Dragonflies (Odonata: Anisoptera) are often used as indicators of habitat type and quality due to their varied use of aquatic and terrestrial habitats. Species differ in their preferences for lotic and lentic waters, but community changes across ecotones, or transitional zones between distinct habitats (e.g. lotic and lentic), are not well understood. We quantified dragonfly species richness, abundance, and composition along a gradient of habitat types, including streams, stream mouths (ecotones), and open waters (lakes and ponds). We tested if dragonfly assemblages in aquatic ecotones differ from adjacent stream and open water habitats, and how species respond to riparian forest cover across these habitat types. Adult dragonflies were sampled in all habitat types at four sites in southwest Ohio during the summer of 2016. Riparian canopy cover and relative densities of algal mats and emergent vegetation were recorded. We sampled 157 individuals of 12 dragonfly species and found significant differences in community composition between stream and ecotone habitats, both forming subsets of the open water community. Canopy cover explained 55% and 75% of abundance and species richness variance across habitat types, respectively, but these relationships were strongest at ecotones. Finally, the Odonata Index of Wetland Integrity (OIWI), which uses sensitivities of adult odonates to habitat disturbances to evaluate wetland conditions, showed that species composition at ecotones uniquely represents the ecological integrity of the entire wetland system. Thus, transition zones may provide an effective and more efficient alternative to rapidly assess wetland quality for conservation monitoring than sampling the entire wetland.

中文翻译：

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蜻蜓群落结构跨水生生态系统的变化

蜻蜓（Odonata：Anisoptera）由于对水生和陆生栖息地的不同利用，经常被用作栖息地类型和质量的指标。物种对激流和滞流水的偏好不同，但跨生态系统或不同栖息地（例如激流和滞流）之间的过渡区的群落变化尚不清楚。我们沿着栖息地类型的梯度量化了蜻蜓物种的丰富度、丰度和组成，包括溪流、溪流口（生态系统）和开阔水域（湖泊和池塘）。我们测试了水生交错带中的蜻蜓组合是否与邻近的溪流和开阔水域栖息地不同，以及物种如何对这些栖息地类型的河岸森林覆盖做出反应。2016 年夏季，在俄亥俄州西南部的四个地点对所有栖息地类型的成年蜻蜓进行了采样。记录了河岸冠层覆盖以及藻垫和挺水植被的相对密度。我们对 12 种蜻蜓物种的 157 个体进行了采样，发现溪流和交错带栖息地之间的群落组成存在显着差异，两者都形成了开阔水域群落的子集。冠层盖度分别解释了栖息地类型之间 55% 和 75% 的丰度和物种丰富度差异，但这些关系在交错带中最强。最后，Odonata Index of Wetland Integrity (OIWI) 使用成虫对栖息地干扰的敏感性来评估湿地条件，表明交错带的物种组成独特地代表了整个湿地系统的生态完整性。因此，