Data from - Myers’ divisions revisited: Contemporary evidence for distinct trait differences among global inland fishes

Article DOI: 10.1111/faf.12832Eighty 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.

论文DOI：10.1111/faf.12832。八十余年前，乔治·S·迈尔斯（George S. Myers）基于盐度耐受性与生态进化历史，将内陆鱼类划分为三大类群（初级、次级与边缘类群）。尽管该分类方案被诸多鱼类学研究沿用，但也受到了大量批评。本研究依托约21000个物种的数据，旨在检验三大类群在盐度与温度耐受性、物种性状及分布格局上的差异。研究结果显示，初级鱼类的盐度耐受性远低于次级与边缘类群物种，部分次级鱼类的盐度耐受性可达最高（>100 ppt）。本研究首次提供了盐度耐受性存在显著系统发育信号的证据，其信号强度可与保守性状相媲美；同时表明，与初级鱼类相反，所研究的边缘与次级类群物种已维持甚至演化出了盐度耐受性。尽管边缘鱼类类群差异最为显著，且部分科内存在较大的性状变异，但初级与次级类群物种在形态学与生活史性状上同样存在差异。初级与次级鱼类类群的分布范围与遗传多样性较为相似，且均与边缘类群存在差异，这表明尽管有证据显示少量次级鱼类在进化时间尺度上存在海洋扩散事件，但此类事件在当代极为罕见。值得注意的是，本研究提出的部分结论（如盐度耐受性差异）依赖于有限的数据。鉴于淡水鱼类盐度耐受性的相关研究仍有大量空白亟待探索，我们呼吁开展更多相关实证研究，以厘清类群间及类群内部的性状差异。