Ecological communities are comprised of species that interact with each other and those interactions ultimately generate community structure. Network theory provides a useful framework to study communities, by simultaneously considering species composition and the interactions among species. In this study, I use mixed‐species flocks as model systems to gain insights on community and network structure. Specifically, I use co‐occurrence network analyses to explore if avian mixed‐species flocks change in richness and composition and/or in network structure and pair‐wise associations, across elevations in the tropical Andes of Bolivia. Networks of flocking species changed both in composition and in the frequency and realization of pair‐wise interactions across elevations, but changes in pair‐wise associations explained most of network turnover along elevation. Pair‐wise interactions changed rapidly, with shared species changing in position and importance within the network. Network dissimilarity was mostly explained by changes in the nature of associations rather than by differences in composition. Altogether, results show that montane mixed‐species flocks are composed of loosely connected species and that most species have the potential of switching associations, often increasing in association strength at high elevations (up to 3150 m). Networks increased in connectivity and cohesion with elevation; flocks in lower elevations had more connections and these were less even. Above 3150 m a.s.l., there was rapid decay suggesting that flocks above this critical point are less connected and cohesive. This study exemplifies how combining community, network and pair‐wise analyses can provide a more holistic view on the responses of species and assemblages to environmental gradients.

中文翻译：

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热带安第斯山脉高海拔地区鸟类混合物种的相互作用网络

生态群落是由相互相互作用的物种组成，这些相互作用最终产生了群落结构。网络理论通过同时考虑物种组成和物种之间的相互作用，为研究群落提供了有用的框架。在本研究中，我使用混合物种群作为模型系统来获取有关社区和网络结构的见解。具体而言，我使用共现网络分析来研究玻利维亚热带安第斯山脉高海拔地区禽类混合种群的丰富度和组成，网络结构和成对关联是否发生变化。成群物种的网络在组成和频率上都发生了变化，并且跨海拔的成对互动发生了变化，但成对关联的变化解释了沿海拔的大部分网络更新。成对互动迅速改变，共享物种在网络中的位置和重要性发生变化。网络不相似主要是由关联性质的变化而不是组成上的差异引起的。总体而言，结果表明，山地混合物种群由松散连接的物种组成，大多数物种具有转换关联的潜力，通常在高海拔（高达3150 m）时会增加关联强度。网络的连接性和与高度的凝聚力增加；海拔较低的羊群有更多的联系，而这些联系较少。在3150 m asl之上，出现快速衰减，表明该临界点以上的群之间的连接和凝聚力较小。