at each factor before summarizing everything by the end of the paper. As a person who is not really familiar with much of ecology, I was wondering how a person determines the limiting factor that could impact niche partitioning (could there be a single limiting factor? Are they always density dependent?). Other than that, I liked the paper.
ReplyDeleteThe companion paper, Remold et al. (2011) was great. I don't have many complaints about this paper, most likely because I found the whole idea fascinating. I would never associate microorganisms and niche partitioning, let alone niche partitioning in a human home (considered an environment in this case). The study seemed relatively thorough. I would like to know what BLAST is. Also, without letting this paper escape criticism, Figure 2 was a bit messy in my opinion. regardless of my nit picking, the paper was a great read.
The MacAuthurs’ paper studied niche partitioning but mentioned “niche” only twice in the whole paper. It is nice that the author mentioned the probable errors in each step and how he corrected the errors. I like the way the author describes how they observe birds feed on different locations of a tree. I also like figure 10 because it is interesting that different warbler species not only have different feeding places on a tree but also barely have overlapping feeding region during winter. However, I have to say that figure 1 ignored the situation that if one species had extremely low density, it tended to be eliminated due to competition, rather than had the highest per capita growth rate. Overall, this is a nice paper about niche partitioning back to that time. Personally, I found that this paper was not clear enough for me to follow, and I had a hard time trying to figure out what was the aim of this study. Maybe it’s just me but I think the author talked a lot about density dependence along with figure 1 at the very beginning, which is confusing. I thought that the author would study density dependence, but it turns out that this paper focuses more about niche partition rather than density dependence.
ReplyDeleteThe companion paper covers an interesting topic. I am confused by the “likelihood recovery of Pseudomonas”, is that analogous to the percentage of a taxon over the total abundance of Pseudomonas? Also, the authors concluded that niche partitioning driven by competition was the important cause to the different recovery, which was not well-supported. Those habitats are hugely different and to me the differences of Pseudomonas proportions are driven by the environment itself rather than competition. For example, soil is a big nutrient pool to microbes, and if one microbe taxon can barely be found in soil, a more reasonable explanation to me is that it cannot survive in soil or it does not have chance to get there, rather than it cannot outcompete for resources and space.
I enjoyed the detailed descriptions of MacArthur’s observations of each species, and the ways he described niches for each of the birds and the factors that reduced their spatial overlap and competition so that all five could co-exist in the same forest. For a short-term observational study, I did find his method of dividing tree branches into three zones to be a bit of a stretch – I see the utility in what he was trying to accomplish, but the cutoffs were somewhat arbitrary and there was likely a lot of variability among trees that is very difficult to account for.
ReplyDeleteI thought the Remold et al. paper was really interesting – we so often discuss niche partitioning and realized niche when thinking about habitats of larger organisms, so it was cool to see these concepts applied to a common bacteria genus. I don’t have a lot of familiarity with the success rates for these isolations; they took 960 samples, 301 showed growth on the isolation agar, but only 163 were confirmed to be within Pseudomonas. Is this a robust “usable” sample size to make inferences about abundance and realized niche, given the number of types of surfaces and habitats that were originally sampled?
I agree with Crystal that the methods of the MacArthur paper are not the strongest, but the conclusions are insightful and of course still relevant to ecologists today.
ReplyDeleteThe Remold paper was an interesting read. It's not often we think of microbes through the lens of an ecological concept like niche partitioning. I am curious as to how certain habits or lifestyles of the human subjects play into their findings. How would a selective pressure - like regular cleaning with various chemicals - alter how the Pseudomonas are distributed across niches? I'd also be curious to see how priority effects play into this. E.g. how does the introduction of a pet or child affect a well-established bacterial community in a house that previously did not have pets/children?
I was excited to read this paper. This is the epitome of a classic ecology in my mind. I was presently surprised that it was an easy and enjoyable read. I appreciated the attempt to standardize complex animal behavior so early on in the field.
ReplyDeleteThe newer paper was a great extension of the classic. AS someone who works on micro organisms, the fact they have niche partitioning is not surprising. Micro organisms have to follow the same rule are macro one. I did think the way this study went about proving it was interesting. I think it would be cool (and disgusting) to do something similar in like a school or hotel.
-Miranda
ReplyDeleteThe MacArthur paper studying niche partitioning provided some key insight into the development of realized niches in instances of co-occurring species. While I was able to follow his overall conclusions that he summarized in his discussion section, I do agree with others that there were some odd parts in the methods behind the study. Although this may be due to the limitations of his time, I still wonder if this caused any skew in his results.
ReplyDeleteI found the Remold study to be super interesting, as I have not read or been taught much about niche partitioning in the case of infection-causing pathogens. When reading I did have some issues with Figure 2. It took some looking at to tease the entire thing out, as it was presented in a pretty messy way that wasn't very intuitive to understand when first glancing at it because of the general messiness of it.
- Elizabeth
I like MacArthur’s general hypothetico-deductive approach to ecology. From my casual impression of his work, he seems most interested in looking at general qualitative patterns, so I’m not particularly bothered by the crudeness of his methods and the low power of his tests since I think they would tend to bias his findings against finding evidence for his hypotheses. I wish he elaborated more on his methods in the first section where he attempted to detect a signal of density dependent regulation. It was hard for me to really evaluate the justification for his approach. Of course, it appears from the footnote on page 1 that this publication is a condensation of his entire dissertation, so it makes sense that he had to be brief.
ReplyDeleteI’m unfamiliar with microbial ecology so the Remold et al. paper was an interesting read. It made we wonder what kinds of work people have done mapping environmental distributions of microbes, particularly pathogens. I wonder how successful microbial ecologists have been at identifying the factors that dictate microbes’ niches. It seems like this would be a highly challenging task for microbes that can’t be cultured, since scientists wouldn’t be able to do controlled experiments to demarcate the fundamental niche. On the other hand, it seems like microbial ecologists might be highly successful at predicting distributions of culturable microbes since these niche quantification experiments could be readily done.
- David
The MacArthur paper was beautifully written, but it was painful to read as someone who has done warbler field work because it underscores how many migratory passerines we've lost. I know the sample sizes don't seem very large, but they actually are in the context of modern warbler ecology studies (This is a major part of the reason I'm not doing a warbler PhD right now). The nest sample sizes in particular are amazing. When I did warbler field work, in a place renowned for warbler density, every 10 nests found was a major cause for celebration. It's really rough to read this knowing that we joke about MacArthur "casually observing some warblers" and making the elegant conclusions found in the work.
ReplyDeleteThe Remold et al. paper was interesting because, as others have noted, we haven't extensively discussed microbial ecology. It made me curious how far concepts of niche partitioning and habitat suitability have percolated into the study of microbes and whether they're applied in medicine.
The MacArthur paper was very well written and easy to follow. I enjoyed seeing the tree diagrams with shaded niche spaces for each species because it was like looking at a relic of ecology and evolutionary biology. I have seen this study referenced many times as the model for demonstrating niche partitioning, and was pleased that it was so well presented in its original form. I was also surprised at the scope of the study because the tree diagrams are the most well known, but he also showed that the warblers partitioned nest habitat and breeding phenology as well as multiple differing life history traits that could be limiting each species population in slightly different ways, allowing for their coexistence. He ultimately concluded that foraging habitat seemed the likeliest factor of population control for warblers, so maybe that is why it is the result that is most commonly discussed.
ReplyDeleteThe Remold et al. paper gave me the willies while reading it. It was awesome. I was hoping they would bring more of the opportunistic pathogen angle into it because it's a slam dunk in terms of direct applications of a study to disease prevention. They did sneak in at the end that the most pathogenic species mostly sticks to drains. PSA remember to wash your hands after you clean your drains out, kids!! Very cool application of niche theory.