Abstract：
Body size is one of the main characteristics of any organism and influences various aspects of individual\'s biology. In animal ecology, it represents a key functional trait that can be quantified using different measures and is often used as a proxy for different organismal functions. The way we quantify body size is critical in any study using this measure alone or to scale other organismal traits. It is especially important in groups that act as model systems across different fields of biological research. One of such groups are amphipods, which are at focus in many ecological studies where appropriate quantification of body size is needed. Here, we explored the relationship between body length and body mass in the largest freshwater amphipod genus Niphargus, and evaluated whether the two measures lead to different conclusions in a putative ecological study of species coexistence. We selected 16 species inhabiting two different subterranean habitats, cave lakes and cave streams. The relationship between log-transformed body mass and body length was linear in all species, but body mass increased steeper among species from cave lakes than from cave streams, reflecting the stouter body shape of the former. In the simulated ecological study, the comparisons of the two measures showed that they may yield different results: in 10 % of cases, body length detected differences between species when body mass did not and vice versa (13 %). Usage of body length or body mass can thus lead to different conclusions. We recommend avoiding direct transformations between body length and body mass in ecological studies. Whenever needed, such transformations should be done with caution using habitat-specific body mass - body length ratios.
摘要：
体型是任何生物体的主要特征之一，影响个体生物学的各个方面。在动物生态学中,它代表了一个关键的功能特征，可以使用不同的度量来量化，并且经常被用作不同的有机功能的代理。我们量化身体大小的方式在任何单独使用这种措施或缩放其他有机体特征的研究中都是至关重要的。在作为生物研究不同领域的模型系统的群体中，这一点尤其重要。其中一个群体是两栖动物，这是许多需要适当量化身体大小的生态研究的重点。这里,我们探索了最大的淡水两栖动物属NiPhargus的体长与体重之间的关系，并评估了这两种措施在假定的物种共存生态学研究中是否会得出不同的结论。我们选择了居住在两个不同地下栖息地的16个物种，洞穴湖泊和洞穴溪流。在所有物种中，对数变换的体重与体长之间的关系是线性的，但是来自洞穴湖泊的物种的体重比来自洞穴溪流的物种增加得更陡，反映前者的稳定身体形状。在模拟生态研究中，这两种措施的比较表明，它们可能会产生不同的结果:在10%的情况下，当体重没有时，体长在物种之间检测到差异，反之亦然(13%)。因此，使用身长或体重可以得出不同的结论。我们建议在生态研究中避免体长和体重之间的直接转换。每当需要时，这种转换应谨慎使用特定栖息地的体重-体长比进行。
