I’m sat in a workshop about the ecological niche. One thing we’ve been discussing is what people understand the ecological niche to mean (don’t worry, we discussed more concrete things too).
(source)
So, here’s a question for you (particularly ecologists), what do you mean by “the niche”? How do you understand it? There’s no right or wrong answer – we’re interested in the breadth of opinion.
There are also some deeper issues that we’d like to bring up too, so I’ll follow up in the comments.
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A species’ niche can be defined as all the combinations of requirements that allow a population to survive and grow in a given place (population growth rate r>0), and the impacts that a species has on the ecological community where it lives.
I’ve always – unwillingly, probably because of my understanding of the word ‘niche’ – pictured an ‘ecological niche’ as a kind of ‘refuge’ of a particular species where it can survive in the face of the stiff competition going on all around it (it’s a rough world out there). In other words: the selective pressure has driven that species into utilising resources that no other species around it utilises or can utilise.
It’s like that gap between the banister rail and the newlpost that’s just big enough to get a bit dusty, but not too dusty, and lets in some light, but not too much, and some moisture, but not too much so that the right little spider can live in there.
The absolutely necessary collection of conditions needed for a species to survive. Overlap between niche commodities drives competition for resources and underlies exploitation of novel niches and thus provides a fertile environment for evolution.
And it is absolutely pronounced niche (neesh) not niche (nitch).
I don’t thinks this because, Mummy is always concern about us ,on our education , on our carrier. So I don’t think mummy is a ecological niche .
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Is there a chicken and egg thing here? Which came first, the niche or the inhabitants?
I am reminded of Henry’s post on ancestors and descendants – do we only know the niche is there because of the species inhabiting it?
(Disclaimer: I am not an ecologist).
Hmmm. I had been wishing for some Deep Thoughts amid the Silliness, but now they’ve arrived, I am not so sure. The problem with the ecological neesh is that it’s not a static box to put things in, or even that gap at the bottom of the stairs so beloved of Dr I. B.
I see it as something more dynamic, and tend to picture it in terms of Darwin’s Tangled Bank. Every second, individuals are interacting with other individuals of the same and different species, and with the changing environment. (BTW, if you haven’t seen the terrific evocation of the Tangled Bank idea in the mob Creation, you should – it’s the best part, I think).
I’d say that the neesh for a species is that set of circumstances in which individuals of that species are more likely to maximise their net fitness than individuals of another species, given the same circumstances.
Frank might not be an ecologist but he’s onto something. Neeshes don’t exist independently of species, as if waiting for them to turn up.Species make neeshes, and neeshes make species. The evolution of new morphologies in new habitats opens more neeshes that hadn’t before existed.
This all reminds me of a story by the late Spike Milligan called ‘The Bald Twit Lion’ and if memory serves it started something like this.
‘Once, twice and thrice upon a time there lived a jungle. It started at the bottom and the trees grew upwards until they reached the monkeys, who had been waiting ages for the trees to reach them, and as soon as the did the monkeys invented climbing down ‘.
My ideas of what an ecological niche might be, probably changes with every other deep thought: survial and growth under particular conditions where species do or might potentially occur and are rewarded with growth and survival is a good first idea in theory. In practice, mummys or any ecologists‘ examples of which properties and dimensions make up the niche of one species may struggle by another species that seems to ignore rules of distinct occurence and growth rates patterns under changing conditions. The puzzle seems to me complete by having an unseizable numbers of species responses and interactions with underlying habitat conditions from one patch to another that are all part of what we can incompletly observe from a species‘ „niche“.
Mummy, should we worry about having some more unique grains adding to the flavour of the overall outcoming dought fromt the flour mill or is it time to bake the cake? With the immediate need to understand species distributionand occurence patterns, keep on milling but putting some more deep thoughts on the grain?
I rarely use a term ‘niche’. To me it is vague enough. But when I think about a niche I take into consideration all interactions of a given population with its environment, both biotic and abiotic. Indeed, this is what you all are saying. Really, a very vague concept. Actually I think niche notion only serves for one purpose: to give a measure (preferably quantitative) of how much populations ‘overlap’.
Thanks for your comments so far. I think most of us have a general idea about the niche (and I like the way Ian expressed). The practical problem we face is estimating the niche for a species (so that we can predict where it can survive when the climate warms up), so how should we formalise and operationalise our definitions?
Just for completeness (and since it occurred to me last weekend while driving around): we forgot to list different temporal patterns of species’ activity, reproduction, etc. as one aspect of specialisation/niche exploitation. I suspect those are going to be the real buggers when you start thinking about species’ survival in a warming climate, especially when they’re interdependent.
In addition to the useful definitions above, there’s a couple of important distinctions to make between different kinds of niches (and I agree, definitely neesh not nitch!). First, ‘fundamental’ vs. ‘realised’, with ‘fundamental’ referring to everywhere where conditions are such that a species could happily exist there, and ‘realised’ being that subset of the fundamental niche in which it is actually found. Generally, the realised is much smaller than the fundamental, due to what I consider to be an under-appreciated set of ecological mechanisms: accidents of history and geography. As a result, most algorithms designed to predict a species’ distribution based on its environmental tolerances overpredict the distribution (to an unpredictable extent…)
Second, Jorge Soberon published a nice, thoughtful and thought-provoking paper in Ecology Letters a couple of years ago, contrasting the ‘Grinnellian’ and ‘Eltonian’ definitions of the niche. He further makes distincitons between definitions of niche as habitat vs. function, as local (ecological) vs. global (biogeographic) phenomena, and as resources vs. conditions. Worth a read if you’re interested (Ecol Letts 10: 1115-1123, 2007).
And as for measuring niches – easiest solution is to work in pelagic systems, where to a first approximation niche = body size. Problem solved!
And another thing – sorry to go on! – one aspect of the niche which interests me is, to what kind of entity does it apply? As in so much of ecology, we tend to assign niches at the species level. But it is individuals that do the local interacting, so is niche is rather an individual-level trait? I suppose that again I am influenced by thinking about size-structured aquatic systems, with individuals often growing through several orders of magnitude as they age, and so frequently switching their ecological roles (big pike eat big perch eat small pike eat smaller perch…)
Coming from an evolutionary stable strategy (ESS) point of view, simply put, I view an ecological niche as a set of a strategies. That is to say, every living organism has two fundamental biological needs: 1) survival, and 2) reproduction. The complete set of strategies that an organism uses to meet their biological needs defines their ecological niche. In my opinion, defining a niche this way allows for niches to be ecologically dynamic. The same species may occupy slightly different niches in different ecosystems. And yet, it only takes variation in a single strategy to establish two separate niches in a single environment. Consequently, defining and ecological niche as a localized ESS helps to reinforce the true dynamics of ecological communities. A species does not evolve independent of the environment/community in which it lives. And as it evolves it does not develop, acquire, or evolve a completely new set of strategies; speciation arises from modification of existing strategies to meet specific needs. Yes, occasionally completely new and novel strategies may evolve, but these will typically only remain in the population if they imbue some level of evolutionary advantage.
Not only does the ESS viewpoint give strong support for competitive exclusion model on a localized as well as global level, but it also helps explain why invasive exotic species can overwhelm an ecosystem. For example, an invasive exotic species has the ability to outcompete local organisms because it has a set of strategies that are not being used in the local community; the exotic basically, steps into an open niche in the system.
One of the most interesting things to me arises when you examine the diversity of tropical and temperate climates. I recently asked a student of mine why there were so many more species in the tropics than in temperate zones. He thought about this overnight, and the next day eloquently stated, “when you think of things in terms of thermodynamics, more species evolve because they can, not because they have to.” Essentially, in temperate climates competition for energy is greater which restricts the number of strategies that can be utilized. Whereas, in tropical climates such a limitation is near non-existent; more species evolve because the variation in strategy only needs to be minimally different. Such an explanation, also helps explain the differences in mimicry as well.
Niche: the pool of conditions (biotic and abiotic) necessary for a community to live. You can have niche partitioning between adults and juveniles, different species, etc. The area and its abiotic proprieties where a community lives is the habitat.
Empty niches should not exist since niche is tightly linked to a given community of organisms. When one community moves away, it does so because the niche (its pool of conditions) moves/ conditions in a given area change. When the pool of conditions become unsustainable for a community to live, the community may disappear, together with its niche.
You can have conditions for life on Mars to survive, but are they called niche in the absence of any organism ?
I believe fuzzy niches do exist, especially when different developmental stages of an organism coexist. Should be this equivalent with different degrees of niche partitioning?
Niche – multivariate space that describes what an organism does for a living. Clearly, niche is context dependent, since a species that does one thing in one place because resource X is found there, may not do the same thing in another place because X is absent.
The ecological space a species occupies. This includes all the resources and services it needs. My favourite orchid (Disa uniflora) needs a particular fungus in the soil, the butterfly Meneris tulbaghii to pollinate it, moisture around the roots during the whole year, direct sunlight, good air movement (transpiration?), a limited set of nutrients, and a soil pH that is distinctly acidic.
The essential ingredients are entirely question driven. What controls where the species occurs is the full set of conditions, but its success (against competition) might depend on many variables (fire to clear competing vegetation, for example). For evolution we need to think about the physiological attributes (not the environmental ones), for ecosystem function we think about the nectar resource for the pollinator (interaction coefficient).
Quantifying these variables: we do not know how many of these variables are autocorrelated . . . . and which may in fact not be limiting at all!
The niche of a species represents the distribution area of a species, i.e., where a species can survive when taking biotic (competition or colonisation limitations,…) and abiotic constraints (climate, soil etc.) in space and time into account. Also land-use plays an important role as it affects both abiotic and biotic conditions, and hence makes it more complicated in clearly grasping or quantifying the niche. Nice examples would be oak versus beech in Central Europe with both having comparable requirements to the environment but with beech being much more competitive in the actual landscape. Here, the effect of biotic factors becomes very clear.
A species’ niche can be defined as all the combinations of requirements that allow a population to survive and grow in a given place (population growth rate r>0), and the impacts that a species has on the ecological community where it lives.
I’m reposting this comment (originally posted by Kissling) because this is the definition of a niche. It melds both the Hutchinsonian and Eltonian views on the subject. Check out “The Ecological Niche” by Chase and Leibold and see their commentary on developing both a tight verbal and mathematical definition of what this means in chapters 1 and 2.
While many of the definitions posted here resonate with me and how I envision the niche, the posted definition actually encompasses all of these thoughts and leaves no room for misinterpretation or ambiguity. No such thing as an empty niche, just unused resources.
Christopher – you’re right that that’s a pretty comprehensive definition, and I agree that the Chase & Leibold book is interesting. I suppose my question then is, how useful is that definition? I mean, it’s going to be impossible to measure ‘all the combinations of requirements…’, let alone ‘the impacts that a species has on the ecological community where it lives’, even for a single species, in one location, and one point of time. Can we derive an operational definition that helps community ecology to progress? One of the interesting things about the neutral theory of biodiversity was it got people asking the question, just how much of this complexity can I safely ignore? I suspect the answer is, quite a lot (but not all of it)…
Unfortunately, while your idea of deriving an operational definition that helps us move forward as a discipline is attractive, I feel that changing the definition ends up muddying the waters of an already muddy subject. At this meeting I saw a number of talks where the word niche was clearly misapplied or misused.
I think that interesting practical questions that face us today are how will species range shifts and how will communities reorganize as our climate changes.
Late to the party, holidays. Fun question, Bob.
A: Niche = n-dimensional hypervolume representing the limiting resource axes required for population growth and persistence (paraphrasecd from May, 1973). Physical and temporal variability could potentially be included as axes here, which allows spatio-temporal niche partitioning to be incorporated. It might also sort of allows for Tom’s historical and geographic accidents (aka evolution). Integral projection models allow us to incorporate size/age/stage structure here in a continuous framework as well.
I sort of thought a niche had to be linked to a population/species concept (not easy things to define, in themselves), but IPMs may allow that to be relaxed. It’s too early for my brain to get round the maths yet though. Need coffee.
To me the niche of a species is a “physiological niche”, defined as the ecological space in which individuals of this species can survive and reproduce. This ecological space depends on an ensemble of abiotic dimensions (temperature, water availability, soil conditions (for plants), energetic requirements (for plants and animals), etc…). On my interpretation, biotic interactions and dispersal are not directly included in the niche of the species, but it is the interplay of these biotic interactions with the physiological niche that then determines the distribution of a species. In theory it is thus possible to define the potential distribution of a species (the geographic realization of the physiological niche), while the observed distribution is the reshaping of this potential distribution because of competition, predation, dispersal constraints, land use… and historical factors. Thus I think the niche should cannot be precisely understood in spatial dimensions.
(Note that strictly speaking, each individual has its own niche because of intra-specific variability)
Problems with this interpretation: some dimensions of the physiological niche may be tricky to assess (like energetic requirements, e.g. for herbivores).
I offer another vote for the definition put forth by Daniel Kissling and Christopher Patrick above, which is extensively discussed in Chase and Leibold’s book. Additionally, I strongly encourage you to read Michel Loreau’s new Princeton Monograph, which just came out this month. In it, he provides a theoretical synthesis that has the potential to make ecology much more predictive. Let me know what you think if you decide to read it.
The niche of a species is best described by the combination of factors – both biotic (including competitive interactions, mutualisms, …) and abiotic (environmental factors, resource availability, …) – that allow the species to persist in a given place and time.
However, I do not consider the niche to be a static construct, but something that can change through time. Species could adapt to changing conditions and what we might percieve simply as a change of the relaized niche might in fact be a shift in the fundamental niche (in which case conditions that previously defined the niche do not allow the existence of the species anymore).