Global Biogeography of Reef Fishes: A Hierarchical Quantitative Delineation of Regions

Delineating regions is an important first step in understanding the evolution and biogeography of faunas. However, quantitative approaches are often limited at a global scale, particularly in the marine realm. Reef fishes are the most diversified group of marine fishes, and compared to most other phyla, their taxonomy and geographical distributions are relatively well known. Based on 169 checklists spread across all tropical oceans, the present work aims to quantitatively delineate biogeographical entities for reef fishes at a global scale. Four different classifications were used to account for uncertainty related to species identification and the quality of checklists. The four classifications delivered converging results, with biogeographical entities that can be hierarchically delineated into realms, regions and provinces. All classifications indicated that the Indo-Pacific has a weak internal structure, with a high similarity from east to west. In contrast, the Atlantic and the Eastern Tropical Pacific were more strongly structured, which may be related to the higher levels of endemism in these two realms. The “Coral Triangle”, an area of the Indo-Pacific which contains the highest species diversity for reef fishes, was not clearly delineated by its species composition. Our results show a global concordance with recent works based upon endemism, environmental factors, expert knowledge, or their combination. Our quantitative delineation of biogeographical entities, however, tests the robustness of the results and yields easily replicated patterns. The similarity between our results and those from other phyla, such as corals, suggests that our approach may be of broad utility in describing and understanding global marine biodiversity patterns.界定生物地理区域，是解析动物群演化与生物地理分布格局的首要关键步骤。然而，定量研究方法在全球尺度的应用常受局限，尤其在海洋生物地理界（biogeographical realm）中。珊瑚礁鱼类是海洋鱼类中物种多样性最为丰富的类群，相较于绝大多数其他动物门，其分类学与地理分布的研究认知程度相对较高。本研究基于遍布全球热带海域的169份物种分布名录，旨在以定量方法在全球尺度下界定珊瑚礁鱼类的生物地理单元。本研究采用四种不同的分类方案，以考量物种鉴定误差与名录质量带来的不确定性。四种分类方案均得到了一致的研究结果，其所界定的生物地理单元可按层级划分为生物地理界（biogeographical realm）、生物地理区域（biogeographical region）与生物地理省（biogeographical province）。所有分类方案均显示，印度-太平洋域的内部结构较弱，东西部间的物种组成相似度极高。与之形成对比的是，大西洋与东热带太平洋域的内部结构更为显著，这或许与这两个生物地理界较高的特有性水平相关。作为印度-太平洋域中珊瑚礁鱼类物种多样性最高的区域，‘珊瑚三角区’并未通过其物种组成得到清晰的界定。本研究结果与近期基于特有性、环境因子、专家认知或三者结合开展的相关研究在全球尺度下具有一致性。然而，本研究对生物地理单元的定量界定，验证了研究结果的稳健性，并得到了易于复现的分布模式。本研究结果与珊瑚等其他动物门的相关研究结果具有相似性，这表明本研究采用的方法可广泛应用于解析与阐明全球海洋生物多样性分布格局。