Hutchinson's duality: The once and future niche

doi:10.1073/pnas.0901650106

Hutchinson's duality: The once and future niche

Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269

Edited by David B. Wake, University of California, Berkeley, CA, and approved August 3, 2009 (received for review March 16, 2009)

Abstract

The duality between “niche” and “biotope” proposed by G. Evelyn Hutchinson provides a powerful way to conceptualize and analyze biogeographical distributions in relation to spatial environmental patterns. Both Joseph Grinnell and Charles Elton had attributed niches to environments. Attributing niches, instead, to species, allowed Hutchinson's key innovation: the formal severing of physical place from environment that is expressed by the duality. In biogeography, the physical world (a spatial extension of what Hutchinson called the biotope) is conceived as a map, each point (or cell) of which is characterized by its geographical coordinates and the local values of n environmental attributes at a given time. Exactly the same n environmental attributes define the corresponding niche space, as niche axes, allowing reciprocal projections between the geographic distribution of a species, actual or potential, past or future, and its niche. In biogeographical terms, the realized niche has come to express not only the effects of species interactions (as Hutchinson intended), but also constraints of dispersal limitation and the lack of contemporary environments corresponding to parts of the fundamental niche. Hutchinson's duality has been used to classify and map environments; model potential species distributions under past, present, and future climates; study the distributions of invasive species; discover new species; and simulate increasingly more realistic worlds, leading to spatially explicit, stochastic models that encompass speciation, extinction, range expansion, and evolutionary adaptation to changing environments.

Footnotes

¹To whom correspondence should be addressed. E-mail: colwell{at}uconn.edu
Author contributions: R.K.C. and T.F.R. wrote the paper.
This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Biogeography, Changing Climates and Niche Evolution,” held December 12–13, 2008, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The complete program and audio files of most presentations are available on the NAS web site at www.nasonline.org/Sackler_Biogeography.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0901650106/DCSupplemental.
↵* In earlier treatments, Hutchinson consistently emphasized competition as the “interaction” of most interest (1, 20), But by 1978 (6) by using the alternative terms “preinteractive” and “postinteractive” niches he appeared to be making an effort not to exclude other kinds of species interactions as causes of differences between the fundamental and realized niches [as urged, for example, by Colwell and Fuentes (39)], But even in 1957, in discussing fundamental vs. realized niches, Hutchinson wrote, “Interaction of any of the considered species is regarded as competitive … negative competition being permissible, though not considered here” (1). Mutualism had been modeled by Gause and Witt (40) by means of competition coefficients with negative signs, giving rise to the oddly litotic term, “negative competition.” The consequence, that positive species interactions (mutualism and commensalism) might imply a realized niche larger than the fundamental niche for one or both partners, has been viewed by some as a “paradox” (3), but in fact is simply a logical and meaningful consequence of Hutchinson's definitions, a consequence that might very well not have troubled him at all.
↵† Apparently, Hutchinson himself either came to realize this or eventually decided to make sure that others had realized it, sometime in the two decades between Concluding remarks (1) and the textbook (6). In Fig. 1, based closely on the latter, the (fundamental) niches for species S₁ and S₂ do not overlap, thus avoiding the issue of competition and the realized niche. But this figure has two direct ancestors (in refs. 1 and 20), both showing overlapping niches, with the accompanying text treating the niche–biotope duality, the realized-fundamental distinction, and competitive exclusion in one long breath. In contrast, the textbook (6) deals with the niche–biotope duality on its own (Fig. 1), with separate consideration of the fundamental-realized distinction, illustrated by a separate figure.
↵‡ The niche to biotope link can also identify sink regions, where individuals may survive but populations cannot sustain themselves. By definition, sink regions cannot map within the fundamental niche, because the latter includes only conditions where a species is self-sustaining. For this reason, Pulliam (2) suggested that sink populations can make the “realized niche larger than the fundamental niche.” The implication is that the realized niche includes the projection in niche space all places that a species actually occurs in the biotope, a view that Hutchinson might well have agreed with in principle, given his inferred acceptance of the potential role of mutualism in extending the realized niche beyond the fundamental niche (see *).
↵§ According to our own analysis, in the 59 journal titles in JSTOR's “ecology and evolutionary biology” archive (www.jstor.org), the word niche peaked in both text and titles in the early 1980s (corrected for number of articles searched). It then declined, especially in titles, until the mid-1990s and appears to have leveled off to about the 1965 level in article titles, with a smaller decline in the text of articles. Chase and Leibold (11) found a similar pattern.