Context

Understanding the specific natural and anthropogenic drivers of aquatic insect assemblages and feeding ecology is critical to managing aquatic ecosystems. Utilizing the counts of benthic specimens found in most studies is suboptimal due to sampling difficulties, lack of taxonomic resolution, and the tacit assumption that specimens of all sizes are ecologically equivalent. These problems may be overcome by measuring the biomass of winged adults instead.

Objectives

This study quantified the importance of natural and anthropogenic variables affecting adult caddisflies in the north-central United States in habitats ranging from designated wilderness to intense agriculture.

Methods

Nearly 650 streams were sampled throughout a 1.2 million km² area. The relative ability of 52 variables to predict (1) caddisfly species assemblages and (2) functional feeding group (FFG) biomass was assessed.

Results

The percentage of intact habitat, particularly at the whole-watershed scale, was most effective at predicting both metrics. The biomass of all FFGs except filtering collectors, and that of 85% of species, decreased as intact habitat decreased. Assemblages of least disturbed streams, conversely, were primarily affected by gradient and width, and generally followed patterns of river continuity. In all streams, increasing stream temperatures associated with decreasing intact habitat led to decreasing species richness; whereas increasing temperatures associated with decreasing gradient or increasing width in least disturbed streams led to increasing species richness.

Conclusions

Natural variables are important predictors of caddisfly assemblages in undisturbed streams; however, habitat loss overwhelms such variables throughout much of the north-central US, leading to declines in nearly all species.

中文翻译：

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如果一棵树倒在森林里：陆地栖息地的丧失可以预测美国中北部河流中的石蛾（昆虫纲：毛翅目）组合和功能性摄食群生物量

语境

了解水生昆虫组合和摄食生态的特定自然和人为驱动因素对于管理水生生态系统至关重要。由于取样困难、缺乏分类分辨率以及各种大小的标本在生态上是等效的默认假设，因此利用大多数研究中发现的底栖标本的数量是次优的。这些问题可以通过测量有翅成虫的生物量来解决。

目标

这项研究量化了自然和人为变量在美国中北部从指定的荒野到密集的农业栖息地影响成年石蛾的重要性。

方法

整个1200000公里近650流取样²区。评估了 52 个变量预测 (1) 石蛾物种组合和 (2) 功能性饲养组 (FFG) 生物量的相对能力。

结果

完整栖息地的百分比，特别是在整个流域范围内，在预测这两个指标方面最有效。除了过滤收集器外，所有 FFG 的生物量以及 85% 的物种的生物量随着完整栖息地的减少而减少。相反，受干扰最少的溪流集合主要受坡度和宽度的影响，并且通常遵循河流连续性的模式。在所有河流中，随着完整栖息地的减少，河流温度升高导致物种丰富度下降；而在最少受干扰的河流中，随着梯度的降低或宽度的增加，温度升高会导致物种丰富度增加。

结论

自然变量是未受干扰的溪流中石蛾组合的重要预测因子；然而，在美国中北部的大部分地区，栖息地丧失压倒了这些变量，导致几乎所有物种的数量减少。