Blog Author:David Nguyen
Citations:
Hutchinson GE (1957) Concluding remarks. Cold Spring Harbor Symp 22:415–427.
Holt RD (2009) Bringing the Hutchinsonian niche into the 21stcentury: ecological and evolutionary perspective. PNAS 106: 19659–19665
Author background:
Hutchinson made important contributions to ecology and evolution during his career, the most famous of which is his definition of the niche in “Concluding remarks.”
Holt is a theoretical ecologist and is most well-known for his theoretical work on community ecology like apparent competition and intraguild predation.
Hutchinson’s paper
The two main niche concepts prior to Hutchinson’s work was the Grinellian niche (the habitat of a species) and the Eltonian niche (a specie’s biotic interactions). To clarify issues surrounding the definition of the ecological niche, Hutchinson took a set-theoretic approach to define the niche concept and analyze the uses and implications of his definition.
Hutchinson defined the fundamental niche (N) by considering some n-dimensional space of environmental variables. If the species can survive and reproduce under the conditions defined by some point in the n-dimensional space, then that point is an element of the specie’s fundamental niche. The fundamental niche is the subset (N) of the n-dimensional environmental space where a species can “exist indefinitely.”
He listed the following limitations of his definition: 1. All points in the fundamental niche correspond to some equal probability of population persistence while all points outside the fundamental niche correspond to zero probability of persistence; 2. Each of the n environmental variables can be linearly ordered; 3. The model captures only a single point in time; 4. Only a few species can be considered at a time.
Hutchinson then uses his niche definition to describe the possible outcomes of interspecific competition and relates his findings to Gause’s work on competitive exclusion. He considers two species, S1 and S2, with the fundamental niches, N1 and N2. If N2 is a proper subset (lies inside) of N1 and S1 is competitively superior, then S1 will exclude S2; however, if S2 is the superior competitor, then S1 will be exclude from any space in the intersection of N1 and N2, with the overall outcome of coexistence. If N1 and N2 partially overlap, then the competition in the intersection of N1 and N2 allows for only one species existence, while the non-intersecting parts of the species fundamental niches serve as refuges from competition. These outcomes define the realized niche of the species.
Following lengthy discussion of empirical evidence for and against the competitive exclusion principle, Hutchinson directs the remained of his analysis to problems in characterizing and explaining patterns of community abundance. Since his discussion relies on MacArthur’s broken stick model, which was later rejected by MacArthur (https://www.jstor.org/stable/1935661) because it lacked empirical support, I won’t go into further details.
Holt’s paper
Holt aimed to expand upon Hutchinson’s niche definition by considering how incorporating the effects of feedbacks, space, and evolution.
As Hutchinson pointed out in his list of limitations, his definition of the niche only allows for a population to persist or not depending on whether it is in its niche. Holt addresses this limitation by introducing the establishment niche, the region of niche space where a species can increase in population when rare, and the persistence niche, which is as it sounds. The establishment niche may e smaller than the persistence niche if the species exhibits positive density dependence. The persistence niche may be smaller than the establishment niche if the species can destroy its environment. Holt points out that these feedbacks are rarely accounted for in current approaches to quantifying the niche.
Holt then explained why spatial considerations must be accounted for. Some species, like weedy plants or diseases, population persistence heavily depends on dispersal rates and metapopulation connectedness. Since species persistence is the main criterion for Hutchinson’s niche concept, Holt argues that spatial processes must be considered when quantifying a specie’s niche.
Holt then explained the importance of evolutionary considerations. The niche of species may be relatively unchanging over time or can change rapidly. Holt argues that a conceptual framework is needed to understand why species can vary so much in rates of niche evolution.
My thoughts
I liked the way Hutchinson defined the niche and I think that it is impressive that his niche definition has had such an impact on ecology. I chose the Holt paper because I thought it would be interesting to see how theoretical perspectives on the niche have changed over time. As expected, much of Holt’s work focused on bringing much of the biological complexities we know about today into Hutchinson’s niche definition. However, I wonder how ecologists might take these nuances and expansions that Holt raised into account. How can current approaches ecologists use to quantify niches, like species distribution models (mechanistic or statistical) take these complexities into account?
Both papers compliment each other well--the Holt (2009) paper being a clear follow up to the Hutchinson (1957) paper. Well done to our blog author for getting two completely complimentary papers! I personally find this to be an interesting case where the new paper (Holt's paper) uses the original paper (Hutchinson's) without refuting much of what was presented. The Holt (2009) paper builds on Hutchinson's commentary regarding the definition of a niche and comments on where gaps still exist in niche research. What I found particularly interesting in the Holt (2009) paper was when he quoted Losos' about there being no comparative study to date about the niche of a clade. This surprised me though I recognize that this may have changed since the paper was published ten years ago. The implications of this from an evolutionary biology standpoint are fascinating. It may be that much of the focus has been on a species and its evolution, not necessarily the evolution of the species and their niche together (or apart). Since I studied the effect of geographic range size on survivibility in a fossil group in my Master's, this resonated with me. I think much of the focus on a species' distribution focuses on geographic range size as a trait, and in this way does not consider what it means for the species to exist in a particular niche. I am not sure how much of a tie in geographic range size is here, but I find this section of the paper very fascinating when considering it.
ReplyDeleteAs for the Hutchinson (1957) paper, I found it to be an interesting read. Hutchinson, in my opinion, did not tear apart common theories of the time but instead presented evidence of where some of them were valid (or not). I am not sure if it is a relic of the time, but what I found most interesting was the way in which he began and ended his essay with discussions of humans. I am not quite sure what he was eluding to, but it struck me as rather odd (as if he were trying to connect to a broader audience?).
My background is in biology education, so reading through the classic ecology papers has been an interesting exercise in comparing what the original materials contain are how those concepts are presented to lower-level biology courses. At the high school level, ecological niches are taught as static: species evolve to occupy a specific niche, and no two species can occupy the same niche. Hutchinson’s original text seems to question the hard-and-fast rules that are taught in introductory courses. Hutchinson considers the validity of the competitive exclusion principle and concluded that “it is reasonable to suppose that there will exist numerous cases in which the direction of competition is never constant enough to allow elimination of one competitor” (p. 230). Holt’s paper also raised questions that upend the static and simplified definitions of niches presented to high school students. Holt asked the question “Across a species’ range, do local populations have different niches?”. This question challenges the implication that the niche is the same for all individuals within the species. I understand why the simplified ideas are presented to lower-level biology classes – the exceptions to the rules can be a barrier to student understanding the generalized concepts – but I think the exceptions are important to acknowledge to demonstrate that living biological systems are never really as cut-and-dry as teachers and textbooks tend to present.
ReplyDeleteHutchinson's definition of a niche was thought out well and explained clearly in his 1957 paper. In general, I though it was elegantly worked out and easy to visualize without too much extraneous writing. Unlike many of the previous classic papers we have read, there was little in Hutchinson's paper that I would fundamentally disagree with. My only comment is that, given the ecological information we have now, Hutchinson's ideas ideas could be more nuanced, which is exactly what Holt does in his paper. I would be interested to see how genetic information can be worked into Hutchinson's ideas of niche space. How does individual genetic variation determine individuals' niches relative to the population, and how can we "see" speciation occur if we look at niches changing over time?
ReplyDeleteOne thing I noticed while reading the Hutchinson paper that caught my attention was his discussion of the identity of fundamental niche, specifically his observation that it would be so unlikely for two species to occupy completely overlapping niches that “the case is of no empirical interest”. While I agree that identical fundamental niches are unlikely, he states that the model is limited in referring to a single instant in time – so what about a case of complete overlap in niche with temporal variability (i.e., a migratory species overlapping with a similar species in a given region for a few months each year)? I wasn’t entirely sure based on Hutchinson’s definition if the fundamental niche would also be specific to a geographic location, or if seasonality/shifts in environmental optima could create overlap. Clearly, Robert Holt also noticed that Hutchinson’s definition neglected the spatiotemporal component, as he addressed this in his critique of the limitations.
ReplyDeleteOn the other hand, despite any overlap that could occur for a short time interval, each species would still have its respective, non-intersecting (both temporally and spatially) portion of its range/niche, so maybe this wouldn’t be as important – I was just thinking from a resource competition perspective during the time period in which the niche would be shared. The Hutchinson article made me assess about how difficult it is for some species, particularly those that occur over large/heterogenous areas, to partition out the degree to which competition for resources influences fundamental niche (if, at all). I think we are quick to attribute the distributions of species’ niches to intentional avoidance of certain competitors, but there are many other factors that determine this – e.g., as Holt argued, positive and negative feedbacks on populations such as dispersal limitations can have significant effects on the distribution (and niche) of a given species.
So first off, a general grip. All the older papers refer heavily to something previous, such as paper or in this case a symposium. This must have been a obstacle for new ecologist at the time. If every new paper is based on an older one, or a symposium you weren't at, information will always be missing. And I can't imagine getting paper was very easy back in the days before google scholar.
ReplyDeleteOverall I found the Hutchinson paper easy to follow. What stuck out most was the line on page 226 comparing mathematical models to a vacuum cleaner. I think this thought is something we have echoed in discussion, that theory is only useful in light of real world phenomena and that theory itself is not necessary to make ecological discoveries.
I have a question related to the Holt paper: what is the difference between an "established" niche and a realized niche?
Forgot to sign it: Miranda
DeleteHutchinson's paper touched on the complexity of identifying the niche of an organism, adding a great deal to the previous, more simplistic, views of the definition of niche in his time. Despite this complexity, it read very easily especially compared to the other papers of the era that we have read. I don't find any huge fault with his work and any gaps that may exist stem from a lack of knowledge/nuance/etc that fundamental result in any old paper due to the limitations of the field at the time in which he wrote it.
ReplyDeleteI found the modern perspective and details present in Holt to be very interesting and a good complement to the classic Hutchinson paper. I thought his brief section on niche destruction was particularly interesting, in which he describes instances of species establishing themselves in well-suited environments for their needs but then proceeding to over-consume those resources and subsequently destroy their own niches and crash.
- Elizabeth
Both papers talked about niche. Hutchison’s paper defined fundamental niche and realized niche clearly. The figure linking the niche space with biotope space makes the context easy to follow. It is amazing that at the end of the paper he moved into the evolutionary aspect of niche questions at that time (it was purely based on morphology I suppose). Also, applying niche concept into human demography is a really interesting point. For this paper I do have a question about the fundamental niche N1 and N2. He talked about a situation where N1 = N2, which confused me. From the context, a niche is an abstract packet of multiple environmental factors with given ranges, and it should be independent from species, then why differentiate N1 and N2 if they are totally the same.
ReplyDeleteHolt’s paper classified niche in more detailed categories. Holt moved steps further into evolutionary niches and brought out the idea of niche conservatisms. And I think it would be interesting to see how the results from today’s molecular studies would influence the traditional concepts of niche.
The Hutchinson paper is one of my absolute favorites. The idea of expressing a niche as a mathematical set was so evocative to me that it made me want to dig deeper into mathematical ecology and played a significant role in my decision to shift my focus to modeling.
ReplyDeleteThe Holt paper adds some much-needed realism to Hutchinson's theory and incorporates much of the fascinating science that was done in the interim. I think Holt is an interesting example of how ecologists are increasingly thinking about the relationships between species and their environments as dynamical systems, a shift from the static relationship standpoint of earlier ecologists.
I liked how both of the papers summarized past work well and built off of existing frameworks for niche theory. I thought both papers were thought-provoking, at least I had lots of questions after reading them that make me excited to dig into this literature more. I also liked Hutchinson's specific definition of environment, which was much clearer than his predecessors, especially Gleason and Clements. This also made me think about scales of environmental variables that might be relevant to species niches—e.g., microhabitat vs climate. I was pleased that Holt had thought about this as well, both at environmental/biogeographical scales and time scales.
ReplyDeleteI want to mention that I disagreed with Hutchinson's comment that two coexisting species without evidence of partitioning or competition was of no empirical interest. I understand that he was trying to make a point, i.e., that such a situation was unlikely to occur in nature. However, I think such a system (if it existed naturally) would be of incredible empirical value, if not to at least break down the system to see if there are other dynamics at play. What conditions might allow for this kind of system (e.g., plentiful resources)? If the case is found to occur in nature, would it not at least be interesting to study the unfolding of niche partitioning or competitive exclusion? This seems like the perfect opportunity to observe whether the Hutchinsonian or other niche theories hold up. I liked that this question was addressed when Holt brought up transplant experiments as a way to directly test niche theory. Hutchinson comes back later in the paper to further justify his remark, saying that if two species appear to be occupying the same niche, you probably are not looking close enough at the differences between them that actually define their niche space (e.g., Galapagos finches). I do think that this is a good point, just not a great justification for his throwaway comment.