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Effects of Organismal and Distance Scaling on Analysis of Species Distribution and Abundance
Scott L. Collins and Susan M. Glenn
Vol. 7, No. 2 (May, 1997), pp. 543-551
Stable URL: http://www.jstor.org/stable/2269519
Page Count: 9
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As communities and populations become increasingly fragmented, much theoretical and some empirical research has focused on the dynamics of metapopulations. Many metapopulation models describe dynamics among populations in a region, yet the scale of the "region" to which different models apply often is undefined. Because the spatial scale is undefined, testing predictions and assumptions of these models is problematic. Our goal is to present two scaling concepts relevant to these models, distance scaling and organismal scaling, and to apply these scaling notions to patterns of species distribution. To determine distance effects, we analyzed patterns of distribution of four taxonomic groups in tallgrass prairie (grasshoppers, small mammals, vascular plants, and breeding birds) at two spatial scales. To asses organismal effects, we held spatial scale constant and we compared patterns of distribution and abundance among these taxonomic groups. Using long-term data from Konza Prairie, Kansas, there were significant differences in the pattern of distribution of grasshoppers, small mammals, vascular plants, and breeding birds within a single spatial scale. The number of core species (species occupying >90% of the sites in a region) of plants and birds was less than the number of satellite species (those occupying <10% of the sites in a region). The opposite was true for grasshoppers and small mammals. All four distribution patterns were significantly nonrandom, but only grasshoppers and small mammals were significantly bimodal at this scale. Plants and birds were unimodal. The patterns of distribution within these taxonomic groups at two spatial scales were significantly different as well. In all cases, the percentage of species in the core group declined, and the percentage of species in the satellite group increased as spatial scale increased. These results demonstrate the difficulty of testing theoretical models with only one taxonomic group at a single spatial scale. One should not accept or reject a model until the spatial domains of organismal and distance scaling have been properly evaluated.
Ecological Applications © 1997 Wiley