Specific concepts of fluvial ecology are well studied in riverine ecosystems of the temperate zone but poorly investigated in the Afrotropical region. Hence, we examined the longitudinal zonation of fish and adult caddisfly (Trichoptera) assemblages in the endorheic Awash River (1,250 km in length), Ethiopia. We expected that species assemblages are structured along environmental gradients, reflecting the pattern of large-scale freshwater ecoregions. We applied multivariate statistical methods to test for differences in spatial species assemblage structure and identified characteristic taxa of the observed biocoenoses by indicator species analyses. Fish and caddisfly assemblages were clustered into highland and lowland communities, following the freshwater ecoregions, but separated by an ecotone with highest biodiversity. Moreover, the caddisfly results suggest separating the heterogeneous highlands into a forested and a deforested zone. Surprisingly, the Awash drainage is rather species-poor: only 11 fish (1 endemic, 2 introduced) and 28 caddisfly species (8 new records for Ethiopia) were recorded from the mainstem and its major tributaries. Nevertheless, specialized species characterize the highland forests, whereas the lowlands primarily host geographically widely distributed species. This study showed that a combined approach of fish and caddisflies is a suitable method for assessing regional characteristics of fluvial ecosystems in the tropics.

中文翻译：

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热带地区的纵向河流分区：埃塞俄比亚内陆阿瓦什河的鱼类和石蛾的例子

河流生态学的具体概念在温带的河流生态系统中得到了很好的研究，但在亚热带地区的研究却很少。因此，我们研究了埃塞俄比亚内陆阿瓦什河（长 1,250 公里）中鱼类和成虫（毛翅目）组合的纵向分带。我们预计物种组合是沿着环境梯度构建的，反映了大规模淡水生态区的模式。我们应用多元统计方法来测试空间物种组合结构的差异，并通过指示物种分析确定观察到的生物群落的特征类群。跟随淡水生态区，鱼类和石蛾群落聚集成高地和低地群落，但被生物多样性最高的交错带隔开。而且，caddisfly 的结果表明，将异质高地分为森林区和森林砍伐区。令人惊讶的是，阿瓦什河的水系物种相当贫乏：在主干及其主要支流中只记录了 11 种鱼类（1 种地方性，2 种引入）和 28 种石蛾（埃塞俄比亚有 8 种新记录）。然而，特殊物种是高地森林的特征，而低地主要是地理上分布广泛的物种。这项研究表明，鱼和石蛾的组合方法是评估热带河流生态系统区域特征的合适方法。2 种）和 28 种石蛾（埃塞俄比亚有 8 种新记录）来自主干及其主要支流。然而，特殊物种是高地森林的特征，而低地主要是地理上分布广泛的物种。这项研究表明，鱼和石蛾的组合方法是评估热带河流生态系统区域特征的合适方法。2 种）和 28 种石蛾（埃塞俄比亚有 8 种新记录）来自主干及其主要支流。然而，特殊物种是高地森林的特征，而低地主要是地理上分布广泛的物种。这项研究表明，鱼和石蛾的组合方法是评估热带河流生态系统区域特征的合适方法。