Abstract We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudinal patterns in richness and community composition between main stem and tributary sites, and 2) to determine the relative importance of the replacement and richness difference component for overall beta diversity and of environmental versus spatial distance on beta diversity among main stem and tributary sites. In total 138 taxa were identified. There were no differences between main stem and tributary sites in mean abundance or taxon richness (67 and 58, respectively). A nMDS and ANOSIM based on Bray-Curtis similarities found no separation of main stem and tributary sites, but that upper (≥880 m a.s.l) and lower sites (≤680 m a.s.l.) formed two different groups. In both main stem and tributaries taxon richness increased only slightly going downstream while the community composition (DCA1) was much better explained by altitude and distance from source. Overall, beta diversity (Sorensen and Bray-Curtis dissimilarity) was similar for the two groups, and total Sorensen dissimilarity was driven mainly by replacement in main stem (78 %) and tributary sites (77 %). Mantel tests showed that main stem dissimilarities were significantly correlated to environmental PCA distance, watercourse distance, overland distance and altitudinal differences. Tributary dissimilarities were not correlated to any of these four factors. GLMs showed that dissimilarity among main stem sites was explained only by altitude difference, while no factors were significant among tributary sites, even though nearly so for environmental PCA distance. The study illustrates the importance of measuring beta diversity along ecological gradients, such as river continua and/or altitudinal gradients, where alpha diversity may fail to detect relatively minor changes in assemblage composition. Such changes are likely to occur due to present and future climate warming.

中文翻译：

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前高山河流主要干流和支流的大型无脊椎动物群落：组成对海拔有反应，丰富度没有

摘要 我们在 13 个地点收集了大型无脊椎动物的定量样本并测量了环境和地理参数：6 个沿主干，7 个位于靠近主河道的支流，海拔高度为 700 m，沿斯洛文尼亚阿尔卑斯山的 Kokra 河纵向距离为 22 km。 . 我们的目标是 1) 比较主干和支流站点之间丰富度和群落组成的纵向模式，以及 2) 确定替换和丰富度差异组件对整体 β 多样性以及环境与空间距离​​对 β 多样性之间的相对重要性。主干和支流部位。总共确定了 138 个分类群。在平均丰度或分类群丰富度方面，主干和支流站点之间没有差异（分别为 67 和 58）。基于 Bray-Curtis 相似性的 nMDS 和 ANOSIM 没有发现主干和支流位点的分离，但上位点（≥880 m asl）和下位点（≤680 m asl）形成了两个不同的组。在主干和支流中，分类群丰富度在下游仅略有增加，而群落组成 (DCA1) 可以用海拔和距源的距离更好地解释。总体而言，两组的β多样性（Sorensen 和 Bray-Curtis 差异）相似，总的 Sorensen 差异主要是由主茎（78%）和支流部位（77%）的更替驱动的。Mantel试验表明，主干差异与环境PCA距离、水道距离、陆上距离和海拔差异显着相关。支流差异与这四个因素中的任何一个都不相关。GLM 表明，主干部位之间的差异仅用海拔差异来解释，而支流部位之间没有显着因素，尽管环境 PCA 距离几乎如此。该研究说明了沿生态梯度测量 β 多样性的重要性，例如河流连续体和/或海拔梯度，其中 α 多样性可能无法检测到组合组成中相对较小的变化。由于当前和未来的气候变暖，这些变化很可能发生。例如河流连续体和/或海拔梯度，其中阿尔法多样性可能无法检测到组合组成中相对较小的变化。由于当前和未来的气候变暖，这些变化很可能发生。例如河流连续体和/或海拔梯度，其中阿尔法多样性可能无法检测到组合组成中相对较小的变化。由于当前和未来的气候变暖，这些变化很可能发生。