Finnish Environment Institute, University of Oulu, P.O. Box 413, FI-90014 Oulu, Finland.
J Anim Ecol. 2012 May;81(3):679-91. doi: 10.1111/j.1365-2656.2011.01938.x. Epub 2012 Jan 4.
1. A fundamental question in ecology is which factors determine species richness. Here, we studied the relative importance of regional species pool and local environmental characteristics in determining local species richness (LSR). Typically, this question has been studied using whole communities or a certain taxonomic group, although including species with widely varying biological traits in the same analysis may hinder the detection of ecologically meaningful patterns. 2. We studied the question above for whole stream macroinvertebrate community and within functional feeding guilds. We defined the local scale as a riffle site and the regional scale (i.e. representing the regional species pool) as a stream. Such intermediate-sized regional scale is rarely studied in this context. 3. We sampled altogether 100 sites, ten riffles (local scale) in each of ten streams (regional scale). We used the local-regional richness regression plots to study the overall effect of regional species pool on LSR. Variation partitioning was used to determine the relative importance of regional species pool and local environmental conditions for species richness. 4. The local-regional richness relationship was mainly linear, suggesting strong species pool effects. Only one guild showed some signs of curvilinearity. However, variation partitioning showed that local environmental characteristics accounted for a larger fraction of variance in LSR than regional species pool. Also, the relative importance of the fractions differed between the whole community and guilds, as well as among guilds. 5. This study indicates that the importance of the local and regional processes may vary depending on feeding guild and trophic level. We conclude that both the size of the regional species pool and local habitat characteristics are important in determining LSR of stream macroinvertebrates. Our results are in agreement with recent large-scale studies conducted in highly different study systems and complement the previous findings by showing that the interplay of regional and local factors is also important at intermediate regional scales.
生态学中的一个基本问题是哪些因素决定了物种丰富度。在这里，我们研究了区域物种库和局部环境特征在决定局部物种丰富度（LSR）方面的相对重要性。通常，这个问题是通过整个群落或特定分类群来研究的，尽管在同一分析中包括具有广泛不同生物学特征的物种可能会阻碍对生态有意义的模式的检测。
我们在整个溪流大型无脊椎动物群落和功能摄食群内研究了上述问题。我们将局部尺度定义为急流点，将区域尺度（即代表区域物种库）定义为溪流。在这种情况下，很少研究这种中等规模的区域尺度。
我们总共采样了 100 个地点，每个溪流（区域尺度）有 10 个急流点（局部尺度）。我们使用局部-区域丰富度回归图来研究区域物种库对 LSR 的总体影响。方差分割用于确定区域物种库和局部环境条件对物种丰富度的相对重要性。
局部-区域丰富度关系主要是线性的，表明物种库效应很强。只有一个群体显示出一些曲线性的迹象。然而，方差分割表明，局部环境特征对 LSR 的方差的解释程度大于区域物种库。此外，局部和区域过程的相对重要性因群落和群而异，以及群之间也不同。
这项研究表明，局部和区域过程的重要性可能因摄食群和营养水平而异。我们得出结论，区域物种库的大小和局部栖息地特征对于确定溪流大型无脊椎动物的 LSR 都很重要。我们的结果与最近在高度不同的研究系统中进行的大规模研究一致，并通过表明区域和局部因素的相互作用在中等区域尺度上也很重要，补充了以前的发现。
