Salinity is a limiting factor for many invertebrates, especially for Odonata which are typically associated with freshwater ecosystems. In Europe, 15 Odonata species inhabit brackish wetlands and only few detailed data on their tolerance towards salinity are available. We investigated Odonata fauna in 11 sampling stations situated in three estuarine areas (northern Adriatic coastline) which differed in salinity conditions (freshwater- polyhaline habitats) in order to assess affinity of Odonata species to brackish habitats and to describe their distribution pattern in coastal wetlands. Adults, exuviae (the remains of the exoskeleton after the last larval instar), and the main chemical and physical water parameters were sampled every 2 weeks for 1 year in each station. In total, 25 species were detected and 56% of them were able to complete their life cycle in brackish water environments. Our results showed that freshwater and oligohaline ponds were the most favorable for dragonflies, with an overall higher species richness. There was a high species turnover along the salinity gradient, with a strong differentiation among the communities along the gradient. Considering the exuviae, we observed a high specificity with respect to the habitat conditions (seven species exclusive of freshwater sites and six of oligohaline ones, respectively). Among the adults, four species were found exclusively in freshwater habitats and no species seemed to be strictly connected with oligohaline habitats. Coastal wetlands are composed by a mosaic of different habitats especially when freshwater and seawater are close together, supporting many Odonata species with different tolerance toward salinity conditions. They also provide useful insights for conservation and management actions.

中文翻译：

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混合盐沿海湿地的蜻蜓（蜻蜓目）多样性模式

盐度是许多无脊椎动物的限制因素，尤其是对于通常与淡水生态系统有关的蜻蜓目。在欧洲，有15种Odonata物种生活在微咸的湿地中，仅有很少的关于其耐盐碱性的详细数据。我们评估了三个盐度条件不同的河口地区（北亚得里亚海海岸线）的11个采样站的Odonata动物区系，这些盐度条件不同（淡水-多盐类栖息地），以便评估Odonata物种对咸淡生境的亲和力并描述它们在沿海湿地中的分布方式。在每个站点中，每隔2周对成虫，足孔虫（末龄幼虫后的外骨骼残骸）以及主要的化学和物理水参数进行采样，为期1年。总共，发现了25种，其中56％能够在微咸水环境中完成其生命周期。我们的结果表明，淡水和寡盐塘最适合蜻蜓，总体物种丰富度更高。沿盐度梯度的物种周转率很高，沿梯度的群落间差异很大。考虑到u虫，我们观察到了对栖息地条件的高度特异性（分别为七个物种，不包括淡水站点和六个，分别属于淡水站点）。在成年动物中，仅在淡水生境中发现了四个物种，似乎没有物种与寡盐生境严格相关。沿海湿地由不同栖息地的马赛克组成，特别是在淡水和海水靠近的时候，支持许多对盐分条件具有不同耐受性的蜻蜓目物种。它们还为保护和管理行动提供了有用的见解。