Hutchinson's duality: the once and future niche

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.

Fig. 1.

Hutchinson's illustration of the niche-biotope duality for a temperate lake with algae and two consumers of algae (species S₁ and S₂). The 1D biotope (red and blue rectangle) is a stratified water column with a strong summer thermocline. The two environmental factors characterizing the biotope (water temperature and food size, both as a function of depth) correspond to niche axes in niche space shown on the right. Red (S₁) and blue (S₂) lines connect representative algal cells of different sizes and at different depths with their corresponding points in the niches of the two consumers. The distribution of species S₁ and S₂ in the water column is the projection of their niches on the biotope. Brown lines show algae that map onto an unutilized region of niche space (small algae in warm water). The yellow region of niche space (large algae living in cold water) is unavailable (not represented in this biotope). The cross-hatched portion of the niche of consumer S₂, which overlaps unavailable niche space, is unexpressed in the biotope. Based on Hutchinson's figure 101 in ref. .

Fig. 2.

The effect of niche conservatism on the niche–biotope duality for three hypothetical species (red, green, and blue), distributed along an elevational gradient, during a series of 100,000-year glacial cycles. A, C, and E show geographical distributions (biotope) from sea level (bottom) to mountaintop (top), and B, D, and F illustrate the projection of these elevational ranges on a temperature axis, assuming a linear decline in temperature with elevation (linear lapse rate). Note that the temperature axis in B, D, and F runs from cold at the top to hot at the bottom, and that the vertical lines are half-cycles, 50,000 years apart. The yellow region outlines the “climate space” (45) available in the biotope during sequential warm interglacial and cold glacial episodes. With perfect niche conservatism (A and B), niches are do not evolve, so that ranges move in synchrony with thermal zones on the mountainside. In contrast, with perfect niche adaptation (E and F), ranges are static and niches shuffle back and forth in niche space by evolutionary change. C and D (moderate niche conservatism) show a more realistic balance between adaptation and conservatism.

Fig. 3.

Stochastic simulation of species distributions in three biotopes (A, C, and E) and in the corresponding niche space (B, D, and F). Biotopes are characterized by a south–north linear gradient of environmental suitability (intensity of green). Shaded areas of niche space in D and F represent environmental conditions not present in the corresponding biotopes (C and E). After many cycles of random speciation and extinction (see ref. for details), species richness (curves on the right side of the biotopes) peaks closer to the more suitable end of the gradient when the suitability gradient is stronger (A). With weaker environmental gradients, species increasingly overlap in the middle of the biotope (geometric constraints on range location are stronger), and a clear middomain pattern of richness arises (C and E).