Museum of Zoology, Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA.
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA.
Nature. 2018 Jul;559(7714):392-395. doi: 10.1038/s41586-018-0273-1. Epub 2018 Jul 4.
Far more species of organisms are found in the tropics than in temperate and polar regions, but the evolutionary and ecological causes of this pattern remain controversial. Tropical marine fish communities are much more diverse than cold-water fish communities found at higher latitudes, and several explanations for this latitudinal diversity gradient propose that warm reef environments serve as evolutionary 'hotspots' for species formation. Here we test the relationship between latitude, species richness and speciation rate across marine fishes. We assembled a time-calibrated phylogeny of all ray-finned fishes (31,526 tips, of which 11,638 had genetic data) and used this framework to describe the spatial dynamics of speciation in the marine realm. We show that the fastest rates of speciation occur in species-poor regions outside the tropics, and that high-latitude fish lineages form new species at much faster rates than their tropical counterparts. High rates of speciation occur in geographical regions that are characterized by low surface temperatures and high endemism. Our results reject a broad class of mechanisms under which the tropics serve as an evolutionary cradle for marine fish diversity and raise new questions about why the coldest oceans on Earth are present-day hotspots of species formation.
与温带和极地地区相比，热带地区的生物物种要丰富得多，但造成这种模式的进化和生态原因仍存在争议。热带海洋鱼类群落比高纬度地区的冷水鱼类群落更加多样化，针对这种纬度多样性梯度，有几种解释认为温暖的珊瑚礁环境是物种形成的进化“热点”。在这里，我们检验了海洋鱼类的纬度、物种丰富度和物种形成率之间的关系。我们组装了所有硬骨鱼类的时间校准系统发育树（31526 个分支，其中 11638 个具有遗传数据），并利用该框架描述了海洋领域物种形成的空间动态。我们发现，在热带以外的物种贫乏地区，物种形成的速度最快，而高纬度鱼类谱系形成新物种的速度比其热带同类快得多。高物种形成率发生在以低表面温度和高特有性为特征的地理区域。我们的研究结果否定了热带作为海洋鱼类多样性进化摇篮的一大类机制，并提出了有关为什么地球上最冷的海洋是当今物种形成热点的新问题。
