Department of Ecology, Biology Institute, P.O. Box 68020, Federal University of Rio de Janeiro, Ilha do Fundao, Rio de Janeiro, RJ, Brazil.
Ecology. 2012 Jul;93(7):1752-9. doi: 10.1890/11-1144.1.
After much debate, there is an emerging consensus that the composition of many ecological communities is determined both by species traits, as proposed by niche theory, as well as by chance events. A critical question for ecology is, therefore, which attributes of species predict the dominance of deterministic or stochastic processes. We outline two hypotheses by which organism size could determine which processes structure ecological communities, and we test these hypotheses by comparing the community structure in bromeliad phytotelmata of three groups of organisms (bacteria, zooplankton, and macroinvertebrates) that encompass a 10 000-fold gradient in body size, but live in the same habitat. Bacteria had no habitat associations, as would be expected from trait-neutral stochastic processes, but still showed exclusion among species pairs, as would be expected from niche-based processes. Macroinvertebrates had strong habitat and species associations, indicating niche-based processes. Zooplankton, with body size between bacteria and macroinvertebrates, showed intermediate habitat associations. We concluded that a key niche process, habitat filtering, strengthened with organism size, possibly because larger organisms are both less plastic in their fundamental niches and more able to be selective in dispersal. These results suggest that the relative importance of deterministic and stochastic processes may be predictable from organism size.
经过长时间的争论，人们逐渐达成共识，即许多生态群落的组成既取决于物种特征（如生态位理论所提出的），也取决于偶然事件。因此，生态学的一个关键问题是，物种的哪些属性可以预测确定性或随机性过程的主导地位。我们概述了两个假设，即生物体大小可以决定哪些过程来构建生态群落，我们通过比较栖息在三种生物体（细菌、浮游动物和大型无脊椎动物）中的凤梨科植物水塔中的群落结构来检验这些假设，这三种生物体的体型差异可达 10000 倍，但生活在相同的栖息地中。细菌没有栖息地关联，这与基于特征的随机过程是一致的，但仍表现出物种对之间的排斥，这与基于生态位的过程是一致的。大型无脊椎动物具有强烈的栖息地和物种关联，表明存在基于生态位的过程。浮游动物的体型介于细菌和大型无脊椎动物之间，表现出中等程度的栖息地关联。我们得出结论，一个关键的生态位过程，即栖息地过滤，随着生物体大小的增强而增强，这可能是因为较大的生物体在其基本生态位上的可塑性较小，在扩散时的选择性更强。这些结果表明，确定性和随机性过程的相对重要性可能可以从生物体大小来预测。
