Analysing body condition: mass, volume or density?
Analysing body condition: mass, volume or density?
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DOI：
10.1111/j.1365-2656.2008.01433.x
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发表时间：
2008-11-01
影响因子：
4.8
通讯作者：
Fernandez-Montraveta, Carmen
中科院分区：
文献类型：
--
作者：
Moya-Larano, Jordi;Macias-Ordonez, Rogelio;Fernandez-Montraveta, Carmen
1.身体状况(定义为体内能量储备的相对数量)是一种具有强烈生态影响的动物特征。在一些动物类群(如节肢动物)中，储存大部分营养物质的身体部分(如腹部)的外部体积可与身体质量互换使用来估计身体状况，从而隐含地假设腹部剩余体积是剩余质量的良好替代。然而，这两个指标之间的相关程度在很大程度上应该取决于储存的营养物质的密度。我们模拟了两组添加食物的实验动物，每组动物在腹部或全身储存的脂类略有不同，并探索(I)对条件的不同估计如何能够检测到组之间的固定差异；以及(Ii)储存的脂类的量如何影响对两个变量(例如，存活、交配成功)的非侵入性条件测量的结果。我们发现，密度身体状态(身体质量，根据结构性身体大小和身体体积进行统计控制)比经典的质量/大小或体积/大小条件指标具有更大的能力来检测实验组之间的差异或对二元反应变量的影响。利用狼蛛Lycoa tarantula(L.)的数据，我们报告了这三个指数在检测成熟期摄食处理对身体状况影响的性别差异方面的显著差异。特别是，反映营养密度的残留量与残留量的曲线图表明，喂食不足的蜘蛛在营养上是不平衡的，因为喂食良好的蜘蛛投资于密度非常不同的养分。此外，利用黄粪蝇Scuphaga stercoraria(L.)的数据，我们发现密度条件指数在区分三个种群之间的条件差异方面比单用质量或体积条件估计更好。我们认为，包括这三个条件(质量、体积和密度)的替代物将大大提高对身体条件的非侵入性估计的准确性，从而提供更强大的工具，直接应用于广泛的学科。
1. Body condition (defined as the relative amount of energy reserves in the body) is an animal trait with strong ecological implications. In some animal taxa (e.g. arthropods), the external volume of the body part in which most nutrients are stored (e.g. abdomen) is used interchangeably with body mass to estimate body condition, making the implicit assumption that abdomen residual volume is a good surrogate of residual mass. However, the degree of correlation between these two measures should largely depend on the density of the nutrients stored.2. We simulated two food-supplemented experimental groups of animals, each storing a slightly different amount of lipids either in their abdomens or in their entire bodies, and explored (i) how different estimates of condition were able to detect fixed differences between the groups; and (ii) how the amount of lipids stored could affect the outcome of non-intrusive measures of condition on a dichotomous variable (e.g. survival, mating success). We found that density body condition (body mass statistically controlled for structural body size and body volume) has much greater power to detect differences between experimental groups or effects on binary response variables than do classic mass/size or volume/size condition indices.3. Using data on Lycosa tarantula (L.), a burrowing wolf spider, we report dramatic differences among these three indices in their ability to detect sex differences in the effect of feeding treatment on body condition at maturity. In particular, a plot of residual mass against residual volume reflecting nutrient density suggests that poorly fed spiders are nutritionally unbalanced, since well-fed spiders invest in nutrients of very different density.4. Furthermore, using data on Scathophaga stercoraria (L.), the yellow dung fly, we found that an index of density condition was better at distinguishing condition differences among three populations than were mass or volume condition estimates alone.5. We propose that including these three surrogates of condition (mass, volume and density) will substantially improve the accuracy of non-intrusive estimates of body condition, thus providing more powerful tools with direct application in a wide range of disciplines.