Amazonian rivers have been proposed to act as geographic barriers to species dispersal, either driving allopatric speciation or defining current distribution limits. The strength of the barrier varies according to the species’ ecological characteristics and the river's physical properties. Environmental heterogeneity may also drive compositional changes but has not been well assessed in Amazonia. Aiming to understand the contributions of riverine barriers and environmental heterogeneity in shaping compositional changes in Amazonian forest bird assemblages, we focus on the Tapajós River. We investigate how spatial variation in species composition is related to physical barriers (Tapajós and Jamanxim rivers), species’ ecological characteristics (distinct guilds), and environmental heterogeneity (canopy reflectance, soils, and elevation). We sampled birds through point‐counts and mist nets on both banks of the Tapajós and Jamanxim rivers. To test for relationships between bird composition and environmental data, we used Mantel and partial Mantel tests, NMDS, and ANOVA + Tukey HSD. The Mantel tests showed that the clearest compositional changes occurred across the Tapajós River, which seems to act unequally as a significant barrier to the bird guilds. The Jamanxim River was not associated with differences in bird communities. Our results reinforce that the Tapajós River is a biogeographical boundary for birds, while environmental heterogeneity influences compositional variation within interfluves. We discuss the combined influence of geographical barriers, environmental heterogeneity, and ecological characteristics of species in shaping species distributions and community composition and the complexity of extrapolating the patterns found for birds to other Amazonian organisms.

中文翻译：

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河流，环境异质性和物种性状在推动东南亚马孙鸟类组合组成变化方面的相对作用

有人提议将亚马逊河作为物种扩散的地理障碍，从而驱动异源物种形成或确定当前的分布极限。屏障的强度根据物种的生态特征和河流的物理特性而变化。环境异质性也可能导致成分变化，但在亚马逊地区尚未得到很好的评估。为了了解河流障碍和环境异质性在塑造亚马逊森林鸟类组合的成分变化中的作用，我们将重点放在塔帕霍斯河上。我们调查物种组成的空间变化如何与物理屏障（塔帕约斯河和贾曼西姆河），物种的生态特征（行会不同）和环境异质性（冠层反射率，土壤和海拔）相关。我们在Tapajós河和Jamanxim河两岸通过点计数和薄雾网采样鸟类。为了测试鸟类组成与环境数据之间的关系，我们使用了Mantel和部分Mantel测试，NMDS和ANOVA + Tukey HSD。壁炉架测试表明，最清晰的成分变化发生在塔帕霍斯河上，这似乎对鸟类行会起了重要的阻碍作用。Jamanxim河与鸟类群落的差异无关。我们的研究结果进一步证明，塔帕霍斯河是鸟类的生物地理边界，而环境异质性会影响到干扰物内部的成分变化。我们讨论了地理障碍，环境异质性，