The River Continuum Concept (RCC) predicts that aquatic insect communities undergo predictable changes in composition from headwaters to downstream regions relative to changes in habitat. An important aspect of this change is stream temperature. Studies have been conducted on thermal partitioning of chironomids within the RCC and across streams with different thermal regimes; however, few have focused on effects of fine-scale within-stream temperature variability on winter chironomid composition. Our objectives were to characterize thermal heterogeneity within a small headwater trout stream during winter using slope and Y-intercepts from linear regressions of air–water temperatures and to document patterns of chironomid emergence and taxonomic composition relative to mean water temperatures, regression slopes, and Y-intercepts along stream length. We developed air–water temperature regressions using mean daily air and water temperatures for three headwater trout streams. We assessed similarity in taxonomic composition across sites by collecting and analyzing chironomid surface floating pupal exuviae. We demonstrate that regressions of mean daily air and water temperatures can characterize fine-scale thermal heterogeneity within and among headwater trout streams during winter. We also demonstrate that chironomid taxonomic composition varied at spatial scales substantially less than a kilometer within a stream that possessed significant thermal heterogeneity.

中文翻译：

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冬季河流内温度梯度对摇蚊出现的影响

河流连续体概念 (RCC) 预测，相对于栖息地的变化，水生昆虫群落从上游到下游地区的组成会发生可预测的变化。这种变化的一个重要方面是流温度。已经对 RCC 内和不同热态的溪流中摇蚊的热分配进行了研究；然而，很少有人关注细尺度河流内温度变化对冬季摇蚊组成的影响。我们的目标是利用气温-水温线性回归的斜率和 Y 截距来表征冬季小河源鳟鱼流内的热异质性，并记录摇蚊出现的模式和相对于平均水温、回归斜率和 Y 的分类组成- 沿流长度截取。我们使用三个源头鳟鱼流的每日平均气温和水温开发了空气-水温回归。我们通过收集和分析摇蚊表面漂浮的蛹蜕皮来评估不同地点的分类组成的相似性。我们证明，日平均气温和水温的回归可以表征冬季上游鳟鱼流内部和之间的精细热异质性。我们还证明了摇蚊的分类组成在具有显着热异质性的溪流内的空间尺度上变化远小于一公里。我们通过收集和分析摇蚊表面漂浮的蛹蜕皮来评估不同地点的分类组成的相似性。我们证明，日平均气温和水温的回归可以表征冬季上游鳟鱼流内部和之间的精细热异质性。我们还证明了摇蚊的分类组成在具有显着热异质性的溪流内的空间尺度上变化远小于一公里。我们通过收集和分析摇蚊表面漂浮的蛹蜕皮来评估不同地点的分类组成的相似性。我们证明，日平均气温和水温的回归可以表征冬季上游鳟鱼流内部和之间的精细热异质性。我们还证明了摇蚊的分类组成在具有显着热异质性的溪流内的空间尺度上变化远小于一公里。