We develop a hierarchical model of heterogeneity that provides a framework for classifying patch structure across a range of scales. Patches at lower levels in the hierarchy are more simplistic and correspond to the traditional view of patches. At levels approaching the upper bounds of the hierarchy the internal structure becomes more heterogeneous and boundaries more ambiguous. At each level in the hierarchy, patch structure will be influenced by both contrast among patches as well as the degree of aggregation of patches at lower levels in the hierarchy. We apply this model to foraging theory, but it has wider applications as in the study of habitat selection, population dynamics, and habitat fragmentation. It may also be useful in expanding

Multiple scales of patchiness and patch structure: a hierarchical framework for the study of heterogeneity

A common assumption historically in ecology is evident in the term "balance of nature." The phrase usually implies that undisturbed nature is ordered and harmonius, and that ecological systems return to a previous equilibrium after disturbances. The more recent concepts of point equilibrium and static stability, which characterize the classical equilibrium paradigm in ecology, are traceable to the assumptions implicit in "balance of nature." The classical equilibrium view, however, has failed not only because equilibrium conditions are rare in nature, but also because of our past inability to incorporate heterogeneity and scale multiplicity into our quantitative expresssions for stability. The theories and models built around these equlibrium and stability principles have misrepresented the foundations of resource management, nature conservation, and environemtnal protection. In this paper, we sysntesize recent developments that advance our understandings of equilibrium vs. nonequilibrium, homogeneity vs....

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From balance of nature to hierarchical patch dynamics: A paradigm shift in ecology

Landscape Ecology in Theory and Practice

1. Positive relationships between the local abundance and the range size of the species in a taxonomic assemblage are very general. 2. Explanations for these relationships typically focus on two mechanisms, based on differences in the niche breadths of species, or metapopulation dynamics. Others have, however, also been suggested. 3. Here we identify and clarify all the principal mechanisms proposed to explain positive interspecific abundance-range size relationships. We critically assess the assumptions and predictions that they make, and the evidence in support of them. 4. A number of predictions are common to all of the biological (as opposed to artefactual) mechanisms, but the combination of predictions and assumptions made by each is unique, suggesting that, in principle, conclusive tests of all of the mechanisms are possible. 5. On present evidence, no single mechanism has unequivocal support. We discuss reasons why this might be the case.

http://www.britishecologicalsociety.org/100papers/100_Ecological_Papers/100_Influential_Papers_084.pdf

Interspecific abundance-range size relationships: An appraisal of mechanisms

Preface 1. Biology and its philosophy 2. Autonomy and provincialism 3. Teleology and the roots of autonomy 4. Reductionism and the temptation of provincialism 5. The structure of evolutionary theory 6. Fitness 7. Species 8. New problems of functionalism Bibliography Index.

The Structure of Biological Science.

Explanation of the patterns of species abundances is important because it may help in understanding mechanisms structuring communities. A general conceptual model is proposed and examined as an alternative to previous propositions, which focused too narrowly on specific mechanisms. According to this model, viewing the structure of an environment as a nested hierarchy of habitat units provides a general mechanism sufficient to account for empirically established regularities in species abundances. Various biotic and abiotic factors can be considered as specific mechanisms sorting biological components into respective levels and compartments of the hierarchical structure of the environment. Because "sizes" of these compartments vary in a predictable way as a function of their position in the hierarchy, so should the abundances. The model may provide a conceptual framework that allows evaluation of the relative contributions of competition, predation, and other biological interactions. The operational and highly simplified version of the model uses spatial or temporal measures of ecological ranges of species to facilitate testing of the general model. The operational model makes three qualitative and quanti- tative predictions: (1) although the species display a continuous gradation of properties, the nested hierarchy of habitat units should lead to clustering of species at distinct levels; (2) generalists should be relatively more successful than specialists; (3) relative abundances of species should be predictable from their position in the hierarchical structure. An analysis of eight communities, including flatworms, aquatic insects, foraminiferans, rodents, and birds, supports these predictions. The clusters, or "breaks" in community structure, appear to be a new and possibly general property. Moreover, quantitative predictions of relative abundances for these communities are in surprisingly good agreement with the actual abundances. A hierarchical structure of the environment appears promising in accounting for some poorly explained community-level phenomena, such as correlation between the species range and abundance, and differences between abundance structures of communities in rigorous and less severe environments. The model is compatible with commonly ob- served as well as irregular patterns of distribution of species abundances, with high local abundance of some species, with differentiation of extinction probabilities, and with scale dependence of ecological phenomena.

Jerzy Kolasa

Papers

Ecological Systems in Hierarchical Perspecitive: Breaks in Community Structure and Other Consequences