Posted by: oikosasa | February 26, 2013

Top of the Pops

One of the most cited papers in Oikos, during 2011 (published 2009 and 2010) is “New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method“, by J Peig and AJ Green.

Here, Jordi Peig gives a short summary of the paper and an explanation to it’s impact:

Jordi and Andy

Body condition (physical or nutritional status) is a widespread concept in the ecological literature. Although usually poorly defined, it encapsulates the animal’s health, quality and vigour, and hence its biological fitness. Scientists have used different approaches to estimate BC, but those based on morphometry and particularly on mass-length relationships have been adopted for routine use due to the ease of application and their ‘a priori’ conceptual simplicity. Briefly, morphometric indices attempt to quantify how heavy is an organism for a given body size, because the extra mass indicates more fat and protein reserves to overcome periods of food scarcity or high energy demand in general. However, larger animals will be inherently heavier, and vice versa, so the standardization of body size is the central challenge that underlies all morphometric methods, and is the subject of our paper. Many mathematical formulas and statistical methods have been proposed to standardise body size, yet there is still much debate among scientists as to the most suitable method.

The work published in Oikos has been popular partly because so many studies included attempts to establish the influence of body condition in population ecology. The idea of the paper was born in 2006 when distinct BC indices reported in the literature yielded opposite results when applied to my own data on small mammals. I found that those contradictory results were each scientifically plausible and arguable from an ecological viewpoint, hence the need to rethink the nature of these methods. After reading in and around the subject, including biostatistics, theoretical biology and epidemiology, I conceived the Scaled mass index. Because of the intrinsic tendency within sciences towards specialization, different disciplines have promoted and advocated their own methods (including the Body Mass Index used in medicine), and I searched for a common, unifying approach. With this complexity in mind, and the difficulty of publishing in this area for a PhD student (introducing alternative methods inevitably meets some scepticism and resistance) led me to seek collaboration with my co-author Andy Green, who had previously published in this field. From our first contact by email Andy was enthusiastic, and made substantial improvements to the manuscript. My original draft was prohibitively long for modern journals, and part of it went into a sister paper in Functional Ecology in 2010.

In the Oikos paper we attempt to explain the complexity of the BC issue from the fundamental viewpoint of allometric growth, and develop the Scaled Mass Index from that perspective. Amongst the papers that have cited our work, there are good independent examples of how our index outperforms previous methods. We can only hope that our future contributions on this topic become as successful as the Oikos’ paper.


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