Maureen McClung
November 18, 2005
Persistence of the Grinnellian Niche
The concept of the ecological niche is one that has been developed and disputed
repeatedly by many scientists over the last century (see reviews in Schoener 1989;
Griesemer 1992). Even the identity of the first person to use the term “niche” as it relates
to ecology is unresolved. However, most authors agree that it was Joseph Grinnell
(1917b) who popularized its use in his paper entitled “The niche-relationships of the
California thrasher”. Since his application of the term “niche” to describe an organism’s
place in nature, the concept has undergone several major shifts towards more
mathematical and operational definitions. With these transitions have come theoretical
difficulties, which have caused some (James et al 1984) to call for a return to the basic
concept put forth by Grinnell. In this paper, I will review the history of the biological
niche concept, discuss its present status, and identify current issues to be addressed.
In his 1917 paper on the California thrasher, Toxostoma redivivum, Grinnell
attributed the severely restricted range of this bird to physiological and psychological
adjustments to a narrow range of environmental conditions. He described the range as
mostly warm, southerly-facing hill slopes in chaparral habitat. Environmental factors
like temperature and humidity seemed to be the most significant determinants of range.
However, he also identified predator avoidance, nesting, and feeding behavior as
important reasons for the thrasher’s dependence on chaparral habitat, thus this concept
was not purely spatial. Grinnell (1917a) believed this association was “distinctive
enough to be included among the characters of the species described along with its
habitat and the features of its bodily structure.” In subsequent works, Grinnell (1928,
cited in Schoener 1989) developed his concept of the niche to be the “ultimate unit in the
general association occupied by each single species”.
In 1927, Elton devoted a section of his book, Animal Ecology, to his version of
the niche concept. He thought that the niche of an animal referred to its place in the
biotic environment, particularly its relation to food and enemies. He later defined the
niche as meaning the “mode of life”, especially the mode of feeding of an animal (Elton
1933). This concept was different from Grinnell’s because it placed more emphasis on
trophic relations than on habitat. For example, birds of prey occupy a niche for eating
mice and rabbits across habitats. In a forest this niche is filled by the tawny owl and in a
grassland it is filled by the kestrel (Elton 1927). This example also illustrates how Elton
thought that different animals could occupy the same niche. For Grinnell (1917a), the
niche was a characteristic specific to a species. Elton’s niche concept is thought to have
marked a transition from a focus on a species’ place in nature to the role of a species in a
community (Griesemer 1992).
The next big leap in the evolution of the niche concept was made by Hutchinson,
who developed the theory of the niche into a geometric definition of the occupant in
terms of environmental dimensions. In 1958, he introduced the n-dimensional
hypervolume, which is a theoretical space defined by points that correspond to states of
the environment which would permit a species to exist indefinitely. This theory
inextricably linked niche theory to the competitive exclusion principle, which states that
no two organisms occupying the same niche (i.e. complete competitors) can coexist
indefinitely (Krebs 1978). Hutchinson thought that the range of niche dimensions (e.g.
temperature, food size, etc.) determined the fundamental niche of a species, but then
interactions such as competition limited species so that they occur in a smaller realized
niche. The concept of a realized niche explained how two species could have similar
fundamental niches and still coexist. Hutchinson’s redefinition shifted thinking of a
niche as an attribute of the environment to an attribute of the population or species in
relation to its environment (Colwell 1992).
The final major development in the concept of the niche was the interpretation of
dimensions of niche space as actual resource utilization (Levins 1966, 1968; MacArthur
and Levins 1967). This final theory is sometimes called “modern niche theory”
(Schoener, 1989). Where Hutchinson’s hypervolume succeeded in theory, it failed in
practice. The main difficulty was how to empirically determine all the dimensional states
permitting a species to survive (Schoener 1989). To simplify this problem, the modern
niche theory took resource dimensions one at a time and located the organisms on the
dimension in terms of utilization rather than fitness (Cooper 1995). Levins (1968)
thought a good niche theory should ask questions about determinants of niche breadth,
the limits to similarity among coexisting species, resource partitioning, and evolution.
This modern theory of the niche had more theoretical fecundity than Hutchinson’s in that
it produced generalizations beyond the competitive exclusion principle. For example,
MacArthur and Levin’s (1967) theory of limiting similarity addressed issues like limits to
species number, degree of invasibility, and niche shifts. Their theory suggested that there
is a universal limit to the similarity in niche dimensions that two sympatric species can
exhibit and still coexist. Although this conclusion has been heavily criticized (Abrams
1983), the general messages from the early models still seem valid. First, there are likely
to be some limits to similarity in coexisting competitors. Second, these limits suggest
more than just differences in species, but also the variability within them, the nature of
the resource and utilization curves, etc. (Begon et al 2006).
Currently, the most common definition of “niche” coincides with the occupantbased niches described by Hutchinson (1957) and MacArthur and Levins (1967). These
theories have generated many questions that tend to be geared towards understanding
resource distributions, utilization curves, and mechanisms underlying exploitative
competition. A review of the many recent studies aimed at exploring the complexity of
niche relations is beyond the scope of this paper, however a few examples will provide a
sample of current work both in the lab and the field.
In order to explore how niche breadth responds to competition, Bolnick (2001)
presented populations of cadmium-intolerant Drosophila melanogaster with both
cadmium-free and cadmium-laced media. He found that populations experiencing high
competition (high density) were more likely to develop cadmium-tolerant flies after
several generations since there was less competition for cadmium-laced media. This
experiment demonstrates that as competition increases, organisms may experience
pressure to expand their niche breadth. This study is an example of how the modern
niche theory, which emphasizes looking at resource dimensions one at a time, can
provide evidence for competitive effects on niche determination.
Harmon et al’s (2005) study on convergence of morphological traits of lizards in
the genus Anolis is another example of how niche dynamics are studied today. The anole
radiation is a classic case of convergent evolution in which different species have evolved
similar ecomorphs in allopatry. Through morphological measurements taken from
different species on different islands, they found that Caribbean anole lizards show
multidimensional convergence in phenotypic characteristics. Single dimension
convergence has been widely reported, but this study is unique in contributing support to
a multidimensional response in phenotype, as would be expected by Hutchinson.
These types of studies are valuable in furthering understanding of the modern
niche theory, however they operate under the assumptions made by Hutchinson’s model
which are subject to several problems. Hutchinson (1958) himself identified the pitfalls
in his theory when he first introduced the n-dimensional hypervolume. His theory
assumes the niche to be equally optimal in all areas, however it is inevitably suboptimal
near borders. It also assumes that all environmental variables can be linearly ordered,
which is not possible. The model also refers to a single instant in time, which is
challenged, for example, when considering nocturnal and diurnal competitors. Only a
few species are considered at a time, which means the abstraction makes little difference
to the whole community. Finally, Hutchinson’s model attributes differences in species to
present or past interspecific interactions a priori.
James et al (1984) suggested reverting to the original Grinnellian niche, with
some adjustments, in order to avoid unrealistic assumptions. For example, they studied
the niche of the wood thrush, Hylocichla mustelina, by employing multiple comparisons
that focused on the geographical ecology of a single species. James et al suggested
beginning with a single species approach before broadening to studies of assemblages.
Perhaps by combining both the “habitat-based” niche model of Grinnell and the
“occupant-based” models of Hutchinson and Levins, the details that define niche
dynamics can be better understood and, of course, generate more questions for research.
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