The Amazon has the highest richness of freshwater organisms in the world, which has led to a multitude of hypotheses on the mechanisms that generated this biodiversity. However, most of these hypotheses focus on the spatial distance of populations, a framework that fails to provide an explicit mechanism of speciation. Ecological conditions in Amazon freshwaters can be strikingly distinct, as it has been recognized since Alfred Russel Wallace’s categorization into black, white, and blue (= clear) waters. Water types reflect differences in turbidity, dissolved organic matter, electrical conductivity, pH, amount of nutrients and lighting environment, characteristics that directly affect the sensory abilities of aquatic organisms. Since natural selection drives evolution of sensory systems to function optimally according to environmental conditions, the sensory systems of Amazon freshwater organisms are expected to vary according to their environment. When differences in sensory systems affect chances of interbreeding between populations, local adaptations may result in speciation. Here, we briefly present the limnologic characteristics of Amazonian water types and how they are expected to influence photo-, chemical-, mechano-, and electro-reception of aquatic organisms, focusing on fish. We put forward that the effect of different water types on the adaptation of sensory systems is an important mechanism that contributed to the evolution of fish diversity. We point toward underexplored research perspectives on how divergent selection may act on sensory systems and thus contribute to the origin and maintenance of the biodiversity of Amazon aquatic environments.

中文翻译：

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鱼类感官系统和亚马逊水类型对生物多样性影响的综述

亚马逊拥有世界上最丰富的淡水生物，因此人们对产生这种生物多样性的机制提出了多种假设。然而，这些假设中的大多数都集中在种群的空间距离上，这一框架未能提供明确的物种形成机制。亚马逊淡水的生态条件可能截然不同，因为自从阿尔弗雷德·罗素·华莱士将其分为黑色、白色和蓝色（= 清澈）水域以来，这一点就得到了认可。水的类型反映了浊度、溶解有机物、电导率、pH值、养分含量和光照环境的差异，这些特性直接影响水生生物的感官能力。由于自然选择驱动感官系统的进化，以根据环境条件发挥最佳功能，亚马逊淡水生物的感官系统预计会因环境而异。当感觉系统的差异影响种群间杂交的机会时，当地的适应可能会导致物种形成。在这里，我们简要介绍亚马逊河水类型的湖沼学特征，以及它们如何影响水生生物的光、化学、机械和电接收，重点是鱼类。我们提出不同水体对感官系统适应的影响是促成鱼类多样性进化的重要机制。我们指出了未充分探索的研究视角，即不同的选择如何作用于感官系统，从而有助于亚马逊水生环境生物多样性的起源和维护。