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Hierarchy underlies patterns of variability in species inhabiting natural microcosms

Kolasa, J., Drake, J.A., Huxel, G.R. and Hewitt, C.L. (1996) Hierarchy underlies patterns of variability in species inhabiting natural microcosms. Oikos, 77 (2). pp. 259-266.

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Relative variability of species has been shown to increase significantly with a decrease in their ecological range. Similarly, the distribution of collapse (e.g., extinctions, disturbances, population declines) magnitudes has also been shown to follow an inverse power-law form described by the 1/f ω curve. We hypothesized that the two, possibly general, patterns associated with ecological systems share a common underlying cause: the hierarchical structure of the system itself. To test the hypothesis we used a model system of 49 natural rock pools inhabited by 40 species of invertebrates. Three measures of species variability based on changes in abundance, distribution, and persistence in individual pools conform with the postulated negative exponential curves. Correspondingly, frequency distributions of changes of various magnitudes conform to the 1/f ω pattern. Examination of the contributions of species to the 1/f ω pattern revealed that species low in the system hierarchy (habitat specialists in this case) are responsible for the majority of small variation events (correlations between the ecological range and position on the 1/f ω curve range from 0.625 to 0.807 on the three measures of variability). This permits the conclusion that the two patterns are linked and constitute different expressions of the same hierarchical system structure.

Item Type: Journal Article
Publisher: Blackwell Publishing Inc.
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