Widespread misperception about a major East Asian biogeographic boundary exposed through bibliographic survey and biogeographic meta-analysis

Aim The Watase line, a major biogeographic boundary between Palearctic and Oriental realms in East Asia, is generally drawn between Akuseki and Kodakara Islands of the Northern Ryukyu archipelago, Japan. However, no evidence can be found to support the positioning of the boundary between these two tiny volcanic islands. This study aimed to confirm whether and where the biogeographical boundary should be drawn. Location East Asia Taxon Land snail, ant, dragonfly, butterfly, amphibian, reptile, bird, plant Methods A bibliographic survey was carried out to revisit an original definition of the Watase line and its usage. Biogeographic and meta-analyses were also performed using a Simpson dissimilarity index calculated from published distribution data to test whether and where any biogeographic boundary exists. To ensure the validity of the study design, similar surveys and analyses were conducted in another region of Southern Ryukyu, where a reliable biogeographic boun...研究目标 渡濑线（Watase Line）是东亚地区分隔古北界（Palearctic Realm）与东洋界（Oriental Realm）的核心生物地理界线，学界通常将其划定于日本北部琉球群岛的恶石岛与Kodakara岛之间。然而目前尚无实证支持该界线被设置于这两座小型火山岛之间。本研究旨在明确该生物地理界线是否存在，以及其确切的划定位置。 研究区域 东亚 研究类群 陆生蜗牛、蚂蚁、蜻蜓、蝴蝶、两栖动物、爬行动物、鸟类、植物 研究方法 本研究首先通过文献调研，重新梳理渡濑线的原始定义及其应用沿革；同时基于已发表的物种分布数据，通过计算辛普森相异指数（Simpson dissimilarity index）开展生物地理学分析与荟萃分析，以验证该生物地理界线是否存在并确定其具体位置。为确保研究设计的严谨性，本研究同时在南琉球的另一区域开展了同类调研与分析，该区域存在公认可靠的生物地理界线……