For most organisms, epistemics a~e a Vital a~pect of thel.r funct~onal ... Rejecting the traditional dualism of organism and environment, ~n ecomche IS defined ~ ...
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THOMAS R. ALLEY
ORGANISM-ENVIRONMENT MUTUALITY EPISTEMICS, AND THE CONCEPT OF AN ECOLOGICAL NICHE*
ABSTRACT. The concept of an ecological niche (econiche) has been used in a v~riety of ways, some of which are incompatible with a reiatio.na.! ~r functional interpretatI~n of the term. This essay seeks to standardize usage by hmltmg the concept to fu~ctlOnal relations between organisms and their surroundings, and to .revise the conce~t to m~lude epistemic relations. For most organisms, epistemics a~e a Vital a~pect of thel.r funct~onal relationships to their surroundings and, hence, a major determmant o! the~r ecomche. Rejecting the traditional dualism of organism and environment, ~n ecomche IS defined ~s the reciprocal (dual) of a functionally specified cla~s of orgamsms ~FSTU). From. this perspective, an econiche necessarily implies. a certa~n type of orgamsm, and a class of functionally similar organisms implies a specml ecomche. . The econiche concept is also discussed in relation to other ecological terms that reflect the distributional patterns of organisms, such as "habitat", and the concept of an "empty niche" is criticized.
The five to ten million species that inhabit Earth are not randomly distributed. Many patterns can be found in the distributions .of organisms whether one observes a small community the ent~re biosphere, and whether one examines only. m?mb~rs of a SIngle species or a broad class of organisms. These dlstnbutIOnal patterns reflect partitionings of the environment among a great diversity ~f .organisms and groups of organisms. The boundaries of these partItIOns are a function of both where and how organisms live and, therefore, both spatial and functional distributional patterns can be found. T~e central problem for ecology is to understand the processes governIng these patterns of distribution and abundance (Krebs 197~).. . Here I will examine the analysis of functional dlstnbuhon patterns using the concept of an ecological niche (or econiche, for short): My main purpose is to clarify and amend the concept of an ecomche, stressing its organism-referential or "organism-centered". (Ma~Mahon et al. 1981) nature, and advocating flexibility in speCificatIon and application of econiche concepts. Two main points. of d.eparture a~e used to achieve these goals. First, the role of eplstemlc factors In econiche specification and differentiation is emphasized. (Epistemics refers to the realm of informational (epistemic) relations between organisms and their surroundings; that is, to organism-environment
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Synrhese 65 (1985) 411-444.
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© 1985 by D. Reidel Publishing Company
THOMAS R. ALLEY
relations are prescribed by perception and cognition, broadly defined.) An analysis of econiches (in terms of "affordances") will be advocated that is particularly compatible with epistemic considerations, and with the inherent interrelatedness of any organism and its surroundings. Second, the concept of an econiche is considered from a broader perspective whence it appears as part of a relationship of dual complementarity between ecological descriptions of the environment and functional classifications of organisms. [Although for both historical and theoretical reasons the concepts of econiche and competition are closely associated, their interrelationship will not be treated in depth herein, the topic having been addressed in several recent papers (Alley 1982; Diamond 1978; Pianka 1976; Schoener 1977).] Unfortunately, the literature contains a confusing variety of usages of basic ecological terms. Thus, before embarking from these departure points, some preliminary discussion of basic terms and concepts is in order. 1.
SOME BASIC TERMS AND DISTINCTIONS
A key characteristic of an ecological viewpoint is its recognition of the inherent and necessary interrelatedness of the organisms and environmental states and processes that compose the biosphere. Ecological analyses include organism-relevant or organism-based spatial partitionings of the environment and functional analyses of ecosystems at varying degrees of "graininess" but do not include organism-indifferent analyses whether they be fine-grained (e.g.. based nn atomic or molecular boundaries) or coarse-grained (e.g., based on the categories of solid, liquid, and gas) (d. McIntosh 1963). Consequently, every system of classifying organisms that is ecological in this sense has a complementary classification of environmental variables, and vice versa; an ecological partition of the environment implies a class of organisms, and an organism, or a functionally equivalent class of organisms, implies a particular type of environmental surrounding. Unfortunately, the analyses and concepts of ecological scientists, including some uses of "ecological niche", are 110t always ecological in the above sense. For instance, a traditional; phylogenetic taxonomic system - a system containing the nested classes of subspecies, species, genus, family, order, etc. - is not an ecological style of classification. In this taxonomy, "taxonomic relationship does not specify ecological relationship" (Krebs 1978, p. 475). An ecological classification is based
EPISTEMICS, DUALITY AND ECONICHES
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on organism-environment relationships rather than on the genetic relationships among organisms. In an ecological system of classification. organisms are classified according to phenotypic charc.lCteristics or phenetic relationships, rather than by their phylogeny or pltyletic relationships. An operational taxonomic unit (OTU), a term introduced by Sokal and Sneath (1
