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Abstract：
Ecological monitoring of streams has often focused on assessing the biotic integrity of individual benthic macroinvertebrate (BMI) communities through local measures of diversity, such as taxonomic or functional richness. However, as individual BMI communities are frequently linked by a variety of ecological processes at a regional scale, there is a need to assess biotic integrity of groups of communities at the scale of watersheds. Using 4,619 sampled communities of streambed BMIs, we investigate this question using co-occurrence networks generated from groups of communities selected within California watersheds under different levels of stress due to upstream land use. Building on a number of arguments in theoretical ecology and network theory, we propose a framework for the assessment of the biotic integrity of watershed-scale groupings of BMI communities using measures of their co-occurrence network topology. We found significant correlations between stress, as described by a mean measure of upstream land use within a watershed, and topological measures of co-occurrence networks such as network size (r = -.81, p < 10-4), connectance (r = .31, p < 10-4), mean co-occurrence strength (r = .25, p < 10-4), degree heterogeneity (r = -.10, p < 10-4), and modularity (r = .11, p < 10-4). Using these five topological measures, we constructed a linear model of biotic integrity, here a composite of taxonomic and functional diversity known as the California Stream Condition Index, of groups of BMI communities within a watershed. This model can account for 66% of among-watershed variation in the mean biotic integrity of communities. These observations imply a role for co-occurrence networks in assessing the current status of biotic integrity for BMI communities, as well as their potential use in assessing other ecological communities.
摘要：
溪流的生态监测通常侧重于通过当地的多样性措施评估单个底栖大型无脊椎动物（BMI）群落的生物完整性，如分类学或功能丰富度。然而,由于各个BMI社区经常在区域范围内通过各种生态过程联系在一起，有必要在流域规模上评估社区群体的生物完整性。使用4,619个河床BMIs采样社区，我们使用从加利福尼亚州流域内选择的社区群体在上游土地利用造成的不同压力水平下产生的共现网络来调查这个问题。在理论生态学和网络理论的许多论点的基础上，我们提出了一个框架,用于评估BMI社区的分水岭尺度分组的生物完整性,使用测量其共现网络拓扑.我们发现压力之间存在显著的相关性，正如流域内上游土地利用的平均衡量标准所描述的那样，以及共现网络的拓扑度量，如网络大小(r=-.81，p<10-4)，连通性（r=.31，p<10-4），平均共生强度(r=.25，p<10-4)，程度异质性(r=-.10，p<10-4)，和模块化(r=.11，p<10-4)。使用这五个拓扑度量，我们构建了一个生物完整性的线性模型，这里是一种分类和功能多样性的组合，被称为加州河流状况指数，分水岭内的BMI社区群体。该模型可以占社区平均生物完整性分水岭间变化的66％。这些观察结果暗示了共现网络在评估BMI社区的生物完整性现状方面的作用。以及它们在评估其他生态社区中的潜在用途。
