|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online April 26, 2005
Journal of Experimental Biology 208, 1731-1747 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01566
Review article: Lifespan, reproduction and ecology |
Problems of allometric scaling analysis: examples from mammalian reproductive biology
1 Academic Affairs, The Field Museum, 1400 S. Lake Shore Drive, Chicago, IL
60605-2496, USA
2 Département d'Ecologie et d'Evolution, Université de
Lausanne, Bâtiment de Biologie, CH-1015 Lausanne, Switzerland
3 Centre for Ecology and Evolutionary Studies, University of Groningen,
Kerklaan 30, 9751 NN Haren, The Netherlands
* Author for correspondence (e-mail: rdmartin{at}fieldmuseum.org)
Accepted 2 March 2005
Summary
Biological scaling analyses employing the widely used bivariate allometric model are beset by at least four interacting problems: (1) choice of an appropriate best-fit line with due attention to the influence of outliers; (2) objective recognition of divergent subsets in the data (allometric grades); (3) potential restrictions on statistical independence resulting from phylogenetic inertia; and (4) the need for extreme caution in inferring causation from correlation. A new non-parametric line-fitting technique has been developed that eliminates requirements for normality of distribution, greatly reduces the influence of outliers and permits objective recognition of grade shifts in substantial datasets. This technique is applied in scaling analyses of mammalian gestation periods and of neonatal body mass in primates. These analyses feed into a re-examination, conducted with partial correlation analysis, of the maternal energy hypothesis relating to mammalian brain evolution, which suggests links between body size and brain size in neonates and adults, gestation period and basal metabolic rate. Much has been made of the potential problem of phylogenetic inertia as a confounding factor in scaling analyses. However, this problem may be less severe than suspected earlier because nested analyses of variance conducted on residual variation (rather than on raw values) reveals that there is considerable variance at low taxonomic levels. In fact, limited divergence in body size between closely related species is one of the prime examples of phylogenetic inertia. One common approach to eliminating perceived problems of phylogenetic inertia in allometric analyses has been calculation of `independent contrast values'. It is demonstrated that the reasoning behind this approach is flawed in several ways. Calculation of contrast values for closely related species of similar body size is, in fact, highly questionable, particularly when there are major deviations from the best-fit line for the scaling relationship under scrutiny.
Key words: best-fit lines, brain size, gestation period, grade shift, maternal energy hypothesis, metabolic scaling, non-parametric line fitting, neonatal body mass, outliers, phylogenetic inertia
Related articles in JEB:
This article has been cited by other articles:
|
|
 |
|
  E. Maranon Inter-specific scaling of phytoplankton production and cell size in the field J. Plankton Res., February 1, 2008; 30(2): 157 - 163. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Ryan, C. Knechtel, and W. Getz Ecological cues, gestation length, and birth timing in African buffalo (Syncerus caffer) Behav. Ecol., July 1, 2007; 18(4): 635 - 644. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Bejan and J. H. Marden Unifying constructal theory for scale effects in running, swimming and flying J. Exp. Biol., January 15, 2006; 209(2): 238 - 248. [Abstract] [Full Text] [PDF]
|
|
