Eighty years ago, George S. Myers classified inland fishes in three divisions (primary, secondary and peripheral) based on their salinity tolerance and eco‐evolutionary history. Although this classification has been followed by many fish studies, it has also received considerable criticism. Here, we aim to test for differences in salinity and thermal tolerance, species traits and distribution patterns among the three divisions using data for about 21,000 species. We found that primary fishes have much less salinity tolerance than secondary and peripheral species, with some secondary fishes displaying the highest tolerances (>100 ppt). We also provide, for the first time, evidence of significant phylogenetic signal of salinity tolerance, comparable in magnitude to conservative traits, and show that studied peripheral and secondary species have maintained or even developed salinity tolerance, in contrast to primary fishes. Although peripheral fishes are the most different, and despite the large variability observed within some families, primary and secondary species also show differences in morphology and life‐history traits. The distribution ranges and genetic diversity of primary and secondary fish divisions are similar and differ from peripheral species, suggesting that although there is evidence of oceanic dispersal of a few secondary fishes at evolutionary time scales, it is a rare contemporary phenomenon. Importantly, a few findings outlined in this study, namely, differences in salinity tolerance, rely on limited data. Thus, we urge for additional empirical research on the salinity tolerance of freshwater fish, which remains largely unexplored, to help clarify differences among and within clades.

中文翻译：

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重新审视迈尔斯的划分：全球内陆鱼类之间明显性状差异的当代证据

八十年前，乔治·迈尔斯 (George S. Myers) 根据内陆鱼类的耐盐性和生态进化历史将其分为三类（初级、次级和外围）。尽管这种分类已被许多鱼类研究所遵循，但它也受到了相当多的批评。在这里，我们的目标是使用约 21,000 个物种的数据来测试这三个科之间盐度和耐热性、物种特征和分布模式的差异。我们发现初级鱼类的盐度耐受性比次生和外围物种低得多，一些次生鱼类表现出最高的耐受性（> 100 ppt）。我们还首次提供了耐盐性的显着系统发育信号的证据，其大小与保守性状相当，并表明与主要鱼类相比，所研究的外围和次生物种保持甚至发展了耐盐性。尽管外围鱼类差异最大，并且尽管在一些科内观察到很大的变异性，但主要和次要物种在形态和生活史特征上也表现出差异。初级和次级鱼类的分布范围和遗传多样性相似，但与外围物种不同，这表明尽管有证据表明少数次级鱼类在进化时间尺度上进行了海洋扩散，但这是一种罕见的当代现象。重要的是，本研究中概述的一些发现，即盐度耐受性的差异，依赖于有限的数据。因此，我们敦促对淡水鱼的耐盐性进行更多的实证研究（这在很大程度上尚未得到探索），以帮助澄清进化枝之间和内部的差异。